Towards the impact of eddies on the response of the global ocean circulation to Southern Ocean gateway opening

NASA Astrophysics Data System (ADS)

Viebahn, Jan; von der Heydt, Anna S.; Dijkstra, Henk A.

2014-05-01

During the past 65 Million (Ma) years, Earth's climate has undergone a major change from warm 'greenhouse' to colder 'icehouse' conditions with extensive ice sheets in the polar regions of both hemispheres. The Eocene-Oligocene (~34 Ma) and Oligocene-Miocene (~23 Ma) boundaries reflect major transitions in Cenozoic global climate change. Proposed mechanisms of these transitions include reorganization of ocean circulation due to critical gateway opening/deepening, changes in atmospheric CO2-concentration, and feedback mechanisms related to land-ice formation. A long-standing hypothesis is that the formation of the Antarctic Circumpolar Current due to opening/deepening of Southern Ocean gateways led to glaciation of the Antarctic continent. However, while this hypothesis remains controversial, its assessment via coupled climate model simulations depends crucially on the spatial resolution in the ocean component. More precisely, only high-resolution modeling of the turbulent ocean circulation is capable of adequately describing reorganizations in the ocean flow field and related changes in turbulent heat transport. In this study, for the first time results of a high-resolution (0.1° horizontally) realistic global ocean model simulation with a closed Drake Passage are presented. Changes in global ocean temperatures, heat transport, and ocean circulation (e.g., Meridional Overturning Circulation and Antarctic Coastal Current) are established by comparison with an open Drake Passage high-resolution reference simulation. Finally, corresponding low-resolution simulations are also analyzed. The results highlight the essential impact of the ocean eddy field in palaeoclimatic change.

Present-day constraint for tropical Pacific precipitation changes due to global warming in CMIP5 models

NASA Astrophysics Data System (ADS)

Ham, Yoo-Geun; Kug, Jong-Seong

2016-11-01

The sensitivity of the precipitation responses to greenhouse warming can depend on the present-day climate. In this study, a robust linkage between the present-day precipitation climatology and precipitation change owing to global warming is examined in inter-model space. A model with drier climatology in the present-day simulation tends to simulate an increase in climatological precipitation owing to global warming. Moreover, the horizontal gradient of the present-day precipitation climatology plays an important role in determining the precipitation changes. On the basis of these robust relationships, future precipitation changes are calibrated by removing the impact of the present-day precipitation bias in the climate models. To validate this result, the perfect model approach is adapted, which treats a particular model's precipitation change as an observed change. The results suggest that the precipitation change pattern can be generally improved by applying the present statistical approach.

Microbial mediation of biogeochemical cycles revealed by simulation of global changes with soil transplant and cropping

PubMed Central

Zhao, Mengxin; Xue, Kai; Wang, Feng; Liu, Shanshan; Bai, Shijie; Sun, Bo; Zhou, Jizhong; Yang, Yunfeng

2014-01-01

Despite microbes' key roles in driving biogeochemical cycles, the mechanism of microbe-mediated feedbacks to global changes remains elusive. Recently, soil transplant has been successfully established as a proxy to simulate climate changes, as the current trend of global warming coherently causes range shifts toward higher latitudes. Four years after southward soil transplant over large transects in China, we found that microbial functional diversity was increased, in addition to concurrent changes in microbial biomass, soil nutrient content and functional processes involved in the nitrogen cycle. However, soil transplant effects could be overridden by maize cropping, which was attributed to a negative interaction. Strikingly, abundances of nitrogen and carbon cycle genes were increased by these field experiments simulating global change, coinciding with higher soil nitrification potential and carbon dioxide (CO2) efflux. Further investigation revealed strong correlations between carbon cycle genes and CO2 efflux in bare soil but not cropped soil, and between nitrogen cycle genes and nitrification. These findings suggest that changes of soil carbon and nitrogen cycles by soil transplant and cropping were predictable by measuring microbial functional potentials, contributing to a better mechanistic understanding of these soil functional processes and suggesting a potential to incorporate microbial communities in greenhouse gas emission modeling. PMID:24694714

Regulators of coastal wetland methane production and responses to simulated global change

Treesearch

Carmella Vizza; William E. West; Stuart E. Jones; Julia A. Hart; Gary A. Lamberti

2017-01-01

Wetlands are the largest natural source of methane (CH4) emissions to the atmosphere, which vary along salinity and productivity gradients. Global change has the potential to reshape these gradients and therefore alter future contributions of wetlands to the global CH4 budget. Our study examined CH4...

A Simple Climate Model Program for High School Education

NASA Astrophysics Data System (ADS)

Dommenget, D.

2012-04-01

The future climate change projections of the IPCC AR4 are based on GCM simulations, which give a distinct global warming pattern, with an arctic winter amplification, an equilibrium land sea contrast and an inter-hemispheric warming gradient. While these simulations are the most important tool of the IPCC predictions, the conceptual understanding of these predicted structures of climate change are very difficult to reach if only based on these highly complex GCM simulations and they are not accessible for ordinary people. In this study presented here we will introduce a very simple gridded globally resolved energy balance model based on strongly simplified physical processes, which is capable of simulating the main characteristics of global warming. The model shall give a bridge between the 1-dimensional energy balance models and the fully coupled 4-dimensional complex GCMs. It runs on standard PC computers computing globally resolved climate simulation with 2yrs per second or 100,000yrs per day. The program can compute typical global warming scenarios in a few minutes on a standard PC. The computer code is only 730 line long with very simple formulations that high school students should be able to understand. The simple model's climate sensitivity and the spatial structure of the warming pattern is within the uncertainties of the IPCC AR4 models simulations. It is capable of simulating the arctic winter amplification, the equilibrium land sea contrast and the inter-hemispheric warming gradient with good agreement to the IPCC AR4 models in amplitude and structure. The program can be used to do sensitivity studies in which students can change something (e.g. reduce the solar radiation, take away the clouds or make snow black) and see how it effects the climate or the climate response to changes in greenhouse gases. This program is available for every one and could be the basis for high school education. Partners for a high school project are wanted!

Using multiple climate projections for assessing hydrological response to climate change in the Thukela River Basin, South Africa

NASA Astrophysics Data System (ADS)

Graham, L. Phil; Andersson, Lotta; Horan, Mark; Kunz, Richard; Lumsden, Trevor; Schulze, Roland; Warburton, Michele; Wilk, Julie; Yang, Wei

This study used climate change projections from different regional approaches to assess hydrological effects on the Thukela River Basin in KwaZulu-Natal, South Africa. Projecting impacts of future climate change onto hydrological systems can be undertaken in different ways and a variety of effects can be expected. Although simulation results from global climate models (GCMs) are typically used to project future climate, different outcomes from these projections may be obtained depending on the GCMs themselves and how they are applied, including different ways of downscaling from global to regional scales. Projections of climate change from different downscaling methods, different global climate models and different future emissions scenarios were used as input to simulations in a hydrological model to assess climate change impacts on hydrology. A total of 10 hydrological change simulations were made, resulting in a matrix of hydrological response results. This matrix included results from dynamically downscaled climate change projections from the same regional climate model (RCM) using an ensemble of three GCMs and three global emissions scenarios, and from statistically downscaled projections using results from five GCMs with the same emissions scenario. Although the matrix of results does not provide complete and consistent coverage of potential uncertainties from the different methods, some robust results were identified. In some regards, the results were in agreement and consistent for the different simulations. For others, particularly rainfall, the simulations showed divergence. For example, all of the statistically downscaled simulations showed an annual increase in precipitation and corresponding increase in river runoff, while the RCM downscaled simulations showed both increases and decreases in runoff. According to the two projections that best represent runoff for the observed climate, increased runoff would generally be expected for this basin in the future. Dealing with such variability in results is not atypical for assessing climate change impacts in Africa and practitioners are faced with how to interpret them. This work highlights the need for additional, well-coordinated regional climate downscaling for the region to further define the range of uncertainties involved.

Calibrating and Updating the Global Forest Products Model (GFPM version 2014 with BPMPD)

Treesearch

Joseph Buongiorno; Shushuai Zhu

2014-01-01

The Global Forest Products Model (GFPM) is an economic model of global production, consumption, and trade of forest products. An earlier version of the model is described in Buongiorno et al. (2003). The GFPM 2014 has data and parameters to simulate changes of the forest sector from 2010 to 2030. Buongiorno and Zhu (2014) describe how to use the model for simulation....

Assessing climate change impacts, benefits of mitigation, and uncertainties on major global forest regions under multiple socioeconomic and emissions scenarios

DOE PAGES

Kim, John B.; Monier, Erwan; Sohngen, Brent; ...

2017-03-28

We analyze a set of simulations to assess the impact of climate change on global forests where MC2 dynamic global vegetation model (DGVM) was run with climate simulations from the MIT Integrated Global System Model-Community Atmosphere Model (IGSM-CAM) modeling framework. The core study relies on an ensemble of climate simulations under two emissions scenarios: a business-as-usual reference scenario (REF) analogous to the IPCC RCP8.5 scenario, and a greenhouse gas mitigation scenario, called POL3.7, which is in between the IPCC RCP2.6 and RCP4.5 scenarios, and is consistent with a 2 °C global mean warming from pre-industrial by 2100. Evaluating the outcomesmore » of both climate change scenarios in the MC2 model shows that the carbon stocks of most forests around the world increased, with the greatest gains in tropical forest regions. Temperate forest regions are projected to see strong increases in productivity offset by carbon loss to fire. The greatest cost of mitigation in terms of effects on forest carbon stocks are projected to be borne by regions in the southern hemisphere. We compare three sources of uncertainty in climate change impacts on the world’s forests: emissions scenarios, the global system climate response (i.e. climate sensitivity), and natural variability. The role of natural variability on changes in forest carbon and net primary productivity (NPP) is small, but it is substantial for impacts of wildfire. Forest productivity under the REF scenario benefits substantially from the CO 2 fertilization effect and that higher warming alone does not necessarily increase global forest carbon levels. Finally, our analysis underlines why using an ensemble of climate simulations is necessary to derive robust estimates of the benefits of greenhouse gas mitigation. It also demonstrates that constraining estimates of climate sensitivity and advancing our understanding of CO 2 fertilization effects may considerably reduce the range of projections.« less

Assessing climate change impacts, benefits of mitigation, and uncertainties on major global forest regions under multiple socioeconomic and emissions scenarios

NASA Astrophysics Data System (ADS)

Kim, John B.; Monier, Erwan; Sohngen, Brent; Pitts, G. Stephen; Drapek, Ray; McFarland, James; Ohrel, Sara; Cole, Jefferson

2017-04-01

We analyze a set of simulations to assess the impact of climate change on global forests where MC2 dynamic global vegetation model (DGVM) was run with climate simulations from the MIT Integrated Global System Model-Community Atmosphere Model (IGSM-CAM) modeling framework. The core study relies on an ensemble of climate simulations under two emissions scenarios: a business-as-usual reference scenario (REF) analogous to the IPCC RCP8.5 scenario, and a greenhouse gas mitigation scenario, called POL3.7, which is in between the IPCC RCP2.6 and RCP4.5 scenarios, and is consistent with a 2 °C global mean warming from pre-industrial by 2100. Evaluating the outcomes of both climate change scenarios in the MC2 model shows that the carbon stocks of most forests around the world increased, with the greatest gains in tropical forest regions. Temperate forest regions are projected to see strong increases in productivity offset by carbon loss to fire. The greatest cost of mitigation in terms of effects on forest carbon stocks are projected to be borne by regions in the southern hemisphere. We compare three sources of uncertainty in climate change impacts on the world’s forests: emissions scenarios, the global system climate response (i.e. climate sensitivity), and natural variability. The role of natural variability on changes in forest carbon and net primary productivity (NPP) is small, but it is substantial for impacts of wildfire. Forest productivity under the REF scenario benefits substantially from the CO2 fertilization effect and that higher warming alone does not necessarily increase global forest carbon levels. Our analysis underlines why using an ensemble of climate simulations is necessary to derive robust estimates of the benefits of greenhouse gas mitigation. It also demonstrates that constraining estimates of climate sensitivity and advancing our understanding of CO2 fertilization effects may considerably reduce the range of projections.

Assessing climate change impacts, benefits of mitigation, and uncertainties on major global forest regions under multiple socioeconomic and emissions scenarios

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, John B.; Monier, Erwan; Sohngen, Brent

We analyze a set of simulations to assess the impact of climate change on global forests where MC2 dynamic global vegetation model (DGVM) was run with climate simulations from the MIT Integrated Global System Model-Community Atmosphere Model (IGSM-CAM) modeling framework. The core study relies on an ensemble of climate simulations under two emissions scenarios: a business-as-usual reference scenario (REF) analogous to the IPCC RCP8.5 scenario, and a greenhouse gas mitigation scenario, called POL3.7, which is in between the IPCC RCP2.6 and RCP4.5 scenarios, and is consistent with a 2 °C global mean warming from pre-industrial by 2100. Evaluating the outcomesmore » of both climate change scenarios in the MC2 model shows that the carbon stocks of most forests around the world increased, with the greatest gains in tropical forest regions. Temperate forest regions are projected to see strong increases in productivity offset by carbon loss to fire. The greatest cost of mitigation in terms of effects on forest carbon stocks are projected to be borne by regions in the southern hemisphere. We compare three sources of uncertainty in climate change impacts on the world’s forests: emissions scenarios, the global system climate response (i.e. climate sensitivity), and natural variability. The role of natural variability on changes in forest carbon and net primary productivity (NPP) is small, but it is substantial for impacts of wildfire. Forest productivity under the REF scenario benefits substantially from the CO 2 fertilization effect and that higher warming alone does not necessarily increase global forest carbon levels. Finally, our analysis underlines why using an ensemble of climate simulations is necessary to derive robust estimates of the benefits of greenhouse gas mitigation. It also demonstrates that constraining estimates of climate sensitivity and advancing our understanding of CO 2 fertilization effects may considerably reduce the range of projections.« less

Changes in yields and their variability at different levels of global warming

NASA Astrophysics Data System (ADS)

Childers, Katelin

2015-04-01

An assessment of climate change impacts at different levels of global warming is crucial to inform the political discussion about mitigation targets as well as for the inclusion of climate change impacts in Integrated Assessment Models (IAMs) that generally only provide global mean temperature change as an indicator of climate change. While there is a well-established framework for the scalability of regional temperature and precipitation changes with global mean temperature change we provide an assessment of the extent to which impacts such as crop yield changes can also be described in terms of global mean temperature changes without accounting for the specific underlying emissions scenario. Based on multi-crop-model simulations of the four major cereal crops (maize, rice, soy, and wheat) on a 0.5 x 0.5 degree global grid generated within ISI-MIP, we show the average spatial patterns of projected crop yield changes at one half degree warming steps. We find that emissions scenario dependence is a minor component of the overall variance of projected yield changes at different levels of global warming. Furthermore, scenario dependence can be reduced by accounting for the direct effects of CO2 fertilization in each global climate model (GCM)/impact model combination through an inclusion of the global atmospheric CO2 concentration as a second predictor. The choice of GCM output used to force the crop model simulations accounts for a slightly larger portion of the total yield variance, but the greatest contributor to variance in both global and regional crop yields and at all levels of warming, is the inter-crop-model spread. The unique multi impact model ensemble available with ISI-MIP data also indicates that the overall variability of crop yields is projected to increase in conjunction with increasing global mean temperature. This result is consistent throughout the ensemble of impact models and across many world regions. Such a hike in yield volatility could have significant policy implications by affecting food prices and supplies.

Adaptation of Land-Use Demands to the Impact of Climate Change on the Hydrological Processes of an Urbanized Watershed

PubMed Central

Lin, Yu-Pin; Hong, Nien-Ming; Chiang, Li-Chi; Liu, Yen-Lan; Chu, Hone-Jay

2012-01-01

The adaptation of land-use patterns is an essential aspect of minimizing the inevitable impact of climate change at regional and local scales; for example, adapting watershed land-use patterns to mitigate the impact of climate change on a region’s hydrology. The objective of this study is to simulate and assess a region’s ability to adapt to hydrological changes by modifying land-use patterns in the Wu-Du watershed in northern Taiwan. A hydrological GWLF (Generalized Watershed Loading Functions) model is used to simulate three hydrological components, namely, runoff, groundwater and streamflow, based on various land-use scenarios under six global climate models. The land-use allocations are simulated by the CLUE-s model for the various development scenarios. The simulation results show that runoff and streamflow are strongly related to the precipitation levels predicted by different global climate models for the wet and dry seasons, but groundwater cycles are more related to land-use. The effects of climate change on groundwater and runoff can be mitigated by modifying current land-use patterns; and slowing the rate of urbanization would also reduce the impact of climate change on hydrological components. Thus, land-use adaptation on a local/regional scale provides an alternative way to reduce the impacts of global climate change on local hydrology. PMID:23202833

Deforestation Induced Climate Change: Effects of Spatial Scale.

PubMed

Longobardi, Patrick; Montenegro, Alvaro; Beltrami, Hugo; Eby, Michael

2016-01-01

Deforestation is associated with increased atmospheric CO2 and alterations to the surface energy and mass balances that can lead to local and global climate changes. Previous modelling studies show that the global surface air temperature (SAT) response to deforestation depends on latitude, with most simulations showing that high latitude deforestation results in cooling, low latitude deforestation causes warming and that the mid latitude response is mixed. These earlier conclusions are based on simulated large scal land cover change, with complete removal of trees from whole latitude bands. Using a global climate model we examine the effects of removing fractions of 5% to 100% of forested areas in the high, mid and low latitudes. All high latitude deforestation scenarios reduce mean global SAT, the opposite occurring for low latitude deforestation, although a decrease in SAT is simulated over low latitude deforested areas. Mid latitude SAT response is mixed. In all simulations deforested areas tend to become drier and have lower SAT, although soil temperatures increase over deforested mid and low latitude grid cells. For high latitude deforestation fractions of 45% and above, larger net primary productivity, in conjunction with colder and drier conditions after deforestation cause an increase in soil carbon large enough to produce a net decrease of atmospheric CO2. Our results reveal the complex interactions between soil carbon dynamics and other climate subsystems in the energy partition responses to land cover change.

Deforestation Induced Climate Change: Effects of Spatial Scale

PubMed Central

Longobardi, Patrick; Montenegro, Alvaro; Beltrami, Hugo; Eby, Michael

2016-01-01

Deforestation is associated with increased atmospheric CO2 and alterations to the surface energy and mass balances that can lead to local and global climate changes. Previous modelling studies show that the global surface air temperature (SAT) response to deforestation depends on latitude, with most simulations showing that high latitude deforestation results in cooling, low latitude deforestation causes warming and that the mid latitude response is mixed. These earlier conclusions are based on simulated large scal land cover change, with complete removal of trees from whole latitude bands. Using a global climate model we examine the effects of removing fractions of 5% to 100% of forested areas in the high, mid and low latitudes. All high latitude deforestation scenarios reduce mean global SAT, the opposite occurring for low latitude deforestation, although a decrease in SAT is simulated over low latitude deforested areas. Mid latitude SAT response is mixed. In all simulations deforested areas tend to become drier and have lower SAT, although soil temperatures increase over deforested mid and low latitude grid cells. For high latitude deforestation fractions of 45% and above, larger net primary productivity, in conjunction with colder and drier conditions after deforestation cause an increase in soil carbon large enough to produce a net decrease of atmospheric CO2. Our results reveal the complex interactions between soil carbon dynamics and other climate subsystems in the energy partition responses to land cover change. PMID:27100667

Cross - Scale Intercomparison of Climate Change Impacts Simulated by Regional and Global Hydrological Models in Eleven Large River Basins

NASA Technical Reports Server (NTRS)

Hattermann, F. F.; Krysanova, V.; Gosling, S. N.; Dankers, R.; Daggupati, P.; Donnelly, C.; Florke, M.; Huang, S.; Motovilov, Y.; Buda, S.;

Cross-scale intercomparison of climate change impacts simulated by regional and global hydrological models in eleven large river basins

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hattermann, F. F.; Krysanova, V.; Gosling, S. N.

Ideally, the results from models operating at different scales should agree in trend direction and magnitude of impacts under climate change. However, this implies that the sensitivity of impact models designed for either scale to climate variability and change is comparable. In this study, we compare hydrological changes simulated by 9 global and 9 regional hydrological models (HM) for 11 large river basins in all continents under reference and scenario conditions. The foci are on model validation runs, sensitivity of annual discharge to climate variability in the reference period, and sensitivity of the long-term average monthly seasonal dynamics to climatemore » change. One major result is that the global models, mostly not calibrated against observations, often show a considerable bias in mean monthly discharge, whereas regional models show a much better reproduction of reference conditions. However, the sensitivity of two HM ensembles to climate variability is in general similar. The simulated climate change impacts in terms of long-term average monthly dynamics evaluated for HM ensemble medians and spreads show that the medians are to a certain extent comparable in some cases with distinct differences in others, and the spreads related to global models are mostly notably larger. Summarizing, this implies that global HMs are useful tools when looking at large-scale impacts of climate change and variability, but whenever impacts for a specific river basin or region are of interest, e.g. for complex water management applications, the regional-scale models validated against observed discharge should be used.« less

Consequences of 1.5 °C and 2 °C global warming levels for temperature and precipitation changes over Central Africa

NASA Astrophysics Data System (ADS)

Pokam Mba, Wilfried; Longandjo, Georges-Noel T.; Moufouma-Okia, Wilfran; Bell, Jean-Pierre; James, Rachel; Vondou, Derbetini A.; Haensler, Andreas; Fotso-Nguemo, Thierry C.; Merlin Guenang, Guy; Djiotang Tchotchou, Angennes Lucie; Kamsu-Tamo, Pierre H.; Takong, Ridick R.; Nikulin, Grigory; Lennard, Christopher J.; Dosio, Alessandro

2018-05-01

Discriminating climate impacts between 1.5 °C and 2 °C warming levels is particularly important for Central Africa, a vulnerable region where multiple biophysical, political, and socioeconomic stresses interact to constrain the region’s adaptive capacity. This study uses an ensemble of 25 transient Regional Climate Model (RCM) simulations from the CORDEX initiative, forced with the Representative Concentration Pathway (RCP) 8.5, to investigate the potential temperature and precipitation changes in Central Africa corresponding to 1.5 °C and 2 °C global warming levels. Global climate model simulations from the Coupled Model Intercomparison Project phase 5 (CMIP5) are used to drive the RCMs and determine timing of the targeted global warming levels. The regional warming differs over Central Africa between 1.5 °C and 2 °C global warming levels. Whilst there are large uncertainties associated with projections at 1.5 °C and 2 °C, the 0.5 °C increase in global temperature is associated with larger regional warming response. Compared to changes in temperature, changes in precipitation are more heterogeneous and climate model simulations indicate a lack of consensus across the region, though there is a tendency towards decreasing seasonal precipitation in March–May, and a reduction of consecutive wet days. As a drought indicator, a significant increase in consecutive dry days was found. Consistent changes of maximum 5 day rainfall are also detected between 1.5 °C vs. 2 °C global warming levels.

Examining global electricity supply vulnerability to climate change using a high-fidelity hydropower dam model.

PubMed

Turner, Sean W D; Ng, Jia Yi; Galelli, Stefano

2017-07-15

An important and plausible impact of a changing global climate is altered power generation from hydroelectric dams. Here we project 21st century global hydropower production by forcing a coupled, global hydrological and dam model with three General Circulation Model (GCM) projections run under two emissions scenarios. Dams are simulated using a detailed model that accounts for plant specifications, storage dynamics, reservoir bathymetry and realistic, optimized operations. We show that the inclusion of these features can have a non-trivial effect on the simulated response of hydropower production to changes in climate. Simulation results highlight substantial uncertainty in the direction of change in globally aggregated hydropower production (~-5 to +5% change in mean global production by the 2080s under a high emissions scenario, depending on GCM). Several clearly impacted hotspots are identified, the most prominent of which encompasses the Mediterranean countries in southern Europe, northern Africa and the Middle East. In this region, hydropower production is projected to be reduced by approximately 40% on average by the end of the century under a high emissions scenario. After accounting for each country's dependence on hydropower for meeting its current electricity demands, the Balkans countries emerge as the most vulnerable (~5-20% loss in total national electricity generation depending on country). On the flipside, a handful of countries in Scandinavia and central Asia are projected to reap a significant increase in total electrical production (~5-15%) without investing in new power generation facilities. Copyright © 2017 Elsevier B.V. All rights reserved.

Examining global electricity supply vulnerability to climate change using a high-fidelity hydropower dam model

DOE PAGES

Turner, Sean W. D.; Ng, Jia Yi; Galelli, Stefano

2017-03-07

Here, an important and plausible impact of a changing global climate is altered power generation from hydroelectric dams. Here we project 21st century global hydropower production by forcing a coupled, global hydrological and dam model with three General Circulation Model (GCM) projections run under two emissions scenarios. Dams are simulated using a detailed model that accounts for plant specifications, storage dynamics, reservoir bathymetry and realistic, optimized operations. We show that the inclusion of these features can have a non-trivial effect on the simulated response of hydropower production to changes in climate. Simulation results highlight substantial uncertainty in the direction ofmore » change in globally aggregated hydropower production (~–5 to + 5% change in mean global production by the 2080s under a high emissions scenario, depending on GCM). Several clearly impacted hotspots are identified, the most prominent of which encompasses the Mediterranean countries in southern Europe, northern Africa and the Middle East. In this region, hydropower production is projected to be reduced by approximately 40% on average by the end of the century under a high emissions scenario. After accounting for each country's dependence on hydropower for meeting its current electricity demands, the Balkans countries emerge as the most vulnerable (~ 5–20% loss in total national electricity generation depending on country). On the flipside, a handful of countries in Scandinavia and central Asia are projected to reap a significant increase in total electrical production (~ 5–15%) without investing in new power generation facilities.« less

Examining global electricity supply vulnerability to climate change using a high-fidelity hydropower dam model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turner, Sean W. D.; Ng, Jia Yi; Galelli, Stefano

Here, an important and plausible impact of a changing global climate is altered power generation from hydroelectric dams. Here we project 21st century global hydropower production by forcing a coupled, global hydrological and dam model with three General Circulation Model (GCM) projections run under two emissions scenarios. Dams are simulated using a detailed model that accounts for plant specifications, storage dynamics, reservoir bathymetry and realistic, optimized operations. We show that the inclusion of these features can have a non-trivial effect on the simulated response of hydropower production to changes in climate. Simulation results highlight substantial uncertainty in the direction ofmore » change in globally aggregated hydropower production (~–5 to + 5% change in mean global production by the 2080s under a high emissions scenario, depending on GCM). Several clearly impacted hotspots are identified, the most prominent of which encompasses the Mediterranean countries in southern Europe, northern Africa and the Middle East. In this region, hydropower production is projected to be reduced by approximately 40% on average by the end of the century under a high emissions scenario. After accounting for each country's dependence on hydropower for meeting its current electricity demands, the Balkans countries emerge as the most vulnerable (~ 5–20% loss in total national electricity generation depending on country). On the flipside, a handful of countries in Scandinavia and central Asia are projected to reap a significant increase in total electrical production (~ 5–15%) without investing in new power generation facilities.« less

Can climate models be tuned to simulate the global mean absolute temperature correctly?

NASA Astrophysics Data System (ADS)

Duan, Q.; Shi, Y.; Gong, W.

2016-12-01

The Inter-government Panel on Climate Change (IPCC) has already issued five assessment reports (ARs), which include the simulation of the past climate and the projection of the future climate under various scenarios. The participating models can simulate reasonably well the trend in global mean temperature change, especially of the last 150 years. However, there is a large, constant discrepancy in terms of global mean absolute temperature simulations over this period. This discrepancy remained in the same range between IPCC-AR4 and IPCC-AR5, which amounts to about 3oC between the coldest model and the warmest model. This discrepancy has great implications to the land processes, particularly the processes related to the cryosphere, and casts doubts over if land-atmosphere-ocean interactions are correctly considered in those models. This presentation aims to explore if this discrepancy can be reduced through model tuning. We present an automatic model calibration strategy to tune the parameters of a climate model so the simulated global mean absolute temperature would match the observed data over the last 150 years. An intermediate complexity model known as LOVECLIM is used in the study. This presentation will show the preliminary results.

Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO2.

PubMed

Friend, Andrew D; Lucht, Wolfgang; Rademacher, Tim T; Keribin, Rozenn; Betts, Richard; Cadule, Patricia; Ciais, Philippe; Clark, Douglas B; Dankers, Rutger; Falloon, Pete D; Ito, Akihiko; Kahana, Ron; Kleidon, Axel; Lomas, Mark R; Nishina, Kazuya; Ostberg, Sebastian; Pavlick, Ryan; Peylin, Philippe; Schaphoff, Sibyll; Vuichard, Nicolas; Warszawski, Lila; Wiltshire, Andy; Woodward, F Ian

2014-03-04

Future climate change and increasing atmospheric CO2 are expected to cause major changes in vegetation structure and function over large fractions of the global land surface. Seven global vegetation models are used to analyze possible responses to future climate simulated by a range of general circulation models run under all four representative concentration pathway scenarios of changing concentrations of greenhouse gases. All 110 simulations predict an increase in global vegetation carbon to 2100, but with substantial variation between vegetation models. For example, at 4 °C of global land surface warming (510-758 ppm of CO2), vegetation carbon increases by 52-477 Pg C (224 Pg C mean), mainly due to CO2 fertilization of photosynthesis. Simulations agree on large regional increases across much of the boreal forest, western Amazonia, central Africa, western China, and southeast Asia, with reductions across southwestern North America, central South America, southern Mediterranean areas, southwestern Africa, and southwestern Australia. Four vegetation models display discontinuities across 4 °C of warming, indicating global thresholds in the balance of positive and negative influences on productivity and biomass. In contrast to previous global vegetation model studies, we emphasize the importance of uncertainties in projected changes in carbon residence times. We find, when all seven models are considered for one representative concentration pathway × general circulation model combination, such uncertainties explain 30% more variation in modeled vegetation carbon change than responses of net primary productivity alone, increasing to 151% for non-HYBRID4 models. A change in research priorities away from production and toward structural dynamics and demographic processes is recommended.

Carbon residence time dominates uncertainty in terrestrial vegetation responses to future climate and atmospheric CO2

PubMed Central

Friend, Andrew D.; Lucht, Wolfgang; Rademacher, Tim T.; Keribin, Rozenn; Betts, Richard; Cadule, Patricia; Ciais, Philippe; Clark, Douglas B.; Dankers, Rutger; Falloon, Pete D.; Ito, Akihiko; Kahana, Ron; Kleidon, Axel; Lomas, Mark R.; Nishina, Kazuya; Ostberg, Sebastian; Pavlick, Ryan; Peylin, Philippe; Schaphoff, Sibyll; Vuichard, Nicolas; Warszawski, Lila; Wiltshire, Andy; Woodward, F. Ian

2014-01-01

Future climate change and increasing atmospheric CO2 are expected to cause major changes in vegetation structure and function over large fractions of the global land surface. Seven global vegetation models are used to analyze possible responses to future climate simulated by a range of general circulation models run under all four representative concentration pathway scenarios of changing concentrations of greenhouse gases. All 110 simulations predict an increase in global vegetation carbon to 2100, but with substantial variation between vegetation models. For example, at 4 °C of global land surface warming (510–758 ppm of CO2), vegetation carbon increases by 52–477 Pg C (224 Pg C mean), mainly due to CO2 fertilization of photosynthesis. Simulations agree on large regional increases across much of the boreal forest, western Amazonia, central Africa, western China, and southeast Asia, with reductions across southwestern North America, central South America, southern Mediterranean areas, southwestern Africa, and southwestern Australia. Four vegetation models display discontinuities across 4 °C of warming, indicating global thresholds in the balance of positive and negative influences on productivity and biomass. In contrast to previous global vegetation model studies, we emphasize the importance of uncertainties in projected changes in carbon residence times. We find, when all seven models are considered for one representative concentration pathway × general circulation model combination, such uncertainties explain 30% more variation in modeled vegetation carbon change than responses of net primary productivity alone, increasing to 151% for non-HYBRID4 models. A change in research priorities away from production and toward structural dynamics and demographic processes is recommended. PMID:24344265

Robust Spring Drying in the Southwestern U.S. and Seasonal Migration of Wet/Dry Patterns in a Warmer Climate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Yang; Leung, Lai-Yung R.; Lu, Jian

2014-03-16

This study compares climate simulations over the United States produced by a regional climate model with the driving global climate simulations as well as a large multi-model ensemble of global climate simulations to investigate robust changes in water availability (precipitation (P) – evapotranspiration (E)). A robust spring dry signal across multiple models is identified in the Southwest that results from a decrease in P and an increase in E in the future. In the boreal winter and summer, the prominent changes in P – E are associated with a north – south dipole pattern, while in spring, the prominent changesmore » in P – E appear as an east – west dipole pattern. The progression of the north – south and east – west dipole patterns through the seasons manifests clearly as a seasonal “clockwise” migration of wet/dry patterns, which is shown to be a robust feature of water availability changes in the US consistent across regional and global climate simulations.« less

Synchronous parallel system for emulation and discrete event simulation

NASA Technical Reports Server (NTRS)

Steinman, Jeffrey S. (Inventor)

1992-01-01

A synchronous parallel system for emulation and discrete event simulation having parallel nodes responds to received messages at each node by generating event objects having individual time stamps, stores only the changes to state variables of the simulation object attributable to the event object, and produces corresponding messages. The system refrains from transmitting the messages and changing the state variables while it determines whether the changes are superseded, and then stores the unchanged state variables in the event object for later restoral to the simulation object if called for. This determination preferably includes sensing the time stamp of each new event object and determining which new event object has the earliest time stamp as the local event horizon, determining the earliest local event horizon of the nodes as the global event horizon, and ignoring the events whose time stamps are less than the global event horizon. Host processing between the system and external terminals enables such a terminal to query, monitor, command or participate with a simulation object during the simulation process.

Synchronous Parallel System for Emulation and Discrete Event Simulation

NASA Technical Reports Server (NTRS)

Steinman, Jeffrey S. (Inventor)

2001-01-01

A synchronous parallel system for emulation and discrete event simulation having parallel nodes responds to received messages at each node by generating event objects having individual time stamps, stores only the changes to the state variables of the simulation object attributable to the event object and produces corresponding messages. The system refrains from transmitting the messages and changing the state variables while it determines whether the changes are superseded, and then stores the unchanged state variables in the event object for later restoral to the simulation object if called for. This determination preferably includes sensing the time stamp of each new event object and determining which new event object has the earliest time stamp as the local event horizon, determining the earliest local event horizon of the nodes as the global event horizon, and ignoring events whose time stamps are less than the global event horizon. Host processing between the system and external terminals enables such a terminal to query, monitor, command or participate with a simulation object during the simulation process.

Analysis of Terrestrial Water Storage Changes from GRACE and GLDAS

NASA Technical Reports Server (NTRS)

Syed, Tajdarul H.; Famiglietti, James S.; Rodell, Matthew; Chen, Jianli; Wilson, Clark R.

2008-01-01

Since March 2002, the Gravity Recovery and Climate Experiment (GRACE) has provided first estimates of land water storage variations by monitoring the time-variable component of Earth's gravity field. Here we characterize spatial-temporal variations in terrestrial water storage changes (TWSC) from GRACE and compare them to those simulated with the Global Land Data Assimilation System (GLDAS). Additionally, we use GLDAS simulations to infer how TWSC is partitioned into snow, canopy water and soil water components, and to understand how variations in the hydrologic fluxes act to enhance or dissipate the stores. Results quantify the range of GRACE-derived storage changes during the studied period and place them in the context of seasonal variations in global climate and hydrologic extremes including drought and flood, by impacting land memory processes. The role of the largest continental river basins as major locations for freshwater redistribution is highlighted. GRACE-based storage changes are in good agreement with those obtained from GLDAS simulations. Analysis of GLDAS-simulated TWSC illustrates several key characteristics of spatial and temporal land water storage variations. Global averages of TWSC were partitioned nearly equally between soil moisture and snow water equivalent, while zonal averages of TWSC revealed the importance of soil moisture storage at low latitudes and snow storage at high latitudes. Evapotranspiration plays a key role in dissipating globally averaged terrestrial water storage. Latitudinal averages showed how precipitation dominates TWSC variations in the tropics, evapotranspiration is most effective in the midlatitudes, and snowmelt runoff is a key dissipating flux at high latitudes. Results have implications for monitoring water storage response to climate variability and change, and for constraining land model hydrology simulations.

Changes of global terrestrial carbon budget and major drivers in recent 30 years simulated using the remote sensing driven BEPS model

NASA Astrophysics Data System (ADS)

Ju, W.; Chen, J.; Liu, R.; Liu, Y.

2013-12-01

The process-based Boreal Ecosystem Productivity Simulator (BEPS) model was employed in conjunction with spatially distributed leaf area index (LAI), land cover, soil, and climate data to simulate the carbon budget of global terrestrial ecosystems during the period from 1981 to 2008. The BEPS model was first calibrated and validated using gross primary productivity (GPP), net primary productivity (NPP), and net ecosystem productivity (NEP) measured in different ecosystems across the word. Then, four global simulations were conducted at daily time steps and a spatial resolution of 8 km to quantify the global terrestrial carbon budget and to identify the relative contributions of changes in climate, atmospheric CO2 concentration, and LAI to the global terrestrial carbon sink. The long term LAI data used to drive the model was generated through fusing Moderate Resolution Imaging Spectroradiometer (MODIS) and historical Advanced Very High Resolution Radiometer (AVHRR) data pixel by pixel. The meteorological fields were interpolated from the 0.5° global daily meteorological dataset produced by the land surface hydrological research group at Princeton University. The results show that the BEPS model was able to simulate carbon fluxes in different ecosystems. Simulated GPP, NPP, and NEP values and their temporal trends exhibited distinguishable spatial patterns. During the period from 1981 to 2008, global terrestrial ecosystems acted as a carbon sink. The averaged global totals of GPP NPP, and NEP were 122.70 Pg C yr-1, 56.89 Pg C yr-1, and 2.76 Pg C yr-1, respectively. The global totals of GPP and NPP increased greatly, at rates of 0.43 Pg C yr-2 (R2=0.728) and 0.26 Pg C yr-2 (R2=0.709), respectively. Global total NEP did not show an apparent increasing trend (R2= 0.036), averaged 2.26 Pg C yr-1, 3.21 Pg C yr-1, and 2.72 Pg C yr-1 for the periods from 1981 to 1989, from 1990 to 1999, and from 2000 to 2008, respectively. The magnitude and temporal trend of global terrestrial carbon budget were similar to the values recently reported by the Global Carbon Project. The obvious increases in global GPP and NPP were mainly driven by the enhancement of atmospheric CO2 fertilization. The change of LAI played the secondary role. Climate had a small negative impact on global terrestrial carbon sequestration. The relative importance of changes in climate, atmospheric CO2 concentration, and LAI in altering the temporal trend of carbon sequestration differed spatially. During the period from 2000 to 2008, terrestrial carbon sinks mainly existed in the northern region of South America, the western region of middle Africa, Southeast Asia, Southeast China, Southeast United States, and some regions of Eurasia.

Coupled Global-Regional Climate Model Simulations of Future Changes in Hydrology over Central America

NASA Astrophysics Data System (ADS)

Oglesby, R. J.; Erickson, D. J.; Hernandez, J. L.; Irwin, D.

2005-12-01

Central America covers a relatively small area, but is topographically very complex, has long coast-lines, large inland bodies of water, and very diverse land cover which is both natural and human-induced. As a result, Central America is plagued by hydrologic extremes, especially major flooding and drought events, in a region where many people still barely manage to eke out a living through subsistence. Therefore, considerable concern exists about whether these extreme events will change, either in magnitude or in number, as climate changes in the future. To address this concern, we have used global climate model simulations of future climate change to drive a regional climate model centered on Central America. We use the IPCC `business as usual' scenario 21st century run made with the NCAR CCSM3 global model to drive the regional model MM5 at 12 km resolution. We chose the `business as usual' scenario to focus on the largest possible changes that are likely to occur. Because we are most interested in near-term changes, our simulations are for the years 2010, 2015, and 2025. A long `present-day run (for 2005) allows us to distinguish between climate variability and any signal due to climate change. Furthermore, a multi-year run with MM5 forced by NCEP reanalyses allows an assessment of how well the coupled global-regional model performs over Central America. Our analyses suggest that the coupled model does a credible job simulating the current climate and hydrologic regime, though lack of sufficient observations strongly complicates this comparison. The suite of model runs for the future years is currently nearing completion, and key results will be presented at the meeting.

Evaluating the impact of role-playing simulations on global competency in an online transnational engineering course

NASA Astrophysics Data System (ADS)

Wold, Kari

Successfully interacting with those from different cultures is essential to excel in any field, particularly when global, transnational collaborations in the workplace are increasingly common. However, many higher education students in engineering are not explicitly taught how to display the global competency skills desired by future employers. To display global competency skills means students must be able to visibly respect and recognize differences among those from different cultures. Global competency also means students must be able to show they can adjust their behaviors and integrate others' ideas when working with those with cultural backgrounds other than their own. While these skills are now deemed essential for future engineers, many institutions are struggling with determining which strategies and activities are universally effective to allow students to practice the global competency skills now crucial for success. Immersing engineering students in interactive role-playing simulations in transnational environments is one way institutions are encouraging students to illustrate and develop global competency skills. Role-playing simulations in transnational education provide environments where students adopt roles, interact with other students, and together explore and address realistic global problems. However, no studies have addressed whether or how role-playing simulations can help develop global competency in transnational engineering courses, students' perceptions regarding whether they change their abilities to display global competency in those environments, and their perspectives the effectiveness of using role-playing simulations for this purpose. To address this gap, this study assesses the impact of two subsequent role-playing simulations involving nuclear energy policy in a transnational course involving engineering students from the University of Virginia in Charlottesville, Virginia, and from Technische Universitat Dortmund in Dortmund, Germany. The differences in students' self-reports regarding whether their behaviors showing global competency skills changed were insignificant from pretests and posttests. However, data obtained from observations, surveys, and interviews showed students did increase their abilities to display global competency, and they believed role-playing simulations were useful in helping them do so. Findings from this study inform program designers and instructors on how to help students display, and improve their abilities to display, the global competency skills that will help them succeed in the world that awaits them.

Glomed-Land: a research project to study the effect of global change in contrasted mediterranean landscapes and future scenarios

NASA Astrophysics Data System (ADS)

Ruiz-Sinoga, José D.; Hueso-González, Paloma; León-Gross, Teodoro; Molina, Julián; Remond, Ricardo; Martínez-Murillo, Juan F.

2017-04-01

The Global Change is referred to the occurrence of great environmental changes associated to climatic fluctuations and human activity as wel (Vitousek et al., 1997; Steffen et al., 2004; Dearing et al., 2006). García-Ruiz et al. (2015) indicated that the relief varies very slowly in time while the changes in vegetation, overland flow generation and erosion occurred very rapidly and conditioned by their interactions and the climate variability as well. The GLOMED-LAND Project has its bases and scientific justification on the combination of the experience of the members of the research team, from one side, in the analysis of the dynamics and eco-geomorphological and climatic processes in Mediterranean environments of southern Spain, in the context of current Global change, and from another, in the study, development and application of new tools for simulation and modelling of future scenarios, and finally, in the analysis of the impact that society exercises the broadcast media related to the problem derived from the awareness and adaptation to Global change. Climate change (CC), directly affects the elements that compose the landscape. Both in the analysis of future climate scenarios raised by the IPCC (2013), such as the regionalisation carried out by AEMET, the Mediterranean region and, especially, the South of Spain, - with its defined longitudinal pluviometric gradient - configured as one of the areas of greatest uncertainty, reflected in a higher concentration of temporal rainfall, and even a reduction in the rainfall. Faced with this situation, the CC can modify the current landscape setting, with all the environmental impacts that this would entail for the terrestrial ecosystems and the systemic services rendered to the society. The combination of different work scales allows the analysis of the dynamics of the landscape and the consequence of its modifications on, hydro-geomorphological processes, closely related to degradation processes that can affect the abiotic, biotic, and human elements of the landscape (soil, plant cover, crops, water resources, etc.). Simulation and modelling is now an essential tool in the study of landscape and of the effects of Climate Change, not only towards the future through scenarios and simulation modelling, also to the past, to better understand what causes have led to effects, and to what extent. In this work we aim to create a set of software tools for analysis, modelling and simulation of the effects of Global change on two Mediterranean catchments: the middle and upper basin of the Grande River and the high Benamargosa River, both of them in the Province of Málaga (South of Spain). This will allow a full analysis, monitor, and predict those effects at local scale. Finally, we analyse the role that the impact of Global Change issues has had from the media point of view and what tendency can follow. References Dearing, J. et al. (2006): «Human-environment interactions: towards synthesis and simulation». Regional Environmental Change, n° 6, 115-123. García-Ruiz et al. (2015): «Los efectos geoecológicos del cambio global en el Pirineo central español: una revisión a distintas escalas espaciales y temporales». Pirineos, 170. Steffen, W. et al. (2004): Global Change and the Earth System: a planet under pressure. Executive summary. The IGBP Global Change Series. Springer-Verlag, Berlin, Heidelburg, 44 pp., New York. Vitousek, P.M. et al. (1997): «Human domination of earth's ecosystems». Science, n° 277, 494-499.

Linking Global and Regional Models to Simulate U.S. Air Quality in the Year 2050

EPA Science Inventory

The potential impact of global climate change on future air quality in the United States is investigated with global and regional-scale models. Regional climate model scenarios are developed by dynamically downscaling the outputs from a global chemistry and climate model and are...

Future change in seasonal march of snow water equivalent due to global climate change

NASA Astrophysics Data System (ADS)

Hara, M.; Kawase, H.; Ma, X.; Wakazuki, Y.; Fujita, M.; Kimura, F.

2012-04-01

Western side of Honshu Island in Japan is one of the heaviest snowfall areas in the world, although the location is relatively lower latitude than other heavy snowfall areas. Snowfall is one of major source for agriculture, industrial, and house-use in Japan. The change in seasonal march of snow water equivalent, e.g., snowmelt season and amount will strongly influence to social-economic activities (ex. Ma et al., 2011). We performed the four numerical experiments including present and future climate simulations and much-snow and less-snow cases using a regional climate model. Pseudo-Global-Warming (PGW) method (Kimura and Kitoh, 2008) is applied for the future climate simulations. NCEP/NCAR reanalysis is used for initial and boundary conditions in present climate simulation and PGW method. MIROC 3.2 medres 2070s output under IPCC SRES A2 scenario and 1990s output under 20c3m scenario used for PGW method. In much-snow cases, Maximum total snow water equivalent over Japan, which is mostly observed in early February, is 49 G ton in the present simulation, the one decreased 26 G ton in the future simulation. The decreasing rate of snow water equivalent due to climate change was 49%. Main cause of the decrease of the total snow water equivalent is strongly affected by the air temperature rise due to global climate change. The difference in present and future precipitation amount is little.

The NASA Global Climate Change Education Project: An Integrated Effort to Improve the Teaching and Learning about Climate Change (Invited)

NASA Astrophysics Data System (ADS)

Chambers, L. H.; Pippin, M. R.; Welch, S.; Spruill, K.; Matthews, M. J.; Person, C.

2010-12-01

The NASA Global Climate Change Education (GCCE) Project, initiated in 2008, seeks to: - improve the teaching and learning about global climate change in elementary and secondary schools, on college campuses, and through lifelong learning; - increase the number of people, particularly high school and undergraduate students, using NASA Earth observation data, Earth system models, and/or simulations to investigate and analyze global climate change issues; - increase the number of undergraduate students prepared for employment and/or to enter graduate school in technical fields relevant to global climate change. Through an annual solicitation, proposals are requested for projects that address these goals using a variety of approaches. These include using NASA Earth system data, interactive models and/or simulations; providing research experiences for undergraduate or community college students, or for pre- or in-service teachers; or creating long-term teacher professional development experiences. To date, 57 projects have been funded to pursue these goals (22 in 2008, 18 in 2009, and 17 in 2010), each for a 2-3 year period. The vast majority of awards address either teacher professional development, or use of data, models, or simulations; only 7 awards have been made for research experiences. NASA, with assistance from the Virginia Space Grant Consortium, is working to develop these awardees into a synergistic community that works together to maximize its impact. This paper will present examples of collaborations that are evolving within this developing community. It will also introduce the opportunities available in fiscal year 2011, when a change in emphasis is expected for the project as it moves within the NASA Office of Education Minority University Research and Education Program (MUREP).

Role of vegetation change in future climate under the A1B scenario and a climate stabilisation scenario, using the HadCM3C earth system model

NASA Astrophysics Data System (ADS)

Falloon, P. D.; Dankers, R.; Betts, R. A.; Jones, C. D.; Booth, B. B. B.; Lambert, F. H.

2012-06-01

The aim of our study was to use the coupled climate-carbon cycle model HadCM3C to quantify climate impact of ecosystem changes over recent decades and under future scenarios, due to changes in both atmospheric CO2 and surface albedo. We use two future scenarios - the IPCC SRES A1B scenario, and a climate stabilisation scenario (2C20), allowing us to assess the impact of climate mitigation on results. We performed a pair of simulations under each scenario - one in which vegetation was fixed at the initial state and one in which vegetation changes dynamically in response to climate change, as determined by the interactive vegetation model within HadCM3C. In our simulations with interactive vegetation, relatively small changes in global vegetation coverage were found, mainly dominated by increases in scrub and needleleaf trees at high latitudes and losses of broadleaf trees and grasses across the Amazon. Globally this led to a loss of terrestrial carbon, mainly from the soil. Global changes in carbon storage were related to the regional losses from the Amazon and gains at high latitude. Regional differences in carbon storage between the two scenarios were largely driven by the balance between warming-enhanced decomposition and altered vegetation growth. Globally, interactive vegetation reduced albedo acting to enhance albedo changes due to climate change. This was mainly related to the darker land surface over high latitudes (due to vegetation expansion, particularly during winter and spring); small increases in albedo occurred over the Amazon. As a result, there was a relatively small impact of vegetation change on most global annual mean climate variables, which was generally greater under A1B than 2C20, with markedly stronger local-to-regional and seasonal impacts. Globally, vegetation change amplified future annual temperature increases by 0.24 and 0.15 K (under A1B and 2C20, respectively) and increased global precipitation, with reductions in precipitation over the Amazon and increases over high latitudes. In general, changes were stronger over land - for example, global temperature changes due to interactive vegetation of 0.43 and 0.28 K under A1B and 2C20, respectively. Regionally, the warming influence of future vegetation change in our simulations was driven by the balance between driving factors. For instance, reduced tree cover over the Amazon reduced evaporation (particularly during summer), outweighing the cooling influence of any small albedo changes. In contrast, at high latitudes the warming impact of reduced albedo (particularly during winter and spring) due to increased vegetation cover appears to have offset any cooling due to small evaporation increases. Climate mitigation generally reduced the impact of vegetation change on future global and regional climate in our simulations. Our study therefore suggests that there is a need to consider both biogeochemical and biophysical effects in climate adaptation and mitigation decision making.

Role of vegetation change in future climate under the A1B scenario and a climate stabilisation scenario, using the HadCM3C Earth system model

NASA Astrophysics Data System (ADS)

Falloon, P. D.; Dankers, R.; Betts, R. A.; Jones, C. D.; Booth, B. B. B.; Lambert, F. H.

2012-11-01

The aim of our study was to use the coupled climate-carbon cycle model HadCM3C to quantify climate impact of ecosystem changes over recent decades and under future scenarios, due to changes in both atmospheric CO2 and surface albedo. We use two future scenarios - the IPCC SRES A1B scenario, and a climate stabilisation scenario (2C20), allowing us to assess the impact of climate mitigation on results. We performed a pair of simulations under each scenario - one in which vegetation was fixed at the initial state and one in which vegetation changes dynamically in response to climate change, as determined by the interactive vegetation model within HadCM3C. In our simulations with interactive vegetation, relatively small changes in global vegetation coverage were found, mainly dominated by increases in shrub and needleleaf trees at high latitudes and losses of broadleaf trees and grasses across the Amazon. Globally this led to a loss of terrestrial carbon, mainly from the soil. Global changes in carbon storage were related to the regional losses from the Amazon and gains at high latitude. Regional differences in carbon storage between the two scenarios were largely driven by the balance between warming-enhanced decomposition and altered vegetation growth. Globally, interactive vegetation reduced albedo acting to enhance albedo changes due to climate change. This was mainly related to the darker land surface over high latitudes (due to vegetation expansion, particularly during December-January and March-May); small increases in albedo occurred over the Amazon. As a result, there was a relatively small impact of vegetation change on most global annual mean climate variables, which was generally greater under A1B than 2C20, with markedly stronger local-to-regional and seasonal impacts. Globally, vegetation change amplified future annual temperature increases by 0.24 and 0.15 K (under A1B and 2C20, respectively) and increased global precipitation, with reductions in precipitation over the Amazon and increases over high latitudes. In general, changes were stronger over land - for example, global temperature changes due to interactive vegetation of 0.43 and 0.28 K under A1B and 2C20, respectively. Regionally, the warming influence of future vegetation change in our simulations was driven by the balance between driving factors. For instance, reduced tree cover over the Amazon reduced evaporation (particularly during June-August), outweighing the cooling influence of any small albedo changes. In contrast, at high latitudes the warming impact of reduced albedo (particularly during December-February and March-May) due to increased vegetation cover appears to have offset any cooling due to small evaporation increases. Climate mitigation generally reduced the impact of vegetation change on future global and regional climate in our simulations. Our study therefore suggests that there is a need to consider both biogeochemical and biophysical effects in climate adaptation and mitigation decision making.

Simulated effects of nitrogen saturation the global carbon budget using the IBIS model

USGS Publications Warehouse

Lu, Xuehe; Jiang, Hong; Liu, Jinxun; Zhang, Xiuying; Jin, Jiaxin; Zhu, Qiuan; Zhang, Zhen; Peng, Changhui

2016-01-01

Over the past 100 years, human activity has greatly changed the rate of atmospheric N (nitrogen) deposition in terrestrial ecosystems, resulting in N saturation in some regions of the world. The contribution of N saturation to the global carbon budget remains uncertain due to the complicated nature of C-N (carbon-nitrogen) interactions and diverse geography. Although N deposition is included in most terrestrial ecosystem models, the effect of N saturation is frequently overlooked. In this study, the IBIS (Integrated BIosphere Simulator) was used to simulate the global-scale effects of N saturation during the period 1961–2009. The results of this model indicate that N saturation reduced global NPP (Net Primary Productivity) and NEP (Net Ecosystem Productivity) by 0.26 and 0.03 Pg C yr−1, respectively. The negative effects of N saturation on carbon sequestration occurred primarily in temperate forests and grasslands. In response to elevated CO2 levels, global N turnover slowed due to increased biomass growth, resulting in a decline in soil mineral N. These changes in N cycling reduced the impact of N saturation on the global carbon budget. However, elevated N deposition in certain regions may further alter N saturation and C-N coupling.

The Context Is the Message?! Learning about the Israeli-Palestinian Conflict through Computerized Simulations in Different National Contexts

ERIC Educational Resources Information Center

Kampf, Ronit

2016-01-01

Two cross-national experimental studies examined the effects of PeaceMaker and Global Conflicts on knowledge acquisition and attitude change regarding the Israeli-Palestinian conflict. PeaceMaker and Global Conflicts are role-playing computerized simulations of this conflict. 248 undergraduate students from Turkey, Israel, Palestine and the US…

A Global Model Simulation of Aerosol Effects of Surface Radiation Budget- Toward Understanding of the "Dimming to Brightening" Transition

NASA Technical Reports Server (NTRS)

Chin, Mian; Diehl, Thomas; Bian, Huisheng; Yu, Hongbin

2008-01-01

We present a global model study on the role aerosols play in the change of solar radiation at Earth's surface that transitioned from a decreasing (dimming) trend to an increasing (brightening) trend. Our primary objective is to understand the relationship between the long-term trends of aerosol emission, atmospheric burden, and surface solar radiation. More specifically, we use the recently compiled comprehensive global emission datasets of aerosols and precursors from fuel combustion, biomass burning, volcanic eruptions and other sources from 1980 to 2006 to simulate long-term variations of aerosol distributions and optical properties, and then calculate the multi-decadal changes of short-wave radiative fluxes at the surface and at the top of the atmosphere by coupling the GOCART model simulated aerosols with the Goddard radiative transfer model. The model results are compared with long-term observational records from ground-based networks and satellite data. We will address the following critical questions: To what extent can the observed surface solar radiation trends, known as the transition from dimming to brightening, be explained by the changes of anthropogenic and natural aerosol loading on global and regional scales? What are the relative contributions of local emission and long-range transport to the surface radiation budget and how do these contributions change with time?

Improved global simulation of groundwater-ecosystem interactions via tight coupling of a dynamic global ecosystem model and a global hydrological model

NASA Astrophysics Data System (ADS)

Braakhekke, Maarten; Rebel, Karin; Dekker, Stefan; Smith, Benjamin; Sutanudjaja, Edwin; van Beek, Rens; van Kampenhout, Leo; Wassen, Martin

2017-04-01

In up to 30% of the global land surface ecosystems are potentially influenced by the presence of a shallow groundwater table. In these regions upward water flux by capillary rise increases soil moisture availability in the root zone, which has a strong effect on evapotranspiration, vegetation dynamics, and fluxes of carbon and nitrogen. Most global hydrological models and several land surface models simulate groundwater table dynamics and their effects on land surface processes. However, these models typically have relatively simplistic representation of vegetation and do not consider changes in vegetation type and structure. Dynamic global vegetation models (DGVMs), describe land surface from an ecological perspective, combining detailed description of vegetation dynamics and structure, and biogeochemical processes and are thus more appropriate to simulate the ecological and biogeochemical effects of groundwater interactions. However, currently virtually all DGVMs ignore these effects, assuming that water tables are too deep to affect soil moisture in the root zone. We have implemented a tight coupling between the dynamic global ecosystem model LPJ-GUESS and the global hydrological model PCR-GLOBWB, which explicitly simulates groundwater dynamics. This coupled model allows us to explicitly account for groundwater effects on terrestrial ecosystem processes at global scale. Results of global simulations indicate that groundwater strongly influences fluxes of water, carbon and nitrogen, in many regions, adding up to a considerable effect at the global scale.

Tropical cyclones in a stabilized 1.5 and 2 degree warmer world.

NASA Astrophysics Data System (ADS)

Wehner, M. F.; Stone, D. A.; Loring, B.; Krishnan, H.

2017-12-01

We present an ensemble of very high resolution global climate model simulations of a stabilized 1.5oC and 2oC warmer climate as envisioned by the Paris COP21 agreement. The resolution of this global climate model (25km) permits simulated tropical cyclones up to Category Five on the Saffir-Simpson scale Projected changes in tropical cyclones are significant. Tropical cyclones in the two stabilization scenarios are less frequent but more intense than in simulations of the present. Output data from these simulations is freely available to all interested parties and should prove a useful resource to those interested in studying the impacts of stabilized global warming.

Hadley circulation strength and width in a wide range of simulated climates

NASA Astrophysics Data System (ADS)

D'Agostino, R.; Adam, O.; Lionello, P.; Schneider, T.

2016-12-01

Understanding how the Hadley circulation (HC) responds to global warming is crucial because it determines climatic features such as the seasonal migration of the ITCZ, the extent of subtropical arid regions and the strength of the monsoons. Here we analyse changes in the HC strength and width in the set of PMIP3 and CMIP5 simulations, spanning a wide range of climate conditions from Last Glacial Maximum to future RCP projections. The large climate change signal emerging from comparing paleoclimate simulations to future scenarios offers the possibility to analyse the corresponding HC change and to investigate its response to large variations of the factors controlling it. The results confirm that the HC generally expands and weakens as the global mean temperature increases, consistent with results from other studies. Furthermore, we find an asymmetric HC response between the northern and southern hemisphere in the rate at which the HC edges shift poleward with global warming. The mid-latitude static stability and meridional temperature gradients affect the HC edges to different degrees in the two hemispheres. In the southern hemisphere the increase in the mid-latitude static stability is associated with a poleward shift of the southern HC edge, while in the northern hemisphere, the reduction in the meridional temperature gradient plays the dominant role in the poleward shift of the northern HC edge. The two hemispheres also exhibit very different changes of HC strength. The HC weakening with global warming occurs primarily in the northern hemisphere, while there is no change, or even a slighter weakening in the southern hemisphere. The HC changes also have pronounced seasonal signatures. The maximum poleward shift of the northern HC edge occurs one month later (from August to September) in future global warming scenarios than when comparing pre-industrial simulations with the Last Glacial Maximum.

Changes in tropical cyclones under stabilized 1.5 and 2.0°C global warming scenarios as simulated by the Community Atmospheric Model under the HAPPI protocols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wehner, Michael F.; Reed, Kevin A.; Loring, Burlen

The United Nations Framework Convention on Climate Change (UNFCCC) invited the scientific community to explore the impacts of a world in which anthropogenic global warming is stabilized at only 1.5°C above preindustrial average temperatures. In this paper, we present a projection of future tropical cyclone statistics for both 1.5 and 2.0°C stabilized warming scenarios with direct numerical simulation using a high-resolution global climate model. As in similar projections at higher warming levels, we find that even at these low warming levels the most intense tropical cyclones become more frequent and more intense, while simultaneously the frequency of weaker tropical stormsmore » is decreased. We also conclude that in the 1.5°C stabilization, the effect of aerosol forcing changes complicates the interpretation of greenhouse gas forcing changes.« less

Changes in tropical cyclones under stabilized 1.5 and 2.0 °C global warming scenarios as simulated by the Community Atmospheric Model under the HAPPI protocols

NASA Astrophysics Data System (ADS)

Wehner, Michael F.; Reed, Kevin A.; Loring, Burlen; Stone, Dáithí; Krishnan, Harinarayan

2018-02-01

The United Nations Framework Convention on Climate Change (UNFCCC) invited the scientific community to explore the impacts of a world in which anthropogenic global warming is stabilized at only 1.5 °C above preindustrial average temperatures. We present a projection of future tropical cyclone statistics for both 1.5 and 2.0 °C stabilized warming scenarios with direct numerical simulation using a high-resolution global climate model. As in similar projections at higher warming levels, we find that even at these low warming levels the most intense tropical cyclones become more frequent and more intense, while simultaneously the frequency of weaker tropical storms is decreased. We also conclude that in the 1.5 °C stabilization, the effect of aerosol forcing changes complicates the interpretation of greenhouse gas forcing changes.

Changes in tropical cyclones under stabilized 1.5 and 2.0°C global warming scenarios as simulated by the Community Atmospheric Model under the HAPPI protocols

DOE PAGES

Wehner, Michael F.; Reed, Kevin A.; Loring, Burlen; ...

2018-02-28

The United Nations Framework Convention on Climate Change (UNFCCC) invited the scientific community to explore the impacts of a world in which anthropogenic global warming is stabilized at only 1.5°C above preindustrial average temperatures. In this paper, we present a projection of future tropical cyclone statistics for both 1.5 and 2.0°C stabilized warming scenarios with direct numerical simulation using a high-resolution global climate model. As in similar projections at higher warming levels, we find that even at these low warming levels the most intense tropical cyclones become more frequent and more intense, while simultaneously the frequency of weaker tropical stormsmore » is decreased. We also conclude that in the 1.5°C stabilization, the effect of aerosol forcing changes complicates the interpretation of greenhouse gas forcing changes.« less

An integrated assessment modeling framework for uncertainty studies in global and regional climate change: the MIT IGSM-CAM (version 1.0)

NASA Astrophysics Data System (ADS)

Monier, E.; Scott, J. R.; Sokolov, A. P.; Forest, C. E.; Schlosser, C. A.

2013-12-01

This paper describes a computationally efficient framework for uncertainty studies in global and regional climate change. In this framework, the Massachusetts Institute of Technology (MIT) Integrated Global System Model (IGSM), an integrated assessment model that couples an Earth system model of intermediate complexity to a human activity model, is linked to the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM). Since the MIT IGSM-CAM framework (version 1.0) incorporates a human activity model, it is possible to analyze uncertainties in emissions resulting from both uncertainties in the underlying socio-economic characteristics of the economic model and in the choice of climate-related policies. Another major feature is the flexibility to vary key climate parameters controlling the climate system response to changes in greenhouse gases and aerosols concentrations, e.g., climate sensitivity, ocean heat uptake rate, and strength of the aerosol forcing. The IGSM-CAM is not only able to realistically simulate the present-day mean climate and the observed trends at the global and continental scale, but it also simulates ENSO variability with realistic time scales, seasonality and patterns of SST anomalies, albeit with stronger magnitudes than observed. The IGSM-CAM shares the same general strengths and limitations as the Coupled Model Intercomparison Project Phase 3 (CMIP3) models in simulating present-day annual mean surface temperature and precipitation. Over land, the IGSM-CAM shows similar biases to the NCAR Community Climate System Model (CCSM) version 3, which shares the same atmospheric model. This study also presents 21st century simulations based on two emissions scenarios (unconstrained scenario and stabilization scenario at 660 ppm CO2-equivalent) similar to, respectively, the Representative Concentration Pathways RCP8.5 and RCP4.5 scenarios, and three sets of climate parameters. Results of the simulations with the chosen climate parameters provide a good approximation for the median, and the 5th and 95th percentiles of the probability distribution of 21st century changes in global mean surface air temperature from previous work with the IGSM. Because the IGSM-CAM framework only considers one particular climate model, it cannot be used to assess the structural modeling uncertainty arising from differences in the parameterization suites of climate models. However, comparison of the IGSM-CAM projections with simulations of 31 CMIP5 models under the RCP4.5 and RCP8.5 scenarios show that the range of warming at the continental scale shows very good agreement between the two ensemble simulations, except over Antarctica, where the IGSM-CAM overestimates the warming. This demonstrates that by sampling the climate system response, the IGSM-CAM, even though it relies on one single climate model, can essentially reproduce the range of future continental warming simulated by more than 30 different models. Precipitation changes projected in the IGSM-CAM simulations and the CMIP5 multi-model ensemble both display a large uncertainty at the continental scale. The two ensemble simulations show good agreement over Asia and Europe. However, the ranges of precipitation changes do not overlap - but display similar size - over Africa and South America, two continents where models generally show little agreement in the sign of precipitation changes and where CCSM3 tends to be an outlier. Overall, the IGSM-CAM provides an efficient and consistent framework to explore the large uncertainty in future projections of global and regional climate change associated with uncertainty in the climate response and projected emissions.

Assessing the impacts of 1.5 °C global warming - simulation protocol of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP2b)

NASA Astrophysics Data System (ADS)

Frieler, Katja; Lange, Stefan; Piontek, Franziska; Reyer, Christopher P. O.; Schewe, Jacob; Warszawski, Lila; Zhao, Fang; Chini, Louise; Denvil, Sebastien; Emanuel, Kerry; Geiger, Tobias; Halladay, Kate; Hurtt, George; Mengel, Matthias; Murakami, Daisuke; Ostberg, Sebastian; Popp, Alexander; Riva, Riccardo; Stevanovic, Miodrag; Suzuki, Tatsuo; Volkholz, Jan; Burke, Eleanor; Ciais, Philippe; Ebi, Kristie; Eddy, Tyler D.; Elliott, Joshua; Galbraith, Eric; Gosling, Simon N.; Hattermann, Fred; Hickler, Thomas; Hinkel, Jochen; Hof, Christian; Huber, Veronika; Jägermeyr, Jonas; Krysanova, Valentina; Marcé, Rafael; Müller Schmied, Hannes; Mouratiadou, Ioanna; Pierson, Don; Tittensor, Derek P.; Vautard, Robert; van Vliet, Michelle; Biber, Matthias F.; Betts, Richard A.; Bodirsky, Benjamin Leon; Deryng, Delphine; Frolking, Steve; Jones, Chris D.; Lotze, Heike K.; Lotze-Campen, Hermann; Sahajpal, Ritvik; Thonicke, Kirsten; Tian, Hanqin; Yamagata, Yoshiki

2017-11-01

In Paris, France, December 2015, the Conference of the Parties (COP) to the United Nations Framework Convention on Climate Change (UNFCCC) invited the Intergovernmental Panel on Climate Change (IPCC) to provide a special report in 2018 on the impacts of global warming of 1.5 °C above pre-industrial levels and related global greenhouse gas emission pathways. In Nairobi, Kenya, April 2016, the IPCC panel accepted the invitation. Here we describe the response devised within the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) to provide tailored, cross-sectorally consistent impact projections to broaden the scientific basis for the report. The simulation protocol is designed to allow for (1) separation of the impacts of historical warming starting from pre-industrial conditions from impacts of other drivers such as historical land-use changes (based on pre-industrial and historical impact model simulations); (2) quantification of the impacts of additional warming up to 1.5 °C, including a potential overshoot and long-term impacts up to 2299, and comparison to higher levels of global mean temperature change (based on the low-emissions Representative Concentration Pathway RCP2.6 and a no-mitigation pathway RCP6.0) with socio-economic conditions fixed at 2005 levels; and (3) assessment of the climate effects based on the same climate scenarios while accounting for simultaneous changes in socio-economic conditions following the middle-of-the-road Shared Socioeconomic Pathway (SSP2, Fricko et al., 2016) and in particular differential bioenergy requirements associated with the transformation of the energy system to comply with RCP2.6 compared to RCP6.0. With the aim of providing the scientific basis for an aggregation of impacts across sectors and analysis of cross-sectoral interactions that may dampen or amplify sectoral impacts, the protocol is designed to facilitate consistent impact projections from a range of impact models across different sectors (global and regional hydrology, lakes, global crops, global vegetation, regional forests, global and regional marine ecosystems and fisheries, global and regional coastal infrastructure, energy supply and demand, temperature-related mortality, and global terrestrial biodiversity).

Terrestrial Feedbacks Incorporated in Global Vegetation Models through Observed Trait-Environment Responses

NASA Astrophysics Data System (ADS)

Bodegom, P. V.

2015-12-01

Most global vegetation models used to evaluate climate change impacts rely on plant functional types to describe vegetation responses to environmental stresses. In a traditional set-up in which vegetation characteristics are considered constant within a vegetation type, the possibility to implement and infer feedback mechanisms are limited as feedback mechanisms will likely involve a changing expression of community trait values. Based on community assembly concepts, we implemented functional trait-environment relationships into a global dynamic vegetation model to quantitatively assess this feature. For the current climate, a different global vegetation distribution was calculated with and without the inclusion of trait variation, emphasizing the importance of feedbacks -in interaction with competitive processes- for the prevailing global patterns. These trait-environmental responses do, however, not necessarily imply adaptive responses of vegetation to changing conditions and may locally lead to a faster turnover in vegetation upon climate change. Indeed, when running climate projections, simulations with trait variation did not yield a more stable or resilient vegetation than those without. Through the different feedback expressions, global and regional carbon and water fluxes were -however- strongly altered. At a global scale, model projections suggest an increased productivity and hence an increased carbon sink in the next decades to come, when including trait variation. However, by the end of the century, a reduced carbon sink is projected. This effect is due to a downregulation of photosynthesis rates, particularly in the tropical regions, even when accounting for CO2-fertilization effects. Altogether, the various global model simulations suggest the critical importance of including vegetation functional responses to changing environmental conditions to grasp terrestrial feedback mechanisms at global scales in the light of climate change.

Improving Subtropical Boundary Layer Cloudiness in the 2011 NCEP GFS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fletcher, J. K.; Bretherton, Christopher S.; Xiao, Heng

2014-09-23

The current operational version of National Centers for Environmental Prediction (NCEP) Global Forecasting System (GFS) shows significant low cloud bias. These biases also appear in the Coupled Forecast System (CFS), which is developed from the GFS. These low cloud biases degrade seasonal and longer climate forecasts, particularly of short-wave cloud radiative forcing, and affect predicted sea surface temperature. Reducing this bias in the GFS will aid the development of future CFS versions and contributes to NCEP's goal of unified weather and climate modelling. Changes are made to the shallow convection and planetary boundary layer parameterisations to make them more consistentmore » with current knowledge of these processes and to reduce the low cloud bias. These changes are tested in a single-column version of GFS and in global simulations with GFS coupled to a dynamical ocean model. In the single-column model, we focus on changing parameters that set the following: the strength of shallow cumulus lateral entrainment, the conversion of updraught liquid water to precipitation and grid-scale condensate, shallow cumulus cloud top, and the effect of shallow convection in stratocumulus environments. Results show that these changes improve the single-column simulations when compared to large eddy simulations, in particular through decreasing the precipitation efficiency of boundary layer clouds. These changes, combined with a few other model improvements, also reduce boundary layer cloud and albedo biases in global coupled simulations.« less

The Detection and Attribution Model Intercomparison Project (DAMIP v1.0)contribution to CMIP6

DOE PAGES

Gillett, Nathan P.; Shiogama, Hideo; Funke, Bernd; ...

2016-10-18

Detection and attribution (D&A) simulations were important components of CMIP5 and underpinned the climate change detection and attribution assessments of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. The primary goals of the Detection and Attribution Model Intercomparison Project (DAMIP) are to facilitate improved estimation of the contributions of anthropogenic and natural forcing changes to observed global warming as well as to observed global and regional changes in other climate variables; to contribute to the estimation of how historical emissions have altered and are altering contemporary climate risk; and to facilitate improved observationally constrained projections of futuremore » climate change. D&A studies typically require unforced control simulations and historical simulations including all major anthropogenic and natural forcings. Such simulations will be carried out as part of the DECK and the CMIP6 historical simulation. In addition D&A studies require simulations covering the historical period driven by individual forcings or subsets of forcings only: such simulations are proposed here. Key novel features of the experimental design presented here include firstly new historical simulations with aerosols-only, stratospheric-ozone-only, CO2-only, solar-only, and volcanic-only forcing, facilitating an improved estimation of the climate response to individual forcing, secondly future single forcing experiments, allowing observationally constrained projections of future climate change, and thirdly an experimental design which allows models with and without coupled atmospheric chemistry to be compared on an equal footing.« less

The Detection and Attribution Model Intercomparison Project (DAMIP v1.0) contribution to CMIP6

NASA Astrophysics Data System (ADS)

Gillett, Nathan P.; Shiogama, Hideo; Funke, Bernd; Hegerl, Gabriele; Knutti, Reto; Matthes, Katja; Santer, Benjamin D.; Stone, Daithi; Tebaldi, Claudia

2016-10-01

Detection and attribution (D&A) simulations were important components of CMIP5 and underpinned the climate change detection and attribution assessments of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. The primary goals of the Detection and Attribution Model Intercomparison Project (DAMIP) are to facilitate improved estimation of the contributions of anthropogenic and natural forcing changes to observed global warming as well as to observed global and regional changes in other climate variables; to contribute to the estimation of how historical emissions have altered and are altering contemporary climate risk; and to facilitate improved observationally constrained projections of future climate change. D&A studies typically require unforced control simulations and historical simulations including all major anthropogenic and natural forcings. Such simulations will be carried out as part of the DECK and the CMIP6 historical simulation. In addition D&A studies require simulations covering the historical period driven by individual forcings or subsets of forcings only: such simulations are proposed here. Key novel features of the experimental design presented here include firstly new historical simulations with aerosols-only, stratospheric-ozone-only, CO2-only, solar-only, and volcanic-only forcing, facilitating an improved estimation of the climate response to individual forcing, secondly future single forcing experiments, allowing observationally constrained projections of future climate change, and thirdly an experimental design which allows models with and without coupled atmospheric chemistry to be compared on an equal footing.

Ocean carbon and heat variability in an Earth System Model

NASA Astrophysics Data System (ADS)

Thomas, J. L.; Waugh, D.; Gnanadesikan, A.

2016-12-01

Ocean carbon and heat content are very important for regulating global climate. Furthermore, due to lack of observations and dependence on parameterizations, there has been little consensus in the modeling community on the magnitude of realistic ocean carbon and heat content variability, particularly in the Southern Ocean. We assess the differences between global oceanic heat and carbon content variability in GFDL ESM2Mc using a 500-year, pre-industrial control simulation. The global carbon and heat content are directly out of phase with each other; however, in the Southern Ocean the heat and carbon content are in phase. The global heat mutli-decadal variability is primarily explained by variability in the tropics and mid-latitudes, while the variability in global carbon content is primarily explained by Southern Ocean variability. In order to test the robustness of this relationship, we use three additional pre-industrial control simulations using different mesoscale mixing parameterizations. Three pre-industrial control simulations are conducted with the along-isopycnal diffusion coefficient (Aredi) set to constant values of 400, 800 (control) and 2400 m2 s-1. These values for Aredi are within the range of parameter settings commonly used in modeling groups. Finally, one pre-industrial control simulation is conducted where the minimum in the Gent-McWilliams parameterization closure scheme (AGM) increased to 600 m2 s-1. We find that the different simulations have very different multi-decadal variability, especially in the Weddell Sea where the characteristics of deep convection are drastically changed. While the temporal frequency and amplitude global heat and carbon content changes significantly, the overall spatial pattern of variability remains unchanged between the simulations.

A New High Resolution Climate Dataset for Climate Change Impacts Assessments in New England

NASA Astrophysics Data System (ADS)

Komurcu, M.; Huber, M.

2016-12-01

Assessing regional impacts of climate change (such as changes in extreme events, land surface hydrology, water resources, energy, ecosystems and economy) requires much higher resolution climate variables than those available from global model projections. While it is possible to run global models in higher resolution, the high computational cost associated with these simulations prevent their use in such manner. To alleviate this problem, dynamical downscaling offers a method to deliver higher resolution climate variables. As part of an NSF EPSCoR funded interdisciplinary effort to assess climate change impacts on New Hampshire ecosystems, hydrology and economy (the New Hampshire Ecosystems and Society project), we create a unique high-resolution climate dataset for New England. We dynamically downscale global model projections under a high impact emissions scenario using the Weather Research and Forecasting model (WRF) with three nested grids of 27, 9 and 3 km horizontal resolution with the highest resolution innermost grid focusing over New England. We prefer dynamical downscaling over other methods such as statistical downscaling because it employs physical equations to progressively simulate climate variables as atmospheric processes interact with surface processes, emissions, radiation, clouds, precipitation and other model components, hence eliminates fix relationships between variables. In addition to simulating mean changes in regional climate, dynamical downscaling also allows for the simulation of climate extremes that significantly alter climate change impacts. We simulate three time slices: 2006-2015, 2040-2060 and 2080-2100. This new high-resolution climate dataset (with more than 200 variables saved in hourly (six hourly) intervals for the highest resolution domain (outer two domains)) along with model input and restart files used in our WRF simulations will be publicly available for use to the broader scientific community to support in-depth climate change impacts assessments for New England. We present results focusing on future changes in New England extreme events.

Watershed scale response to climate change--Yampa River Basin, Colorado

USGS Publications Warehouse

Hay, Lauren E.; Battaglin, William A.; Markstrom, Steven L.

2012-01-01

General Circulation Model simulations of future climate through 2099 project a wide range of possible scenarios. To determine the sensitivity and potential effect of long-term climate change on the freshwater resources of the United States, the U.S. Geological Survey Global Change study, "An integrated watershed scale response to global change in selected basins across the United States" was started in 2008. The long-term goal of this national study is to provide the foundation for hydrologically based climate change studies across the nation. Fourteen basins for which the Precipitation Runoff Modeling System has been calibrated and evaluated were selected as study sites. Precipitation Runoff Modeling System is a deterministic, distributed parameter watershed model developed to evaluate the effects of various combinations of precipitation, temperature, and land use on streamflow and general basin hydrology. Output from five General Circulation Model simulations and four emission scenarios were used to develop an ensemble of climate-change scenarios for each basin. These ensembles were simulated with the corresponding Precipitation Runoff Modeling System model. This fact sheet summarizes the hydrologic effect and sensitivity of the Precipitation Runoff Modeling System simulations to climate change for the Yampa River Basin at Steamboat Springs, Colorado.

Global change and terrestrial hydrology - A review

NASA Technical Reports Server (NTRS)

Dickinson, Robert E.

1991-01-01

This paper reviews the role of terrestrial hydrology in determining the coupling between the surface and atmosphere. Present experience with interactive numerical simulation is discussed and approaches to the inclusion of land hydrology in global climate models ae considered. At present, a wide range of answers as to expected changes in surface hydrology is given by nominally similar models. Studies of the effects of tropical deforestation and global warming illustrate this point.

Future productivity and phenology changes in European grasslands for different warming levels: implications for grassland management and carbon balance.

PubMed

Chang, Jinfeng; Ciais, Philippe; Viovy, Nicolas; Soussana, Jean-François; Klumpp, Katja; Sultan, Benjamin

2017-12-01

Europe has warmed more than the global average (land and ocean) since pre-industrial times, and is also projected to continue to warm faster than the global average in the twenty-first century. According to the climate models ensemble projections for various climate scenarios, annual mean temperature of Europe for 2071-2100 is predicted to be 1-5.5 °C higher than that for 1971-2000. Climate change and elevated CO 2 concentration are anticipated to affect grassland management and livestock production in Europe. However, there has been little work done to quantify the European-wide response of grassland to future climate change. Here we applied ORCHIDEE-GM v2.2, a grid-based model for managed grassland, over European grassland to estimate the impacts of future global change. Increases in grassland productivity are simulated in response to future global change, which are mainly attributed to the simulated fertilization effect of rising CO 2 . The results show significant phenology shifts, in particular an earlier winter-spring onset of grass growth over Europe. A longer growing season is projected over southern and southeastern Europe. In other regions, summer drought causes an earlier end to the growing season, overall reducing growing season length. Future global change allows an increase of management intensity with higher than current potential annual grass forage yield, grazing capacity and livestock density, and a shift in seasonal grazing capacity. We found a continual grassland soil carbon sink in Mediterranean, Alpine, North eastern, South eastern and Eastern regions under specific warming level (SWL) of 1.5 and 2 °C relative to pre-industrial climate. However, this carbon sink is found to saturate, and gradually turn to a carbon source at warming level reaching 3.5 °C. This study provides a European-wide assessment of the future changes in productivity and phenology of grassland, and their consequences for the management intensity and the carbon balance. The simulated productivity increase in response to future global change enables an intensification of grassland management over Europe. However, the simulated increase in the interannual variability of grassland productivity over some regions may reduce the farmers' ability to take advantage of the increased long-term mean productivity in the face of more frequent, and more severe drops of productivity in the future.

The land-ice contribution to 21st-century dynamic sea level rise

NASA Astrophysics Data System (ADS)

Howard, T.; Ridley, J.; Pardaens, A. K.; Hurkmans, R. T. W. L.; Payne, A. J.; Giesen, R. H.; Lowe, J. A.; Bamber, J. L.; Edwards, T. L.; Oerlemans, J.

2014-06-01

Climate change has the potential to influence global mean sea level through a number of processes including (but not limited to) thermal expansion of the oceans and enhanced land ice melt. In addition to their contribution to global mean sea level change, these two processes (among others) lead to local departures from the global mean sea level change, through a number of mechanisms including the effect on spatial variations in the change of water density and transport, usually termed dynamic sea level changes. In this study, we focus on the component of dynamic sea level change that might be given by additional freshwater inflow to the ocean under scenarios of 21st-century land-based ice melt. We present regional patterns of dynamic sea level change given by a global-coupled atmosphere-ocean climate model forced by spatially and temporally varying projected ice-melt fluxes from three sources: the Antarctic ice sheet, the Greenland Ice Sheet and small glaciers and ice caps. The largest ice melt flux we consider is equivalent to almost 0.7 m of global mean sea level rise over the 21st century. The temporal evolution of the dynamic sea level changes, in the presence of considerable variations in the ice melt flux, is also analysed. We find that the dynamic sea level change associated with the ice melt is small, with the largest changes occurring in the North Atlantic amounting to 3 cm above the global mean rise. Furthermore, the dynamic sea level change associated with the ice melt is similar regardless of whether the simulated ice fluxes are applied to a simulation with fixed CO2 or under a business-as-usual greenhouse gas warming scenario of increasing CO2.

Impacts of Stratospheric Black Carbon on Agriculture

NASA Astrophysics Data System (ADS)

Xia, L.; Robock, A.; Elliott, J. W.

2017-12-01

A regional nuclear war between India and Pakistan could inject 5 Tg of soot into the stratosphere, which would absorb sunlight, decrease global surface temperature by about 1°C for 5-10 years and have major impacts on precipitation and the amount of solar radiation reaching Earth's surface. Using two global gridded crop models forced by one global climate model simulation, we investigate the impacts on agricultural productivity in various nations. The crop model in the Community Land Model 4.5 (CLM-crop4.5) and the parallel Decision Support System for Agricultural Technology (pDSSAT) in the parallel System for Integrating Impact Models and Sectors are participating in the Global Gridded Crop Model Intercomparison. We force these two crop models with output from the Whole Atmospheric Community Climate Model to characterize the global agricultural impact from climate changes due to a regional nuclear war. Crops in CLM-crop4.5 include maize, rice, soybean, cotton and sugarcane, and crops in pDSSAT include maize, rice, soybean and wheat. Although the two crop models require a different time frequency of weather input, we downscale the climate model output to provide consistent temperature, precipitation and solar radiation inputs. In general, CLM-crop4.5 simulates a larger global average reduction of maize and soybean production relative to pDSSAT. Global rice production shows negligible change with climate anomalies from a regional nuclear war. Cotton and sugarcane benefit from a regional nuclear war from CLM-crop4.5 simulation, and global wheat production would decrease significantly in the pDSSAT simulation. The regional crop yield responses to a regional nuclear conflict are different for each crop, and we present the changes in production on a national basis. These models do not include the crop responses to changes in ozone, ultraviolet radiation, or diffuse radiation, and we would like to encourage more modelers to improve crop models to account for those impacts. We present these results as a demonstration of using different crop models to study this problem, and we invite more global crop modeling groups to use the same climate forcing, which we would be happy to provide, to gain a better understanding of global agricultural responses under different future climate scenarios with stratospheric aerosols.

Agricultural Water Use under Global Change

NASA Astrophysics Data System (ADS)

Zhu, T.; Ringler, C.; Rosegrant, M. W.

2008-12-01

Irrigation is by far the single largest user of water in the world and is projected to remain so in the foreseeable future. Globally, irrigated agricultural land comprises less than twenty percent of total cropland but produces about forty percent of the world's food. Increasing world population will require more food and this will lead to more irrigation in many areas. As demands increase and water becomes an increasingly scarce resource, agriculture's competition for water with other economic sectors will be intensified. This water picture is expected to become even more complex as climate change will impose substantial impacts on water availability and demand, in particular for agriculture. To better understand future water demand and supply under global change, including changes in demographic, economic and technological dimensions, the water simulation module of IMPACT, a global water and food projection model developed at the International Food Policy Research Institute, is used to analyze future water demand and supply in agricultural and several non-agricultural sectors using downscaled GCM scenarios, based on water availability simulation done with a recently developed semi-distributed global hydrological model. Risk analysis is conducted to identify countries and regions where future water supply reliability for irrigation is low, and food security may be threatened in the presence of climate change. Gridded shadow values of irrigation water are derived for global cropland based on an optimization framework, and they are used to illustrate potential irrigation development by incorporating gridded water availability and existing global map of irrigation areas.

Evaluation of methodology for detecting/predicting migration of forest species

Treesearch

Dale S. Solomon; William B. Leak

1996-01-01

Available methods for analyzing migration of forest species are evaluated, including simulation models, remeasured plots, resurveys, pollen/vegetation analysis, and age/distance trends. Simulation models have provided some of the most drastic estimates of species changes due to predicted changes in global climate. However, these models require additional testing...

Assessing carbon dioxide removal through global and regional ocean alkalinization under high and low emission pathways

NASA Astrophysics Data System (ADS)

Lenton, Andrew; Matear, Richard J.; Keller, David P.; Scott, Vivian; Vaughan, Naomi E.

2018-04-01

Atmospheric carbon dioxide (CO2) levels continue to rise, increasing the risk of severe impacts on the Earth system, and on the ecosystem services that it provides. Artificial ocean alkalinization (AOA) is capable of reducing atmospheric CO2 concentrations and surface warming and addressing ocean acidification. Here, we simulate global and regional responses to alkalinity (ALK) addition (0.25 PmolALK yr-1) over the period 2020-2100 using the CSIRO-Mk3L-COAL Earth System Model, under high (Representative Concentration Pathway 8.5; RCP8.5) and low (RCP2.6) emissions. While regionally there are large changes in alkalinity associated with locations of AOA, globally we see only a very weak dependence on where and when AOA is applied. On a global scale, while we see that under RCP2.6 the carbon uptake associated with AOA is only ˜ 60 % of the total, under RCP8.5 the relative changes in temperature are larger, as are the changes in pH (140 %) and aragonite saturation state (170 %). The simulations reveal AOA is more effective under lower emissions, therefore the higher the emissions the more AOA is required to achieve the same reduction in global warming and ocean acidification. Finally, our simulated AOA for 2020-2100 in the RCP2.6 scenario is capable of offsetting warming and ameliorating ocean acidification increases at the global scale, but with highly variable regional responses.

Biomes computed from simulated climatologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Claussen, M.; Esch, M.

1994-01-01

The biome model of Prentice et al. is used to predict global patterns of potential natural plant formations, or biomes, from climatologies simulated by ECHAM, a model used for climate simulations at the Max-Planck-Institut fuer Meteorologie. This study undertaken in order to show the advantage of this biome model in diagnosing the performance of a climate model and assessing effects of past and future climate changes predicted by a climate model. Good overall agreement is found between global patterns of biomes computed from observed and simulated data of present climate. But there are also major discrepancies indicated by a differencemore » in biomes in Australia, in the Kalahari Desert, and in the Middle West of North America. These discrepancies can be traced back to in simulated rainfall as well as summer or winter temperatures. Global patterns of biomes computed from an ice age simulation reveal that North America, Europe, and Siberia should have been covered largely by tundra and taiga, whereas only small differences are for the tropical rain forests. A potential northeast shift of biomes is expected from a simulation with enhanced CO{sub 2} concentration according to the IPCC Scenario A. Little change is seen in the tropical rain forest and the Sahara. Since the biome model used is not capable of predicting chances in vegetation patterns due to a rapid climate change, the latter simulation to be taken as a prediction of chances in conditions favourable for the existence of certain biomes, not as a reduction of a future distribution of biomes. 15 refs., 8 figs., 2 tabs.« less

The Role of Atmospheric Heating over the South China Sea and Western Pacific Regions in Modulating Asian Summer Climate under the Global Warming Background

NASA Astrophysics Data System (ADS)

He, B.

2015-12-01

Global warming is one of the most significant climate change signals at the earth's surface. However, the responses of monsoon precipitation to global warming show very distinct regional features, especially over the South China Sea (SCS) and surrounding regions during boreal summer. To understand the possible dynamics in these specific regions under the global warming background, the changes in atmospheric latent heating and their possible influences on global climate are investigated by both observational diagnosis and numerical sensitivity simulations. Results indicate that summertime latent heating has intensified in the SCS and western Pacific, accompanied by increased precipitation, cloud cover, lower-tropospheric convergence, and decreased sea level pressure. Sensitivity experiments show that middle and upper tropospheric heating causes an east-west feedback pattern between SCS-western Pacific and South Asia, which strengthens the South Asian High in the upper troposphere and moist convergence in the lower troposphere, consequently forcing a descending motion and adiabatic warming over continental South Asia and leading to a warm and dry climate. When air-sea interaction is considered, the simulation results are overall more similar to observations, and in particular the bias of precipitation over the Indian Ocean simulated by AGCMs has been reduced. The results highlight the important role of latent heating in adjusting the changes in sea surface temperature through atmospheric dynamics.

Regional Climate Simulation and Data Assimilation with Variable-Resolution GCMs

NASA Technical Reports Server (NTRS)

Fox-Rabinovitz, Michael S.

2002-01-01

Variable resolution GCMs using a global stretched grid (SG) with enhanced regional resolution over one or multiple areas of interest represents a viable new approach to regional climateklimate change and data assimilation studies and applications. The multiple areas of interest, at least one within each global quadrant, include the major global mountains and major global monsoonal circulations over North America, South America, India-China, and Australia. They also can include the polar domains, and the European and African regions. The SG-approach provides an efficient regional downscaling to mesoscales, and it is an ideal tool for representing consistent interactions of globaYlarge- and regionallmeso- scales while preserving the high quality of global circulation. Basically, the SG-GCM simulations are no different from those of the traditional uniform-grid GCM simulations besides using a variable-resolution grid. Several existing SG-GCMs developed by major centers and groups are briefly described. The major discussion is based on the GEOS (Goddard Earth Observing System) SG-GCM regional climate simulations.

Evaluating the accuracy of climate change pattern emulation for low warming targets

NASA Astrophysics Data System (ADS)

Tebaldi, Claudia; Knutti, Reto

2018-05-01

Global climate policy is increasingly debating the value of very low warming targets, yet not many experiments conducted with global climate models in their fully coupled versions are currently available to help inform studies of the corresponding impacts. This raises the question whether a map of warming or precipitation change in a world 1.5 °C warmer than preindustrial can be emulated from existing simulations that reach higher warming targets, or whether entirely new simulations are required. Here we show that also for this type of low warming in strong mitigation scenarios, climate change signals are quite linear as a function of global temperature. Therefore, emulation techniques amounting to linear rescaling on the basis of global temperature change ratios (like simple pattern scaling) provide a viable way forward. The errors introduced are small relative to the spread in the forced response to a given scenario that we can assess from a multi-model ensemble. They are also small relative to the noise introduced into the estimates of the forced response by internal variability within a single model, which we can assess from either control simulations or initial condition ensembles. Challenges arise when scaling inadvertently reduces the inter-model spread or suppresses the internal variability, both important sources of uncertainty for impact assessment, or when the scenarios have very different characteristics in the composition of the forcings. Taking advantage of an available suite of coupled model simulations under low-warming and intermediate scenarios, we evaluate the accuracy of these emulation techniques and show that they are unlikely to represent a substantial contribution to the total uncertainty.

Simulated effects of nitrogen saturation on the global carbon budget using the IBIS model

PubMed Central

Lu, Xuehe; Jiang, Hong; Liu, Jinxun; Zhang, Xiuying; Jin, Jiaxin; Zhu, Qiuan; Zhang, Zhen; Peng, Changhui

2016-01-01

Over the past 100 years, human activity has greatly changed the rate of atmospheric N (nitrogen) deposition in terrestrial ecosystems, resulting in N saturation in some regions of the world. The contribution of N saturation to the global carbon budget remains uncertain due to the complicated nature of C-N (carbon-nitrogen) interactions and diverse geography. Although N deposition is included in most terrestrial ecosystem models, the effect of N saturation is frequently overlooked. In this study, the IBIS (Integrated BIosphere Simulator) was used to simulate the global-scale effects of N saturation during the period 1961–2009. The results of this model indicate that N saturation reduced global NPP (Net Primary Productivity) and NEP (Net Ecosystem Productivity) by 0.26 and 0.03 Pg C yr−1, respectively. The negative effects of N saturation on carbon sequestration occurred primarily in temperate forests and grasslands. In response to elevated CO2 levels, global N turnover slowed due to increased biomass growth, resulting in a decline in soil mineral N. These changes in N cycling reduced the impact of N saturation on the global carbon budget. However, elevated N deposition in certain regions may further alter N saturation and C-N coupling. PMID:27966643

Modeling the Impacts of Global Climate and Regional Land Use Change on Regional Climate, Air Quality and Public Health in the New York Metropolitan Region

NASA Astrophysics Data System (ADS)

Rosenthal, J. E.; Knowlton, K. M.; Kinney, P. L.

2002-12-01

There is an imminent need to downscale the global climate models used by international consortiums like the IPCC (Intergovernmental Panel on Climate Change) to predict the future regional impacts of climate change. To meet this need, a "place-based" climate model that makes specific regional projections about future environmental conditions local inhabitants could face is being created by the Mailman School of Public Health at Columbia University, in collaboration with other researchers and universities, for New York City and the 31 surrounding counties. This presentation describes the design and initial results of this modeling study, aimed at simulating the effects of global climate change and regional land use change on climate and air quality over the northeastern United States in order to project the associated public health impacts in the region. Heat waves and elevated concentrations of ozone and fine particles are significant current public health stressors in the New York metropolitan area. The New York Climate and Health Project is linking human dimension and natural sciences models to assess the potential for future public health impacts from heat stress and air quality, and yield improved tools for assessing climate change impacts. The model will be applied to the NY metropolitan east coast region. The following questions will be addressed: 1. What changes in the frequency and severity of extreme heat events are likely to occur over the next 80 years due to a range of possible scenarios of land use and land cover (LU/LC) and climate change in the region? 2. How might the frequency and severity of episodic concentrations of ozone (O3) and airborne particulate matter smaller than 2.5 æm in diameter (PM2.5) change over the next 80 years due to a range of possible scenarios of land use and climate change in the metropolitan region? 3. What is the range of possible human health impacts of these changes in the region? 4. How might projected future human exposures and responses to heat stress and air quality differ as a function of socio-economic status and race/ethnicity across the region? The model systems used for this study are the Goddard Institute for Space Studies (GISS) Global Atmosphere-Ocean Model; the Regional Atmospheric Modeling System (RAMS) and PennState/NCAR MM5 mesoscale meteorological models; the SLEUTH land use model; the Sparse Matrix Operator Kernel Emissions Modeling System (SMOKE); the Community Multiscale Air Quality (CMAQ) and Comprehensive Air Quality Model with Extensions (CAMx) models for simulating regional air quality; and exposure-risk coefficients for assessing population health impacts based on exposure to extreme heat, fine particulates (PM2.5) and ozone. Two different IPCC global emission scenarios and two different regional land use growth scenarios are considered in the simulations, spanning a range of possible futures. In addition to base simulations for selected time periods in the decade 1990 - 2000, the integrated model is used to simulate future scenarios in the 2020s, 2050s, and 2080s. Predictions from both the meteorological models and the air quality models are compared against available observations for the simulations in the 1990s to establish baseline model performance. A series of sensitivity tests will address whether changes in meteorology due to global climate change, changes in regional land use, or changes in emissions have the largest impact on predicted ozone and particulate matter concentrations.

The effect of future outdoor air pollution on human health and the contribution of climate change

NASA Astrophysics Data System (ADS)

Silva, R.; West, J. J.; Lamarque, J.; Shindell, D.; Collins, W.; Dalsoren, S. B.; Faluvegi, G. S.; Folberth, G.; Horowitz, L. W.; Nagashima, T.; Naik, V.; Rumbold, S.; Skeie, R.; Sudo, K.; Takemura, T.; Bergmann, D. J.; Cameron-Smith, P. J.; Cionni, I.; Doherty, R. M.; Eyring, V.; Josse, B.; MacKenzie, I. A.; Plummer, D.; Righi, M.; Stevenson, D. S.; Strode, S. A.; Szopa, S.; Zeng, G.

2013-12-01

At present, exposure to outdoor air pollution from ozone and fine particulate matter (PM2.5) causes over 2 million deaths per year, due to respiratory and cardiovascular diseases and lung cancer. Future ambient concentrations of ozone and PM2.5 will be affected by both air pollutant emissions and climate change. Here we estimate the potential impact of future outdoor air pollution on premature human mortality, and isolate the contribution of future climate change due to its effect on air quality. We use modeled present-day (2000) and future global ozone and PM2.5 concentrations from simulations with an ensemble of chemistry-climate models from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP). Future air pollution was modeled for global greenhouse gas and air pollutant emissions in the four IPCC AR5 Representative Concentration Pathway (RCP) scenarios, for 2030, 2050 and 2100. All model outputs are regridded to a common 0.5°x0.5° horizontal resolution. Future premature mortality is estimated for each RCP scenario and year based on changes in concentrations of ozone and PM2.5 relative to 2000. Using a health impact function, changes in concentrations for each RCP scenario are combined with future population and cause-specific baseline mortality rates as projected by a single independent scenario in which the global incidence of cardiopulmonary diseases is expected to increase. The effect of climate change is isolated by considering the difference between air pollutant concentrations from simulations with 2000 emissions and a future year climate and simulations with 2000 emissions and climate. Uncertainties in the results reflect the uncertainty in the concentration-response function and that associated with variability among models. Few previous studies have quantified the effects of future climate change on global human health via changes in air quality, and this is the first such study to use an ensemble of global models.

Multi-year global climatic effects of atmospheric dust from large bolide impacts

NASA Technical Reports Server (NTRS)

Thompson, Starley L.

1988-01-01

The global climatic effects of dust generated by the impact of a 10 km-diameter bolide was simulated using a one-dimensional (vertical only) globally-averaged climate model by Pollack et al. The goal of the simulation is to examine the regional climate effects, including the possibility of coastal refugia, generated by a global dust cloud in a model having realistic geographic resolution. The climate model assumes the instantaneous appearance of a global stratospheric dust cloud with initial optical depth of 10,000. The time history of optical depth decreases according to the detailed calculations of Pollack et al., reaching an optical depth of unity at day 160, and subsequently decreasing with an e-folding time of 1 year. The simulation is carried out for three years in order to examine the atmospheric effects and recovery over several seasons. The simulation does not include any effects of NOx, CO2, or wildfire smoke injections that may accompany the creation of the dust cloud. The global distribution of surface temperature changes, freezing events, precipitation and soil moisture effects and sea ice increases will be discussed.

On the global limits of bioenergy and land use for climate change mitigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strapasson, Alexandre; Woods, Jeremy; Chum, Helena

Across energy, agricultural and forestry landscapes, the production of biomass for energy has emerged as a controversial driver of land-use change. We present a novel, simple methodology, to probe the potential global sustainability limits of bioenergy over time for energy provision and climate change mitigation using a complex-systems approach for assessing land-use dynamics. Primary biomass that could provide between 70 EJ year -1 and 360 EJ year -1, globally, by 2050 was simulated in the context of different land-use futures, food diet patterns and climate change mitigation efforts. Our simulations also show ranges of potential greenhouse gas emissions for agriculture,more » forestry and other land uses by 2050, including not only above-ground biomass-related emissions, but also from changes in soil carbon, from as high as 24 GtCO 2eq year-1 to as low as minus 21 GtCO 2eq year -1, which would represent a significant source of negative emissions. Based on the modelling simulations, the discussions offer novel insights about bioenergy as part of a broader integrated system. As a result, there are sustainability limits to the scale of bioenergy provision, they are dynamic over time, being responsive to land management options deployed worldwide.« less

On the global limits of bioenergy and land use for climate change mitigation

DOE PAGES

Strapasson, Alexandre; Woods, Jeremy; Chum, Helena; ...

2017-05-24

Across energy, agricultural and forestry landscapes, the production of biomass for energy has emerged as a controversial driver of land-use change. We present a novel, simple methodology, to probe the potential global sustainability limits of bioenergy over time for energy provision and climate change mitigation using a complex-systems approach for assessing land-use dynamics. Primary biomass that could provide between 70 EJ year -1 and 360 EJ year -1, globally, by 2050 was simulated in the context of different land-use futures, food diet patterns and climate change mitigation efforts. Our simulations also show ranges of potential greenhouse gas emissions for agriculture,more » forestry and other land uses by 2050, including not only above-ground biomass-related emissions, but also from changes in soil carbon, from as high as 24 GtCO 2eq year-1 to as low as minus 21 GtCO 2eq year -1, which would represent a significant source of negative emissions. Based on the modelling simulations, the discussions offer novel insights about bioenergy as part of a broader integrated system. As a result, there are sustainability limits to the scale of bioenergy provision, they are dynamic over time, being responsive to land management options deployed worldwide.« less

Changes in Benefits of Flood Protection Standard under Climate Change

NASA Astrophysics Data System (ADS)

Lim, W. H.; Koirala, S.; Yamazaki, D.; Hirabayashi, Y.; Kanae, S.

2014-12-01

Understanding potential risk of river flooding under future climate scenarios might be helpful for developing risk management strategies (including mitigation, adaptation). Such analyses are typically performed at the macro scales (e.g., regional, global) where the climate model output could support (e.g., Hirabayashi et al., 2013, Arnell and Gosling, 2014). To understand the potential benefits of infrastructure upgrading as part of climate adaptation strategies, it is also informative to understand the potential impact of different flood protection standards (in terms of return periods) on global river flooding under climate change. In this study, we use a baseline period (forced by observed hydroclimate conditions) and CMIP5 model output (historic and future periods) to drive a global river routing model called CaMa-Flood (Yamazaki et al., 2011) and simulate the river water depth at a spatial resolution of 15 min x 15 min. From the simulated results of baseline period, we use the annual maxima river water depth to fit the Gumbel distribution and prepare the return period-flood risk relationship (involving population and GDP). From the simulated results of CMIP5 model, we also used the annual maxima river water depth to obtain the Gumbel distribution and then estimate the exceedance probability (historic and future periods). We apply the return period-flood risk relationship (above) to the exceedance probability and evaluate the potential risk of river flooding and changes in the benefits of flood protection standard (e.g., 100-year flood of the baseline period) from the past into the future (represented by the representative concentration pathways). In this presentation, we show our preliminary results. References: Arnell, N.W, Gosling, S., N., 2014. The impact of climate change on river flood risk at the global scale. Climatic Change 122: 127-140, doi: 10.1007/s10584-014-1084-5. Hirabayashi et al., 2013. Global flood risk under climate change. Nature Climate Change 3: 816-821, doi: 10.1038/nclimate1911. Yamazaki et al., 2011. A physically based description of floodplain inundation dynamics in a global river routing model. Water Resources Research 47, W04501, doi: 10.1029/2010wr009726.

Evaluating the Contribution of Natural Variability and Climate Model Response to Uncertainty in Projections of Climate Change Impacts on U.S. Air Quality

EPA Science Inventory

We examine the effects of internal variability and model response in projections of climate impacts on U.S. ground-level ozone across the 21st century using integrated global system modeling and global atmospheric chemistry simulations. The impact of climate change on air polluti...

Inability of CMIP5 Climate Models to Simulate Recent Multi-decadal Climate Change in the Tropical Pacific.

NASA Astrophysics Data System (ADS)

Power, S.; Delage, F.; Kociuba, G.; Wang, G.; Smith, I.

2017-12-01

Observed 15-year surface temperature trends beginning 1998 or later have attracted a great deal of interest because of an apparent slowdown in the rate of global warming, and contrasts between climate model simulations and observations of such trends. Many studies have addressed the statistical significance of these relatively short trends, whether they indicate a possible bias in models and the implications for global warming generally. Here we analyse historical and projected changes in 38 CMIP5 climate models. All of the models simulate multi-decadal warming in the Pacific over the past half-century that exceeds observed values. This stark difference cannot be fully explained by observed, internal multi-decadal climate variability, even if allowance is made for an apparent tendency for models to underestimate internal multi-decadal variability in the Pacific. We also show that CMIP5 models are not able to simulate the magnitude of the strengthening of the Walker Circulation over the past thirty years. Some of the reasons for these major shortcomings in the ability of models to simulate multi-decadal variability in the Pacific, and the impact these findings have on our confidence in global 21st century projections, will be discussed.

Calibration-induced uncertainty of the EPIC model to estimate climate change impact on global maize yield

NASA Astrophysics Data System (ADS)

Xiong, Wei; Skalský, Rastislav; Porter, Cheryl H.; Balkovič, Juraj; Jones, James W.; Yang, Di

2016-09-01

Understanding the interactions between agricultural production and climate is necessary for sound decision-making in climate policy. Gridded and high-resolution crop simulation has emerged as a useful tool for building this understanding. Large uncertainty exists in this utilization, obstructing its capacity as a tool to devise adaptation strategies. Increasing focus has been given to sources of uncertainties for climate scenarios, input-data, and model, but uncertainties due to model parameter or calibration are still unknown. Here, we use publicly available geographical data sets as input to the Environmental Policy Integrated Climate model (EPIC) for simulating global-gridded maize yield. Impacts of climate change are assessed up to the year 2099 under a climate scenario generated by HadEM2-ES under RCP 8.5. We apply five strategies by shifting one specific parameter in each simulation to calibrate the model and understand the effects of calibration. Regionalizing crop phenology or harvest index appears effective to calibrate the model for the globe, but using various values of phenology generates pronounced difference in estimated climate impact. However, projected impacts of climate change on global maize production are consistently negative regardless of the parameter being adjusted. Different values of model parameter result in a modest uncertainty at global level, with difference of the global yield change less than 30% by the 2080s. The uncertainty subjects to decrease if applying model calibration or input data quality control. Calibration has a larger effect at local scales, implying the possible types and locations for adaptation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiong, Wei; Balkovic, Juraj; van der Velde, M.

Crop models are increasingly used to assess impacts of climate change/variability and management practices on productivity and environmental performance of alternative cropping systems. Calibration is an important procedure to improve reliability of model simulations, especially for large area applications. However, global-scale crop model calibration has rarely been exercised due to limited data availability and expensive computing cost. Here we present a simple approach to calibrate Environmental Policy Integrated Climate (EPIC) model for a global implementation of rice. We identify four parameters (potential heat unit – PHU, planting density – PD, harvest index – HI, and biomass energy ratio – BER)more » and calibrate them regionally to capture the spatial pattern of reported rice yield in 2000. Model performance is assessed by comparing simulated outputs with independent FAO national data. The comparison demonstrates that the global calibration scheme performs satisfactorily in reproducing the spatial pattern of rice yield, particularly in main rice production areas. Spatial agreement increases substantially when more parameters are selected and calibrated, but with varying efficiencies. Among the parameters, PHU and HI exhibit the highest efficiencies in increasing the spatial agreement. Simulations with different calibration strategies generate a pronounced discrepancy of 5–35% in mean yields across latitude bands, and a small to moderate difference in estimated yield variability and yield changing trend for the period of 1981–2000. Present calibration has little effects in improving simulated yield variability and trends at both regional and global levels, suggesting further works are needed to reproduce temporal variability of reported yields. This study highlights the importance of crop models’ calibration, and presents the possibility of a transparent and consistent up scaling approach for global crop simulations given current availability of global databases of weather, soil, crop calendar, fertilizer and irrigation management information, and reported yield.« less

Importance of vegetation distribution for future carbon balance

NASA Astrophysics Data System (ADS)

Ahlström, A.; Xia, J.; Arneth, A.; Luo, Y.; Smith, B.

2015-12-01

Projections of future terrestrial carbon uptake vary greatly between simulations. Net primary production (NPP), wild fires, vegetation dynamics (including biome shifts) and soil decomposition constitute the main processes governing the response of the terrestrial carbon cycle in a changing climate. While primary production and soil respiration are relatively well studied and implemented in all global ecosystem models used to project the future land sink of CO2, vegetation dynamics are less studied and not always represented in global models. Here we used a detailed second generation dynamic global vegetation model with advanced representation of vegetation growth and mortality and the associated turnover and proven skill in predicting vegetation distribution and succession. We apply an emulator that describes the carbon flows and pools exactly as in simulations with the full model. The emulator simulates ecosystem dynamics in response to 13 different climate or Earth system model simulations from the CMIP5 ensemble under RCP8.5 radiative forcing at year 2085. We exchanged carbon cycle processes between these 13 simulations and investigate the changes predicted by the emulator. This method allowed us to partition the entire ensemble carbon uptake uncertainty into individual processes. We found that NPP, vegetation dynamics (including biome shifts, wild fires and mortality) and soil decomposition rates explained 49%, 17% and 33% respectively of uncertainties in modeled global C-uptake. Uncertainty due to vegetation dynamics was further partitioned into stand-clearing disturbances (16%), wild fires (0%), stand dynamics (7%), reproduction (10%) and biome shifts (67%) globally. We conclude that while NPP and soil decomposition rates jointly account for 83% of future climate induced C-uptake uncertainties, vegetation turnover and structure, dominated by shifts in vegetation distribution, represent a significant fraction globally and regionally (tropical forests: 40%), strongly motivating their representation and analysis in future C-cycle studies.

The contribution of future agricultural trends in the US Midwest to global climate change mitigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomson, Allison M.; Kyle, G. Page; Zhang, Xuesong

2014-01-19

Land use change is a complex response to changing environmental and socioeconomic systems. Historical drivers of land use change include changes in the natural resource availability of a region, changes in economic conditions for production of certain products and changing policies. Most recently, introduction of policy incentives for biofuel production have influenced land use change in the US Midwest, leading to concerns that bioenergy production systems may compete with food production and land conservation. Here we explore how land use may be impacted by future climate mitigation measures by nesting a high resolution agricultural model (EPIC – Environmental Policy Indicatormore » Climate) for the US Midwest within a global integrated assessment model (GCAM – Global Change Assessment Model). This approach is designed to provide greater spatial resolution and detailed agricultural practice information by focusing on the climate mitigation potential of agriculture and land use in a specific region, while retaining the global economic context necessary to understand the far ranging effects of climate mitigation targets. We find that until the simulated carbon prices are very high, the US Midwest has a comparative advantage in producing traditional food and feed crops over bioenergy crops. Overall, the model responds to multiple pressures by adopting a mix of future responses. We also find that the GCAM model is capable of simulations at multiple spatial scales and agricultural technology resolution, which provides the capability to examine regional response to global policy and economic conditions in the context of climate mitigation.« less

Sensitivity of Global Terrestrial Gross Primary Production to Hydrologic States Simulated by the Community Land Model Using Two Runoff Parameterizations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lei, Huimin; Huang, Maoyi; Leung, Lai-Yung R.

2014-09-01

The terrestrial water and carbon cycles interact strongly at various spatio-temporal scales. To elucidate how hydrologic processes may influence carbon cycle processes, differences in terrestrial carbon cycle simulations induced by structural differences in two runoff generation schemes were investigated using the Community Land Model 4 (CLM4). Simulations were performed with runoff generation using the default TOPMODEL-based and the Variable Infiltration Capacity (VIC) model approaches under the same experimental protocol. The comparisons showed that differences in the simulated gross primary production (GPP) are mainly attributed to differences in the simulated leaf area index (LAI) rather than soil moisture availability. More specifically,more » differences in runoff simulations can influence LAI through changes in soil moisture, soil temperature, and their seasonality that affect the onset of the growing season and the subsequent dynamic feedbacks between terrestrial water, energy, and carbon cycles. As a result of a relative difference of 36% in global mean total runoff between the two models and subsequent changes in soil moisture, soil temperature, and LAI, the simulated global mean GPP differs by 20.4%. However, the relative difference in the global mean net ecosystem exchange between the two models is small (2.1%) due to competing effects on total mean ecosystem respiration and other fluxes, although large regional differences can still be found. Our study highlights the significant interactions among the water, energy, and carbon cycles and the need for reducing uncertainty in the hydrologic parameterization of land surface models to better constrain carbon cycle modeling.« less

On the influence of simulated SST warming on rainfall projections in the Indo-Pacific domain: an AGCM study

NASA Astrophysics Data System (ADS)

Zhang, Huqiang; Zhao, Y.; Moise, A.; Ye, H.; Colman, R.; Roff, G.; Zhao, M.

2018-02-01

Significant uncertainty exists in regional climate change projections, particularly for rainfall and other hydro-climate variables. In this study, we conduct a series of Atmospheric General Circulation Model (AGCM) experiments with different future sea surface temperature (SST) warming simulated by a range of coupled climate models. They allow us to assess the extent to which uncertainty from current coupled climate model rainfall projections can be attributed to their simulated SST warming. Nine CMIP5 model-simulated global SST warming anomalies have been super-imposed onto the current SSTs simulated by the Australian climate model ACCESS1.3. The ACCESS1.3 SST-forced experiments closely reproduce rainfall means and interannual variations as in its own fully coupled experiments. Although different global SST warming intensities explain well the inter-model difference in global mean precipitation changes, at regional scales the SST influence vary significantly. SST warming explains about 20-25% of the patterns of precipitation changes in each of the four/five models in its rainfall projections over the oceans in the Indo-Pacific domain, but there are also a couple of models in which different SST warming explains little of their precipitation pattern changes. The influence is weaker again for rainfall changes over land. Roughly similar levels of contribution can be attributed to different atmospheric responses to SST warming in these models. The weak SST influence in our study could be due to the experimental setup applied: superimposing different SST warming anomalies onto the same SSTs simulated for current climate by ACCESS1.3 rather than directly using model-simulated past and future SSTs. Similar modelling and analysis from other modelling groups with more carefully designed experiments are needed to tease out uncertainties caused by different SST warming patterns, different SST mean biases and different model physical/dynamical responses to the same underlying SST forcing.

Modeling and Analysis of Global and Regional Climate Change in Relation to Atmospheric Hydrologic Processes

NASA Technical Reports Server (NTRS)

Johnson, Donald R.

2001-01-01

This research was directed to the development and application of global isentropic modeling and analysis capabilities to describe hydrologic processes and energy exchange in the climate system, and discern regional climate change. An additional objective was to investigate the accuracy and theoretical limits of global climate predictability which are imposed by the inherent limitations of simulating trace constituent transport and the hydrologic processes of condensation, precipitation and cloud life cycles.

Projected Future Vegetation Changes for the Northwest United States and Southwest Canada at a Fine Spatial Resolution Using a Dynamic Global Vegetation Model.

PubMed

Shafer, Sarah L; Bartlein, Patrick J; Gray, Elizabeth M; Pelltier, Richard T

2015-01-01

Future climate change may significantly alter the distributions of many plant taxa. The effects of climate change may be particularly large in mountainous regions where climate can vary significantly with elevation. Understanding potential future vegetation changes in these regions requires methods that can resolve vegetation responses to climate change at fine spatial resolutions. We used LPJ, a dynamic global vegetation model, to assess potential future vegetation changes for a large topographically complex area of the northwest United States and southwest Canada (38.0-58.0°N latitude by 136.6-103.0°W longitude). LPJ is a process-based vegetation model that mechanistically simulates the effect of changing climate and atmospheric CO2 concentrations on vegetation. It was developed and has been mostly applied at spatial resolutions of 10-minutes or coarser. In this study, we used LPJ at a 30-second (~1-km) spatial resolution to simulate potential vegetation changes for 2070-2099. LPJ was run using downscaled future climate simulations from five coupled atmosphere-ocean general circulation models (CCSM3, CGCM3.1(T47), GISS-ER, MIROC3.2(medres), UKMO-HadCM3) produced using the A2 greenhouse gases emissions scenario. Under projected future climate and atmospheric CO2 concentrations, the simulated vegetation changes result in the contraction of alpine, shrub-steppe, and xeric shrub vegetation across the study area and the expansion of woodland and forest vegetation. Large areas of maritime cool forest and cold forest are simulated to persist under projected future conditions. The fine spatial-scale vegetation simulations resolve patterns of vegetation change that are not visible at coarser resolutions and these fine-scale patterns are particularly important for understanding potential future vegetation changes in topographically complex areas.

Responses of Terrestrial Ecosystems’ Net Primary Productivity to Future Regional Climate Change in China

PubMed Central

Zhao, Dongsheng; Wu, Shaohong; Yin, Yunhe

2013-01-01

The impact of regional climate change on net primary productivity (NPP) is an important aspect in the study of ecosystems’ response to global climate change. China’s ecosystems are very sensitive to climate change owing to the influence of the East Asian monsoon. The Lund–Potsdam–Jena Dynamic Global Vegetation Model for China (LPJ-CN), a global dynamical vegetation model developed for China’s terrestrial ecosystems, was applied in this study to simulate the NPP changes affected by future climate change. As the LPJ-CN model is based on natural vegetation, the simulation in this study did not consider the influence of anthropogenic activities. Results suggest that future climate change would have adverse effects on natural ecosystems, with NPP tending to decrease in eastern China, particularly in the temperate and warm temperate regions. NPP would increase in western China, with a concentration in the Tibetan Plateau and the northwest arid regions. The increasing trend in NPP in western China and the decreasing trend in eastern China would be further enhanced by the warming climate. The spatial distribution of NPP, which declines from the southeast coast to the northwest inland, would have minimal variation under scenarios of climate change. PMID:23593325

Responses of terrestrial ecosystems' net primary productivity to future regional climate change in China.

PubMed

Zhao, Dongsheng; Wu, Shaohong; Yin, Yunhe

2013-01-01

The impact of regional climate change on net primary productivity (NPP) is an important aspect in the study of ecosystems' response to global climate change. China's ecosystems are very sensitive to climate change owing to the influence of the East Asian monsoon. The Lund-Potsdam-Jena Dynamic Global Vegetation Model for China (LPJ-CN), a global dynamical vegetation model developed for China's terrestrial ecosystems, was applied in this study to simulate the NPP changes affected by future climate change. As the LPJ-CN model is based on natural vegetation, the simulation in this study did not consider the influence of anthropogenic activities. Results suggest that future climate change would have adverse effects on natural ecosystems, with NPP tending to decrease in eastern China, particularly in the temperate and warm temperate regions. NPP would increase in western China, with a concentration in the Tibetan Plateau and the northwest arid regions. The increasing trend in NPP in western China and the decreasing trend in eastern China would be further enhanced by the warming climate. The spatial distribution of NPP, which declines from the southeast coast to the northwest inland, would have minimal variation under scenarios of climate change.

Climate implications of including albedo effects in terrestrial carbon policy

NASA Astrophysics Data System (ADS)

Jones, A. D.; Collins, W.; Torn, M. S.; Calvin, K. V.

2012-12-01

Proposed strategies for managing terrestrial carbon in order to mitigate anthropogenic climate change, such as financial incentives for afforestation, soil carbon sequestration, or biofuel production, largely ignore the direct effects of land use change on climate via biophysical processes that alter surface energy and water budgets. Subsequent influences on temperature, hydrology, and atmospheric circulation at regional and global scales could potentially help or hinder climate stabilization efforts. Because these policies often rely on payments or credits expressed in units of CO2-equivalents, accounting for biophysical effects would require a metric for comparing the strength of biophysical climate perturbation from land use change to that of emitting CO2. One such candidate metric that has been suggested in the literature on land use impacts is radiative forcing, which underlies the global warming potential metric used to compare the climate effects of various greenhouse gases with one another. Expressing land use change in units of radiative forcing is possible because albedo change results in a net top-of-atmosphere radiative flux change. However, this approach has also been critiqued on theoretical grounds because not all climatic changes associated with land use change are principally radiative in nature, e.g. changes in hydrology or the vertical distribution of heat within the atmosphere, and because the spatial scale of land use change forcing differs from that of well-mixed greenhouse gases. To explore the potential magnitude of this discrepancy in the context of plausible scenarios of future land use change, we conduct three simulations with the Community Climate System Model 4 (CCSM4) utilizing a slab ocean model. Each simulation examines the effect of a stepwise change in forcing relative to a pre-industrial control simulation: 1) widespread conversion of forest land to crops resulting in approximately 1 W/m2 global-mean radiative forcing from albedo change, 2) an increase in CO2 concentrations that exactly balances the forcing from land use change at the global level, and 3) a simulation combining the first two effects, resulting in net zero global-mean forcing as would occur in an idealized carbon cap-and-trade scheme that accounts for the albedo effect of land use change. The pattern of land use change that we examine is derived from an integrated assessment model that accounts for population, demographic, technological, and policy changes over the 21st century. We find significant differences in the pattern of climate change associated with each of these forcing scenarios, demonstrating the non-additivity of radiative forcing from land-use change and greenhouse gases in the context of a hypothetical scenario of future land use change. These results have implications for the development of land use and climate policies.

Changes in crop yields and their variability at different levels of global warming

NASA Astrophysics Data System (ADS)

Ostberg, Sebastian; Schewe, Jacob; Childers, Katelin; Frieler, Katja

2018-05-01

An assessment of climate change impacts at different levels of global warming is crucial to inform the policy discussion about mitigation targets, as well as for the economic evaluation of climate change impacts. Integrated assessment models often use global mean temperature change (ΔGMT) as a sole measure of climate change and, therefore, need to describe impacts as a function of ΔGMT. There is already a well-established framework for the scalability of regional temperature and precipitation changes with ΔGMT. It is less clear to what extent more complex biological or physiological impacts such as crop yield changes can also be described in terms of ΔGMT, even though such impacts may often be more directly relevant for human livelihoods than changes in the physical climate. Here we show that crop yield projections can indeed be described in terms of ΔGMT to a large extent, allowing for a fast estimation of crop yield changes for emissions scenarios not originally covered by climate and crop model projections. We use an ensemble of global gridded crop model simulations for the four major staple crops to show that the scenario dependence is a minor component of the overall variance of projected yield changes at different levels of ΔGMT. In contrast, the variance is dominated by the spread across crop models. Varying CO2 concentrations are shown to explain only a minor component of crop yield variability at different levels of global warming. In addition, we find that the variability in crop yields is expected to increase with increasing warming in many world regions. We provide, for each crop model, geographical patterns of mean yield changes that allow for a simplified description of yield changes under arbitrary pathways of global mean temperature and CO2 changes, without the need for additional climate and crop model simulations.

Comparing the model-simulated global warming signal to observations using empirical estimates of unforced noise.

PubMed

Brown, Patrick T; Li, Wenhong; Cordero, Eugene C; Mauget, Steven A

2015-04-21

The comparison of observed global mean surface air temperature (GMT) change to the mean change simulated by climate models has received much public and scientific attention. For a given global warming signal produced by a climate model ensemble, there exists an envelope of GMT values representing the range of possible unforced states of the climate system (the Envelope of Unforced Noise; EUN). Typically, the EUN is derived from climate models themselves, but climate models might not accurately simulate the correct characteristics of unforced GMT variability. Here, we simulate a new, empirical, EUN that is based on instrumental and reconstructed surface temperature records. We compare the forced GMT signal produced by climate models to observations while noting the range of GMT values provided by the empirical EUN. We find that the empirical EUN is wide enough so that the interdecadal variability in the rate of global warming over the 20(th) century does not necessarily require corresponding variability in the rate-of-increase of the forced signal. The empirical EUN also indicates that the reduced GMT warming over the past decade or so is still consistent with a middle emission scenario's forced signal, but is likely inconsistent with the steepest emission scenario's forced signal.

Comparing the model-simulated global warming signal to observations using empirical estimates of unforced noise

PubMed Central

Brown, Patrick T.; Li, Wenhong; Cordero, Eugene C.; Mauget, Steven A.

2015-01-01

The comparison of observed global mean surface air temperature (GMT) change to the mean change simulated by climate models has received much public and scientific attention. For a given global warming signal produced by a climate model ensemble, there exists an envelope of GMT values representing the range of possible unforced states of the climate system (the Envelope of Unforced Noise; EUN). Typically, the EUN is derived from climate models themselves, but climate models might not accurately simulate the correct characteristics of unforced GMT variability. Here, we simulate a new, empirical, EUN that is based on instrumental and reconstructed surface temperature records. We compare the forced GMT signal produced by climate models to observations while noting the range of GMT values provided by the empirical EUN. We find that the empirical EUN is wide enough so that the interdecadal variability in the rate of global warming over the 20th century does not necessarily require corresponding variability in the rate-of-increase of the forced signal. The empirical EUN also indicates that the reduced GMT warming over the past decade or so is still consistent with a middle emission scenario's forced signal, but is likely inconsistent with the steepest emission scenario's forced signal. PMID:25898351

Gap models and their individual-based relatives in the assessment of the consequences of global change

NASA Astrophysics Data System (ADS)

Shugart, Herman H.; Wang, Bin; Fischer, Rico; Ma, Jianyong; Fang, Jing; Yan, Xiaodong; Huth, Andreas; Armstrong, Amanda H.

2018-03-01

Individual-based models (IBMs) of complex systems emerged in the 1960s and early 1970s, across diverse disciplines from astronomy to zoology. Ecological IBMs arose with seemingly independent origins out of the tradition of understanding the ecosystems dynamics of ecosystems from a ‘bottom-up’ accounting of the interactions of the parts. Individual trees are principal among the parts of forests. Because these models are computationally demanding, they have prospered as the power of digital computers has increased exponentially over the decades following the 1970s. This review will focus on a class of forest IBMs called gap models. Gap models simulate the changes in forests by simulating the birth, growth and death of each individual tree on a small plot of land. The summation of these plots comprise a forest (or set of sample plots on a forested landscape or region). Other, more aggregated forest IBMs have been used in global applications including cohort-based models, ecosystem demography models, etc. Gap models have been used to provide the parameters for these bulk models. Currently, gap models have grown from local-scale to continental-scale and even global-scale applications to assess the potential consequences of climate change on natural forests. Modifications to the models have enabled simulation of disturbances including fire, insect outbreak and harvest. Our objective in this review is to provide the reader with an overview of the history, motivation and applications, including theoretical applications, of these models. In a time of concern over global changes, gap models are essential tools to understand forest responses to climate change, modified disturbance regimes and other change agents. Development of forest surveys to provide the starting points for simulations and better estimates of the behavior of the diversity of tree species in response to the environment are continuing needs for improvement for these and other IBMs.

Does internal variability change in response to global warming? A large ensemble modelling study of tropical rainfall

NASA Astrophysics Data System (ADS)

Milinski, S.; Bader, J.; Jungclaus, J. H.; Marotzke, J.

2017-12-01

There is some consensus on mean state changes of rainfall under global warming; changes of the internal variability, on the other hand, are more difficult to analyse and have not been discussed as much despite their importance for understanding changes in extreme events, such as droughts or floodings. We analyse changes in the rainfall variability in the tropical Atlantic region. We use a 100-member ensemble of historical (1850-2005) model simulations with the Max Planck Institute for Meteorology Earth System Model (MPI-ESM1) to identify changes of internal rainfall variability. To investigate the effects of global warming on the internal variability, we employ an additional ensemble of model simulations with stronger external forcing (1% CO2-increase per year, same integration length as the historical simulations) with 68 ensemble members. The focus of our study is on the oceanic Atlantic ITCZ. We find that the internal variability of rainfall over the tropical Atlantic does change due to global warming and that these changes in variability are larger than changes in the mean state in some regions. From splitting the total variance into patterns of variability, we see that the variability on the southern flank of the ITCZ becomes more dominant, i.e. explaining a larger fraction of the total variance in a warmer climate. In agreement with previous studies, we find that changes in the mean state show an increase and narrowing of the ITCZ. The large ensembles allow us to do a statistically robust differentiation between the changes in variability that can be explained by internal variability and those that can be attributed to the external forcing. Furthermore, we argue that internal variability in a transient climate is only well defined in the ensemble domain and not in the temporal domain, which requires the use of a large ensemble.

Modelling carbon responses of tundra ecosystems to historical and projected climate: A comparison of a plot- and a global-scale ecosystem model to identify process-based uncertainties

USGS Publications Warehouse

Clein, Joy S.; Kwiatkowski, B.L.; McGuire, A.D.; Hobbie, J.E.; Rastetter, E.B.; Melillo, J.M.; Kicklighter, D.W.

2000-01-01

We are developing a process-based modelling approach to investigate how carbon (C) storage of tundra across the entire Arctic will respond to projected climate change. To implement the approach, the processes that are least understood, and thus have the most uncertainty, need to be identified and studied. In this paper, we identified a key uncertainty by comparing the responses of C storage in tussock tundra at one site between the simulations of two models - one a global-scale ecosystem model (Terrestrial Ecosystem Model, TEM) and one a plot-scale ecosystem model (General Ecosystem Model, GEM). The simulations spanned the historical period (1921-94) and the projected period (1995-2100). In the historical period, the model simulations of net primary production (NPP) differed in their sensitivity to variability in climate. However, the long-term changes in C storage were similar in both simulations, because the dynamics of heterotrophic respiration (RH) were similar in both models. In contrast, the responses of C storage in the two model simulations diverged during the projected period. In the GEM simulation for this period, increases in RH tracked increases in NPP, whereas in the TEM simulation increases in RH lagged increases in NPP. We were able to make the long-term C dynamics of the two simulations agree by parameterizing TEM to the fast soil C pools of GEM. We concluded that the differences between the long-term C dynamics of the two simulations lay in modelling the role of the recalcitrant soil C. These differences, which reflect an incomplete understanding of soil processes, lead to quite different projections of the response of pan-Arctic C storage to global change. For example, the reference parameterization of TEM resulted in an estimate of cumulative C storage of 2032 g C m-2 for moist tundra north of 50??N, which was substantially higher than the 463 g C m-2 estimated for a parameterization of fast soil C dynamics. This uncertainty in the depiction of the role of recalcitrant soil C in long-term ecosystem C dynamics resulted from our incomplete understanding of controls over C and N transformations in Arctic soils. Mechanistic studies of these issues are needed to improve our ability to model the response of Arctic ecosystems to global change.

Global estimation of evapotranspiration using a leaf area index-based surface energy and water balance model

USDA-ARS?s Scientific Manuscript database

Studies of global hydrologic cycles, carbon cycles and climate change are greatly facilitated when global estimates of evapotranspiration (E) are available. We have developed an air-relative-humidity-based two-source (ARTS) E model that simulates the surface energy balance, soil water balance, and e...

Simulating the effects of climate and agricultural management practices on global crop yield

NASA Astrophysics Data System (ADS)

Deryng, D.; Sacks, W. J.; Barford, C. C.; Ramankutty, N.

2011-06-01

Climate change is expected to significantly impact global food production, and it is important to understand the potential geographic distribution of yield losses and the means to alleviate them. This study presents a new global crop model, PEGASUS 1.0 (Predicting Ecosystem Goods And Services Using Scenarios) that integrates, in addition to climate, the effect of planting dates and cultivar choices, irrigation, and fertilizer application on crop yield for maize, soybean, and spring wheat. PEGASUS combines carbon dynamics for crops with a surface energy and soil water balance model. It also benefits from the recent development of a suite of global data sets and analyses that serve as model inputs or as calibration data. These include data on crop planting and harvesting dates, crop-specific irrigated areas, a global analysis of yield gaps, and harvested area and yield of major crops. Model results for present-day climate and farm management compare reasonably well with global data. Simulated planting and harvesting dates are within the range of crop calendar observations in more than 75% of the total crop-harvested areas. Correlation of simulated and observed crop yields indicates a weighted coefficient of determination, with the weighting based on crop-harvested area, of 0.81 for maize, 0.66 for soybean, and 0.45 for spring wheat. We found that changes in temperature and precipitation as predicted by global climate models for the 2050s lead to a global yield reduction if planting and harvesting dates remain unchanged. However, adapting planting dates and cultivar choices increases yield in temperate regions and avoids 7-18% of global losses.

Understanding the varied response of the extratropical storm tracks to climate change

PubMed Central

O’Gorman, Paul A.

2010-01-01

Transient eddies in the extratropical storm tracks are a primary mechanism for the transport of momentum, energy, and water in the atmosphere, and as such are a major component of the climate system. Changes in the extratropical storm tracks under global warming would impact these transports, the ocean circulation and carbon cycle, and society through changing weather patterns. I show that the southern storm track intensifies in the multimodel mean of simulations of 21st century climate change, and that the seasonal cycle of storm-track intensity increases in amplitude in both hemispheres. I use observations of the present-day seasonal cycle to confirm the relationship between storm-track intensity and the mean available potential energy of the atmosphere, and show how this quantitative relationship can be used to account for much of the varied response in storm-track intensity to global warming, including substantially different responses in simulations with different climate models. The results suggest that storm-track intensity is not related in a simple way to global-mean surface temperature, so that, for example, a stronger southern storm track in response to present-day global warming does not imply it was also stronger in hothouse climates of the past. PMID:20974916

Understanding the varied response of the extratropical storm tracks to climate change.

PubMed

O'Gorman, Paul A

2010-11-09

Transient eddies in the extratropical storm tracks are a primary mechanism for the transport of momentum, energy, and water in the atmosphere, and as such are a major component of the climate system. Changes in the extratropical storm tracks under global warming would impact these transports, the ocean circulation and carbon cycle, and society through changing weather patterns. I show that the southern storm track intensifies in the multimodel mean of simulations of 21st century climate change, and that the seasonal cycle of storm-track intensity increases in amplitude in both hemispheres. I use observations of the present-day seasonal cycle to confirm the relationship between storm-track intensity and the mean available potential energy of the atmosphere, and show how this quantitative relationship can be used to account for much of the varied response in storm-track intensity to global warming, including substantially different responses in simulations with different climate models. The results suggest that storm-track intensity is not related in a simple way to global-mean surface temperature, so that, for example, a stronger southern storm track in response to present-day global warming does not imply it was also stronger in hothouse climates of the past.

The Impact of Continental Configuration on Global Response to Large Igneous Province Eruptions

NASA Astrophysics Data System (ADS)

Stellmann, J.; West, A. J.; Ridgwell, A.; Becker, T. W.

2017-12-01

The impact of Large Igneous Province eruptions as recorded in the geologic record varies widely; some eruptions cause global warming, large scale ocean acidification and anoxia and mass extinctions while others cause some or none of these phenomena. There are several potential factors which may determine the global response to a Large Igneous Province eruption; here we consider continental configuration. The arrangement of continents controls the extent of shallow seas, ocean circulation and planetary albedo; all factors which impact global climate and its response to sudden changes in greenhouse gas concentrations. To assess the potential impact of continental configuration, a suite of simulated eruptions was carried out using the cGENIE Earth system model in two end-member continental configurations: the end-Permian supercontinent and the modern. Eruptions simulated are comparable to an individual pulse of a Large Igneous Province eruption with total CO2 emissions of 1,000 or 10,000 GtC erupted over 1,000 or 10,000 years, spanning eruptions rates of .1-10 GtC/yr. Global response is characterized by measuring the magnitude and duration of changes to atmospheric concentration of CO2, saturation state of calcite and ocean oxygen levels. Preliminary model results show that end-Permian continental configuration and conditions (radiative balance, ocean chemistry) lead to smaller magnitude and shorter duration changes in atmospheric pCO2 and ocean saturation state of calcite following the simulated eruption than the modern configuration.

Impact of Future Emissions and Climate Change on Surface Ozone over China

NASA Astrophysics Data System (ADS)

Ma, C. T.; Westervelt, D. M.; Fiore, A. M.; Rieder, H. E.; Kinney, P.; Wang, S.; Correa, G. J. P.

2017-12-01

China's immense ambient air pollution problem and world-leading greenhouse gas emissions place it at the forefront of global efforts to address these related environmental concerns. Here, we analyze the impact of ECLIPSE (Evaluating the Climate and Air Quality Impacts of Short-Lived Pollutants) future emissions scenarios representative of current legislation (CLE) and maximum technically feasible emissions reductions (MFR) on surface ozone (O3) concentrations over China in the 2030s and 2050s, in the context of a changing climate. We use a suite of simulations performed with the NOAA Geophysical Fluid Dynamics Laboratory's AM3 global chemistry-climate model. To estimate the impact of climate change in isolation on Chinese air quality, we hold emissions of air pollutants including O3 precursors fixed at 2015 levels but allow climate (global sea surface temperatures and sea ice cover) to change according to decadal averages for the years 2026-2035 and 2046-2055 from a three-member ensemble of GFDL-CM3 simulations under the RCP8.5 high warming scenario. Evaluation of the present-day simulation (2015 CLE) with observations from 1497 chiefly urban air quality monitoring stations shows that simulated surface O3 is positively biased by 26 ppb on average over the domain of China. Previous studies, however, have shown that the modeled ozone response to changes in NOx emissions over the Eastern United States mirrors the magnitude and structure of observed changes in maximum daily average 8-hour (MDA8) O3 distributions. Therefore, we use the model's simulated changes for the 2030s and 2050s to project changes in policy-relevant MDA8 O3 concentrations. We find an overall increase in MDA8 O3 for CLE scenarios in which emissions of NOx precursors are projected to increase, and under MFR scenarios, an overall decrease, with the highest changes occurring in summertime for both 2030 and 2050 MFR. Under climate change alone, the model simulates a mean summertime decrease of 1.3 ppb and wintertime increase of 3.3 ppb by 2050. Adjustment of the observed site-level MDA8 O3 distribution to reflect regionally interpolated projected changes from AM3 allows us to examine changes in the number of days in exceedance of MDA8 O3 Level I (50 ppb) and Level II (80 ppb) Chinese national ambient air quality standards.

Dynamics of global vegetation biomass simulated by the integrated Earth System Model

NASA Astrophysics Data System (ADS)

Mao, J.; Shi, X.; Di Vittorio, A. V.; Thornton, P. E.; Piao, S.; Yang, X.; Truesdale, J. E.; Bond-Lamberty, B. P.; Chini, L. P.; Thomson, A. M.; Hurtt, G. C.; Collins, W.; Edmonds, J.

2014-12-01

The global vegetation biomass stores huge amounts of carbon and is thus important to the global carbon budget (Pan et al., 2010). For the past few decades, different observation-based estimates and modeling of biomass in the above- and below-ground vegetation compartments have been comprehensively conducted (Saatchi et al., 2011; Baccini et al., 2012). However, uncertainties still exist, in particular for the simulation of biomass magnitude, tendency, and the response of biomass to climatic conditions and natural and human disturbances. The recently successful coupling of the integrated Earth System Model (iESM) (Di Vittorio et al., 2014; Bond-Lamberty et al., 2014), which links the Global Change Assessment Model (GCAM), Global Land-use Model (GLM), and Community Earth System Model (CESM), offers a great opportunity to understand the biomass-related dynamics in a fully-coupled natural and human modeling system. In this study, we focus on the systematic analysis and evaluation of the iESM simulated historical (1850-2005) and future (2006-2100) biomass changes and the response of the biomass dynamics to various impact factors, in particular the human-induced Land Use/Land Cover Change (LULCC). By analyzing the iESM simulations with and without the interactive LULCC feedbacks, we further study how and where the climate feedbacks affect socioeconomic decisions and LULCC, such as to alter vegetation carbon storage. References Pan Y et. al: A large and persistent carbon sink in the World's forests. Science 2011, 333:988-993. Saatchi SS et al: Benchmark map of forest carbon stocks in tropical regions across three continents. Proc Natl Acad Sci 2011, 108:9899-9904. Baccini A et al: Estimated carbon dioxide emissions from tropical deforestation improved by carbon-density maps. Nature Clim Change 2012, 2:182-185. Di Vittorio AV et al: From land use to land cover: restoring the afforestation signal in a coupled integrated assessment-earth system model and the implications for CMIP5 RCP simulations. Biogeosciences Discuss 2014, 11:7151-7188. Bond-Lamberty, B et al: Coupling earth system and integrated assessment models: The problem of steady state. Geosci. Model Dev. Discuss 2014, 7: 1499-1524, doi:10.5194/gmdd-7-1499-2014.

Projected changes of the southwest Australian wave climate under two atmospheric greenhouse gas concentration pathways

NASA Astrophysics Data System (ADS)

Wandres, Moritz; Pattiaratchi, Charitha; Hemer, Mark A.

2017-09-01

Incident wave energy flux is responsible for sediment transport and coastal erosion in wave-dominated regions such as the southwestern Australian (SWA) coastal zone. To evaluate future wave climates under increased greenhouse gas concentration scenarios, past studies have forced global wave simulations with wind data sourced from global climate model (GCM) simulations. However, due to the generally coarse spatial resolution of global climate and wave simulations, the effects of changing offshore wave conditions and sea level rise on the nearshore wave climate are still relatively unknown. To address this gap of knowledge, we investigated the projected SWA offshore, shelf, and nearshore wave climate under two potential future greenhouse gas concentration trajectories (representative concentration pathways RCP4.5 and RCP8.5). This was achieved by downscaling an ensemble of global wave simulations, forced with winds from GCMs participating in the Coupled Model Inter-comparison Project (CMIP5), into two regional domains, using the Simulating WAves Nearshore (SWAN) wave model. The wave climate is modeled for a historical 20-year time slice (1986-2005) and a projected future 20-year time-slice (2081-2100) for both scenarios. Furthermore, we compare these scenarios to the effects of considering sea-level rise (SLR) alone (stationary wave climate), and to the effects of combined SLR and projected wind-wave change. Results indicated that the SWA shelf and nearshore wave climate is more sensitive to changes in offshore mean wave direction than offshore wave heights. Nearshore, wave energy flux was projected to increase by ∼10% in exposed areas and decrease by ∼10% in sheltered areas under both climate scenarios due to a change in wave directions, compared to an overall increase of 2-4% in offshore wave heights. With SLR, the annual mean wave energy flux was projected to increase by up to 20% in shallow water (< 30 m) as a result of decreased wave dissipation. In winter months, the longshore wave energy flux, which is responsible for littoral drift, is expected to increase by up to 39% (62%) under the RCP4.5 (RCP8.5) greenhouse gas concentration pathway with SLR. The study highlights the importance of using high-resolution wave simulations to evaluate future regional wave climates, since the coastal wave climate is more responsive to changes in wave direction and sea level than offshore wave heights.

Global Qualitative Flow-Path Modeling for Local State Determination in Simulation and Analysis

NASA Technical Reports Server (NTRS)

Malin, Jane T. (Inventor); Fleming, Land D. (Inventor)

1998-01-01

For qualitative modeling and analysis, a general qualitative abstraction of power transmission variables (flow and effort) for elements of flow paths includes information on resistance, net flow, permissible directions of flow, and qualitative potential is discussed. Each type of component model has flow-related variables and an associated internal flow map, connected into an overall flow network of the system. For storage devices, the implicit power transfer to the environment is represented by "virtual" circuits that include an environmental junction. A heterogeneous aggregation method simplifies the path structure. A method determines global flow-path changes during dynamic simulation and analysis, and identifies corresponding local flow state changes that are effects of global configuration changes. Flow-path determination is triggered by any change in a flow-related device variable in a simulation or analysis. Components (path elements) that may be affected are identified, and flow-related attributes favoring flow in the two possible directions are collected for each of them. Next, flow-related attributes are determined for each affected path element, based on possibly conflicting indications of flow direction. Spurious qualitative ambiguities are minimized by using relative magnitudes and permissible directions of flow, and by favoring flow sources over effort sources when comparing flow tendencies. The results are output to local flow states of affected components.

Multi-millennia simulation of Greenland deglaciation from the Max-Plank-Institute Model (MPI-ISM) 2xCO2 simulation

NASA Astrophysics Data System (ADS)

Cabot, Vincent; Vizcaino, Miren; Mikolajewicz, Uwe

2016-04-01

Long-term ice sheet and climate coupled simulations are of great interest since they assess how the Greenland Ice Sheet (GrIS) will respond to global warming and how GrIS changes will impact on the climate system. We have run the Max-Plank-Institute Earth System Model coupled with an Ice Sheet Model (SICOPOLIS) over a time period of 10500 years under two times CO2 forcing. This is a coupled atmosphere (ECHAM5T31), ocean (MPI-OM), dynamic vegetation (LPJ), and ice sheet (SICOPOLIS, 10 km horizontal resolution) model. Given the multi-millennia simulation, the horizontal spatial resolution of the atmospheric component is relatively coarse (3.75°). A time-saving technique (asynchronous coupling) is used once the global climate reaches quasi-equilibrium. In our doubling-CO2 simulation, the GrIS is expected to break up into two pieces (one ice cap in the far north on one ice sheet in the south and east) after 3000 years. During the first 500 simulation years, the GrIS climate and surface mass balance (SMB) are mainly affected by the greenhouse effect-forced climate change. After the simulated year 500, the global climate reaches quasi-equilibrium. Henceforth Greenland climate change is mainly due to ice sheet decay. GrIS albedo reduction enhances melt and acts as a powerful feedback for deglaciation. Due to increased cloudiness in the Arctic region as a result of global climate change, summer incoming shortwave radiation is substantially reduced over Greenland, reducing deglaciation rates. At the end of the simulation, Greenland becomes green with forest growing over the newly deglaciated regions. References: Helsen, M. M., van de Berg, W. J., van de Wal, R. S. W., van den Broeke, M. R., and Oerlemans, J. (2013), Coupled regional climate-ice-sheet simulation shows limited Greenland ice loss during the Eemian, Climate of the Past, 9, 1773-1788, doi: 10.5194/cp-9-1773-2013 Helsen, M. M., van de Wal, R. S. W., van den Broeke, M. R., van de Berg, W. J., and Oerlemans, J. (2015), Coupling of climate models and ice sheet models by the surface mass balance gradients: application to the Greenland Ice Sheet, The Cryosphere, 6, 255-272, doi: 10.5194/tc-6-255-2012 Robinson, A., Calov, R., and Ganopolski, A. (2011), Greenland ice sheet model parameters constrained using simulations of the Eemian Interglacial, Climate of the Past, 7, 381-396, doi: 10.5194/cp-7-381-2011 Vizcaino, M., Mikolajewicz, U., Ziemen, F., Rodehacke, C. B., Greve, R., and van den Broeke, M. R. (2015), Coupled simulations of Greenland Ice Sheet and climate change up to A.D. 2300, Geophysical Research Letters, 42, doi: 10.1002/2014GL061142

Different Mechanisms of Soil Microbial Response to Global Change Result in Different Outcomes in the MIMICS-CN Model

NASA Astrophysics Data System (ADS)

Kyker-Snowman, E.; Wieder, W. R.; Grandy, S.

2017-12-01

Microbial-explicit models of soil carbon (C) and nitrogen (N) cycling have improved upon simulations of C and N stocks and flows at site-to-global scales relative to traditional first-order linear models. However, the response of microbial-explicit soil models to global change factors depends upon which parameters and processes in a model are altered by those factors. We used the MIcrobial-MIneral Carbon Stabilization Model with coupled N cycling (MIMICS-CN) to compare modeled responses to changes in temperature and plant inputs at two previously-modeled sites (Harvard Forest and Kellogg Biological Station). We spun the model up to equilibrium, applied each perturbation, and evaluated 15 years of post-perturbation C and N pools and fluxes. To model the effect of increasing temperatures, we independently examined the impact of decreasing microbial C use efficiency (CUE), increasing the rate of microbial turnover, and increasing Michaelis-Menten kinetic rates of litter decomposition, plus several combinations of the three. For plant inputs, we ran simulations with stepwise increases in metabolic litter, structural litter, whole litter (structural and metabolic), or labile soil C. The cumulative change in soil C or N varied in both sign and magnitude across simulations. For example, increasing kinetic rates of litter decomposition resulted in net releases of both C and N from soil pools, while decreasing CUE produced short-term increases in respiration but long-term accumulation of C in litter pools and shifts in soil C:N as microbial demand for C increased and biomass declined. Given that soil N cycling constrains the response of plant productivity to global change and that soils generate a large amount of uncertainty in current earth system models, microbial-explicit models are a critical opportunity to advance the modeled representation of soils. However, microbial-explicit models must be improved by experiments to isolate the physiological and stoichiometric parameters of soil microbes that shift under global change.

Tropical forests and global change: filling knowledge gaps.

PubMed

Zuidema, Pieter A; Baker, Patrick J; Groenendijk, Peter; Schippers, Peter; van der Sleen, Peter; Vlam, Mart; Sterck, Frank

2013-08-01

Tropical forests will experience major changes in environmental conditions this century. Understanding their responses to such changes is crucial to predicting global carbon cycling. Important knowledge gaps exist: the causes of recent changes in tropical forest dynamics remain unclear and the responses of entire tropical trees to environmental changes are poorly understood. In this Opinion article, we argue that filling these knowledge gaps requires a new research strategy, one that focuses on trees instead of leaves or communities, on long-term instead of short-term changes, and on understanding mechanisms instead of documenting changes. We propose the use of tree-ring analyses, stable-isotope analyses, manipulative field experiments, and well-validated simulation models to improve predictions of forest responses to global change. Copyright © 2013 Elsevier Ltd. All rights reserved.

Coordinating AgMIP data and models across global and regional scales for 1.5°C and 2.0°C assessments

NASA Astrophysics Data System (ADS)

Rosenzweig, Cynthia; Ruane, Alex C.; Antle, John; Elliott, Joshua; Ashfaq, Muhammad; Chatta, Ashfaq Ahmad; Ewert, Frank; Folberth, Christian; Hathie, Ibrahima; Havlik, Petr; Hoogenboom, Gerrit; Lotze-Campen, Hermann; MacCarthy, Dilys S.; Mason-D'Croz, Daniel; Contreras, Erik Mencos; Müller, Christoph; Perez-Dominguez, Ignacio; Phillips, Meridel; Porter, Cheryl; Raymundo, Rubi M.; Sands, Ronald D.; Schleussner, Carl-Friedrich; Valdivia, Roberto O.; Valin, Hugo; Wiebe, Keith

2018-05-01

The Agricultural Model Intercomparison and Improvement Project (AgMIP) has developed novel methods for Coordinated Global and Regional Assessments (CGRA) of agriculture and food security in a changing world. The present study aims to perform a proof of concept of the CGRA to demonstrate advantages and challenges of the proposed framework. This effort responds to the request by the UN Framework Convention on Climate Change (UNFCCC) for the implications of limiting global temperature increases to 1.5°C and 2.0°C above pre-industrial conditions. The protocols for the 1.5°C/2.0°C assessment establish explicit and testable linkages across disciplines and scales, connecting outputs and inputs from the Shared Socio-economic Pathways (SSPs), Representative Agricultural Pathways (RAPs), Half a degree Additional warming, Prognosis and Projected Impacts (HAPPI) and Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble scenarios, global gridded crop models, global agricultural economics models, site-based crop models and within-country regional economics models. The CGRA consistently links disciplines, models and scales in order to track the complex chain of climate impacts and identify key vulnerabilities, feedbacks and uncertainties in managing future risk. CGRA proof-of-concept results show that, at the global scale, there are mixed areas of positive and negative simulated wheat and maize yield changes, with declines in some breadbasket regions, at both 1.5°C and 2.0°C. Declines are especially evident in simulations that do not take into account direct CO2 effects on crops. These projected global yield changes mostly resulted in increases in prices and areas of wheat and maize in two global economics models. Regional simulations for 1.5°C and 2.0°C using site-based crop models had mixed results depending on the region and the crop. In conjunction with price changes from the global economics models, productivity declines in the Punjab, Pakistan, resulted in an increase in vulnerable households and the poverty rate. This article is part of the theme issue `The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'.

Coordinating AgMIP data and models across global and regional scales for 1.5°C and 2.0°C assessments.

PubMed

Rosenzweig, Cynthia; Ruane, Alex C; Antle, John; Elliott, Joshua; Ashfaq, Muhammad; Chatta, Ashfaq Ahmad; Ewert, Frank; Folberth, Christian; Hathie, Ibrahima; Havlik, Petr; Hoogenboom, Gerrit; Lotze-Campen, Hermann; MacCarthy, Dilys S; Mason-D'Croz, Daniel; Contreras, Erik Mencos; Müller, Christoph; Perez-Dominguez, Ignacio; Phillips, Meridel; Porter, Cheryl; Raymundo, Rubi M; Sands, Ronald D; Schleussner, Carl-Friedrich; Valdivia, Roberto O; Valin, Hugo; Wiebe, Keith

2018-05-13

The Agricultural Model Intercomparison and Improvement Project (AgMIP) has developed novel methods for Coordinated Global and Regional Assessments (CGRA) of agriculture and food security in a changing world. The present study aims to perform a proof of concept of the CGRA to demonstrate advantages and challenges of the proposed framework. This effort responds to the request by the UN Framework Convention on Climate Change (UNFCCC) for the implications of limiting global temperature increases to 1.5°C and 2.0°C above pre-industrial conditions. The protocols for the 1.5°C/2.0°C assessment establish explicit and testable linkages across disciplines and scales, connecting outputs and inputs from the Shared Socio-economic Pathways (SSPs), Representative Agricultural Pathways (RAPs), Half a degree Additional warming, Prognosis and Projected Impacts (HAPPI) and Coupled Model Intercomparison Project Phase 5 (CMIP5) ensemble scenarios, global gridded crop models, global agricultural economics models, site-based crop models and within-country regional economics models. The CGRA consistently links disciplines, models and scales in order to track the complex chain of climate impacts and identify key vulnerabilities, feedbacks and uncertainties in managing future risk. CGRA proof-of-concept results show that, at the global scale, there are mixed areas of positive and negative simulated wheat and maize yield changes, with declines in some breadbasket regions, at both 1.5°C and 2.0°C. Declines are especially evident in simulations that do not take into account direct CO 2 effects on crops. These projected global yield changes mostly resulted in increases in prices and areas of wheat and maize in two global economics models. Regional simulations for 1.5°C and 2.0°C using site-based crop models had mixed results depending on the region and the crop. In conjunction with price changes from the global economics models, productivity declines in the Punjab, Pakistan, resulted in an increase in vulnerable households and the poverty rate.This article is part of the theme issue 'The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'. © 2018 The Authors.

The 'Blue-Shift' in midlatitude dynamics in a Changing Climate

NASA Astrophysics Data System (ADS)

Carvalho, L. V.

2013-12-01

Global surface temperature variations and changes result from intricate interplay of phenomena varying on scales ranging from fraction of seconds (turbulence) to thousands of years (e.g. glaciations). To complicate these issues further, the contribution of the anthropogenic forcing on the observed changes in surface temperatures varies over time and is spatially non-uniform. While evaluating all individual bands of this broad spectrum is virtually impossible, the availability of global daily datasets in the last few decades from reanalyses and Global Climate Models (GCMs) simulations allows estimating the contribution of phenomena varying on synoptic-to-interannual timescales. Previous studies using GCM simulations for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment (IPCC AR4) have documented a consistent poleward shift in the storm tracks related to changes in baroclinicity resulting from global warming. However, our recent research (Cannon et al. 2013) indicated that the pattern of changes in the storm tracks observed in the last few decades is much more complex in both space and time. Complex terrain and the relative distribution of continents, oceans and icecaps play a significant role for changes in synoptic activity. Coupled modes such as the Northern and Southern annular modes, the El Nino-Southern Oscillation (ENSO) and respective teleconnections with changes in baroclinicity have been identified as relevant dynamical forcings for variations of the midlatitude storm tracks, increasing the uncertainties in future projections. Moreover, global warming has modified the amplitude of the annual cycles of temperature, moisture and circulation throughout the planet and there is strong indication that these changes have mostly affected the tropics and Polar Regions. The present study advances these findings by investigating the 'blue-shift' in the underlying dynamics causing surface temperature anomalies and investigates relationships with low and upper level circulation. This research uses two sources of data: global daily Climate Forecast System Reanalysis (CFSR) (1979- 2010) and the Geophysical Fluid Dynamics Laboratory (GFDL) global daily simulations from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Two sets of simulations are investigated: the Historic and Pi-control runs. Here the term ';blue-shift' is used to indicate long-term increase in the amplitude of the synoptic scale relatively to the annual cycle amplitude derived from wavelet analysis as an analogy to the definition commonly used in physics (i.e., a shift toward shorter wavelengths of the spectral lines). It is shown that the blue-shift has been observed in midlatitudes of some continental areas of the Northern Hemisphere and North Pacific but in relatively higher latitudes in the Southern Hemisphere. Tropical areas and high latitudes of the Northern Hemisphere have experienced opposite trend (red-shift). Moreover, the pattern of the blue and red-shifts exhibits seasonal changes. References: Cannon, F., L. M. V. Carvalho, C. Jones, B. Bookhagen, 2013: Multi-Annual Variations in Winter Westerly Disturbance Activity Affecting the Himalaya. Submitted to Climate Dynamics

Tail reconnection in the global magnetospheric context: Vlasiator first results

NASA Astrophysics Data System (ADS)

Palmroth, Minna; Hoilijoki, Sanni; Juusola, Liisa; Pulkkinen, Tuija I.; Hietala, Heli; Pfau-Kempf, Yann; Ganse, Urs; von Alfthan, Sebastian; Vainio, Rami; Hesse, Michael

2017-11-01

The key dynamics of the magnetotail have been researched for decades and have been associated with either three-dimensional (3-D) plasma instabilities and/or magnetic reconnection. We apply a global hybrid-Vlasov code, Vlasiator, to simulate reconnection self-consistently in the ion kinetic scales in the noon-midnight meridional plane, including both dayside and nightside reconnection regions within the same simulation box. Our simulation represents a numerical experiment, which turns off the 3-D instabilities but models ion-scale reconnection physically accurately in 2-D. We demonstrate that many known tail dynamics are present in the simulation without a full description of 3-D instabilities or without the detailed description of the electrons. While multiple reconnection sites can coexist in the plasma sheet, one reconnection point can start a global reconfiguration process, in which magnetic field lines become detached and a plasmoid is released. As the simulation run features temporally steady solar wind input, this global reconfiguration is not associated with sudden changes in the solar wind. Further, we show that lobe density variations originating from dayside reconnection may play an important role in stabilising tail reconnection.

A Projection of Changes in Landfilling Atmospheric River Frequency and Extreme Precipitation over Western North America from the Large Ensemble CESM Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagos, Samson M.; Leung, Lai-Yung R.; Yoon, Jin-Ho

Simulations from the Community Earth System Model Large Ensemble project are analyzed to investigate the impact of global warming on atmospheric rivers (ARs). The model has notable biases in simulating the subtropical jet position and the relationship between extreme precipitation and moisture transport. After accounting for these biases, the model projects an ensemble mean increase of 35% in the number of landfalling AR days between the last twenty years of the 20th and 21st centuries. However, the number of AR associated extreme precipitation days increases only by 28% because the moisture transport required to produce extreme precipitation also increases withmore » warming. Internal variability introduces an uncertainty of ±8% and ±7% in the projected changes in AR days and associated extreme precipitation days. In contrast, accountings for model biases only change the projected changes by about 1%. The significantly larger mean changes compared to internal variability and to the effects of model biases highlight the robustness of AR responses to global warming.« less

Regional climate change predictions from the Goddard Institute for Space Studies high resolution GCM

NASA Technical Reports Server (NTRS)

Crane, Robert G.; Hewitson, Bruce

1990-01-01

Model simulations of global climate change are seen as an essential component of any program aimed at understanding human impact on the global environment. A major weakness of current general circulation models (GCMs), however, is their inability to predict reliably the regional consequences of a global scale change, and it is these regional scale predictions that are necessary for studies of human/environmental response. This research is directed toward the development of a methodology for the validation of the synoptic scale climatology of GCMs. This is developed with regard to the Goddard Institute for Space Studies (GISS) GCM Model 2, with the specific objective of using the synoptic circulation form a doubles CO2 simulation to estimate regional climate change over North America, south of Hudson Bay. This progress report is specifically concerned with validating the synoptic climatology of the GISS GCM, and developing the transfer function to derive grid-point temperatures from the synoptic circulation. Principal Components Analysis is used to characterize the primary modes of the spatial and temporal variability in the observed and simulated climate, and the model validation is based on correlations between component loadings, and power spectral analysis of the component scores. The results show that the high resolution GISS model does an excellent job of simulating the synoptic circulation over the U.S., and that grid-point temperatures can be predicted with reasonable accuracy from the circulation patterns.

Does air-sea coupling influence model projections of the effects of the Paris Agreement?

NASA Astrophysics Data System (ADS)

Klingaman, Nicholas; Suckling, Emma; Sutton, Rowan; Dong, Buwen

2017-04-01

The 2015 Paris Agreement includes the long-term goal to hold global-mean temperature to "well below 2°C above pre-industrial levels", with the further stated aim of limiting the global-mean warming to 1.5°C, in the belief that this would "significantly reduce the risks and impacts of climate change". However, it is not clear which risks and impacts would be avoided, or reduced, by achieving a 1.5°C warming instead of a 2.0°C warming. Initial efforts to quantify changes in risk have focused on analysis of existing CMIP5 simulations at levels of global-mean warming close to 1.5°C or 2.0°C, by taking averages over ≈20 year periods. This framework suffers from several drawbacks, however, including the effect of model internal multi-decadal variability, the influence of coupled-model systematic errors on regional circulation patterns, and the presence of a warming trend across the averaging period (i.e., the model is not in steady state). To address these issues, the "Half a degree Additional warming, Prognosis and Projected Impacts" (HAPPI) project is performing large ensembles of atmosphere-only experiments with prescribed sea-surface temperatures (SSTs) for present-day and 1.5°C and 2.0°C scenarios. While these experiments reduce the complications from a limited dataset and coupled-model systematic errors, the use of atmosphere-only models neglects feedbacks between the atmosphere and ocean, which may have substantial effects on the representation of local and regional extremes, and hence on the response of these extremes to global-mean warming. We introduce a set of atmosphere-ocean coupled simulations that incorporate much of the HAPPI experiment design, yet retain a representation of air-sea feedbacks. We use the Met Office Unified Model Global Ocean Mixed Layer (MetUM-GOML) model, which comprises the MetUM atmospheric model coupled to many columns of the one-dimensional K Profile Parameterization mixed-layer ocean. Critically, the MetUM-GOML ocean mean state can be controlled by prescribed, seasonally varying corrections to temperature and salinity, which substantially reduce SST biases without damping variability. This allows the present-day MetUM-GOML experiment to have a ocean mean state very close to the observed climatology (global RMSE ≈ 0.25°C). We perform three 150-year experiments with MetUM-GOML for (a) present-day (1976-2005 climatology) and for future scenarios with global-mean temperatures (b) 1.5°C and (c) 2.0°C above pre-industrial levels. For (b) and (c), we achieve these warming levels by increasing the CO2 concentrations in MetUM-GOML, as well as by adjusting the prescribed sea ice using change factors derived from a transient simulation with the fully coupled Met Office model. We analyse projected global and regional changes in temperature, precipitation and atmospheric circulation in our MetUM-GOML simulations, focusing on seasonal means, multi-annual persistence of seasonal extremes (e.g., the probability of consecutive wet summers) and intra-seasonal extremes (e.g., heatwaves, droughts, floods). To identify the influence of air-sea coupling on these projections, we compare the MetUM-GOML simulations to 150-year atmosphere-only simulations with prescribed daily SSTs from the corresponding MetUM-GOML runs. This comparison demonstrates whether atmosphere-ocean feedbacks influence the projections of changes hydro-meteorological extremes in a warmer world, as well as whether these feedbacks affect the assessment of the impacts avoided by limiting global-mean temperature change to 1.5°C. Our results will inform the choice of model framework for, and hence the experiment design of, further efforts to characterise the response to a fixed global-mean temperature increase, as well as future climate-change attribution experiments.

Changes on Mid-Latitude Cyclones due to Global Warming Simulated by a Global 20-km-mesh Atmospheric Model

NASA Astrophysics Data System (ADS)

Miyamoto, K.

2005-12-01

I investigate how the intensity and the activity of mid-latitude cyclones change as a result of global warming, based on a time-slice experiment with a super-high resolution Atmospheric General Circulation Model (20-km mesh TL959L60 MRI/JMA AGCM). The model was developed by the RR2002 project "Development of Super High Resolution Global and Regional Climate Models" funded by the Japanese Ministry of Education, Culture, Sports, Science and Technology. In this context, I use a 10-year control simulation with the climatological SST and a 10-year time-slice global warming simulation using the SST anomalies derived from the SRES A1B scenario run with the MRI-CGCM2.3 (T42L30 atmosphere, 0.5-2.0 x 2.5 L23 ocean) corresponding to the end of the 21st century. I have analyzed the sea-level pressure field and the kinetic energy field of the wind at the 500 hPa pressure level associated with mid-latitude transients from October through April. According to a comparison of 10-day average fields between present and future in the North Pacific, some statistically significant changes are found in a warmer climate for the both of sea-level pressure and the kinetic energy fields. In particular, from late winter through early spring, the sea-level pressure decreases on many parts of the whole Pacific. The kinetic energy of the wind becomes higher on center of the basin. Therefore, I suppose the Aleutian Low is likely to settle in longer by about one month than the present. Hereafter, I plan to investigate what kind of phenomena may accompany the changes on mid-latitude transients.

CYCLIC THERMAL SIGNATURE IN A GLOBAL MHD SIMULATION OF SOLAR CONVECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cossette, Jean-Francois; Charbonneau, Paul; Smolarkiewicz, Piotr K.

Global magnetohydrodynamical simulations of the solar convection zone have recently achieved cyclic large-scale axisymmetric magnetic fields undergoing polarity reversals on a decadal time scale. In this Letter, we show that these simulations also display a thermal convective luminosity that varies in-phase with the magnetic cycle, and trace this modulation to deep-seated magnetically mediated changes in convective flow patterns. Within the context of the ongoing debate on the physical origin of the observed 11 yr variations in total solar irradiance, such a signature supports the thesis according to which all, or part, of the variations on decadal time scales and longermore » could be attributed to a global modulation of the Sun's internal thermal structure by magnetic activity.« less

Changes in regional climate extremes as a function of global mean temperature: an interactive plotting framework

NASA Astrophysics Data System (ADS)

Wartenburger, Richard; Hirschi, Martin; Donat, Markus G.; Greve, Peter; Pitman, Andy J.; Seneviratne, Sonia I.

2017-09-01

This article extends a previous study Seneviratne et al. (2016) to provide regional analyses of changes in climate extremes as a function of projected changes in global mean temperature. We introduce the DROUGHT-HEAT Regional Climate Atlas, an interactive tool to analyse and display a range of well-established climate extremes and water-cycle indices and their changes as a function of global warming. These projections are based on simulations from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). A selection of example results are presented here, but users can visualize specific indices of interest using the online tool. This implementation enables a direct assessment of regional climate changes associated with global mean temperature targets, such as the 2 and 1.5° limits agreed within the 2015 Paris Agreement.

Global River Water Temperature Modelling at Hyper-Resolution

NASA Astrophysics Data System (ADS)

Wanders, N.; van Vliet, M. T. H.; Wada, Y.; Van Beek, L. P.

2017-12-01

The temperature of river water plays a crucial role in many physical, chemical and biological aquatic processes. The influence of changing water temperatures is not only felt locally, but also has regional and downstream impacts. Sectors that might be affected by sudden or gradual changes in the water temperature are: energy production, industry and recreation. Although it is very important to have detailed information on this environmental variable, high-resolution simulations of water temperature on a large scale are currently lacking. Here we present a novel hyper-resolution water temperature dataset at the global scale. We developed the 1-D energy routing model WARM, to simulate river temperature for the period 1980-2014 at 10 km and 50 km resolution. The WARM model accounts for surface water abstraction, reservoirs, riverine flooding and formation of ice, therefore enabling a realistic representation of the water temperature. The water temperature simulations have been validated against 358 river monitoring stations globally for the period 1980 to 2014. The results indicate the increase in resolution significantly improves the simulation performance with a decrease in the water temperature RMSE from 3.5°C to 3.0°C and an increase in the mean correlation of the daily discharge simulations, from R=0.4 to 0.6. We find an average global increase in water temperature of 0.22°C per decade between 1960-2014, with increasing trends towards the end of the simulations period. Strong increasing trends in maxima in the Northern Hemisphere (0.62°C per decade) and minima in the Southern Hemisphere (0.45°C per decade). Finally, we show the impact of major heatwaves and drought events on the water temperature and water availability. The high resolution not only improves the model performance; it also positively impacts the relevancy of the simulation for local and regional scale studies and impact assessments. This new global water temperature dataset could help to develop decision-support system related to water quality with increasing precision and accuracy.

Reconstructing a lost Eocene paradise: Part I. Simulating the change in global floral distribution at the initial Eocene thermal maximum

NASA Astrophysics Data System (ADS)

Shellito, Cindy J.; Sloan, Lisa C.

2006-02-01

This study utilizes the NCAR Land Surface Model (LSM1.2) integrated with dynamic global vegetation to recreate the early Paleogene global distribution of vegetation and to examine the response of the vegetation distribution to changes in climate at the Paleocene-Eocene boundary (˜ 55 Ma). We run two simulations with Eocene geography driven by climatologies generated in two atmosphere global modeling experiments: one with atmospheric pCO 2 at 560 ppm, and another at 1120 ppm. In both scenarios, the model produces the best match with fossil flora in the low latitudes. A comparison of model output from the two scenarios suggests that the greatest impact of climate on vegetation will occur in the high latitudes, in the Arctic Circle and in Antarctica. In these regions, greater accumulated summertime warmth in the 1120 ppm simulation allows temperate plant functional types to expand further poleward. Additionally, the high pCO 2 scenario produces a greater abundance of trees over grass at these high latitudes. In the middle and low latitudes, the general distribution of plant functional types is similar in both pCO 2 scenarios. Likely, a greater increment of greenhouse gases is necessary to produce the type of change evident in the mid-latitude paleobotanical record. Overall, differences between model output and fossil flora are greatest at high latitudes.

Multi-Model Simulations of Aerosol and Ozone Radiative Forcing Due to Anthropogenic Emission Changes During the Period 1990-2015

NASA Technical Reports Server (NTRS)

Myhre, Gunnar; Aas, Wenche; Ribu, Cherian; Collins, William; Faluvegi, Gregory S.; Flanner, Mark; Forster, Piers; Hodnebrog, Oivind; Klimont, Zbigniew; Lund, Marianne T.

2017-01-01

Over the past few decades, the geographical distribution of emissions of substances that alter the atmospheric energy balance has changed due to economic growth and air pollution regulations. Here, we show the resulting changes to aerosol and ozone abundances and their radiative forcing using recently updated emission data for the period 1990-2015, as simulated by seven global atmospheric composition models. The models broadly reproduce large-scale changes in surface aerosol and ozone based on observations (e.g. 1 to 3 percent per year in aerosols over the USA and Europe). The global mean radiative forcing due to ozone and aerosol changes over the 1990-2015 period increased by 0.17 plus or minus 0.08 watts per square meter, with approximately one-third due to ozone. This increase is more strongly positive than that reported in IPCC AR5 (Intergovernmental Panel on Climate Change Fifth Assessment Report). The main reasons for the increased positive radiative forcing of aerosols over this period are the substantial reduction of global mean SO2 emissions, which is stronger in the new emission inventory compared to that used in the IPCC analysis, and higher black carbon emissions.

Global climate change and US agriculture

NASA Technical Reports Server (NTRS)

Adams, Richard M.; Rosenzweig, Cynthia; Peart, Robert M.; Ritchie, Joe T.; Mccarl, Bruce A.

1990-01-01

Agricultural productivity is expected to be sensitive to global climate change. Models from atmospheric science, plant science, and agricultural economics are linked to explore this sensitivity. Although the results depend on the severity of climate change and the compensating effects of carbon dioxide on crop yields, the simulation suggests that irrigated acreage will expand and regional patterns of U.S. agriculture will shift. The impact of the U.S. economy strongly depends on which climate model is used.

Probabilistic Change of Wheat Productivity and Water Use in China

NASA Astrophysics Data System (ADS)

Liu, Yujie; Chen, Qiaomin

2017-04-01

Impacts of climate change on agriculture are a major concern worldwide, but uncertainties of climate models and emission scenarios may hamper efforts to adapt to climate change. In this paper, a probabilistic approach is used to estimate the uncertainties and simulate impacts of global warming on wheat production and water use in the main wheat cultivation regions of China, with a global mean temperature (GMT) increase scale relative to 1961-90 values. From output of 20 climate scenarios of the Intergovernmental Panel on Climate Change Data Distribution Centre, median values of projected changes in monthly mean climate variables for representative stations are adapted. These are used to drive the Crop Environment Resource Synthesis (CERES)-Wheat model to simulate wheat production and water use under baseline and global warming scenarios, with and without consideration of carbon dioxide (CO2) fertilization effects. Results show that, because of temperature increase, projected wheat-growing periods for GMT changes of 18, 28, and 38C would shorten, with averaged median values of 3.94%, 6.90%, and 9.67%, respectively. There is a high probability of decreasing (increasing) changes in yield and water-use efficiency under higher temperature scenarios without (with) consideration of CO2 fertilization effects. Elevated CO2 concentration generally compensates for the negative effects of warming temperatures on production. Moreover, positive effects of elevated CO2 concentration on grain yield increase with warming temperatures. The findings could be critical for climate-change-driven agricultural production that ensures global food security.

Early-Holocene warming in Beringia and its mediation by sea-level and vegetation changes

USGS Publications Warehouse

Bartlein, P.J.; Edwards, M.E.; Hostetler, Steven W.; Shafer, Sarah; Anderson, P.M.; Brubaker, L. B; Lozhkin, A. V

2015-01-01

Arctic land-cover changes induced by recent global climate change (e.g., expansion of woody vegetation into tundra and effects of permafrost degradation) are expected to generate further feedbacks to the climate system. Past changes can be used to assess our understanding of feedback mechanisms through a combination of process modeling and paleo-observations. The subcontinental region of Beringia (northeastern Siberia, Alaska, and northwestern Canada) was largely ice-free at the peak of deglacial warming and experienced both major vegetation change and loss of permafrost when many arctic regions were still ice covered. The evolution of Beringian climate at this time was largely driven by global features, such as the amplified seasonal cycle of Northern Hemisphere insolation and changes in global ice volume and atmospheric composition, but changes in regional land-surface controls, such as the widespread development of thaw lakes, the replacement of tundra by deciduous forest or woodland, and the flooding of the Bering–Chukchi land bridge, were probably also important. We examined the sensitivity of Beringia's early Holocene climate to these regional-scale controls using a regional climate model (RegCM). Lateral and oceanic boundary conditions were provided by global climate simulations conducted using the GENESIS V2.01 atmospheric general circulation model (AGCM) with a mixed-layer ocean. We carried out two present-day simulations of regional climate – one with modern and one with 11 ka geography – plus another simulation for 6 ka. In addition, we performed five ~ 11 ka climate simulations, each driven by the same global AGCM boundary conditions: (i) 11 ka Control, which represents conditions just prior to the major transitions (exposed land bridge, no thaw lakes or wetlands, widespread tundra vegetation), (ii) sea-level rise, which employed present-day continental outlines, (iii) vegetation change, with deciduous needleleaf and deciduous broadleaf boreal vegetation types distributed as suggested by the paleoecological record, (iv) thaw lakes, which used the present-day distribution of lakes and wetlands, and (v) post-11 ka All, incorporating all boundary conditions changed in experiments (ii)–(iv). We find that regional-scale controls strongly mediate the climate responses to changes in the large-scale controls, amplifying them in some cases, damping them in others, and, overall, generating considerable spatial heterogeneity in the simulated climate changes. The change from tundra to deciduous woodland produces additional widespread warming in spring and early summer over that induced by the 11 ka insolation regime alone, and lakes and wetlands produce modest and localized cooling in summer and warming in winter. The greatest effect is the flooding of the land bridge and shelves, which produces generally cooler conditions in summer but warmer conditions in winter and is most clearly manifest on the flooded shelves and in eastern Beringia. By 6 ka continued amplification of the seasonal cycle of insolation and loss of the Laurentide ice sheet produce temperatures similar to or higher than those at 11 ka, plus a longer growing season.

Global Sensitivity of Simulated Water Balance Indicators Under Future Climate Change in the Colorado Basin

NASA Astrophysics Data System (ADS)

Bennett, Katrina E.; Urrego Blanco, Jorge R.; Jonko, Alexandra; Bohn, Theodore J.; Atchley, Adam L.; Urban, Nathan M.; Middleton, Richard S.

2018-01-01

The Colorado River Basin is a fundamentally important river for society, ecology, and energy in the United States. Streamflow estimates are often provided using modeling tools which rely on uncertain parameters; sensitivity analysis can help determine which parameters impact model results. Despite the fact that simulated flows respond to changing climate and vegetation in the basin, parameter sensitivity of the simulations under climate change has rarely been considered. In this study, we conduct a global sensitivity analysis to relate changes in runoff, evapotranspiration, snow water equivalent, and soil moisture to model parameters in the Variable Infiltration Capacity (VIC) hydrologic model. We combine global sensitivity analysis with a space-filling Latin Hypercube Sampling of the model parameter space and statistical emulation of the VIC model to examine sensitivities to uncertainties in 46 model parameters following a variance-based approach. We find that snow-dominated regions are much more sensitive to uncertainties in VIC parameters. Although baseflow and runoff changes respond to parameters used in previous sensitivity studies, we discover new key parameter sensitivities. For instance, changes in runoff and evapotranspiration are sensitive to albedo, while changes in snow water equivalent are sensitive to canopy fraction and Leaf Area Index (LAI) in the VIC model. It is critical for improved modeling to narrow uncertainty in these parameters through improved observations and field studies. This is important because LAI and albedo are anticipated to change under future climate and narrowing uncertainty is paramount to advance our application of models such as VIC for water resource management.

Malaria and global change: Insights, uncertainties and possible surprises

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martin, P.H.; Steel, A.

Malaria may change with global change. Indeed, global change may affect malaria risk and malaria epidemiology. Malaria risk may change in response to a greenhouse warming; malaria epidemiology, in response to the social, economic, and political developments which a greenhouse warming may trigger. To date, malaria receptivity and epidemiology futures have been explored within the context of equilibrium studies. Equilibrium studies of climate change postulate an equilibrium present climate (the starting point) and a doubled-carbon dioxide climate (the end point), simulate conditions in both instances, and compare the two. What happens while climate changes, i.e., between the starting point andmore » the end point, is ignored. The present paper focuses on malaria receptivity and addresses what equilibrium studies miss, namely transient malaria dynamics.« less

Meridional Circulation Dynamics from 3D Magnetohydrodynamic Global Simulations of Solar Convection

NASA Astrophysics Data System (ADS)

Passos, Dário; Charbonneau, Paul; Miesch, Mark

2015-02-01

The form of solar meridional circulation is a very important ingredient for mean field flux transport dynamo models. However, a shroud of mystery still surrounds this large-scale flow, given that its measurement using current helioseismic techniques is challenging. In this work, we use results from three-dimensional global simulations of solar convection to infer the dynamical behavior of the established meridional circulation. We make a direct comparison between the meridional circulation that arises in these simulations and the latest observations. Based on our results, we argue that there should be an equatorward flow at the base of the convection zone at mid-latitudes, below the current maximum depth helioseismic measures can probe (0.75 {{R}⊙ }). We also provide physical arguments to justify this behavior. The simulations indicate that the meridional circulation undergoes substantial changes in morphology as the magnetic cycle unfolds. We close by discussing the importance of these dynamical changes for current methods of observation which involve long averaging periods of helioseismic data. Also noteworthy is the fact that these topological changes indicate a rich interaction between magnetic fields and plasma flows, which challenges the ubiquitous kinematic approach used in the vast majority of mean field dynamo simulations.

Ocean-Atmosphere Interactions Modulate Irrigation's Climate Impacts

NASA Technical Reports Server (NTRS)

Krakauer, Nir Y.; Puma, Michael J.; Cook, Benjamin I.; Gentine, Pierre; Nazarenko, Larissa

2016-01-01

Numerous studies have focused on the local and regional climate effects of irrigated agriculture and other land cover and land use change (LCLUC) phenomena, but there are few studies on the role of ocean- atmosphere interaction in modulating irrigation climate impacts. Here, we compare simulations with and without interactive sea surface temperatures of the equilibrium effect on climate of contemporary (year 2000) irrigation geographic extent and intensity. We find that ocean-atmosphere interaction does impact the magnitude of global-mean and spatially varying climate impacts, greatly increasing their global reach. Local climate effects in the irrigated regions remain broadly similar, while non-local effects, particularly over the oceans, tend to be larger. The interaction amplifies irrigation-driven standing wave patterns in the tropics and mid-latitudes in our simulations, approximately doubling the global-mean amplitude of surface temperature changes due to irrigation. The fractions of global area experiencing significant annual-mean surface air temperature and precipitation change also approximately double with ocean-atmosphere interaction. Subject to confirmation with other models, these findings imply that LCLUC is an important contributor to climate change even in remote areas such as the Southern Ocean, and that attribution studies should include interactive oceans and need to consider LCLUC, including irrigation, as a truly global forcing that affects climate and the water cycle over ocean as well as land areas.

Exploring the Mass Balance and Sea Level Contribution of Global Glaciers During the Last Interglaciation and Mid-Holocene

NASA Astrophysics Data System (ADS)

Smith, S.; Ullman, D. J.; He, F.; Carlson, A. E.; Marzeion, B.; Maussion, F.

2017-12-01

Understanding the behavior of the world's glaciers during previous interglaciations is key to interpreting the sensitivity and behavior of the cryosphere under scenarios of future anthropogenic warming. Previous studies of the Last Interglaciation (LIG, 130 ka to 116 ka) indicate elevated global temperatures and higher sea levels than the Holocene, but most assessments of the impact on the cryosphere have focused on the mass balance and volume change of polar ice sheets. In assessing sea-level sources, most studies assume complete deglacation of global glaciers, but this has yet to be tested. In addition, the significant changes in orbital forcing during the LIG and the associated impacts on climate seasonality and variability may have led to unique glacier evolution.Here, we explore the effect of LIG climate on the global glacier budget. We employ the Open Global Glacier Model (OGGM), forced by simulated LIG equilibrium climate anomalies (127 ka) from the Community Climate System Model Version 3 (CCSM3). OGGM is a glacier mass balance and dynamics model, specifically designed to reconstruct global glacier volume change. Our simulations have been conducted in an equilibrium state to determine the effect of the prolonged climate forcing of the LIG. Due to unknown flow characteristics of glaciers during the LIG, we explore the parametric uncertainty in the mass balance and flow sensitivity parameters. As a point of comparison, we also conduct a series of simulations using forcing anomalies from the CCSM3 mid-Holocene (6 ka) experiment. Results from both experiments show that glacier mass balance is highly sensitive to these sensitivity parameters, pointing at the need for glacier margin calibration for OGGM in paleoclimate applications.

The accuracy of climate models' simulated season lengths and the effectiveness of grid scale correction factors

DOE PAGES

Winterhalter, Wade E.

2011-09-01

Global climate change is expected to impact biological populations through a variety of mechanisms including increases in the length of their growing season. Climate models are useful tools for predicting how season length might change in the future. However, the accuracy of these models tends to be rather low at regional geographic scales. Here, I determined the ability of several atmosphere and ocean general circulating models (AOGCMs) to accurately simulate historical season lengths for a temperate ectotherm across the continental United States. I also evaluated the effectiveness of regional-scale correction factors to improve the accuracy of these models. I foundmore » that both the accuracy of simulated season lengths and the effectiveness of the correction factors to improve the model's accuracy varied geographically and across models. These results suggest that regional specific correction factors do not always adequately remove potential discrepancies between simulated and historically observed environmental parameters. As such, an explicit evaluation of the correction factors' effectiveness should be included in future studies of global climate change's impact on biological populations.« less

Impacts of future radiation management scenarios on terrestrial carbon dynamics simulated with fully coupled NorESM

NASA Astrophysics Data System (ADS)

Ekici, Altug; Tjiputra, Jerry; Grini, Alf; Muri, Helene

2017-04-01

We have simulated 3 different radiation management geoengineering methods (CCT - cirrus cloud thinning; SAI - stratospheric aerosol injection; MSB - marine sky brightening) on top of future RCP8.5 scenario with the fully coupled Norwegian Earth System Model (NorESM). A globally consistent cooling in both atmosphere and soil is observed with all methods. However, precipitation patterns are dependent on the used method. Globally CCT and MSB methods do not affect the vegetation carbon budget, while SAI leads to a loss compared to RCP8.5 simulations. Spatially the most sensitive region is the tropics. Here, the changes in vegetation carbon content are related to the precipitation changes. Increase in soil carbon is projected in all three methods, the biggest change seen in SAI method. Simulations with CCT method leads to twice as much soil carbon retention in the tropics compared to the MSB method. Our findings show that there are unforeseen regional consequences of such geoengineering methods in the biogeochemical cycles and they should be considered with care in future climate policies.

The Role of Atmospheric Deposition on the Input of Trace Elements to the Surface Ocean: the Bermuda Wet and Dry Record

NASA Astrophysics Data System (ADS)

Church, T. M.; Sedwick, P. N.; Sholkovitz, E. R.

2011-12-01

Global surface temperature variations and changes result from intricate interplay of phenomena varying on scales ranging from fraction of seconds (turbulence) to thousands of years (e.g. glaciations). To complicate these issues further, the contribution of the anthropogenic forcing on the observed changes in surface temperatures varies over time and is spatially non-uniform. While evaluating all individual bands of this broad spectrum is virtually impossible, the availability of global daily datasets in the last few decades from reanalyses and Global Climate Models (GCMs) simulations allows estimating the contribution of phenomena varying on synoptic-to-interannual timescales. Previous studies using GCM simulations for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment (IPCC AR4) have documented a consistent poleward shift in the storm tracks related to changes in baroclinicity resulting from global warming. However, our recent research (Cannon et al. 2013) indicated that the pattern of changes in the storm tracks observed in the last few decades is much more complex in both space and time. Complex terrain and the relative distribution of continents, oceans and icecaps play a significant role for changes in synoptic activity. Coupled modes such as the Northern and Southern annular modes, the El Nino-Southern Oscillation (ENSO) and respective teleconnections with changes in baroclinicity have been identified as relevant dynamical forcings for variations of the midlatitude storm tracks, increasing the uncertainties in future projections. Moreover, global warming has modified the amplitude of the annual cycles of temperature, moisture and circulation throughout the planet and there is strong indication that these changes have mostly affected the tropics and Polar Regions. The present study advances these findings by investigating the 'blue-shift' in the underlying dynamics causing surface temperature anomalies and investigates relationships with low and upper level circulation. This research uses two sources of data: global daily Climate Forecast System Reanalysis (CFSR) (1979- 2010) and the Geophysical Fluid Dynamics Laboratory (GFDL) global daily simulations from the fifth phase of the Coupled Model Intercomparison Project (CMIP5). Two sets of simulations are investigated: the Historic and Pi-control runs. Here the term ';blue-shift' is used to indicate long-term increase in the amplitude of the synoptic scale relatively to the annual cycle amplitude derived from wavelet analysis as an analogy to the definition commonly used in physics (i.e., a shift toward shorter wavelengths of the spectral lines). It is shown that the blue-shift has been observed in midlatitudes of some continental areas of the Northern Hemisphere and North Pacific but in relatively higher latitudes in the Southern Hemisphere. Tropical areas and high latitudes of the Northern Hemisphere have experienced opposite trend (red-shift). Moreover, the pattern of the blue and red-shifts exhibits seasonal changes. References: Cannon, F., L. M. V. Carvalho, C. Jones, B. Bookhagen, 2013: Multi-Annual Variations in Winter Westerly Disturbance Activity Affecting the Himalaya. Submitted to Climate Dynamics

Modeling global vegetation in the late Quaternary: What progress have we made and what are the priorities for the future?

NASA Astrophysics Data System (ADS)

Kaplan, Jed

2017-04-01

More than two decades ago, the development of the first global biogeography models led to an interest in simulating global land cover in the past. These models promised the possibility of creating a coherent picture of the Earth's vegetation that went beyond qualitative extrapolation of site-based observations, e.g., from paleoecological archives, and was not limited to areas with a high density of sites. Then as now, the goal of much work simulating past vegetation was to explore and understand the role of biogeophysical and biogeochemical feedbacks between the Earth's land surface and the climate system. Paleovegetation modeling for the late Quaternary has also influenced debates on the character of natural vegetation, conservation and ecological restoration goals, and the co-evolution of humans, civilizations, and the landscapes in which they live. The first simulations of global land cover in the past used equilibrium vegetation models, e.g., BIOME1, BIOME3, and BIOME4, and focused on well-known timeslices of interest in paleoclimate research, including the Last Glacial Maximum (21,000 BP) and the mid-Holocene (6,000 BP). Questions addressed included: quantification of the importance of terrestrial vegetation in the glacial carbon cycle, the role of changing vegetation cover on glacial inception, and the influence of biogeophysical feedbacks on the amplitude and spatial pattern of the mid-Holocene African Monsoon. In the intervening years, as both vegetation and climate models evolved and improved, the spatial resolution, number of periods studied, and the type of research questions addressed expanded greatly. Studies covered the dynamics of Arctic vegetation, wetland area, wetland methane emissions, and paleo-atmospheric chemistry, dust emissions and effects on paleoclimate, among others. A major recent advance in paleovegetation modeling for the late Quaternary has come with the development of Dynamic Global Vegetation Models (DGVMs) that are capable of simulating changing vegetation cover over time, continuously. Several DGVMs have been directly incorporated into the land surface scheme of modern Earth System Models (ESMs), further allowing the exploration of land-atmosphere feedbacks, e.g., during abrupt climate change events, such as those that occurred during the last deglaciation. Recent increases in computer power have also allowed offline simulations, i.e., not directly coupled to an ESM, with DGVMs to simulate vegetation change over long time periods, e.g., continuously for the entire Holocene. Realizing that climate change alone was not the only driver of land cover change over the late Quaternary, the most recent developments in paleovegetation modeling for this period have incorporated human agency as an influence on vegetation. Incorporation of scenarios of Anthropogenic Land Cover Change into DGVMs has allowed a quantitative contribution to the ongoing, lively debate regarding the role of humans in influencing Holocene atmospheric greenhouse gas concentrations. With the further advances in ESMs and the availability of very long climate model simulations, e.g., TraCE-21ka, improvements to DGVMs such as the explicit representation of age structure and plant traits, and the increasing awareness of the importance of human-environment interactions, the future of paleovegetation modeling for the late Quaternary presents a variety of opportunities. One important focus for future modeling should be on simulating the dynamics of ecotones, e.g., forest-grassland boundaries, over time, particularly during abrupt transient climate change events. Accurate simulation of ecotone boundaries is traditionally a weakness in DGVMs, yet these environments are highly valued by humans for their ecosystem services both at present and in the past, paleoecological evidence suggests that ecotone boundaries were very sensitive to past climate change, and they are critical locations where land-atmosphere feedbacks could have amplified or attenuated ongoing, externally-forced climate change. Lessons drawn from paleovegetation simulations may shed new light on the behavior of the earth system that will be valuable for understanding the future.

Changes in Concurrent Precipitation and Temperature Extremes

DOE PAGES

Hao, Zengchao; AghaKouchak, Amir; Phillips, Thomas J.

2013-08-01

While numerous studies have addressed changes in climate extremes, analyses of concurrence of climate extremes are scarce, and climate change effects on joint extremes are rarely considered. This study assesses the occurrence of joint (concurrent) monthly continental precipitation and temperature extremes in Climate Research Unit (CRU) and University of Delaware (UD) observations, and in 13 Coupled Model Intercomparison Project Phase 5 (CMIP5) global climate simulations. Moreover, the joint occurrences of precipitation and temperature extremes simulated by CMIP5 climate models are compared with those derived from the CRU and UD observations for warm/wet, warm/dry, cold/wet, and cold/dry combinations of joint extremes.more » The number of occurrences of these four combinations during the second half of the 20th century (1951–2004) is assessed on a common global grid. CRU and UD observations show substantial increases in the occurrence of joint warm/dry and warm/wet combinations for the period 1978–2004 relative to 1951–1977. The results show that with respect to the sign of change in the concurrent extremes, the CMIP5 climate model simulations are in reasonable overall agreement with observations. The results reveal notable discrepancies between regional patterns and the magnitude of change in individual climate model simulations relative to the observations of precipitation and temperature.« less

Assessing Climate Change Risks Using a Multi-Model Approach

NASA Astrophysics Data System (ADS)

Knorr, W.; Scholze, M.; Prentice, C.

2007-12-01

We quantify the risks of climate-induced changes in key ecosystem processes during the 21st century by forcing a dynamic global vegetation model with multiple scenarios from the IPCC AR4 data archive using 16 climate models and mapping the proportions of model runs showing exceedance of natural variability in wildfire frequency and freshwater supply or shifts in vegetation cover. Our analysis does not assign probabilities to scenarios. Instead, we consider the distribution of outcomes within three sets of model runs grouped according to the amount of global warming they simulate: < 2 degree C (including committed climate change simulations), 2-3 degree C, and >3 degree C. Here, we are contrasting two different methods for calculating the risks: first we use an equal weighting approach giving every model within one of the three sets the same weight, and second, we weight the models according to their ability to model ENSO. The differences are underpinning the need for the development of more robust performance metrics for global climate models.

Global and Arctic climate engineering: numerical model studies.

PubMed

Caldeira, Ken; Wood, Lowell

2008-11-13

We perform numerical simulations of the atmosphere, sea ice and upper ocean to examine possible effects of diminishing incoming solar radiation, insolation, on the climate system. We simulate both global and Arctic climate engineering in idealized scenarios in which insolation is diminished above the top of the atmosphere. We consider the Arctic scenarios because climate change is manifesting most strongly there. Our results indicate that, while such simple insolation modulation is unlikely to perfectly reverse the effects of greenhouse gas warming, over a broad range of measures considering both temperature and water, an engineered high CO2 climate can be made much more similar to the low CO2 climate than would be a high CO2 climate in the absence of such engineering. At high latitudes, there is less sunlight deflected per unit albedo change but climate system feedbacks operate more powerfully there. These two effects largely cancel each other, making the global mean temperature response per unit top-of-atmosphere albedo change relatively insensitive to latitude. Implementing insolation modulation appears to be feasible.

Representing anthropogenic gross land use change, wood harvest, and forest age dynamics in a global vegetation model ORCHIDEE-MICT v8.4.2

NASA Astrophysics Data System (ADS)

Yue, Chao; Ciais, Philippe; Luyssaert, Sebastiaan; Li, Wei; McGrath, Matthew J.; Chang, Jinfeng; Peng, Shushi

2018-01-01

Land use change (LUC) is among the main anthropogenic disturbances in the global carbon cycle. Here we present the model developments in a global dynamic vegetation model ORCHIDEE-MICT v8.4.2 for a more realistic representation of LUC processes. First, we included gross land use change (primarily shifting cultivation) and forest wood harvest in addition to net land use change. Second, we included sub-grid evenly aged land cohorts to represent secondary forests and to keep track of the transient stage of agricultural lands since LUC. Combination of these two features allows the simulation of shifting cultivation with a rotation length involving mainly secondary forests instead of primary ones. Furthermore, a set of decision rules regarding the land cohorts to be targeted in different LUC processes have been implemented. Idealized site-scale simulation has been performed for miombo woodlands in southern Africa assuming an annual land turnover rate of 5 % grid cell area between forest and cropland. The result shows that the model can correctly represent forest recovery and cohort aging arising from agricultural abandonment. Such a land turnover process, even though without a net change in land cover, yields carbon emissions largely due to the imbalance between the fast release from forest clearing and the slow uptake from agricultural abandonment. The simulation with sub-grid land cohorts gives lower emissions than without, mainly because the cleared secondary forests have a lower biomass carbon stock than the mature forests that are otherwise cleared when sub-grid land cohorts are not considered. Over the region of southern Africa, the model is able to account for changes in different forest cohort areas along with the historical changes in different LUC activities, including regrowth of old forests when LUC area decreases. Our developments provide possibilities to account for continental or global forest demographic change resulting from past anthropogenic and natural disturbances.

The implications of rebasing global mean temperature timeseries for GCM based climate projections

NASA Astrophysics Data System (ADS)

Stainforth, David; Chapman, Sandra; Watkins, Nicholas

2017-04-01

Global climate and earth system models are assessed by comparison with observations through a number of metrics. The InterGovernmental Panel on Climate Change (IPCC) highlights in particular their ability to reproduce "general features of the global and annual mean surface temperature changes over the historical period" [1,2] and to simulate "a trend in global-mean surface temperature from 1951 to 2012 that agrees with the observed trend" [3]. This focus on annual mean global mean temperature (hereafter GMT) change is presented as an important element in demonstrating the relevance of these models for climate projections. Any new model or new model version whose historic simulations fail to reproduce the "general features " and 20th century trends is likely therefore to undergo further tuning. Thus this focus could have implications for model development. Here we consider a formal interpretation of "general features" and discuss the implications of this approach to model assessment and intercomparison, for the interpretation of GCM projections. Following the IPCC, we interpret a major element of "general features" as being the slow timescale response to external forcings. (Shorter timescale behaviour such as the response to volcanic eruptions are also elements of "general features" but are not considered here.) Also following the IPCC, we consider only GMT anomalies i.e. changes with respect to some period. Since the models have absolute temperatures which range over about 3K (roughly observed GMT +/- 1.5K) this means their timeseries (and the observations) are rebased. We present timeseries of the slow timescale response of the CMIP5 models rebased to late-20th century temperatures and to mid-19th century temperatures. We provide a mathematical interpretation of this approach to model assessment and discuss two consequences. First is a separation of scales which limits the degree to which sub-global behaviour can feedback on the global response. Second, is an implication of linearity in the GMT response (to the extent that the slow-timescale response of the historic simulations is consistent with observations, and given their uncertainties). For each individual model these consequences only apply over the range of absolute temperatures simulated by the model in historic simulations. Taken together, however, they imply consequences over a much wider range of GMTs. The analysis suggests that this aspect of model evaluation risks providing a model development pressure which acts against a wide exploration of physically plausible responses; in particular against an exploration of potentially globally significant nonlinear responses and feedbacks. [1] IPCC, Fifth Assessment Report, Working Group 1, Technical Summary: Stocker et al. 2013. [2] IPCC, Fifth Assessment Report, Working Group 1, Chapter 9 - "Evaluation of Climate Models": Flato et al. 2013. [3] IPCC, Fifth Assessment Report, Working Group 1, Summary for Policy Makers: IPCC, 2013.

Southwestern Pine Forests Likely to Disappear

ScienceCinema

McDowell, Nathan

2018-01-16

A new study, led by Los Alamos National Laboratory's Nathan McDowell, suggests that widespread loss of a major forest type, the pine-juniper woodlands of the Southwestern U.S., could be wiped out by the end of this century due to climate change, and that conifers throughout much of the Northern Hemisphere may be on a similar trajectory. New results, reported in the journal Nature Climate Change, suggest that global models may underestimate predictions of forest death. McDowell and his large international team strove to provide the missing pieces of understanding tree death at three levels: plant, regional and global. The team rigorously developed and evaluated multiple process-based and empirical models against experimental results, and then compared these models to results from global vegetation models to examine independent simulations. They discovered that the global models simulated mortality throughout the Northern Hemisphere that was of similar magnitude, but much broader spatial scale, as the evaluated ecosystem models predicted for in the Southwest.

Southwestern Pine Forests Likely to Disappear

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDowell, Nathan

A new study, led by Los Alamos National Laboratory's Nathan McDowell, suggests that widespread loss of a major forest type, the pine-juniper woodlands of the Southwestern U.S., could be wiped out by the end of this century due to climate change, and that conifers throughout much of the Northern Hemisphere may be on a similar trajectory. New results, reported in the journal Nature Climate Change, suggest that global models may underestimate predictions of forest death. McDowell and his large international team strove to provide the missing pieces of understanding tree death at three levels: plant, regional and global. The teammore » rigorously developed and evaluated multiple process-based and empirical models against experimental results, and then compared these models to results from global vegetation models to examine independent simulations. They discovered that the global models simulated mortality throughout the Northern Hemisphere that was of similar magnitude, but much broader spatial scale, as the evaluated ecosystem models predicted for in the Southwest.« less

Reliability ensemble averaging of 21st century projections of terrestrial net primary productivity reduces global and regional uncertainties

NASA Astrophysics Data System (ADS)

Exbrayat, Jean-François; Bloom, A. Anthony; Falloon, Pete; Ito, Akihiko; Smallman, T. Luke; Williams, Mathew

2018-02-01

Multi-model averaging techniques provide opportunities to extract additional information from large ensembles of simulations. In particular, present-day model skill can be used to evaluate their potential performance in future climate simulations. Multi-model averaging methods have been used extensively in climate and hydrological sciences, but they have not been used to constrain projected plant productivity responses to climate change, which is a major uncertainty in Earth system modelling. Here, we use three global observationally orientated estimates of current net primary productivity (NPP) to perform a reliability ensemble averaging (REA) method using 30 global simulations of the 21st century change in NPP based on the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) business as usual emissions scenario. We find that the three REA methods support an increase in global NPP by the end of the 21st century (2095-2099) compared to 2001-2005, which is 2-3 % stronger than the ensemble ISIMIP mean value of 24.2 Pg C y-1. Using REA also leads to a 45-68 % reduction in the global uncertainty of 21st century NPP projection, which strengthens confidence in the resilience of the CO2 fertilization effect to climate change. This reduction in uncertainty is especially clear for boreal ecosystems although it may be an artefact due to the lack of representation of nutrient limitations on NPP in most models. Conversely, the large uncertainty that remains on the sign of the response of NPP in semi-arid regions points to the need for better observations and model development in these regions.

Particulate Matter and Ozone Prediction and Source Attribution for U.S. Air Quality Management in a Changing World

NASA Astrophysics Data System (ADS)

Sanyal, S.; Wuebbles, D. J.

2017-12-01

In this study, the focus is on how global changes in climate and emissions will affect the U.S. air quality, especially on fine particulate matter and ozone, projecting their future trends and quantifying key source attribution. We are conducting three primary experiments : (1) historical simulations for period 1994-2013 to establish the credibility of the system and refine process-level understanding of U.S. regional air quality; (2) projections for period 2041-2060 to quantify individual and combined impacts of global climate and emissions changes under multiple scenarios; (3) sensitivity analyses to determine future changes in pollution sources and their relative contributions from anthropogenic and natural emissions, long-range pollutant transport, and climate change effects. Here we will present the result from the first experiment with the global model CESM1.2 (with fully coupled chemistry using CAM-chem5) driven by NASA Modern-Era Retrospective analysis for Research and Applications (MERRA) reanalysis data at 0.9o x 1.25o resolution. We will present the comparison between the results from model simulation with observation data from EPA database. Since there is always a challenge in comparing gridded prediction from model data with point data from the observation databases, because the model simulations calculate the average outcome over a grid for a given set of conditions while the stochastic component (e.g. sub-grid variations) embedded in the observations are not accounted for, we are using extensive statistical measure to do the comparison. We will also determine relative contributions from multiscale (local, regional, global) processes, major source regions (Mexico, Canada, Asia, Africa) and types (natural, anthropogenic) and associated uncertainties (climate decadal oscillations/interannual variations, emissions and model structure errors).

Modelling the impact of Global Change on the hydrological system of the Aral Sea basin

NASA Astrophysics Data System (ADS)

Aus der Beek, T.; Voß, F.; Flörke, M.

During the last decades the Aral Sea basin has suffered an enormous depletion of water resources within its lakes and rivers with consequences for society, economy, and nature. Within this model study, Global Change impacts on the Amu Darya and Syr Darya rivers, as well as on the Aral Sea itself, are being analysed for the period 1958-2002. In a first step, a multi-annual data base on crop specific irrigated areas has been set-up, which has then been integrated in the hydrology and water use model WaterGAP3. As a second step, anthropogenic water abstractions have been calculated, which were then assimilated in the simulation of river runoff of the Amu Darya and Syr Darya. The last step includes the simulation of the water balance of the Aral Sea, by taking into account modelled river inflow. Within WaterGAP3, the water use module has been switched on and off to separate the impacts of Climate and Global Change (i.e. water abstractions). Irrigation water abstractions are very well represented by WaterGAP3 and lie within the range of reported values. Modelled river discharge also shows a good fit to observed data, whereas phases are in sync but volumes are slightly overestimated. Simulated volumes of the Aral Sea itself are well reflected by the model, though results for the period 1990-2002 are too high. In this study, the Climate Change impacts are much smaller (14%) than the water use impacts (86%) on the shrinkage of the Aral Sea. Finally, an outlook on potential scenario model studies is given, which could analyse the different strategies of mitigation and adaptation of Global Change in the Aral Sea basin.

High Resolution Modeling of Hurricanes in a Climate Context

NASA Astrophysics Data System (ADS)

Knutson, T. R.

2007-12-01

Modeling of tropical cyclone activity in a climate context initially focused on simulation of relatively weak tropical storm-like disturbances as resolved by coarse grid (200 km) global models. As computing power has increased, multi-year simulations with global models of grid spacing 20-30 km have become feasible. Increased resolution also allowed for simulation storms of increasing intensity, and some global models generate storms of hurricane strength, depending on their resolution and other factors, although detailed hurricane structure is not simulated realistically. Results from some recent high resolution global model studies are reviewed. An alternative for hurricane simulation is regional downscaling. An early approach was to embed an operational (GFDL) hurricane prediction model within a global model solution, either for 5-day case studies of particular model storm cases, or for "idealized experiments" where an initial vortex is inserted into an idealized environments derived from global model statistics. Using this approach, hurricanes up to category five intensity can be simulated, owing to the model's relatively high resolution (9 km grid) and refined physics. Variants on this approach have been used to provide modeling support for theoretical predictions that greenhouse warming will increase the maximum intensities of hurricanes. These modeling studies also simulate increased hurricane rainfall rates in a warmer climate. The studies do not address hurricane frequency issues, and vertical shear is neglected in the idealized studies. A recent development is the use of regional model dynamical downscaling for extended (e.g., season-length) integrations of hurricane activity. In a study for the Atlantic basin, a non-hydrostatic model with grid spacing of 18km is run without convective parameterization, but with internal spectral nudging toward observed large-scale (basin wavenumbers 0-2) atmospheric conditions from reanalyses. Using this approach, our model reproduces the observed increase in Atlantic hurricane activity (numbers, Accumulated Cyclone Energy (ACE), Power Dissipation Index (PDI), etc.) over the period 1980-2006 fairly realistically, and also simulates ENSO-related interannual variations in hurricane counts. Annual simulated hurricane counts from a two-member ensemble correlate with observed counts at r=0.86. However, the model does not simulate hurricanes as intense as those observed, with minimum central pressures of 937 hPa (category 4) and maximum surface winds of 47 m/s (category 2) being the most intense simulated so far in these experiments. To explore possible impacts of future climate warming on Atlantic hurricane activity, we are re-running the 1980- 2006 seasons, keeping the interannual to multidecadal variations unchanged, but altering the August-October mean climate according to changes simulated by an 18-member ensemble of AR4 climate models (years 2080- 2099, A1B emission scenario). The warmer climate state features higher Atlantic SSTs, and also increased vertical wind shear across the Caribbean (Vecchi and Soden, GRL 2007). A key assumption of this approach is that the 18-model ensemble-mean climate change is the best available projection of future climate change in the Atlantic. Some of the 18 global models show little increase in wind shear, or even a decrease, and thus there will be considerable uncertainty associated with the hurricane frequency results, which will require further exploration. Results from our simulations will be presented at the meeting.

Using Interactive Online Role-Playing Simulations to Develop Global Competency and to Prepare Engineering Students for a Globalised World

ERIC Educational Resources Information Center

May, Dominik; Wold, Kari; Moore, Stephanie

2015-01-01

The world is changing significantly, and it is becoming increasingly globalised. This means that countries, businesses, and professionals must think and act globally to be successful. Many individuals, however, are not prepared with the global competency skills needed to communicate and perform effectively in a globalised system. To address this…

Impact of fire on global land surface air temperature and energy budget for the 20th century due to changes within ecosystems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Fang; Lawrence, David M.; Bond-Lamberty, Ben

Fire is a global phenomenon and tightly interacts with the biosphere and climate. This study provides the first quantitative assessment of fire’s influence on the global land air temperature during the 20th century through its impact on terrestrial ecosystems. We quantify the impact of fire by comparing 20th century fire-on and fire-off simulations with the Community Earth System Model (CESM) as the model platform. Here, results show that fire-induced changes in terrestrial ecosystems increased global land surface air temperature by 0.04 °C. Such changes significantly warmed the tropical savannas and southern Asia mainly by reducing latent heat flux, but cooledmore » Southeast China by enhancing the East Asian winter monsoon. 20% of the early 20th century global land warming can be attributed to fire-induced changes in terrestrial ecosystems, providing a new mechanism for explaining the poorly-understood climate change.« less

Impact of fire on global land surface air temperature and energy budget for the 20th century due to changes within ecosystems

DOE PAGES

Li, Fang; Lawrence, David M.; Bond-Lamberty, Ben

2017-04-03

Fire is a global phenomenon and tightly interacts with the biosphere and climate. This study provides the first quantitative assessment of fire’s influence on the global land air temperature during the 20th century through its impact on terrestrial ecosystems. We quantify the impact of fire by comparing 20th century fire-on and fire-off simulations with the Community Earth System Model (CESM) as the model platform. Here, results show that fire-induced changes in terrestrial ecosystems increased global land surface air temperature by 0.04 °C. Such changes significantly warmed the tropical savannas and southern Asia mainly by reducing latent heat flux, but cooledmore » Southeast China by enhancing the East Asian winter monsoon. 20% of the early 20th century global land warming can be attributed to fire-induced changes in terrestrial ecosystems, providing a new mechanism for explaining the poorly-understood climate change.« less

Coupled model simulations of climate changes in the 20th century and beyond

NASA Astrophysics Data System (ADS)

Yu, Yongqiang; Zhi, Hai; Wang, Bin; Wan, Hui; Li, Chao; Liu, Hailong; Li, Wei; Zheng, Weipeng; Zhou, Tianjun

2008-07-01

Several scenario experiments of the IPCC 4th Assessment Report (AR4) are performed by version g1.0 of a Flexible coupled Ocean-Atmosphere-Land System Model (FGOALS) developed at the Institute of Atmospheric Physics, Chinese Academy of Sciences (IAP/CAS), including the “Climate of the 20th century experiment”, “CO2 1% increase per year to doubling experiment” and two separate IPCC greenhouse gases emission scenarios A1B and B1 experiments. To distinguish between the different impacts of natural variations and human activities on the climate change, three-member ensemble runs are performed for each scenario experiment. The coupled model simulations show: (1) from 1900 to 2000, the global mean temperature increases about 0.5°C and the major increase occurs during the later half of the 20th century, which is in consistent with the observations that highlights the coupled model’s ability to reproduce the climate changes since the industrial revolution; (2) the global mean surface air temperature increases about 1.6°C in the CO2 doubling experiment and 1.5°C and 2.4°C in the A1B and B1 scenarios, respectively. The global warming is indicated by not only the changes of the surface temperature and precipitation but also the temperature increase in the deep ocean. The thermal expansion of the sea water would induce the rise of the global mean sea level. Both the control run and the 20th century climate change run are carried out again with version g1.1 of FGOALS, in which the cold biases in the high latitudes were removed. They are then compared with those from version g1.0 of FGOALS in order to distinguish the effect of the model biases on the simulation of global warming.

The impact of past and future climate change on global human mortality due to ozone and PM2.5 outdoor air pollution

NASA Astrophysics Data System (ADS)

Silva, R.; West, J.; Anenberg, S.; Lamarque, J.; Shindell, D. T.; Bergmann, D. J.; Berntsen, T.; Cameron-Smith, P. J.; Collins, B.; Ghan, S. J.; Josse, B.; Nagashima, T.; Naik, V.; Plummer, D.; Rodriguez, J. M.; Szopa, S.; Zeng, G.

2012-12-01

Climate change can adversely affect air quality, through changes in meteorology, atmospheric chemistry, and emissions. Future changes in air pollutant emissions will also profoundly influence air quality. These changes in air quality can affect human health, as exposure to ground-level ozone and fine particulate matter (PM2.5) has been associated with premature human mortality. Here we will quantify the global mortality impacts of past and future climate change, considering the effects of climate change on air quality isolated from emission changes. The Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP) has simulated the past and future surface concentrations of ozone and PM2.5 from each of several GCMs, for emissions from 1850 ("preindustrial") to 2000 ("present-day"), and for the IPCC AR5 Representative Concentration Pathways (RCPs) scenarios to 2100. We will use ozone and PM2.5 concentrations from simulations from five or more global models of atmospheric dynamics and chemistry, for a base year (present-day), pre-industrial conditions, and future scenarios, considering changes in climate and emissions. We will assess the mortality impacts of past climate change by using one simulation ensemble with present emissions and climate and one with present emissions but 1850 climate. We will similarly quantify the potential impacts of future climate change under the four RCP scenarios in 2030, 2050 and 2100. All model outputs will be regridded to the same resolution to estimate multi-model medians and range in each grid cell. Resulting premature deaths will be calculated using these medians along with epidemiologically-derived concentration-response functions, and present-day or future projections of population and baseline mortality rates, considering aging and transitioning disease rates over time. The spatial distributions of current and future global premature mortalities due to ozone and PM2.5 outdoor air pollution will be presented separately. These results will strengthen our understanding of the impacts of climate change today, and in future years considering different plausible scenarios.

Economic impacts of climate change on agriculture: the AgMIP approach

NASA Astrophysics Data System (ADS)

Delincé, Jacques; Ciaian, Pavel; Witzke, Heinz-Peter

2015-01-01

The current paper investigates the long-term global impacts on crop productivity under different climate scenarios using the AgMIP approach (Agricultural Model Intercomparison and Improvement Project). The paper provides horizontal model intercomparison from 11 economic models as well as a more detailed analysis of the simulated effects from the Common Agricultural Policy Regionalized Impact (CAPRI) model to systematically compare its performance with other AgMIP models and specifically for the Chinese agriculture. CAPRI is a comparative static partial equilibrium model extensively used for medium and long-term economic and environmental policy impact applications. The results indicate that, at the global level, the climate change will cause an agricultural productivity decrease (between -2% and -15% by 2050), a food price increase (between 1.3% and 56%) and an expansion of cultivated area (between 1% and 4%) by 2050. The results for China indicate that the climate change effects tend to be smaller than the global impacts. The CAPRI-simulated effects are, in general, close to the median across all AgMIP models. Model intercomparison analyses reveal consistency in terms of direction of change to climate change but relatively strong heterogeneity in the magnitude of the effects between models.

Tree cover in Central Africa: determinants and sensitivity under contrasted scenarios of global change.

PubMed

Aleman, Julie C; Blarquez, Olivier; Gourlet-Fleury, Sylvie; Bremond, Laurent; Favier, Charly

2017-01-30

Tree cover is a key variable for ecosystem functioning, and is widely used to study tropical ecosystems. But its determinants and their relative importance are still a matter of debate, especially because most regional and global analyses have not considered the influence of agricultural practices. More information is urgently needed regarding how human practices influence vegetation structure. Here we focused in Central Africa, a region still subjected to traditional agricultural practices with a clear vegetation gradient. Using remote sensing data and global databases, we calibrated a Random Forest model to correlatively link tree cover with climatic, edaphic, fire and agricultural practices data. We showed that annual rainfall and accumulated water deficit were the main drivers of the distribution of tree cover and vegetation classes (defined by the modes of tree cover density), but agricultural practices, especially pastoralism, were also important in determining tree cover. We simulated future tree cover with our model using different scenarios of climate and land-use (agriculture and population) changes. Our simulations suggest that tree cover may respond differently regarding the type of scenarios, but land-use change was an important driver of vegetation change even able to counterbalance the effect of climate change in Central Africa.

Tree cover in Central Africa: determinants and sensitivity under contrasted scenarios of global change

NASA Astrophysics Data System (ADS)

Aleman, Julie C.; Blarquez, Olivier; Gourlet-Fleury, Sylvie; Bremond, Laurent; Favier, Charly

2017-01-01

Tree cover is a key variable for ecosystem functioning, and is widely used to study tropical ecosystems. But its determinants and their relative importance are still a matter of debate, especially because most regional and global analyses have not considered the influence of agricultural practices. More information is urgently needed regarding how human practices influence vegetation structure. Here we focused in Central Africa, a region still subjected to traditional agricultural practices with a clear vegetation gradient. Using remote sensing data and global databases, we calibrated a Random Forest model to correlatively link tree cover with climatic, edaphic, fire and agricultural practices data. We showed that annual rainfall and accumulated water deficit were the main drivers of the distribution of tree cover and vegetation classes (defined by the modes of tree cover density), but agricultural practices, especially pastoralism, were also important in determining tree cover. We simulated future tree cover with our model using different scenarios of climate and land-use (agriculture and population) changes. Our simulations suggest that tree cover may respond differently regarding the type of scenarios, but land-use change was an important driver of vegetation change even able to counterbalance the effect of climate change in Central Africa.

Projected future vegetation changes for the northwest United States and southwest Canada at a fine spatial resolution using a dynamic global vegetation model.

USGS Publications Warehouse

Shafer, Sarah; Bartlein, Patrick J.; Gray, Elizabeth M.; Pelltier, Richard T.

2015-01-01

Future climate change may significantly alter the distributions of many plant taxa. The effects of climate change may be particularly large in mountainous regions where climate can vary significantly with elevation. Understanding potential future vegetation changes in these regions requires methods that can resolve vegetation responses to climate change at fine spatial resolutions. We used LPJ, a dynamic global vegetation model, to assess potential future vegetation changes for a large topographically complex area of the northwest United States and southwest Canada (38.0–58.0°N latitude by 136.6–103.0°W longitude). LPJ is a process-based vegetation model that mechanistically simulates the effect of changing climate and atmospheric CO2 concentrations on vegetation. It was developed and has been mostly applied at spatial resolutions of 10-minutes or coarser. In this study, we used LPJ at a 30-second (~1-km) spatial resolution to simulate potential vegetation changes for 2070–2099. LPJ was run using downscaled future climate simulations from five coupled atmosphere-ocean general circulation models (CCSM3, CGCM3.1(T47), GISS-ER, MIROC3.2(medres), UKMO-HadCM3) produced using the A2 greenhouse gases emissions scenario. Under projected future climate and atmospheric CO2 concentrations, the simulated vegetation changes result in the contraction of alpine, shrub-steppe, and xeric shrub vegetation across the study area and the expansion of woodland and forest vegetation. Large areas of maritime cool forest and cold forest are simulated to persist under projected future conditions. The fine spatial-scale vegetation simulations resolve patterns of vegetation change that are not visible at coarser resolutions and these fine-scale patterns are particularly important for understanding potential future vegetation changes in topographically complex areas.

Projected Future Vegetation Changes for the Northwest United States and Southwest Canada at a Fine Spatial Resolution Using a Dynamic Global Vegetation Model

PubMed Central

Shafer, Sarah L.; Bartlein, Patrick J.; Gray, Elizabeth M.; Pelltier, Richard T.

2015-01-01

Future climate change may significantly alter the distributions of many plant taxa. The effects of climate change may be particularly large in mountainous regions where climate can vary significantly with elevation. Understanding potential future vegetation changes in these regions requires methods that can resolve vegetation responses to climate change at fine spatial resolutions. We used LPJ, a dynamic global vegetation model, to assess potential future vegetation changes for a large topographically complex area of the northwest United States and southwest Canada (38.0–58.0°N latitude by 136.6–103.0°W longitude). LPJ is a process-based vegetation model that mechanistically simulates the effect of changing climate and atmospheric CO2 concentrations on vegetation. It was developed and has been mostly applied at spatial resolutions of 10-minutes or coarser. In this study, we used LPJ at a 30-second (~1-km) spatial resolution to simulate potential vegetation changes for 2070–2099. LPJ was run using downscaled future climate simulations from five coupled atmosphere-ocean general circulation models (CCSM3, CGCM3.1(T47), GISS-ER, MIROC3.2(medres), UKMO-HadCM3) produced using the A2 greenhouse gases emissions scenario. Under projected future climate and atmospheric CO2 concentrations, the simulated vegetation changes result in the contraction of alpine, shrub-steppe, and xeric shrub vegetation across the study area and the expansion of woodland and forest vegetation. Large areas of maritime cool forest and cold forest are simulated to persist under projected future conditions. The fine spatial-scale vegetation simulations resolve patterns of vegetation change that are not visible at coarser resolutions and these fine-scale patterns are particularly important for understanding potential future vegetation changes in topographically complex areas. PMID:26488750

An Assessment of IPCC 20th Century Climate Simulations Using the 15-year Sea Level Record from Altimetry

NASA Astrophysics Data System (ADS)

Leuliette, E.; Nerem, S.; Jakub, T.

2006-07-01

Recen tly, multiple ensemble climate simulations h ave been produced for th e forthco ming Fourth A ssessment Report of the Intergovernmental Panel on Climate Change (IPCC). N early two dozen coupled ocean- atmo sphere models have contr ibuted output for a variety of climate scen arios. One scenar io, the climate of the 20th century exper imen t (20C3 M), produces model output that can be comp ared to th e long record of sea level provided by altimetry . Generally , the output from the 20C3M runs is used to initialize simulations of future climate scenar ios. Hence, v alidation of the 20 C3 M experiment resu lts is crucial to the goals of th e IPCC. We present compar isons of global mean sea level (G MSL) , global mean steric sea level change, and regional patterns of sea lev el chang e from these models to r esults from altimetry, tide gauge measurements, and reconstructions.

Impacts Of Global/Regional Climate Changes On Environment And Health: Need For Integrated Research And Education Collaboration (Invited)

NASA Astrophysics Data System (ADS)

Tuluri, F.

2013-12-01

The realization of long term changes in climate in research community has to go beyond the comfort zone through climate literacy in academics. Higher education on climate change is the platform to bring together the otherwise disconnected factors such as effective discovery, decision making, innovation, interdisciplinary collaboration, Climate change is a complex process that may be due to natural internal processes within the climate system, or to variations in natural or anthropogenic (human-driven) external forcing. Global climate change indicates a change in either the mean state of the climate or in its variability, persisting for several decades or longer. This includes changes in average weather conditions on Earth, such as a change in average global temperature, as well as changes in how frequently regions experience heat waves, droughts, floods, storms, and other extreme weather. It is important to examine the effects of climate variations on human health and disorders in order to take preventive measures. Similarly, the influence of climate changes on animal management practices, pests and pest management systems, and high value crops such as citrus and vegetables is also equally important for investigation. New genetic agricultural varieties must be explored, and pilot studies should examine biotechnology transfer. Recent climate model improvements have resulted in an enhanced ability to simulate many aspects of climate variability and extremes. However, they are still characterized by systematic errors and limitations in accurately simulating more precisely regional climate conditions. The present situations warrant developing climate literacy on the synergistic impacts of environmental change, and improve development, testing and validation of integrated stress impacts through computer modeling. In the present study we present a detailed study of the current status on the impacts of global/regional climate changes on environment and health with a view to highlighting the need for integrated research and education collaboration at national and global level.

Modeling a polycentric approach to the problem of climate change. Comment on "Climate change governance, cooperation and self-organization" by Pacheco, Vasconcelos & Santos

NASA Astrophysics Data System (ADS)

Milinski, Manfred

2014-12-01

Climate change is a global problem. Because of unlimited use of fossil energy and resulting greenhouse gas emissions the global temperature is rising causing floods, draughts and storms in all parts of the world with increasing frequency and strength. Dangerous climate change will occur with high probability after the global temperature has passed a certain threshold [1]. To avoid dangerous climate change global greenhouse gas emissions must be reduced to a level of 50% or less of the year-2000 emissions by 2050 [2-4]. All people on earth take part in this global target public goods game, "a game that we cannot afford to loose" [5]. Simulating this scenario in a nutshell a collective risk social dilemma game has shown that a small group of subjects can achieve a collective goal by sequential individual contributions but only when the risk of loosing their not invested money is high, e.g. 90% [6]. Cooperation in public goods games usually decreases with increasing group size [7]. Thus, does this mean that the global game will be lost?

Effects of Drake Passage on a strongly eddying global ocean

NASA Astrophysics Data System (ADS)

Viebahn, Jan; von der Heydt, Anna S.; Dijkstra, Henk A.

2015-04-01

During the past 65 Million (Ma) years, Earth's climate has undergone a major change from warm 'greenhouse' to colder 'icehouse' conditions with extensive ice sheets in the polar regions of both hemispheres. The Eocene-Oligocene (~34 Ma) and Oligocene-Miocene (~23 Ma) boundaries reflect major transitions in Cenozoic global climate change. Proposed mechanisms of these transitions include reorganization of ocean circulation due to critical gateway opening/deepening, changes in atmospheric CO2-concentration, and feedback mechanisms related to land-ice formation. Drake Passage (DP) is an intensively studied gateway because it plays a central role in closing the transport pathways of heat and chemicals in the ocean. The climate response to a closed DP has been explored with a variety of general circulation models, however, all of these models employ low model-grid resolutions such that the effects of subgrid-scale fluctuations ('eddies') are parameterized. We present results of the first high-resolution (0.1° horizontally) realistic global ocean model simulation with a closed DP in which the eddy field is largely resolved. The simulation extends over more than 200 years such that the strong transient adjustment process is passed and a near-equilibrium ocean state is reached. The effects of DP are diagnosed by comparing with both an open DP high-resolution control simulation (of same length) and corresponding low-resolution simulations. By focussing on the heat/tracer transports we demonstrate that the results are twofold: Considering spatially integrated transports the overall response to a closed DP is well captured by low-resolution simulations. However, looking at the actual spatial distributions drastic differences appear between far-scattered high-resolution and laminar-uniform low-resolution fields. We conclude that sparse and highly localized tracer proxy observations have to be interpreted carefully with the help of high-resolution model simulations.

Empirically Derived and Simulated Sensitivity of Vegetation to Climate Across Global Gradients of Temperature and Precipitation

NASA Astrophysics Data System (ADS)

Quetin, G. R.; Swann, A. L. S.

2017-12-01

Successfully predicting the state of vegetation in a novel environment is dependent on our process level understanding of the ecosystem and its interactions with the environment. We derive a global empirical map of the sensitivity of vegetation to climate using the response of satellite-observed greenness and leaf area to interannual variations in temperature and precipitation. Our analysis provides observations of ecosystem functioning; the vegetation interactions with the physical environment, across a wide range of climates and provide a functional constraint for hypotheses engendered in process-based models. We infer mechanisms constraining ecosystem functioning by contrasting how the observed and simulated sensitivity of vegetation to climate varies across climate space. Our analysis yields empirical evidence for multiple physical and biological mediators of the sensitivity of vegetation to climate as a systematic change across climate space. Our comparison of remote sensing-based vegetation sensitivity with modeled estimates provides evidence for which physiological mechanisms - photosynthetic efficiency, respiration, water supply, atmospheric water demand, and sunlight availability - dominate the ecosystem functioning in places with different climates. Earth system models are generally successful in reproducing the broad sign and shape of ecosystem functioning across climate space. However, this general agreement breaks down in hot wet climates where models simulate less leaf area during a warmer year, while observations show a mixed response but overall more leaf area during warmer years. In addition, simulated ecosystem interaction with temperature is generally larger and changes more rapidly across a gradient of temperature than is observed. We hypothesize that the amplified interaction and change are both due to a lack of adaptation and acclimation in simulations. This discrepancy with observations suggests that simulated responses of vegetation to global warming, and feedbacks between vegetation and climate, are too strong in the models.

Numerical Simulation of the Water Cycle Change Over the 20th Century

NASA Technical Reports Server (NTRS)

Bosilovich, Michael G.; Schubert, Siegfried D.

2003-01-01

We have used numerical models to test the impact of the change in Sea Surface Temperatures (SSTs) and carbon dioxide (CO2) concentration on the global circulation, particularly focusing on the hydrologic cycle, namely the global cycling of water and continental recycling of water. We have run four numerical simulations using mean annual SST from the early part of the 20th century (1900-1920) and the later part (1980-2000). In addition, we vary the CO2 concentrations for these periods as well. The duration of the simulations is 15 years, and the spatial resolution is 2 degrees. We use passive tracers to study the geographical sources of water. Surface evaporation from predetermined continental and oceanic regions provides the source of water for each passive tracer. In this way, we compute the percent of precipitation of each region over the globe. This can also be used to estimate precipitation recycling. In addition, we are using the passive tracers to independently compute the global cycling of water (compared to the traditional, Q/P calculation).

Challenges and needs in fire management: A landscape simulation modeling perspective [chapter 4

Treesearch

Robert E. Keane; Geoffrey J. Cary; Mike D. Flannigan

2011-01-01

Fire management will face many challenges in the future from global climate change to protecting people, communities, and values at risk. Simulation modeling will be a vital tool for addressing these challenges but the next generation of simulation models must be spatially explicit to address critical landscape ecology relationships and they must use mechanistic...

Future Change of Snow Water Equivalent over Japan

NASA Astrophysics Data System (ADS)

Hara, M.; Kawase, H.; Kimura, F.; Fujita, M.; Ma, X.

2012-12-01

Western side of Honshu Island and Hokkaido Island in Japan are ones of the heaviest snowfall areas in the world. Although a heavy snowfall often brings disaster, snow is one of the major sources for agriculture, industrial, and house-use in Japan. Even during the winter, the monthly mean of the surface air temperature often exceeds 0 C in large parts of the heavy snow areas along the Sea of Japan. Thus, snow cover may be seriously reduced in these areas as a result of the global warming, which is caused by an increase in greenhouse gases. The change in seasonal march of snow water equivalent, e.g., snowmelt season and amount will strongly influence to social-economic activities. We performed a series of numerical experiments including present and future climate simulations and much-snow and less-snow cases using a regional climate model. Pseudo-Global-Warming (PGW) method (Kimura and Kitoh, 2008) is applied for the future climate simulations. MIROC 3.2 medres 2070s output under IPCC SRES A2 scenario and 1990s output under 20c3m scenario used for PGW method. The precipitation, snow depth, and surface air temperature of the hindcast simulations show good agreement with the AMeDAS station data. In much-snow cases, The decreasing rate of maximum total snow water equivalent over Japan due to climate change was 49%. Main cause of the decrease of the total snow water equivalent is the air temperature rise due to global climate change. The difference in the precipitation amount between the present and the future simulations is small.

Coupled Climate Model Simulations to Bracket the Impacts of Increasing Asian Aerosols Emissions and Aggressive Future Clean Air Policies

NASA Astrophysics Data System (ADS)

Dubey, M. K.; Zhang, Y.; Sun, S.; Olsen, S.; Dean, S.; Bleck, R.; Chylek, P.; Lohmann, U.

2007-12-01

We report ensemble simulations of the climatic impacts of changing anthropogenic aerosols (sulfate, organic and black carbon), which bracket two policy scenarios: increased emissions over China and India by a factor of three over current levels and a global reduction of aerosols by a factor of ten, using the NCAR-CCSM3 and NASA- GISS coupled ocean atmosphere models. Tripling the anthropogenic aerosols over China and India has a small cooling effect (about -0.12°C) on the global mean surface air temperature with a slight reduction in global mean precipitation by ~ -0.8%. On the other hand, global reduction of anthropogenic aerosols by a factor of ten would warm the global surface temperatures by 0.4 °C - 0.8 °C in less than 10 years after the reduction takes place as well as an increase in global precipitation by 3.0% - 3.3%. Comparisons of NCAR and NASA model simulations also suggest that the indirect effects of aerosols are about 1-2 times the direct effects of aerosols. Tripling Asian anthropogenic aerosols results in regional cooling and a reduction in precipitation primarily in Asia, with cooling (warming) also noted over the high latitudes of Northern (Southern) Hemisphere. Warming and increase in precipitation in the case of global reduction of aerosols are concentrated mainly over polluted land areas in both hemispheres. Tropical regions experience large changes in precipitation in both scenarios. We provide new insights into the climate model sensitivities of global mean temperatures and rainfall to aerosol forcing. Our results underscore the urgency of reducing greenhouse gas accumulation rates as the world reduces air pollution to improve human health and that potential increased Asian pollution, offsets only a small fraction of the warming by greenhouse gases.

Modelling the influence of land-use changes on biophysical and biochemical interactions at regional and global scales.

PubMed

Devaraju, N; Bala, G; Nemani, R

2015-09-01

Land-use changes since the start of the industrial era account for nearly one-third of the cumulative anthropogenic CO2 emissions. In addition to the greenhouse effect of CO2 emissions, changes in land use also affect climate via changes in surface physical properties such as albedo, evapotranspiration and roughness length. Recent modelling studies suggest that these biophysical components may be comparable with biochemical effects. In regard to climate change, the effects of these two distinct processes may counterbalance one another both regionally and, possibly, globally. In this article, through hypothetical large-scale deforestation simulations using a global climate model, we contrast the implications of afforestation on ameliorating or enhancing anthropogenic contributions from previously converted (agricultural) land surfaces. Based on our review of past studies on this subject, we conclude that the sum of both biophysical and biochemical effects should be assessed when large-scale afforestation is used for countering global warming, and the net effect on global mean temperature change depends on the location of deforestation/afforestation. Further, although biochemical effects trigger global climate change, biophysical effects often cause strong local and regional climate change. The implication of the biophysical effects for adaptation and mitigation of climate change in agriculture and agroforestry sectors is discussed. © 2014 John Wiley & Sons Ltd.

Climate and marine biogeochemistry during the Holocene from transient model simulations

NASA Astrophysics Data System (ADS)

Segschneider, Joachim; Schneider, Birgit; Khon, Vyacheslav

2018-06-01

Climate and marine biogeochemistry changes over the Holocene are investigated based on transient global climate and biogeochemistry model simulations over the last 9500 years. The simulations are forced by accelerated and non-accelerated orbital parameters, respectively, and atmospheric pCO2, CH4, and N2O. The analysis focusses on key climatic parameters of relevance to the marine biogeochemistry, and on the physical and biogeochemical processes that drive atmosphere-ocean carbon fluxes and changes in the oxygen minimum zones (OMZs). The simulated global mean ocean temperature is characterized by a mid-Holocene cooling and a late Holocene warming, a common feature among Holocene climate simulations which, however, contradicts a proxy-derived mid-Holocene climate optimum. As the most significant result, and only in the non-accelerated simulation, we find a substantial increase in volume of the OMZ in the eastern equatorial Pacific (EEP) continuing into the late Holocene. The concurrent increase in apparent oxygen utilization (AOU) and age of the water mass within the EEP OMZ can be attributed to a weakening of the deep northward inflow into the Pacific. This results in a large-scale mid-to-late Holocene increase in AOU in most of the Pacific and hence the source regions of the EEP OMZ waters. The simulated expansion of the EEP OMZ raises the question of whether the deoxygenation that has been observed over the last 5 decades could be a - perhaps accelerated - continuation of an orbitally driven decline in oxygen. Changes in global mean biological production and export of detritus remain of the order of 10 %, with generally lower values in the mid-Holocene. The simulated atmosphere-ocean CO2 flux would result in atmospheric pCO2 changes of similar magnitudes to those observed for the Holocene, but with different timing. More technically, as the increase in EEP OMZ volume can only be simulated with the non-accelerated model simulation, non-accelerated model simulations are required for an analysis of the marine biogeochemistry in the Holocene. Notably, the long control experiment also displays similar magnitude variability to the transient experiment for some parameters. This indicates that also long control runs are required when investigating Holocene climate and marine biogeochemistry, and that some of the Holocene variations could be attributed to internal variability of the atmosphere-ocean system.

Nitrogen leaching from natural ecosystems under global change: a modelling study

NASA Astrophysics Data System (ADS)

Braakhekke, Maarten C.; Rebel, Karin T.; Dekker, Stefan C.; Smith, Benjamin; Beusen, Arthur H. W.; Wassen, Martin J.

2017-12-01

To study global nitrogen (N) leaching from natural ecosystems under changing N deposition, climate, and atmospheric CO2, we performed a factorial model experiment for the period 1901-2006 with the N-enabled global terrestrial ecosystem model LPJ-GUESS (Lund-Potsdam-Jena General Ecosystem Simulator). In eight global simulations, we used either the true transient time series of N deposition, climate, and atmospheric CO2 as input or kept combinations of these drivers constant at initial values. The results show that N deposition is globally the strongest driver of simulated N leaching, individually causing an increase of 88 % by 1997-2006 relative to pre-industrial conditions. Climate change led globally to a 31 % increase in N leaching, but the size and direction of change varied among global regions: leaching generally increased in regions with high soil organic carbon storage and high initial N status, and decreased in regions with a positive trend in vegetation productivity or decreasing precipitation. Rising atmospheric CO2 generally caused decreased N leaching (33 % globally), with strongest effects in regions with high productivity and N availability. All drivers combined resulted in a rise of N leaching by 73 % with strongest increases in Europe, eastern North America and South-East Asia, where N deposition rates are highest. Decreases in N leaching were predicted for the Amazon and northern India. We further found that N loss by fire regionally is a large term in the N budget, associated with lower N leaching, particularly in semi-arid biomes. Predicted global N leaching from natural lands rose from 13.6 Tg N yr-1 in 1901-1911 to 18.5 Tg N yr-1 in 1997-2006, accounting for reductions of natural land cover. Ecosystem N status (quantified as the reduction of vegetation productivity due to N limitation) shows a similar positive temporal trend but large spatial variability. Interestingly, this variability is more strongly related to vegetation type than N input. Similarly, the relationship between N status and (relative) N leaching is highly variable due to confounding factors such as soil water fluxes, fire occurrence, and growing season length. Nevertheless, our results suggest that regions with very high N deposition rates are approaching a state of N saturation.

Global Mean Temperature Timeseries Projections from GCMs: The Implications of Rebasing

NASA Astrophysics Data System (ADS)

Chapman, S. C.; Stainforth, D. A.; Watkins, N. W.

2017-12-01

Global climate models are assessed by comparison with observations through several benchmarks. One highlighted by the InterGovernmental Panel on Climate Change (IPCC) is their ability to reproduce "general features of the global and annual mean surface temperature changes over the historical period" [1,2] and to simulate "a trend in global-mean surface temperature from 1951 to 2012 that agrees with the observed trend" [3]. These aspects of annual mean global mean temperature (GMT) change are presented as one feature demonstrating the relevance of these models for climate projections. Here we consider a formal interpretation of "general features" and discuss the implications of this approach to model assessment and intercomparison, for the interpretation of GCM projections. Following the IPCC, we interpret a major element of "general features" as being the slow timescale response to external forcings. (Shorter timescale behaviour such as the response to volcanic eruptions are also elements of "general features" but are not considered here.) Also following the IPCC, we consider only GMT anomalies. The models have absolute temperatures which range over about 3K so this means their timeseries (and the observations) are rebased. We show that rebasing in combination with general agreement, implies a separation of scales which limits the degree to which sub-global behaviour can feedback on the global response. It also implies a degree of linearity in the GMT slow timescale response. For each individual model these implications only apply over the range of absolute temperatures simulated by the model in historic simulations. Taken together, however, they imply consequences over a wider range of GMTs. [1] IPCC, Fifth Assessment Report, Working Group 1, Technical Summary: Stocker et al. 2013. [2] IPCC, Fifth Assessment Report, Working Group 1, Chapter 9 - "Evaluation of Climate Models": Flato et al. 2013. [3] IPCC, Fifth Assessment Report, Working Group 1, Summary for Policy Makers: IPCC, 2013.

Climate mitigation and the future of tropical landscapes.

PubMed

Thomson, Allison M; Calvin, Katherine V; Chini, Louise P; Hurtt, George; Edmonds, James A; Bond-Lamberty, Ben; Frolking, Steve; Wise, Marshall A; Janetos, Anthony C

2010-11-16

Land-use change to meet 21st-century demands for food, fuel, and fiber will depend on many interactive factors, including global policies limiting anthropogenic climate change and realized improvements in agricultural productivity. Climate-change mitigation policies will alter the decision-making environment for land management, and changes in agricultural productivity will influence cultivated land expansion. We explore to what extent future increases in agricultural productivity might offset conversion of tropical forest lands to crop lands under a climate mitigation policy and a contrasting no-policy scenario in a global integrated assessment model. The Global Change Assessment Model is applied here to simulate a mitigation policy that stabilizes radiative forcing at 4.5 W m(-2) (approximately 526 ppm CO(2)) in the year 2100 by introducing a price for all greenhouse gas emissions, including those from land use. These scenarios are simulated with several cases of future agricultural productivity growth rates and the results downscaled to produce gridded maps of potential land-use change. We find that tropical forests are preserved near their present-day extent, and bioenergy crops emerge as an effective mitigation option, only in cases in which a climate mitigation policy that includes an economic price for land-use emissions is in place, and in which agricultural productivity growth continues throughout the century. We find that idealized land-use emissions price assumptions are most effective at limiting deforestation, even when cropland area must increase to meet future food demand. These findings emphasize the importance of accounting for feedbacks from land-use change emissions in global climate change mitigation strategies.

The uncertainty of crop yield projections is reduced by improved temperature response functions.

PubMed

Wang, Enli; Martre, Pierre; Zhao, Zhigan; Ewert, Frank; Maiorano, Andrea; Rötter, Reimund P; Kimball, Bruce A; Ottman, Michael J; Wall, Gerard W; White, Jeffrey W; Reynolds, Matthew P; Alderman, Phillip D; Aggarwal, Pramod K; Anothai, Jakarat; Basso, Bruno; Biernath, Christian; Cammarano, Davide; Challinor, Andrew J; De Sanctis, Giacomo; Doltra, Jordi; Fereres, Elias; Garcia-Vila, Margarita; Gayler, Sebastian; Hoogenboom, Gerrit; Hunt, Leslie A; Izaurralde, Roberto C; Jabloun, Mohamed; Jones, Curtis D; Kersebaum, Kurt C; Koehler, Ann-Kristin; Liu, Leilei; Müller, Christoph; Naresh Kumar, Soora; Nendel, Claas; O'Leary, Garry; Olesen, Jørgen E; Palosuo, Taru; Priesack, Eckart; Eyshi Rezaei, Ehsan; Ripoche, Dominique; Ruane, Alex C; Semenov, Mikhail A; Shcherbak, Iurii; Stöckle, Claudio; Stratonovitch, Pierre; Streck, Thilo; Supit, Iwan; Tao, Fulu; Thorburn, Peter; Waha, Katharina; Wallach, Daniel; Wang, Zhimin; Wolf, Joost; Zhu, Yan; Asseng, Senthold

2017-07-17

Increasing the accuracy of crop productivity estimates is a key element in planning adaptation strategies to ensure global food security under climate change. Process-based crop models are effective means to project climate impact on crop yield, but have large uncertainty in yield simulations. Here, we show that variations in the mathematical functions currently used to simulate temperature responses of physiological processes in 29 wheat models account for >50% of uncertainty in simulated grain yields for mean growing season temperatures from 14 °C to 33 °C. We derived a set of new temperature response functions that when substituted in four wheat models reduced the error in grain yield simulations across seven global sites with different temperature regimes by 19% to 50% (42% average). We anticipate the improved temperature responses to be a key step to improve modelling of crops under rising temperature and climate change, leading to higher skill of crop yield projections.

The Uncertainty of Crop Yield Projections Is Reduced by Improved Temperature Response Functions

NASA Technical Reports Server (NTRS)

Wang, Enli; Martre, Pierre; Zhao, Zhigan; Ewert, Frank; Maiorano, Andrea; Rotter, Reimund P.; Kimball, Bruce A.; Ottman, Michael J.; White, Jeffrey W.; Reynolds, Matthew P.;

The Impact of Sea Ice Concentration Accuracies on Climate Model Simulations with the GISS GCM

NASA Technical Reports Server (NTRS)

Parkinson, Claire L.; Rind, David; Healy, Richard J.; Martinson, Douglas G.; Zukor, Dorothy J. (Technical Monitor)

2000-01-01

The Goddard Institute for Space Studies global climate model (GISS GCM) is used to examine the sensitivity of the simulated climate to sea ice concentration specifications in the type of simulation done in the Atmospheric Modeling Intercomparison Project (AMIP), with specified oceanic boundary conditions. Results show that sea ice concentration uncertainties of +/- 7% can affect simulated regional temperatures by more than 6 C, and biases in sea ice concentrations of +7% and -7% alter simulated annually averaged global surface air temperatures by -0.10 C and +0.17 C, respectively, over those in the control simulation. The resulting 0.27 C difference in simulated annual global surface air temperatures is reduced by a third, to 0.18 C, when considering instead biases of +4% and -4%. More broadly, least-squares fits through the temperature results of 17 simulations with ice concentration input changes ranging from increases of 50% versus the control simulation to decreases of 50% yield a yearly average global impact of 0.0107 C warming for every 1% ice concentration decrease, i.e., 1.07 C warming for the full +50% to -50% range. Regionally and on a monthly average basis, the differences can be far greater, especially in the polar regions, where wintertime contrasts between the +50% and -50% cases can exceed 30 C. However, few statistically significant effects are found outside the polar latitudes, and temperature effects over the non-polar oceans tend to be under 1 C, due in part to the specification of an unvarying annual cycle of sea surface temperatures. The +/- 7% and 14% results provide bounds on the impact (on GISS GCM simulations making use of satellite data) of satellite-derived ice concentration inaccuracies, +/- 7% being the current estimated average accuracy of satellite retrievals and +/- 4% being the anticipated improved average accuracy for upcoming satellite instruments. Results show that the impact on simulated temperatures of imposed ice concentration changes is least in summer, encouragingly the same season in which the satellite accuracies are thought to be worst. Hence the impact of satellite inaccuracies is probably less than the use of an annually averaged satellite inaccuracy would suggest.

The effects of 1.5 and 2 degrees of global warming on Africa in the CORDEX ensemble

NASA Astrophysics Data System (ADS)

Nikulin, Grigory; Lennard, Chris; Dosio, Alessandro; Kjellström, Erik; Chen, Youmin; Hänsler, Andreas; Kupiainen, Marco; Laprise, René; Mariotti, Laura; Fox Maule, Cathrine; van Meijgaard, Erik; Panitz, Hans-Jürgen; Scinocca, John F.; Somot, Samuel

2018-06-01

There is a general lack of information about the potential effects of 1.5, 2 or more degrees of global warming on the regional climates within Africa, and most studies that address this use data from coarse resolution global models. Using a large ensemble of CORDEX Africa simulations, we present a pan-African overview of the effects of 1.5 and 2 °C global warming levels (GWLs) on the African climate. The CORDEX simulations, consistent with their driving global models, show a robust regional warming exceeding the mean global one over most of Africa. The highest increase in annual mean temperature is found over the subtropics and the smallest one over many coastal regions. Projected changes in annual mean precipitation have a tendency to wetter conditions in some parts of Africa (e.g. central/eastern Sahel and eastern Africa) at both GWLs, but models’ agreement on the sign of change is low. In contrast to mean precipitation, there is a consistent increase in daily precipitation intensity of wet days over a large fraction of tropical Africa emerging already at 1.5 °C GWL and strengthening at 2 °C. A consistent difference between 2 °C and 1.5 °C warmings is also found for projected changes in annual mean temperature and daily precipitation intensity. Our study indicates that a 0.5 °C further warming (from 1.5 °C–2 °C) can indeed produce a robust change in some aspects of the African climate and its extremes.

Climate change effects on landslides in southern B.C.

NASA Astrophysics Data System (ADS)

Jakob, M.

2009-04-01

Two mechanisms that contribute to the temporal occurrence of landslides in coastal British Columbia are ante¬cedent rainfall and short-term intense rainfall. These two quantities can be extracted from the precipitation regimes simulated by climate models. This makes such models an attractive tool for use in the investigation of the effect of global warming on landslide fre¬quencies. In order to provide some measure of the reliability of models used to address the landslide question, the present-day simulation of the antecedent precipitation and short- term rainfall using the daily data from the Canadian Centre for Climate Modelling and Analysis model (CGCM) is compared to observations along the south coast of British Colum¬bia. This evaluation showed that the model was reasonably successful in simulating sta¬tistics of the antecedent rainfall but was less successful in simulating the short-term rainfall. The monthly mean precipitation data from an ensemble of 19 of the world's global climate models were available to study potential changes in landslide frequencies with global warming. Most of the models were used to produce simulations with three scenar¬ios with different levels of prescribed greenhouse gas concentrations during the twenty-first century. The changes in the antecedent precipitation were computed from the resulting monthly and seasonal means. In order to deal with models' suspected difficulties in sim¬ulating the short-term precipitation and lack of daily data, a statistical procedure was used to relate the short-term precipitation to the monthly means. The qualitative model results agree reasonably well, and when averaged over all models and the three scenarios, the change in the antecedent precipitation is predicted to be about 10% and the change in the short-term precipitation about 6%. Because the antecedent precipitation and the short-term precipitation contribute to the occurrence of landslides, the results of this study support the prediction of increased landslide frequency along the British Columbia south coast during the twenty-first century.

Calibrating and updating the Global Forest Products Model (GFPM version 2016 with BPMPD)

Treesearch

Joseph Buongiorno; Shushuai  Zhu

2016-01-01

The Global Forest Products Model (GFPM) is an economic model of global production, consumption, and trade of forest products. An earlier version of the model is described in Buongiorno et al. (2003). The GFPM 2016 has data and parameters to simulate changes of the forest sector from 2013 to 2030. Buongiorno and Zhu (2015) describe how to use the model for...

Pairing FLUXNET sites to validate model representations of land-use/land-cover change

NASA Astrophysics Data System (ADS)

Chen, Liang; Dirmeyer, Paul A.; Guo, Zhichang; Schultz, Natalie M.

2018-01-01

Land surface energy and water fluxes play an important role in land-atmosphere interactions, especially for the climatic feedback effects driven by land-use/land-cover change (LULCC). These have long been documented in model-based studies, but the performance of land surface models in representing LULCC-induced responses has not been investigated well. In this study, measurements from proximate paired (open versus forest) flux tower sites are used to represent observed deforestation-induced changes in surface fluxes, which are compared with simulations from the Community Land Model (CLM) and the Noah Multi-Parameterization (Noah-MP) land model. Point-scale simulations suggest the CLM can represent the observed diurnal and seasonal changes in net radiation (Rnet) and ground heat flux (G), but difficulties remain in the energy partitioning between latent (LE) and sensible (H) heat flux. The CLM does not capture the observed decreased daytime LE, and overestimates the increased H during summer. These deficiencies are mainly associated with models' greater biases over forest land-cover types and the parameterization of soil evaporation. Global gridded simulations with the CLM show uncertainties in the estimation of LE and H at the grid level for regional and global simulations. Noah-MP exhibits a similar ability to simulate the surface flux changes, but with larger biases in H, G, and Rnet change during late winter and early spring, which are related to a deficiency in estimating albedo. Differences in meteorological conditions between paired sites is not a factor in these results. Attention needs to be devoted to improving the representation of surface heat flux processes in land models to increase confidence in LULCC simulations.

Uncertainties in Past and Future Global Water Availability

NASA Astrophysics Data System (ADS)

Sheffield, J.; Kam, J.

2014-12-01

Understanding how water availability changes on inter-annual to decadal time scales and how it may change in the future under climate change are a key part of understanding future stresses on water and food security. Historic evaluations of water availability on regional to global scales are generally based on large-scale model simulations with their associated uncertainties, in particular for long-term changes. Uncertainties are due to model errors and missing processes, parameter uncertainty, and errors in meteorological forcing data. Recent multi-model inter-comparisons and impact studies have highlighted large differences for past reconstructions, due to different simplifying assumptions in the models or the inclusion of physical processes such as CO2 fertilization. Modeling of direct anthropogenic factors such as water and land management also carry large uncertainties in their physical representation and from lack of socio-economic data. Furthermore, there is little understanding of the impact of uncertainties in the meteorological forcings that underpin these historic simulations. Similarly, future changes in water availability are highly uncertain due to climate model diversity, natural variability and scenario uncertainty, each of which dominates at different time scales. In particular, natural climate variability is expected to dominate any externally forced signal over the next several decades. We present results from multi-land surface model simulations of the historic global availability of water in the context of natural variability (droughts) and long-term changes (drying). The simulations take into account the impact of uncertainties in the meteorological forcings and the incorporation of water management in the form of reservoirs and irrigation. The results indicate that model uncertainty is important for short-term drought events, and forcing uncertainty is particularly important for long-term changes, especially uncertainty in precipitation due to reduced gauge density in recent years. We also discuss uncertainties in future projections from these models as driven by bias-corrected and downscaled CMIP5 climate projections, in the context of the balance between climate model robustness and climate model diversity.

Modeling and Analysis of Global and Regional Climate Change in Relation to Atmospheric Hydrologic Processes

NASA Technical Reports Server (NTRS)

Johnson, Donald R.

1998-01-01

The goal of this research is the continued development and application of global isentropic modeling and analysis capabilities to describe hydrologic processes and energy exchange in the climate system, and discern regional climate change. This work involves a combination of modeling and analysis efforts involving 4DDA datasets and simulations from the University of Wisconsin (UW) hybrid isentropic-sigma (theta-sigma) coordinate model and the GEOS GCM.

Attribution of changes in global wetland methane emissions from pre-industrial to present using CLM4.5-BGC

DOE PAGES

Paudel, Rajendra; Mahowald, Natalie M.; Hess, Peter G. M.; ...

2016-03-10

An understanding of potential factors controlling methane emissions from natural wetlands is important to accurately project future atmospheric methane concentrations. Here, we examine the relative contributions of climatic and environmental factors, such as precipitation, temperature, atmospheric CO 2 concentration, nitrogen deposition, wetland inundation extent, and land-use and land-cover change, on changes in wetland methane emissions from preindustrial to present day (i.e., 1850-2005). We apply a mechanistic methane biogeochemical model integrated in the Community Land Model version 4.5 (CLM4.5), the land component of the Community Earth System Model. The methane model explicitly simulates methane production, oxidation, ebullition, transport through aerenchyma ofmore » plants, and aqueous and gaseous diffusion. We conduct a suite of model simulations from 1850 to 2005, with all changes in environmental factors included, and sensitivity studies isolating each factor. Globally, we estimate that preindustrial methane emissions were higher by 10% than present-day emissions from natural wetlands, with emissions changes from preindustrial to the present of +15%, -41%, and -11% for the high latitudes, temperate regions, and tropics, respectively. The most important change is due to the estimated change in wetland extent, due to the conversion of wetland areas to drylands by humans. This effect alone leads to higher preindustrial global methane fluxes by 33% relative to the present, with the largest change in temperate regions (+80%). These increases were partially offset by lower preindustrial emissions due to lower CO 2 levels (10%), shifts in precipitation (7%), lower nitrogen deposition (3%), and changes in land-use and land-cover (2%). Cooler temperatures in the preindustrial regions resulted in our simulations in an increase in global methane emissions of 6% relative to present day. Much of the sensitivity to these perturbations is mediated in the model by changes in methane substrate production and the areal extent of wetlands. The detrended interannual variability of high-latitude methane emissions is explained by the variation in substrate production and wetland inundation extent, whereas the tropical emission variability is explained by both of those variables and precipitation.« less

Attribution of changes in global wetland methane emissions from pre-industrial to present using CLM4.5-BGC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paudel, Rajendra; Mahowald, Natalie M.; Hess, Peter G. M.

An understanding of potential factors controlling methane emissions from natural wetlands is important to accurately project future atmospheric methane concentrations. Here, we examine the relative contributions of climatic and environmental factors, such as precipitation, temperature, atmospheric CO 2 concentration, nitrogen deposition, wetland inundation extent, and land-use and land-cover change, on changes in wetland methane emissions from preindustrial to present day (i.e., 1850-2005). We apply a mechanistic methane biogeochemical model integrated in the Community Land Model version 4.5 (CLM4.5), the land component of the Community Earth System Model. The methane model explicitly simulates methane production, oxidation, ebullition, transport through aerenchyma ofmore » plants, and aqueous and gaseous diffusion. We conduct a suite of model simulations from 1850 to 2005, with all changes in environmental factors included, and sensitivity studies isolating each factor. Globally, we estimate that preindustrial methane emissions were higher by 10% than present-day emissions from natural wetlands, with emissions changes from preindustrial to the present of +15%, -41%, and -11% for the high latitudes, temperate regions, and tropics, respectively. The most important change is due to the estimated change in wetland extent, due to the conversion of wetland areas to drylands by humans. This effect alone leads to higher preindustrial global methane fluxes by 33% relative to the present, with the largest change in temperate regions (+80%). These increases were partially offset by lower preindustrial emissions due to lower CO 2 levels (10%), shifts in precipitation (7%), lower nitrogen deposition (3%), and changes in land-use and land-cover (2%). Cooler temperatures in the preindustrial regions resulted in our simulations in an increase in global methane emissions of 6% relative to present day. Much of the sensitivity to these perturbations is mediated in the model by changes in methane substrate production and the areal extent of wetlands. The detrended interannual variability of high-latitude methane emissions is explained by the variation in substrate production and wetland inundation extent, whereas the tropical emission variability is explained by both of those variables and precipitation.« less

Changes in U.S. Regional-Scale Air Quality at 2030 Simulated Using RCP 6.0

NASA Astrophysics Data System (ADS)

Nolte, C. G.; Otte, T.; Pinder, R. W.; Faluvegi, G.; Shindell, D. T.

2012-12-01

Recent improvements in air quality in the United States have been due to significant reductions in emissions of ozone and particulate matter (PM) precursors, and these downward emissions trends are expected to continue in the next few decades. To ensure that planned air quality regulations are robust under a range of possible future climates and to consider possible policy actions to mitigate climate change, it is important to characterize and understand the effects of climate change on air quality. Recent work by several research groups using global and regional models has demonstrated that there is a "climate penalty," in which climate change leads to increases in surface ozone levels in polluted continental regions. One approach to simulating future air quality at the regional scale is via dynamical downscaling, in which fields from a global climate model are used as input for a regional climate model, and these regional climate data are subsequently used for chemical transport modeling. However, recent studies using this approach have encountered problems with the downscaled regional climate fields, including unrealistic surface temperatures and misrepresentation of synoptic pressure patterns such as the Bermuda High. We developed a downscaling methodology and showed that it now reasonably simulates regional climate by evaluating it against historical data. In this work, regional climate simulations created by downscaling the NASA/GISS Model E2 global climate model are used as input for the Community Multiscale Air Quality (CMAQ) model. CMAQ simulations over the continental United States are conducted for two 11-year time slices, one representing current climate (1995-2005) and one following Representative Concentration Pathway 6.0 from 2025-2035. Anthropogenic emissions of ozone and PM precursors are held constant at year 2006 levels for both the current and future periods. In our presentation, we will examine the changes in ozone and PM concentrations, with particular focus on exceedances of the current U.S. air quality standards, and attempt to relate the changes in air quality to the projected changes in regional climate.

Studies of climate dynamics with innovative global-model simulations

NASA Astrophysics Data System (ADS)

Shi, Xiaoming

Climate simulations with different degrees of idealization are essential for the development of our understanding of the climate system. Studies in this dissertation employ carefully designed global-model simulations for the goal of gaining theoretical and conceptual insights into some problems of climate dynamics. Firstly, global warming-induced changes in extreme precipitation are investigated using a global climate model with idealized geography. The precipitation changes over an idealized north-south mid-latitude mountain barrier at the western margin of an otherwise flat continent are studied. The intensity of the 40 most intense events on the western slopes increases by about ~4°C of surface warming. In contrast, the intensity of the top 40 events on the eastern mountain slopes increases at about ~6°C. This higher sensitivity is due to enhanced ascent during the eastern-slope events, which can be explained in terms of linear mountain-wave theory relating to global warming-induced changes in the upper-tropospheric static stability and the tropopause level. Dominated by different dynamical factors, changes in the intensity of extreme precipitation events over plains and oceans might differ from changes over mountains. So the response of extreme precipitation over mountains and flat areas are further compared using larger data sets of simulated extreme events over the two types of surfaces. It is found that the sensitivity of extreme precipitation to increases in global mean surface temperature is 3% per °C lower over mountains than over the oceans or the plains. The difference in sensitivity among these regions is not due to thermodynamic effects, but rather to differences between the gravity-wave dynamics governing vertical velocities over the mountains and the cyclone dynamics governing vertical motions over the oceans and plains. The strengthening of latent heating in the storms over oceans and plains leads to stronger ascent in the warming climate. Motivated by the fact that natural variability of the atmosphere could obscure the signal of anthropogenic warming on time scales of years to decades, the large scale variability of the atmosphere is also studied. Analysis using simulations in the Community Earth System Model Large Ensemble project reveals that the Northern Annular Mode (NAM) does not have a stable spatial pattern when 50-year long segments of data are used to calculate it. Some segments of data result in NAM-like variability with a very strong North Pacific center of action, while in some others it exhibits a more symmetric structure, with North Pacific and Euro-Atlantic centers of comparable strength. Perhaps somewhat puzzling, the NAM's North Pacific center of action is found to have a strengthening trend under anthropogenic warming. Lastly, the large-scale character of an atmosphere in rotating Radiative-Convective Equilibrium (RCE) is studied, using a global atmospheric model with prescribed globally uniform sea surface temperature and no insolation. In such an equilibrium state, numerous tropical cyclone-like vortices develop in the extratropics, which move slowly poleward and westward. The typical spacing of simulated tropical cyclone-like vortices is comparable to the Rossby radius of deformation, while the production of available potential energy is at a scale slightly smaller than that of the vortices. It is hypothesized that the growth of tropical cyclone-like vortices is driven by the self-aggregation of convection, while baroclinic instability destabilizes any vortices that grow significantly larger than the deformation radius. A weak Hadley circulation dominates in the deep tropics, and an eastward-propagating wavenumber one MJO-like mode with a period of 30 to 40 days develops along the equator.

Model-data integration to improve the LPJmL dynamic global vegetation model

NASA Astrophysics Data System (ADS)

Forkel, Matthias; Thonicke, Kirsten; Schaphoff, Sibyll; Thurner, Martin; von Bloh, Werner; Dorigo, Wouter; Carvalhais, Nuno

2017-04-01

Dynamic global vegetation models show large uncertainties regarding the development of the land carbon balance under future climate change conditions. This uncertainty is partly caused by differences in how vegetation carbon turnover is represented in global vegetation models. Model-data integration approaches might help to systematically assess and improve model performances and thus to potentially reduce the uncertainty in terrestrial vegetation responses under future climate change. Here we present several applications of model-data integration with the LPJmL (Lund-Potsdam-Jena managed Lands) dynamic global vegetation model to systematically improve the representation of processes or to estimate model parameters. In a first application, we used global satellite-derived datasets of FAPAR (fraction of absorbed photosynthetic activity), albedo and gross primary production to estimate phenology- and productivity-related model parameters using a genetic optimization algorithm. Thereby we identified major limitations of the phenology module and implemented an alternative empirical phenology model. The new phenology module and optimized model parameters resulted in a better performance of LPJmL in representing global spatial patterns of biomass, tree cover, and the temporal dynamic of atmospheric CO2. Therefore, we used in a second application additionally global datasets of biomass and land cover to estimate model parameters that control vegetation establishment and mortality. The results demonstrate the ability to improve simulations of vegetation dynamics but also highlight the need to improve the representation of mortality processes in dynamic global vegetation models. In a third application, we used multiple site-level observations of ecosystem carbon and water exchange, biomass and soil organic carbon to jointly estimate various model parameters that control ecosystem dynamics. This exercise demonstrates the strong role of individual data streams on the simulated ecosystem dynamics which consequently changed the development of ecosystem carbon stocks and fluxes under future climate and CO2 change. In summary, our results demonstrate challenges and the potential of using model-data integration approaches to improve a dynamic global vegetation model.

MERIDIONAL CIRCULATION DYNAMICS FROM 3D MAGNETOHYDRODYNAMIC GLOBAL SIMULATIONS OF SOLAR CONVECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Passos, Dário; Charbonneau, Paul; Miesch, Mark, E-mail: dariopassos@ist.utl.pt

The form of solar meridional circulation is a very important ingredient for mean field flux transport dynamo models. However, a shroud of mystery still surrounds this large-scale flow, given that its measurement using current helioseismic techniques is challenging. In this work, we use results from three-dimensional global simulations of solar convection to infer the dynamical behavior of the established meridional circulation. We make a direct comparison between the meridional circulation that arises in these simulations and the latest observations. Based on our results, we argue that there should be an equatorward flow at the base of the convection zone atmore » mid-latitudes, below the current maximum depth helioseismic measures can probe (0.75 R{sub ⊙}). We also provide physical arguments to justify this behavior. The simulations indicate that the meridional circulation undergoes substantial changes in morphology as the magnetic cycle unfolds. We close by discussing the importance of these dynamical changes for current methods of observation which involve long averaging periods of helioseismic data. Also noteworthy is the fact that these topological changes indicate a rich interaction between magnetic fields and plasma flows, which challenges the ubiquitous kinematic approach used in the vast majority of mean field dynamo simulations.« less

Increased future ice discharge from Antarctica owing to higher snowfall.

PubMed

Winkelmann, R; Levermann, A; Martin, M A; Frieler, K

2012-12-13

Anthropogenic climate change is likely to cause continuing global sea level rise, but some processes within the Earth system may mitigate the magnitude of the projected effect. Regional and global climate models simulate enhanced snowfall over Antarctica, which would provide a direct offset of the future contribution to global sea level rise from cryospheric mass loss and ocean expansion. Uncertainties exist in modelled snowfall, but even larger uncertainties exist in the potential changes of dynamic ice discharge from Antarctica and thus in the ultimate fate of the precipitation-deposited ice mass. Here we show that snowfall and discharge are not independent, but that future ice discharge will increase by up to three times as a result of additional snowfall under global warming. Our results, based on an ice-sheet model forced by climate simulations through to the end of 2500 (ref. 8), show that the enhanced discharge effect exceeds the effect of surface warming as well as that of basal ice-shelf melting, and is due to the difference in surface elevation change caused by snowfall on grounded versus floating ice. Although different underlying forcings drive ice loss from basal melting versus increased snowfall, similar ice dynamical processes are nonetheless at work in both; therefore results are relatively independent of the specific representation of the transition zone. In an ensemble of simulations designed to capture ice-physics uncertainty, the additional dynamic ice loss along the coastline compensates between 30 and 65 per cent of the ice gain due to enhanced snowfall over the entire continent. This results in a dynamic ice loss of up to 1.25 metres in the year 2500 for the strongest warming scenario. The reported effect thus strongly counters a potential negative contribution to global sea level by the Antarctic Ice Sheet.

Molecular Dynamics Simulations of KirBac1.1 Mutants Reveal Global Gating Changes of Kir Channels.

PubMed

Linder, Tobias; Wang, Shizhen; Zangerl-Plessl, Eva-Maria; Nichols, Colin G; Stary-Weinzinger, Anna

2015-04-27

Prokaryotic inwardly rectifying (KirBac) potassium channels are homologous to mammalian Kir channels. Their activity is controlled by dynamical conformational changes that regulate ion flow through a central pore. Understanding the dynamical rearrangements of Kir channels during gating requires high-resolution structure information from channels crystallized in different conformations and insight into the transition steps, which are difficult to access experimentally. In this study, we use MD simulations on wild type KirBac1.1 and an activatory mutant to investigate activation gating of KirBac channels. Full atomistic MD simulations revealed that introducing glutamate in position 143 causes significant widening at the helix bundle crossing gate, enabling water flux into the cavity. Further, global rearrangements including a twisting motion as well as local rearrangements at the subunit interface in the cytoplasmic domain were observed. These structural rearrangements are similar to recently reported KirBac3.1 crystal structures in closed and open conformation, suggesting that our simulations capture major conformational changes during KirBac1.1 opening. In addition, an important role of protein-lipid interactions during gating was observed. Slide-helix and C-linker interactions with lipids were strengthened during activation gating.

Sensitivity of global and regional terrestrial carbon storage to the direct CO2 effect and climate change based on the CMIP5 model intercomparison.

PubMed

Peng, Jing; Dan, Li; Huang, Mei

2014-01-01

Global and regional land carbon storage has been significantly affected by increasing atmospheric CO2 concentration and climate change. Based on fully coupled climate-carbon-cycle simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5), we investigate sensitivities of land carbon storage to rising atmospheric CO2 concentration and climate change over the world and 21 regions during the 130 years. Overall, the simulations suggest that consistently spatial positive effects of the increasing CO2 concentrations on land carbon storage are expressed with a multi-model averaged value of 1.04 PgC per ppm. The stronger positive values are mainly located in the broad areas of temperate and tropical forest, especially in Amazon basin and western Africa. However, large heterogeneity distributed for sensitivities of land carbon storage to climate change. Climate change causes decrease in land carbon storage in most tropics and the Southern Hemisphere. In these regions, decrease in soil moisture (MRSO) and enhanced drought somewhat contribute to such a decrease accompanied with rising temperature. Conversely, an increase in land carbon storage has been observed in high latitude and altitude regions (e.g., northern Asia and Tibet). The model simulations also suggest that global negative impacts of climate change on land carbon storage are predominantly attributed to decrease in land carbon storage in tropics. Although current warming can lead to an increase in land storage of high latitudes of Northern Hemisphere due to elevated vegetation growth, a risk of exacerbated future climate change may be induced due to release of carbon from tropics.

Sensitivity of Global and Regional Terrestrial Carbon Storage to the Direct CO2 Effect and Climate Change Based on the CMIP5 Model Intercomparison

PubMed Central

Peng, Jing; Dan, Li; Huang, Mei

2014-01-01

Global and regional land carbon storage has been significantly affected by increasing atmospheric CO2 concentration and climate change. Based on fully coupled climate-carbon-cycle simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5), we investigate sensitivities of land carbon storage to rising atmospheric CO2 concentration and climate change over the world and 21 regions during the 130 years. Overall, the simulations suggest that consistently spatial positive effects of the increasing CO2 concentrations on land carbon storage are expressed with a multi-model averaged value of 1.04PgC per ppm. The stronger positive values are mainly located in the broad areas of temperate and tropical forest, especially in Amazon basin and western Africa. However, large heterogeneity distributed for sensitivities of land carbon storage to climate change. Climate change causes decrease in land carbon storage in most tropics and the Southern Hemisphere. In these regions, decrease in soil moisture (MRSO) and enhanced drought somewhat contribute to such a decrease accompanied with rising temperature. Conversely, an increase in land carbon storage has been observed in high latitude and altitude regions (e.g., northern Asia and Tibet). The model simulations also suggest that global negative impacts of climate change on land carbon storage are predominantly attributed to decrease in land carbon storage in tropics. Although current warming can lead to an increase in land storage of high latitudes of Northern Hemisphere due to elevated vegetation growth, a risk of exacerbated future climate change may be induced due to release of carbon from tropics. PMID:24748331

A Global System for Transportation Simulation and Visualization in Emergency Evacuation Scenarios

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Wei; Liu, Cheng; Thomas, Neil

2015-01-01

Simulation-based studies are frequently used for evacuation planning and decision making processes. Given the transportation systems complexity and data availability, most evacuation simulation models focus on certain geographic areas. With routine improvement of OpenStreetMap road networks and LandScanTM global population distribution data, we present WWEE, a uniform system for world-wide emergency evacuation simulations. WWEE uses unified data structure for simulation inputs. It also integrates a super-node trip distribution model as the default simulation parameter to improve the system computational performance. Two levels of visualization tools are implemented for evacuation performance analysis, including link-based macroscopic visualization and vehicle-based microscopic visualization. Formore » left-hand and right-hand traffic patterns in different countries, the authors propose a mirror technique to experiment with both scenarios without significantly changing traffic simulation models. Ten cities in US, Europe, Middle East, and Asia are modeled for demonstration. With default traffic simulation models for fast and easy-to-use evacuation estimation and visualization, WWEE also retains the capability of interactive operation for users to adopt customized traffic simulation models. For the first time, WWEE provides a unified platform for global evacuation researchers to estimate and visualize their strategies performance of transportation systems under evacuation scenarios.« less

Similar Estimates of Temperature Impacts on Global Wheat Yield by Three Independent Methods

NASA Technical Reports Server (NTRS)

Liu, Bing; Asseng, Senthold; Muller, Christoph; Ewart, Frank; Elliott, Joshua; Lobell, David B.; Martre, Pierre; Ruane, Alex C.; Wallach, Daniel; Jones, James W.;

Similar estimates of temperature impacts on global wheat yield by three independent methods

NASA Astrophysics Data System (ADS)

Liu, Bing; Asseng, Senthold; Müller, Christoph; Ewert, Frank; Elliott, Joshua; Lobell, David B.; Martre, Pierre; Ruane, Alex C.; Wallach, Daniel; Jones, James W.; Rosenzweig, Cynthia; Aggarwal, Pramod K.; Alderman, Phillip D.; Anothai, Jakarat; Basso, Bruno; Biernath, Christian; Cammarano, Davide; Challinor, Andy; Deryng, Delphine; Sanctis, Giacomo De; Doltra, Jordi; Fereres, Elias; Folberth, Christian; Garcia-Vila, Margarita; Gayler, Sebastian; Hoogenboom, Gerrit; Hunt, Leslie A.; Izaurralde, Roberto C.; Jabloun, Mohamed; Jones, Curtis D.; Kersebaum, Kurt C.; Kimball, Bruce A.; Koehler, Ann-Kristin; Kumar, Soora Naresh; Nendel, Claas; O'Leary, Garry J.; Olesen, Jørgen E.; Ottman, Michael J.; Palosuo, Taru; Prasad, P. V. Vara; Priesack, Eckart; Pugh, Thomas A. M.; Reynolds, Matthew; Rezaei, Ehsan E.; Rötter, Reimund P.; Schmid, Erwin; Semenov, Mikhail A.; Shcherbak, Iurii; Stehfest, Elke; Stöckle, Claudio O.; Stratonovitch, Pierre; Streck, Thilo; Supit, Iwan; Tao, Fulu; Thorburn, Peter; Waha, Katharina; Wall, Gerard W.; Wang, Enli; White, Jeffrey W.; Wolf, Joost; Zhao, Zhigan; Zhu, Yan

2016-12-01

The potential impact of global temperature change on global crop yield has recently been assessed with different methods. Here we show that grid-based and point-based simulations and statistical regressions (from historic records), without deliberate adaptation or CO2 fertilization effects, produce similar estimates of temperature impact on wheat yields at global and national scales. With a 1 °C global temperature increase, global wheat yield is projected to decline between 4.1% and 6.4%. Projected relative temperature impacts from different methods were similar for major wheat-producing countries China, India, USA and France, but less so for Russia. Point-based and grid-based simulations, and to some extent the statistical regressions, were consistent in projecting that warmer regions are likely to suffer more yield loss with increasing temperature than cooler regions. By forming a multi-method ensemble, it was possible to quantify `method uncertainty’ in addition to model uncertainty. This significantly improves confidence in estimates of climate impacts on global food security.

Input-driven versus turnover-driven controls of simulated changes in soil carbon due to land-use change

NASA Astrophysics Data System (ADS)

Nyawira, Sylvia; Nabel, Julia; Brovkin, Victor; Pongratz, Julia

2017-04-01

Modelling studies estimate a global loss in soil carbon caused by land-use changes (LUCs) over the last century. Although it is known that this loss stems from the changes in quantity of litter inputs from the vegetation to the soil (input-driven) and the changes in turnover of carbon in the soil (turnover-driven) associated with LUC, the individual contribution of these two controls to the total changes have not been assessed. Using the dynamic global vegetation model JSBACH, we apply a factor separation approach to isolate the contribution of the input-driven and turnover-driven changes, as well as their synergies, to the total changes in soil carbon from LUC. To assess how land management through crop and wood harvest influences the controls, we compare our results for simulations with and without land management. Our results reveal that for the afforested regions both the input-driven and turnover-driven changes generally result in soil carbon gain, whereas deforested regions exhibit a loss. However, for regions where croplands have increased at the expense of grasslands and pastures, the input-driven changes result in a loss that is partly offset by a gain via the turnover-driven changes. This gain stems from a decrease in the fire-related carbon losses when grasslands or pastures are replaced with croplands. Omitting land management reduces the carbon losses in regions where natural vegetation has been converted to croplands and enhances the gain in afforested regions. The global simulated losses are substantially reduced from 54.0 Pg C to 22.0 Pg C, with the input-driven losses reducing from 54.7 Pg C to 24.9 Pg C. Our study shows that the dominating control of soil carbon losses is through the input-driven changes, which are more directly influenced by human management than the turnover-driven ones.

Directional and Spectral Irradiance in Ocean Models: Effects on Simulated Global Phytoplankton, Nutrients, and Primary Production

NASA Technical Reports Server (NTRS)

Gregg, Watson W.; Rousseaux, Cecile S.

2016-01-01

The importance of including directional and spectral light in simulations of ocean radiative transfer was investigated using a coupled biogeochemical-circulation-radiative model of the global oceans. The effort focused on phytoplankton abundances, nutrient concentrations and vertically-integrated net primary production. The importance was approached by sequentially removing directional (i.e., direct vs. diffuse) and spectral irradiance and comparing results of the above variables to a fully directionally and spectrally-resolved model. In each case the total irradiance was kept constant; it was only the pathways and spectral nature that were changed. Assuming all irradiance was diffuse had negligible effect on global ocean primary production. Global nitrate and total chlorophyll concentrations declined by about 20% each. The largest changes occurred in the tropics and sub-tropics rather than the high latitudes, where most of the irradiance is already diffuse. Disregarding spectral irradiance had effects that depended upon the choice of attenuation wavelength. The wavelength closest to the spectrally-resolved model, 500 nm, produced lower nitrate (19%) and chlorophyll (8%) and higher primary production (2%) than the spectral model. Phytoplankton relative abundances were very sensitive to the choice of non-spectral wavelength transmittance. The combined effects of neglecting both directional and spectral irradiance exacerbated the differences, despite using attenuation at 500 nm. Global nitrate decreased 33% and chlorophyll decreased 24%. Changes in phytoplankton community structure were considerable, representing a change from chlorophytes to cyanobacteria and coccolithophores. This suggested a shift in community function, from light-limitation to nutrient limitation: lower demands for nutrients from cyanobacteria and coccolithophores favored them over the more nutrient-demanding chlorophytes. Although diatoms have the highest nutrient demands in the model, their relative abundances were generally unaffected because they only prosper in nutrient-rich regions, such as the high latitudes and upwelling regions, which showed the fewest effects from the changes in radiative simulations. The results showed that including directional and spectral irradiance when simulating the ocean light field can be important for ocean biology, but the magnitude varies with variables and regions. The quantitative results are intended to assist ocean modelers when considering improved irradiance representations relative to other processes or variables associated with the issues of interest.

Impact of global warming on tropical cyclone genesis in coupled and forced simulations: role of SST spatial anomalies

NASA Astrophysics Data System (ADS)

Royer, Jean-François; Chauvin, Fabrice; Daloz, Anne-Sophie

2010-05-01

The response of tropical cyclones (TC) activity to global warming has not yet reached a clear consensus in the Fourth Assessment Report (AR4) published by the Intergovernmental Panel on Climate Change (IPCC, 2007) or in the recent scientific literature. Observed series are neither long nor reliable enough for a statistically significant detection and attribution of past TC trends, and coupled climate models give widely divergent results for the future evolution of TC activity in the different ocean basins. The potential importance of the spatial structure of the future SST warming has been pointed out by Chauvin et al. (2006) in simulations performed at CNRM with the ARPEGE-Climat GCM. The current presentation describes a new set of simulations that have been performed with the ARPEGE-Climat model to try to understand the possible role of SST patterns in the TC cyclogenesis response in 15 CMIP3 coupled simulations analysed by Royer et al (2009). The new simulations have been performed with the atmospheric component of the ARPEGE-Climat GCM forced in 10 year simulations by the SST patterns from each of 15 CMIP3 simulations with different climate model at the end of the 21st century according to scenario A2. The TC analysis is based on the computation of a Convective Yearly Genesis Parameter (CYGP) and the Genesis Potential Index (GPI). The computed genesis indices for each of the ARPEGE-Climat forced simulations is compared with the indices computed directly from the initial coupled simulation. The influence of SST patterns can then be more easily assessed since all the ARPEGE-Climat simulations are performed with the same atmospheric model, whereas the original simulations used models with different parameterization and resolutions. The analysis shows that CYGP or GPI anomalies obtained with ARPEGE are as variable between each other as those obtained originally by the different IPCC models. The variety of SST patterns used to force ARPEGE explains a large part of the dispersion, though for a given SST pattern, ARPEGE does not necessarily reproduce the anomaly produced originally by the IPCC model which produced the SST anomaly. Many factors can contribute to this discrepancy, but the most prominent seems to be the absence of coupling between the forced atmospheric ARPEGE simulation and the underlying ocean. When the atmospheric model is forced by prescribed SST anomalies some retroactions between cyclogenesis and ocean are missing. There are however areas over the globe were models agree about the CYGP or GPI anomalies induced by global warming, such as the Indian Ocean that shows a better coherency in the coupled and forced responses. This could be an indication that interaction between ocean and atmosphere is not as strong there as in the other basins. Details of the results for all the other ocean basins will be presented. References: Chauvin F. and J.-F. Royer and M. Déqué , 2006: Response of hurricane-type vortices to global warming as simulated by ARPEGE-Climat at high resolution. Climate Dynamics 27(4), 377-399. IPCC [Intergovernmental Panel for Climate Change], Climate change 2007: The physical science basis, in: S. Solomon et al. (eds.), Cambridge University Press. Royer JF, F Chauvin, 2009: Response of tropical cyclogenesis to global warming in an IPCC AR-4 scenario assessed by a modified yearly genesis parameter. "Hurricanes and Climate Change", J. B. Elsner and T. H. Jagger (Eds.), Springer, ISBN: 978-0-387-09409-0, pp 213-234.

Assessing the Global Climate Response to Freshwater Forcing from the Antarctic Ice Sheet Under Future Climate Scenarios

NASA Astrophysics Data System (ADS)

Rogstad, S.; Condron, A.; DeConto, R.; Pollard, D.

2017-12-01

Observational evidence indicates that the West Antarctic Ice Sheet (WAIS) is losing mass at an accelerating rate. Impacts to global climate resulting from changing ocean circulation patterns due to increased freshwater runoff from Antarctica in the future could have significant implications for global heat transport, but to-date this topic has not been investigated using complex numerical models with realistic freshwater forcing. Here, we present results from a high resolution fully coupled ocean-atmosphere model (CESM 1.2) forced with runoff from Antarctica prescribed from a high resolution regional ice sheet-ice shelf model. Results from the regional simulations indicate a potential freshwater contribution from Antarctica of up to 1 m equivalent sea level rise by the end of the century under RCP 8.5 indicating that a substantial input of freshwater into the Southern Ocean is possible. Our high resolution global simulations were performed under IPCC future climate scenarios RCP 4.5 and 8.5. We will present results showing the impact of WAIS collapse on global ocean circulation, sea ice, air temperature, and salinity in order to assess the potential for abrupt climate change triggered by WAIS collapse.

Hydrological droughts in the 21st century, hotspots and uncertainties from a global multimodel ensemble experiment

PubMed Central

Prudhomme, Christel; Giuntoli, Ignazio; Robinson, Emma L.; Clark, Douglas B.; Arnell, Nigel W.; Dankers, Rutger; Fekete, Balázs M.; Franssen, Wietse; Gerten, Dieter; Gosling, Simon N.; Hagemann, Stefan; Hannah, David M.; Kim, Hyungjun; Masaki, Yoshimitsu; Satoh, Yusuke; Stacke, Tobias; Wada, Yoshihide; Wisser, Dominik

2014-01-01

Increasing concentrations of greenhouse gases in the atmosphere are expected to modify the global water cycle with significant consequences for terrestrial hydrology. We assess the impact of climate change on hydrological droughts in a multimodel experiment including seven global impact models (GIMs) driven by bias-corrected climate from five global climate models under four representative concentration pathways (RCPs). Drought severity is defined as the fraction of land under drought conditions. Results show a likely increase in the global severity of hydrological drought at the end of the 21st century, with systematically greater increases for RCPs describing stronger radiative forcings. Under RCP8.5, droughts exceeding 40% of analyzed land area are projected by nearly half of the simulations. This increase in drought severity has a strong signal-to-noise ratio at the global scale, and Southern Europe, the Middle East, the Southeast United States, Chile, and South West Australia are identified as possible hotspots for future water security issues. The uncertainty due to GIMs is greater than that from global climate models, particularly if including a GIM that accounts for the dynamic response of plants to CO2 and climate, as this model simulates little or no increase in drought frequency. Our study demonstrates that different representations of terrestrial water-cycle processes in GIMs are responsible for a much larger uncertainty in the response of hydrological drought to climate change than previously thought. When assessing the impact of climate change on hydrology, it is therefore critical to consider a diverse range of GIMs to better capture the uncertainty. PMID:24344266

Hydrological droughts in the 21st century, hotspots and uncertainties from a global multimodel ensemble experiment.

PubMed

Prudhomme, Christel; Giuntoli, Ignazio; Robinson, Emma L; Clark, Douglas B; Arnell, Nigel W; Dankers, Rutger; Fekete, Balázs M; Franssen, Wietse; Gerten, Dieter; Gosling, Simon N; Hagemann, Stefan; Hannah, David M; Kim, Hyungjun; Masaki, Yoshimitsu; Satoh, Yusuke; Stacke, Tobias; Wada, Yoshihide; Wisser, Dominik

2014-03-04

Increasing concentrations of greenhouse gases in the atmosphere are expected to modify the global water cycle with significant consequences for terrestrial hydrology. We assess the impact of climate change on hydrological droughts in a multimodel experiment including seven global impact models (GIMs) driven by bias-corrected climate from five global climate models under four representative concentration pathways (RCPs). Drought severity is defined as the fraction of land under drought conditions. Results show a likely increase in the global severity of hydrological drought at the end of the 21st century, with systematically greater increases for RCPs describing stronger radiative forcings. Under RCP8.5, droughts exceeding 40% of analyzed land area are projected by nearly half of the simulations. This increase in drought severity has a strong signal-to-noise ratio at the global scale, and Southern Europe, the Middle East, the Southeast United States, Chile, and South West Australia are identified as possible hotspots for future water security issues. The uncertainty due to GIMs is greater than that from global climate models, particularly if including a GIM that accounts for the dynamic response of plants to CO2 and climate, as this model simulates little or no increase in drought frequency. Our study demonstrates that different representations of terrestrial water-cycle processes in GIMs are responsible for a much larger uncertainty in the response of hydrological drought to climate change than previously thought. When assessing the impact of climate change on hydrology, it is therefore critical to consider a diverse range of GIMs to better capture the uncertainty.

Modeling global yield growth of major crops under multiple socioeconomic pathways

NASA Astrophysics Data System (ADS)

Iizumi, T.; Kim, W.; Zhihong, S.; Nishimori, M.

2016-12-01

Global gridded crop models (GGCMs) are a key tool in deriving global food security scenarios under climate change. However, it is difficult for GGCMs to reproduce the reported yield growth patterns—rapid growth, yield stagnation and yield collapse. Here, we propose a set of parameterizations for GGCMs to capture the contributions to yield from technological improvements at the national and multi-decadal scales. These include country annual per capita gross domestic product (GDP)-based parameterizations for the nitrogen application rate and crop tolerance to stresses associated with high temperature, low temperature, water deficit and water excess. Using a GGCM combined with the parameterizations, we present global 140-year (1961-2100) yield growth simulations for maize, soybean, rice and wheat under multiple shared socioeconomic pathways (SSPs) and no climate change. The model reproduces the major characteristics of reported global and country yield growth patterns over the 1961-2013 period. Under the most rapid developmental pathway SSP5, the simulated global yields for 2091-2100, relative to 2001-2010, are the highest (1.21-1.82 times as high, with variations across the crops), followed by SSP1 (1.14-1.56 times as high), SSP2 (1.12-1.49 times as high), SSP4 (1.08-1.38 times as high) and SSP3 (1.08-1.36 times as high). Future country yield growth varies substantially by income level as well as by crop and by SSP. These yield pathways offer a new baseline for addressing the interdisciplinary questions related to global agricultural development, food security and climate change.

ICPP: Approach for Understanding Complexity of Plasma

NASA Astrophysics Data System (ADS)

Sato, Tetsuya

2000-10-01

In this talk I wish to present an IT system that could promote Science of Complexity. In order to deal with a seemingly `complex' phenomenon, which means `beyond analytical manipulation', computer simulation is a viable powerful tool. However, complexity implies a concept beyond the horizon of reductionism. Therefore, rather than simply solving a complex phenomenon for a given boundary condition, one must establish an intelligent way of attacking mutual evolution of a system and its environment. NIFS-TCSC has been developing a prototype system that consists of supercomputers, virtual reality devices and high-speed network system. Let us explain this by picking up a global atmospheric circulation group, global oceanic circulation group and local weather prediction group. Local weather prediction group predicts the local change of the weather such as the creation of cloud and rain in the near future under the global conditions obtained by the global atmospheric and ocean groups. The global groups run simulations by modifying the local heat source/sink evaluated by the local weather prediction and then obtain the global conditions in the next time step. By repeating such a feedback performance one can predict the mutual evolution of the local system and its environment. Mutual information exchanges among multiple groups are carried out instantaneously by the networked common virtual reality space in which 3-D global and local images of the atmospheric and oceanic circulation and the cloud and rain maps are arbitrarily manipulated by any of the groups and commonly viewed. The present networking system has a great advantage that any simulation groups can freely and arbitrarily change their alignment, so that mutual evolution of any stratum system can become tractable by utilizing this network system.

Global temperature definition affects achievement of long-term climate goals

NASA Astrophysics Data System (ADS)

Richardson, Mark; Cowtan, Kevin; Millar, Richard J.

2018-05-01

The Paris Agreement on climate change aims to limit ‘global average temperature’ rise to ‘well below 2 °C’ but reported temperature depends on choices about how to blend air and water temperature data, handle changes in sea ice and account for regions with missing data. Here we use CMIP5 climate model simulations to estimate how these choices affect reported warming and carbon budgets consistent with the Paris Agreement. By the 2090s, under a low-emissions scenario, modelled global near-surface air temperature rise is 15% higher (5%–95% range 6%–21%) than that estimated by an approach similar to the HadCRUT4 observational record. The difference reduces to 8% with global data coverage, or 4% with additional removal of a bias associated with changing sea-ice cover. Comparison of observational datasets with different data sources or infilling techniques supports our model results regarding incomplete coverage. From high-emission simulations, we find that a HadCRUT4 like definition means higher carbon budgets and later exceedance of temperature thresholds, relative to global near-surface air temperature. 2 °C warming is delayed by seven years on average, to 2048 (2035–2060), and CO2 emissions budget for a >50% chance of <2 °C warming increases by 67 GtC (246 GtCO2).

Global climate simulations at 3000-year intervals for the last 21 000 years with the GENMOM coupled atmosphere–ocean model

USGS Publications Warehouse

Alder, Jay R.; Hostetler, Steven W.

2015-01-01

We apply GENMOM, a coupled atmosphere–ocean climate model, to simulate eight equilibrium time slices at 3000-year intervals for the past 21 000 years forced by changes in Earth–Sun geometry, atmospheric greenhouse gases (GHGs), continental ice sheets, and sea level. Simulated global cooling during the Last Glacial Maximum (LGM) is 3.8 ◦C and the rate of post-glacial warming is in overall agreement with recently published temperature reconstructions. The greatest rate of warming occurs between 15 and 12 ka (2.4 ◦C over land, 0.7 ◦C over oceans, and 1.4 ◦C globally) in response to changes in radiative forcing from the diminished extent of the Northern Hemisphere (NH) ice sheets and increases in GHGs and NH summer insolation. The modeled LGM and 6 ka temperature and precipitation climatologies are generally consistent with proxy reconstructions, the PMIP2 and PMIP3 simulations, and other paleoclimate data–model analyses. The model does not capture the mid-Holocene “thermal maximum” and gradual cooling to preindustrial (PI) global temperature found in the data. Simulated monsoonal precipitation in North Africa peaks between 12 and 9 ka at values ∼ 50 % greater than those of the PI, and Indian monsoonal precipitation peaks at 12 and 9 ka at values ∼ 45 % greater than the PI. GENMOM captures the reconstructed LGM extent of NH and Southern Hemisphere (SH) sea ice. The simulated present-day Antarctica Circumpolar Current (ACC) is ∼ 48 % weaker than the observed (62 versus 119 Sv). The simulated present-day Atlantic Meridional Overturning Circulation (AMOC) of 19.3 ± 1.4 Sv on the Bermuda Rise (33◦ N) is comparable with observed value of 18.7 ± 4.8 Sv. AMOC at 33◦ N is reduced by ∼ 15 % during the LGM, and the largest post-glacial increase (∼ 11 %) occurs during the 15 ka time slice.

: “Developing Regional Modeling Techniques Applicable for Simulating Future Climate Conditions in the Carolinas”

EPA Science Inventory

Global climate models (GCMs) are currently used to obtain information about future changes in the large-scale climate. However, such simulations are typically done at coarse spatial resolutions, with model grid boxes on the order of 100 km on a horizontal side. Therefore, techniq...

Predictions of extreme precipitation and sea-level rise under climate change.

PubMed

Senior, C A; Jones, R G; Lowe, J A; Durman, C F; Hudson, D

2002-07-15

Two aspects of global climate change are particularly relevant to river and coastal flooding: changes in extreme precipitation and changes in sea level. In this paper we summarize the relevant findings of the IPCC Third Assessment Report and illustrate some of the common results found by the current generation of coupled atmosphere-ocean general circulation models (AOGCMs), using the Hadley Centre models. Projections of changes in extreme precipitation, sea-level rise and storm surges affecting the UK will be shown from the Hadley Centre regional models and the Proudman Oceanographic Laboratory storm-surge model. A common finding from AOGCMs is that in a warmer climate the intensity of precipitation will increase due to a more intense hydrological cycle. This leads to reduced return periods (i.e. more frequent occurrences) of extreme precipitation in many locations. The Hadley Centre regional model simulates reduced return periods of extreme precipitation in a number of flood-sensitive areas of the UK. In addition, simulated changes in storminess and a rise in average sea level around the UK lead to reduced return periods of extreme high coastal water events. The confidence in all these results is limited by poor spatial resolution in global coupled models and by uncertainties in the physical processes in both global and regional models, and is specific to the climate change scenario used.

AgMIP Coordinated Global and Regional Assessments for 1.5°C and 2.0°C

NASA Astrophysics Data System (ADS)

Rosenzweig, C.

2017-12-01

The Agricultural Model Intercomparison and Improvement Project (AgMIP) has developed novel methods for Coordinated Global and Regional Assessments (CGRA) of agriculture and food security in a changing world. The present study performs a proof-of-concept of the CGRA to demonstrate advantages and challenges of the framework. This effort responds to the request by UNFCCC for the implications of limiting global temperature increases to 1.5°C and 2.0°C above pre-industrial conditions. The protocols for the 1.5°C/2.0°C assessment establish explicit and testable linkages across disciplines and scales, connecting outputs and inputs from the Shared Socio-economic Pathways (SSPs), Representative Agricultural Pathways (RAPs), HAPPI and CMIP5 ensemble scenarios, global gridded crop models, global agricultural economic models, site-based crop models, and within-country regional economic models. CGRA results show that at the global scale, mixed areas of positive and negative simulated yield changes, with declines in some breadbasket regions led to overall declines in productivity at both 1.5°C and 2.0°C. These projected global yield changes resulted in increases in prices of major commodities in a global economic model. Simulations for 1.5°C and 2.0°C using site-based crop models had mixed results depending on region and crop, but with more negative effects on productivity at 2.0°C than at 1.5°C for the most part. In conjunction with price changes from the global economics models, these productivity declines resulted generally in small positive effects on regional farm livelihoods, showing that farming systems should continue to be viable under high mitigation scenarios. CGRA protocols focus on how mitigation actions and effects differ across scales, with main mechanisms studied in the integrated assessment models being policies and technologies that reduce direct non-CO2 emissions from agriculture, reduce CO2 emissions from land use change and forest sink enhancement, and utilize biomass for energy production. At regional scales, increasing soil organic carbon (SOC) is of active interest.

Native temperature regime influences soil response to simulated warming

Treesearch

Timothy G. Whitby; Michael D. Madritch

2013-01-01

Anthropogenic climate change is expected to increase global temperatures and potentially increase soil carbon (C) mineralization, which could lead to a positive feedback between global warming and soil respiration. However the magnitude and spatial variability of belowground responses to warming are not yet fully understood. Some of the variability may depend...

The Agricultural Model Intercomparison and Improvement Project (AgMIP): Protocols and Pilot Studies

NASA Technical Reports Server (NTRS)

Rosenzweig, C.; Jones, J. W.; Hatfield, J. L.; Ruane, A. C.; Boote, K. J.; Thorburn, P.; Antle, J. M.; Nelson, G. C.; Porter, C.; Janssen, S.;

Quantification of increased flood risk due to global climate change for urban river management planning.

PubMed

Morita, M

2011-01-01

Global climate change is expected to affect future rainfall patterns. These changes should be taken into account when assessing future flooding risks. This study presents a method for quantifying the increase in flood risk caused by global climate change for use in urban flood risk management. Flood risk in this context is defined as the product of flood damage potential and the probability of its occurrence. The study uses a geographic information system-based flood damage prediction model to calculate the flood damage caused by design storms with different return periods. Estimation of the monetary damages these storms produce and their return periods are precursors to flood risk calculations. The design storms are developed from modified intensity-duration-frequency relationships generated by simulations of global climate change scenarios (e.g. CGCM2A2). The risk assessment method is applied to the Kanda River basin in Tokyo, Japan. The assessment provides insights not only into the flood risk cost increase due to global warming, and the impact that increase may have on flood control infrastructure planning.

On the role of ozone feedback in the ENSO amplitude response under global warming

NASA Astrophysics Data System (ADS)

Nowack, P. J.; Braesicke, P.; Abraham, N. L.; Pyle, J. A.

2017-12-01

The El Niño-Southern Oscillation (ENSO) in the tropical Pacific is of key importance to global climate and weather. However, climate models still disagree on the ENSO's response under climate change. Here we show that typical model representations of ozone can have a first-order impact on ENSO amplitude projections in climate sensitivity simulations (i.e. standard abrupt 4xCO2). We mainly explain this effect by the lapse rate adjustment of the tropical troposphere to ozone changes in the upper troposphere and lower stratosphere (UTLS) under 4xCO2. The ozone-induced lapse rate changes modify the Walker circulation response to the CO2 forcing and consequently tropical Pacific surface temperature gradients. Therefore, not including ozone feedbacks increases the number of extreme ENSO events in our model. In addition, we demonstrate that even if ozone changes in the tropical UTLS are included in the simulations, the neglect of the ozone response in the middle-upper stratosphere still leads to significantly larger ENSO amplitudes (compared to simulations run with a fully interactive atmospheric chemistry scheme). Climate modeling studies of the ENSO often neglect changes in ozone. Our results imply that this could affect the inter-model spread found in ENSO projections and, more generally, surface climate change simulations. We discuss the additional complexity in quantifying such ozone-related effects that arises from the apparent model dependency of chemistry-climate feedbacks and, possibly, their range of surface climate impacts. In conclusion, we highlight the need to understand better the coupling between ozone, the tropospheric circulation, and climate variability. Reference: Nowack PJ, Braesicke P, Abraham NL, and Pyle JA (2017), On the role of ozone feedback in the ENSO amplitude response under global warming, Geophys. Res. Lett. 44, 3858-3866, doi:10.1002/2016GL072418.

Simulated responses of terrestrial aridity to black carbon and sulfate aerosols: LIN: SIMULATED RESPONSES ARIDITY

DOE PAGES

Lin, L.; Gettelman, A.; Xu, Y.; ...

2016-01-27

Aridity index (AI), defined as the ratio of precipitation to potential evapotranspiration (PET), is a measure of the dryness of terrestrial climate. Global climate models generally project future decreases of AI (drying) associated with global warming scenarios driven by increasing greenhouse gas and declining aerosols. Given their different effects in the climate system, scattering and absorbing aerosols may affect AI differently. Here we explore the terrestrial aridity responses to anthropogenic black carbon (BC) and sulfate (SO4) aerosols with Community Earth System Model simulations. Positive BC radiative forcing decreases precipitation averaged over global land at a rate of 0.9%/°C of globalmore » mean surface temperature increase (moderate drying), while BC radiative forcing increases PET by 1.0%/°C (also drying). BC leads to a global decrease of 1.9%/°C in AI (drying). SO4 forcing is negative and causes precipitation a decrease at a rate of 6.7%/°C cooling (strong drying). PET also decreases in response to SO4 aerosol cooling by 6.3%/°C cooling (contributing to moistening). Thus, SO4 cooling leads to a small decrease in AI (drying) by 0.4%/°C cooling. Despite the opposite effects on global mean temperature, BC and SO4 both contribute to the twentieth century drying (AI decrease). Sensitivity test indicates that surface temperature and surface available energy changes dominate BC- and SO4-induced PET changes.« less

Drivers and uncertainties of future global marine primary production in marine ecosystem models

NASA Astrophysics Data System (ADS)

Laufkötter, C.; Vogt, M.; Gruber, N.; Aita-Noguchi, M.; Aumont, O.; Bopp, L.; Buitenhuis, E.; Doney, S. C.; Dunne, J.; Hashioka, T.; Hauck, J.; Hirata, T.; John, J.; Le Quéré, C.; Lima, I. D.; Nakano, H.; Seferian, R.; Totterdell, I.; Vichi, M.; Völker, C.

2015-12-01

Past model studies have projected a global decrease in marine net primary production (NPP) over the 21st century, but these studies focused on the multi-model mean rather than on the large inter-model differences. Here, we analyze model-simulated changes in NPP for the 21st century under IPCC's high-emission scenario RCP8.5. We use a suite of nine coupled carbon-climate Earth system models with embedded marine ecosystem models and focus on the spread between the different models and the underlying reasons. Globally, NPP decreases in five out of the nine models over the course of the 21st century, while three show no significant trend and one even simulates an increase. The largest model spread occurs in the low latitudes (between 30° S and 30° N), with individual models simulating relative changes between -25 and +40 %. Of the seven models diagnosing a net decrease in NPP in the low latitudes, only three simulate this to be a consequence of the classical interpretation, i.e., a stronger nutrient limitation due to increased stratification leading to reduced phytoplankton growth. In the other four, warming-induced increases in phytoplankton growth outbalance the stronger nutrient limitation. However, temperature-driven increases in grazing and other loss processes cause a net decrease in phytoplankton biomass and reduce NPP despite higher growth rates. One model projects a strong increase in NPP in the low latitudes, caused by an intensification of the microbial loop, while NPP in the remaining model changes by less than 0.5 %. While models consistently project increases NPP in the Southern Ocean, the regional inter-model range is also very substantial. In most models, this increase in NPP is driven by temperature, but it is also modulated by changes in light, macronutrients and iron as well as grazing. Overall, current projections of future changes in global marine NPP are subject to large uncertainties and necessitate a dedicated and sustained effort to improve the models and the concepts and data that guide their development.

Modeling Modern Methane Emissions from Natural Wetlands. 2; Interannual Variations 1982-1993

NASA Technical Reports Server (NTRS)

Walter, Bernadette P.; Heimann, Martin; Mattews, Elaine; Hansen, James E. (Technical Monitor)

2001-01-01

A global run of a process-based methane model [Walter et al., this issue] is performed using high-frequency atmospheric forcing fields from ECMWF reanalyses of the period from 1982 to 1993. We calculate global annual methane emissions to be 260 Tg/ yr. 25% of methane emissions originate from wetlands north of 30 deg. N. Only 60% of the produced methane is emitted, while the rest is re-oxidized. A comparison of zonal integrals of simulated global wetland emissions and results obtained by an inverse modeling approach shows good agreement. In a test with data from two wetlands, the seasonality of simulated and observed methane emissions agrees well. The effects of sub-grid scale variations in model parameters and input data are examined. Modeled methane emissions show high regional, seasonal and interannual variability. Seasonal cycles of methane emissions are dominated by temperature in high latitude wetlands, and by changes in the water table in tropical wetlands. Sensitivity tests show that +/- 1 C changes in temperature lead to +/- 20 % changes in methane emissions from wetlands. Uniform changes of +/- 20% in precipitation alter methane emissions by about +/- 18%. Limitations in the model are analyzed. Simulated interannual variations in methane emissions from wetlands are compared to observed atmospheric growth rate anomalies. Our model simulation results suggest that contributions from other sources than wetlands and/or the sinks are more important in the tropics than north-of 30 deg. N. In higher northern latitudes, it seems that a large part, of the observed interannual variations can be explained by variations in wetland emissions. Our results also suggest that reduced wetland emissions played an important role in the observed negative methane growth rate anomaly in 1992.

A simulation of orientation dependent, global changes in camera sensitivity in ECT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bieszk, J.A.; Hawman, E.G.; Malmin, R.E.

1984-01-01

ECT promises the abilities to: 1) observe radioisotope distributions in a patient without the summation of overlying activity to reduce contrast, and 2) measure quantitatively these distributions to further and more accurately assess organ function. Ideally, camera-based ECT systems should have a performance that is independent of camera orientation or gantry angle. This study is concerned with ECT quantitation errors that can arise from angle-dependent variations of camera sensitivity. Using simulated phantoms representative of heart and liver sections, the effects of sensitivity changes on reconstructed images were assessed both visually and quantitatively based on ROI sums. The sinogram for eachmore » test image was simulated with 128 linear digitization and 180 angular views. The global orientation-dependent sensitivity was modelled by applying an angular sensitivity dependence to the sinograms of the test images. Four sensitivity variations were studied. Amplitudes of 0% (as a reference), 5%, 10%, and 25% with a costheta dependence were studied as well as a cos2theta dependence with a 5% amplitude. Simulations were done with and without Poisson noise to: 1) determine trends in the quantitative effects as a function of the magnitude of the variation, and 2) to see how these effects are manifested in studies having statistics comparable to clinical cases. For the most realistic sensitivity variation (costheta, 5% ampl.), the ROIs chosen in the present work indicated changes of <0.5% in the noiseless case and <5% for the case with Poisson noise. The effects of statistics appear to dominate any effects due to global, sinusoidal, orientation-dependent sensitivity changes in the cases studied.« less

Evaluation of a Cloud Resolving Model Using TRMM Observations for Multiscale Modeling Applications

NASA Technical Reports Server (NTRS)

Posselt, Derek J.; L'Ecuyer, Tristan; Tao, Wei-Kuo; Hou, Arthur Y.; Stephens, Graeme L.

2007-01-01

The climate change simulation community is moving toward use of global cloud resolving models (CRMs), however, current computational resources are not sufficient to run global CRMs over the hundreds of years necessary to produce climate change estimates. As an intermediate step between conventional general circulation models (GCMs) and global CRMs, many climate analysis centers are embedding a CRM in each grid cell of a conventional GCM. These Multiscale Modeling Frameworks (MMFs) represent a theoretical advance over the use of conventional GCM cloud and convection parameterizations, but have been shown to exhibit an overproduction of precipitation in the tropics during the northern hemisphere summer. In this study, simulations of clouds, precipitation, and radiation over the South China Sea using the CRM component of the NASA Goddard MMF are evaluated using retrievals derived from the instruments aboard the Tropical Rainfall Measuring Mission (TRMM) satellite platform for a 46-day time period that spans 5 May - 20 June 1998. The NASA Goddard Cumulus Ensemble (GCE) model is forced with observed largescale forcing derived from soundings taken during the intensive observing period of the South China Sea Monsoon Experiment. It is found that the GCE configuration used in the NASA Goddard MMF responds too vigorously to the imposed large-scale forcing, accumulating too much moisture and producing too much cloud cover during convective phases, and overdrying the atmosphere and suppressing clouds during monsoon break periods. Sensitivity experiments reveal that changes to ice cloud microphysical parameters have a relatively large effect on simulated clouds, precipitation, and radiation, while changes to grid spacing and domain length have little effect on simulation results. The results motivate a more detailed and quantitative exploration of the sources and magnitude of the uncertainty associated with specified cloud microphysical parameters in the CRM components of MMFs.

Tree cover in Central Africa: determinants and sensitivity under contrasted scenarios of global change

PubMed Central

Aleman, Julie C.; Blarquez, Olivier; Gourlet-Fleury, Sylvie; Bremond, Laurent; Favier, Charly

2017-01-01

Tree cover is a key variable for ecosystem functioning, and is widely used to study tropical ecosystems. But its determinants and their relative importance are still a matter of debate, especially because most regional and global analyses have not considered the influence of agricultural practices. More information is urgently needed regarding how human practices influence vegetation structure. Here we focused in Central Africa, a region still subjected to traditional agricultural practices with a clear vegetation gradient. Using remote sensing data and global databases, we calibrated a Random Forest model to correlatively link tree cover with climatic, edaphic, fire and agricultural practices data. We showed that annual rainfall and accumulated water deficit were the main drivers of the distribution of tree cover and vegetation classes (defined by the modes of tree cover density), but agricultural practices, especially pastoralism, were also important in determining tree cover. We simulated future tree cover with our model using different scenarios of climate and land-use (agriculture and population) changes. Our simulations suggest that tree cover may respond differently regarding the type of scenarios, but land-use change was an important driver of vegetation change even able to counterbalance the effect of climate change in Central Africa. PMID:28134259

The biogeophysical climatic impacts of anthropogenic land use change during the Holocene

NASA Astrophysics Data System (ADS)

Smith, M. Clare; Singarayer, Joy S.; Valdes, Paul J.; Kaplan, Jed O.; Branch, Nicholas P.

2016-04-01

The first agricultural societies were established around 10 ka BP and had spread across much of Europe and southern Asia by 5.5 ka BP with resultant anthropogenic deforestation for crop and pasture land. Various studies (e.g. Joos et al., 2004; Kaplan et al., 2011; Mitchell et al., 2013) have attempted to assess the biogeochemical implications for Holocene climate in terms of increased carbon dioxide and methane emissions. However, less work has been done to examine the biogeophysical impacts of this early land use change. In this study, global climate model simulations with Hadley Centre Coupled Model version 3 (HadCM3) were used to examine the biogeophysical effects of Holocene land cover change on climate, both globally and regionally, from the early Holocene (8 ka BP) to the early industrial era (1850 CE). Two experiments were performed with alternative descriptions of past vegetation: (i) one in which potential natural vegetation was simulated by Top-down Representation of Interactive Foliage and Flora Including Dynamics (TRIFFID) but without land use changes and (ii) one where the anthropogenic land use model Kaplan and Krumhardt 2010 (KK10; Kaplan et al., 2009, 2011) was used to set the HadCM3 crop regions. Snapshot simulations were run at 1000-year intervals to examine when the first signature of anthropogenic climate change can be detected both regionally, in the areas of land use change, and globally. Results from our model simulations indicate that in regions of early land disturbance such as Europe and south-east Asia detectable temperature changes, outside the normal range of variability, are encountered in the model as early as 7 ka BP in the June-July-August (JJA) season and throughout the entire annual cycle by 2-3 ka BP. Areas outside the regions of land disturbance are also affected, with virtually the whole globe experiencing significant temperature changes (predominantly cooling) by the early industrial period. The global annual mean temperature anomalies found in our single model simulations were -0.22 at 1850 CE, -0.11 at 2 ka BP, and -0.03 °C at 7 ka BP. Regionally, the largest temperature changes were in Europe with anomalies of -0.83 at 1850 CE, -0.58 at 2 ka BP, and -0.24 °C at 7 ka BP. Large-scale precipitation features such as the Indian monsoon, the Intertropical Convergence Zone (ITCZ), and the North Atlantic storm track are also impacted by local land use and remote teleconnections. We investigated how advection by surface winds, mean sea level pressure (MSLP) anomalies, and tropospheric stationary wave train disturbances in the mid- to high latitudes led to remote teleconnections.

The effects of global change upon United States air quality

NASA Astrophysics Data System (ADS)

Gonzalez-Abraham, R.; Chung, S. H.; Avise, J.; Lamb, B.; Salathé, E. P., Jr.; Nolte, C. G.; Loughlin, D.; Guenther, A.; Wiedinmyer, C.; Duhl, T.; Zhang, Y.; Streets, D. G.

2015-11-01

To understand more fully the effects of global changes on ambient concentrations of ozone and particulate matter with aerodynamic diameter smaller than 2.5 μm (PM2.5) in the United States (US), we conducted a comprehensive modeling effort to evaluate explicitly the effects of changes in climate, biogenic emissions, land use and global/regional anthropogenic emissions on ozone and PM2.5 concentrations and composition. Results from the ECHAM5 global climate model driven with the A1B emission scenario from the Intergovernmental Panel on Climate Change (IPCC) were downscaled using the Weather Research and Forecasting (WRF) model to provide regional meteorological fields. We developed air quality simulations using the Community Multiscale Air Quality Model (CMAQ) chemical transport model for two nested domains with 220 and 36 km horizontal grid cell resolution for a semi-hemispheric domain and a continental United States (US) domain, respectively. The semi-hemispheric domain was used to evaluate the impact of projected global emissions changes on US air quality. WRF meteorological fields were used to calculate current (2000s) and future (2050s) biogenic emissions using the Model of Emissions of Gases and Aerosols from Nature (MEGAN). For the semi-hemispheric domain CMAQ simulations, present-day global emissions inventories were used and projected to the 2050s based on the IPCC A1B scenario. Regional anthropogenic emissions were obtained from the US Environmental Protection Agency National Emission Inventory 2002 (EPA NEI2002) and projected to the future using the MARKet ALlocation (MARKAL) energy system model assuming a business as usual scenario that extends current decade emission regulations through 2050. Our results suggest that daily maximum 8 h average ozone (DM8O) concentrations will increase in a range between 2 to 12 parts per billion (ppb) across most of the continental US. The highest increase occurs in the South, Central and Midwest regions of the US due to increases in temperature, enhanced biogenic emissions and changes in land use. The model predicts an average increase of 1-6 ppb in DM8O due to projected increase in global emissions of ozone precursors. The effects of these factors are only partially offset by reductions in DM8O associated with decreasing US anthropogenic emissions. Increases in PM2.5 levels between 4 and 10 μg m-3 in the Northeast, Southeast, Midwest and South regions are mostly a result of increase in primary anthropogenic particulate matter (PM), enhanced biogenic emissions and land use changes. Changes in boundary conditions shift the composition but do not alter overall simulated PM2.5 mass concentrations.

Cloud radiative effects and changes simulated by the Coupled Model Intercomparison Project Phase 5 models

NASA Astrophysics Data System (ADS)

Shin, Sun-Hee; Kim, Ok-Yeon; Kim, Dongmin; Lee, Myong-In

2017-07-01

Using 32 CMIP5 (Coupled Model Intercomparison Project Phase 5) models, this study examines the veracity in the simulation of cloud amount and their radiative effects (CREs) in the historical run driven by observed external radiative forcing for 1850-2005, and their future changes in the RCP (Representative Concentration Pathway) 4.5 scenario runs for 2006-2100. Validation metrics for the historical run are designed to examine the accuracy in the representation of spatial patterns for climatological mean, and annual and interannual variations of clouds and CREs. The models show large spread in the simulation of cloud amounts, specifically in the low cloud amount. The observed relationship between cloud amount and the controlling large-scale environment are also reproduced diversely by various models. Based on the validation metrics, four models—ACCESS1.0, ACCESS1.3, HadGEM2-CC, and HadGEM2-ES—are selected as best models, and the average of the four models performs more skillfully than the multimodel ensemble average. All models project global-mean SST warming at the increase of the greenhouse gases, but the magnitude varies across the simulations between 1 and 2 K, which is largely attributable to the difference in the change of cloud amount and distribution. The models that simulate more SST warming show a greater increase in the net CRE due to reduced low cloud and increased incoming shortwave radiation, particularly over the regions of marine boundary layer in the subtropics. Selected best-performing models project a significant reduction in global-mean cloud amount of about -0.99% K-1 and net radiative warming of 0.46 W m-2 K-1, suggesting a role of positive feedback to global warming.

Global Famine after a Regional Nuclear War

NASA Astrophysics Data System (ADS)

Robock, A.; Xia, L.; Mills, M. J.; Stenke, A.; Helfand, I.

2014-12-01

A regional nuclear war between India and Pakistan, using 100 15-kt atomic bombs, could inject 5 Tg of soot into the upper troposphere from fires started in urban and industrial areas. Simulations by three different general circulation models, GISS ModelE, WACCM, and SOCOL, all agree that global surface temperature would decrease by 1 to 2°C for 5 to 10 years, and have major impacts on precipitation and solar radiation reaching Earth's surface. Local summer climate changes over land would be larger. Using the DSSAT crop simulation model forced by these three global climate model simulations, we investigate the impacts on agricultural production in China, the largest grain producer in the world. In the first year after the regional nuclear war, a cooler, drier, and darker environment would reduce annual rice production by 23 Mt (24%), maize production by 41 Mt (23%), and wheat production by 23 Mt (50%). This reduction of food availability would continue, with gradually decreasing amplitude, for more than a decade. Results from simulations in other major grain producing regions produce similar results. Thus a nuclear war using much less than 1% of the current global arsenal could produce a global food crisis and put a billion people at risk of famine.

Global Changes of the Water Cycle Intensity

NASA Technical Reports Server (NTRS)

Bosilovich, Michael G.; Schubert, Siegfried D.; Walker, Gregory K.

2003-01-01

In this study, we evaluate numerical simulations of the twentieth century climate, focusing on the changes in the intensity of the global water cycle. A new diagnostic of atmospheric water vapor cycling rate is developed and employed, that relies on constituent tracers predicted at the model time step. This diagnostic is compared to a simplified traditional calculation of cycling rate, based on monthly averages of precipitation and total water content. The mean sensitivity of both diagnostics to variations in climate forcing is comparable. However, the new diagnostic produces systematically larger values and more variability than the traditional average approach. Climate simulations were performed using SSTs of the early (1902-1921) and late (1979- 1998) twentieth century along with the appropriate C02 forcing. In general, the increase of global precipitation with the increases in SST that occurred between the early and late twentieth century is small. However, an increase of atmospheric temperature leads to a systematic increase in total precipitable water. As a result, the residence time of water in the atmosphere increased, indicating a reduction of the global cycling rate. This result was explored further using a number of 50-year climate simulations from different models forced with observed SST. The anomalies and trends in the cycling rate and hydrologic variables of different GCMs are remarkably similar. The global annual anomalies of precipitation show a significant upward trend related to the upward trend of surface temperature, during the latter half of the twentieth century. While this implies an increase in the hydrologic cycle intensity, a concomitant increase of total precipitable water again leads to a decrease in the calculated global cycling rate. An analysis of the land/sea differences shows that the simulated precipitation over land has a decreasing trend while the oceanic precipitation has an upward trend consistent with previous studies and the available observations. The decreasing continental trend in precipitation is located primarily over tropical land regions, with some other regions, such as North America experiencing an increasing trend. Precipitation trends are diagnosed further using the water tracers to delineate the precipitation that occurs because of continental evaporation, as opposed to oceanic evaporation. These diagnostics show that over global land areas, the recycling of continental moisture is decreasing in time. However, the recycling changes are not spatially uniform so that some regions, most notably over the United States, experience continental recycling of water that increases in time.

Insight into global trends in aerosol composition from 2005 to 2015 inferred from the OMI Ultraviolet Aerosol Index

NASA Astrophysics Data System (ADS)

Hammer, Melanie S.; Martin, Randall V.; Li, Chi; Torres, Omar; Manning, Max; Boys, Brian L.

2018-06-01

Observations of aerosol scattering and absorption offer valuable information about aerosol composition. We apply a simulation of the Ultraviolet Aerosol Index (UVAI), a method of detecting aerosol absorption from satellite observations, to interpret UVAI values observed by the Ozone Monitoring Instrument (OMI) from 2005 to 2015 to understand global trends in aerosol composition. We conduct our simulation using the vector radiative transfer model VLIDORT with aerosol fields from the global chemical transport model GEOS-Chem. We examine the 2005-2015 trends in individual aerosol species from GEOS-Chem and apply these trends to the UVAI simulation to calculate the change in simulated UVAI due to the trends in individual aerosol species. We find that global trends in the UVAI are largely explained by trends in absorption by mineral dust, absorption by brown carbon, and scattering by secondary inorganic aerosol. Trends in absorption by mineral dust dominate the simulated UVAI trends over North Africa, the Middle East, East Asia, and Australia. The UVAI simulation resolves observed negative UVAI trends well over Australia, but underestimates positive UVAI trends over North Africa and Central Asia near the Aral Sea and underestimates negative UVAI trends over East Asia. We find evidence of an increasing dust source from the desiccating Aral Sea that may not be well represented by the current generation of models. Trends in absorption by brown carbon dominate the simulated UVAI trends over biomass burning regions. The UVAI simulation reproduces observed negative trends over central South America and West Africa, but underestimates observed UVAI trends over boreal forests. Trends in scattering by secondary inorganic aerosol dominate the simulated UVAI trends over the eastern United States and eastern India. The UVAI simulation slightly overestimates the observed positive UVAI trends over the eastern United States and underestimates the observed negative UVAI trends over India. Quantitative simulation of the OMI UVAI offers new insight into global trends in aerosol composition.

Biodiversity Hotspots, Climate Change, and Agricultural Development: Global Limits of Adaptation

NASA Astrophysics Data System (ADS)

Schneider, U. A.; Rasche, L.; Schmid, E.; Habel, J. C.

2017-12-01

Terrestrial ecosystems are threatened by climate and land management change. These changes result from complex and heterogeneous interactions of human activities and natural processes. Here, we study the potential change in pristine area in 33 global biodiversity hotspots within this century under four climate projections (representative concentration pathways) and associated population and income developments (shared socio-economic pathways). A coupled modelling framework computes the regional net expansion of crop and pasture lands as result of changes in food production and consumption. We use a biophysical crop simulation model to quantify climate change impacts on agricultural productivity, water, and nutrient emissions for alternative crop management systems in more than 100 thousand agricultural land polygons (homogeneous response units) and for each climate projection. The crop simulation model depicts detailed soil, weather, and management information and operates with a daily time step. We use time series of livestock statistics to link livestock production to feed and pasture requirements. On the food consumption side, we estimate national demand shifts in all countries by processing population and income growth projections through econometrically estimated Engel curves. Finally, we use a global agricultural sector optimization model to quantify the net change in pristine area in all biodiversity hotspots under different adaptation options. These options include full-scale global implementation of i) crop yield maximizing management without additional irrigation, ii) crop yield maximizing management with additional irrigation, iii) food yield maximizing crop mix adjustments, iv) food supply maximizing trade flow adjustments, v) healthy diets, and vi) combinations of the individual options above. Results quantify the regional potentials and limits of major agricultural producer and consumer adaptation options for the preservation of pristine areas in biodiversity hotspots. Results also quantify the conflicts between food and water security, biodiversity protection, and climate change mitigation.

Using DOUBLE STAR and CLUSTER Synoptic Observations to Test Global MHD Simulations of the Large-scale Topology of the Dayside Merging Region

NASA Astrophysics Data System (ADS)

Berchem, J.; Marchaudon, A.; Bosqued, J.; Escoubet, C. P.; Dunlop, M.; Owen, C. J.; Reme, H.; Balogh, A.; Carr, C.; Fazakerley, A. N.; Cao, J. B.

2005-12-01

Synoptic measurements from the DOUBLE STAR and CLUSTER spacecraft offer a unique opportunity to evaluate global models in simulating the complex topology and dynamics of the dayside merging region. We compare observations from the DOUBLE STAR TC-1 and CLUSTER spacecraft on May 8, 2004 with the predictions from a three-dimensional magnetohydrodynamic (MHD) simulation that uses plasma and magnetic field parameters measured upstream of the bow shock by the WIND spacecraft. Results from the global simulation are consistent with the large-scale features observed by CLUSTER and TC-1. We discuss topological changes and plasma flows at the dayside magnetospheric boundary inferred from the simulation results. The simulation shows that the DOUBLE STAR spacecraft passed through the dawn side merging region as the IMF rotated. In particular, the simulation indicates that at times TC-1 was very close to the merging region. In addition, we found that the bifurcation of the merging region in the simulation results is consistent with predictions by the antiparallel merging model. However, because of the draping of the magnetosheath field lines over the magnetopause, the positions and shape of the merging region differ significantly from those predicted by the model.

The Impacts of a 2-Degree Rise in Global Temperatures upon Gas-Phase Air Pollutants in Europe

NASA Astrophysics Data System (ADS)

Watson, Laura; Josse, Béatrice; Marecal, Virginie; Lacressonnière, Gwendoline; Vautard, Robert; Gauss, Michael; Engardt, Magnuz; Nyiri, Agnes; Siour, Guillaume

2014-05-01

The 15th session of the Conference of Parties (COP 15) in 2009 ratified the Copenhagen Accord, which "recognises the scientific view that" global temperature rise should be held below 2 degrees C above pre-industrial levels in order to limit the impacts of climate change. Due to the fact that a 2-degree limit has been frequently referred to by policy makers in the context of the Copenhagen Accord and many other high-level policy statements, it is important that the impacts of this 2-degree increase in temperature are adequately analysed. To this end, the European Union sponsored the project IMPACT2C, which uses a multi-disciplinary international team to assess a wide variety of impacts of a 2-degree rise in global temperatures. For example, this future increase in temperature is expected to have a significant influence upon meteorological conditions such as temperature, precipitation, and wind direction and intensity; which will in turn affect the production, deposition, and distribution of air pollutants. For the first part of the air quality analysis within the IMPACT2C project, the impact of meteorological forcings on gas phase air pollutants over Europe was studied using four offline atmospheric chemistry transport models. Two sets of meteorological forcings were used for each model: reanalysis of past observation data and global climate model output. Anthropogenic emissions of ozone precursors for the year 2005 were used for all simulations in order to isolate the impact of meteorology and assess the robustness of the results across the different models. The differences between the simulations that use reanalysis of past observation data and the simulations that use global climate model output show how global climate models modify climate hindcasts by boundary conditions inputs: information that is necessary in order to interpret simulations of future climate. The baseline results were assessed by comparison with AirBase (Version 7) measurement data, and were then used as a reference for an analysis of future climate scenarios upon European air quality. The future scenarios included two types of emission data for the year 2050: one set of emission data corresponding to a current legislation scenario and another corresponding to a scenario with a maximum feasible reduction in emissions. The future scenarios were run for the time period that corresponds to a 2-degree increase in global temperatures; a time period that varies depending on which global climate model is used. In order to calculate the effect of climate change on emission reduction scenarios, the "climate penalty", the future simulations were compared to a simulation using the same future emissions but with current (2005) climate. Results show that climate change will have consequential impacts with regards to the production and geographical distribution of ozone and nitrogen oxides.

Global Change and Human Vulnerability to Vector-Borne Diseases

PubMed Central

Sutherst, Robert W.

2004-01-01

Global change includes climate change and climate variability, land use, water storage and irrigation, human population growth and urbanization, trade and travel, and chemical pollution. Impacts on vector-borne diseases, including malaria, dengue fever, infections by other arboviruses, schistosomiasis, trypanosomiasis, onchocerciasis, and leishmaniasis are reviewed. While climate change is global in nature and poses unknown future risks to humans and natural ecosystems, other local changes are occurring more rapidly on a global scale and are having significant effects on vector-borne diseases. History is invaluable as a pointer to future risks, but direct extrapolation is no longer possible because the climate is changing. Researchers are therefore embracing computer simulation models and global change scenarios to explore the risks. Credible ranking of the extent to which different vector-borne diseases will be affected awaits a rigorous analysis. Adaptation to the changes is threatened by the ongoing loss of drugs and pesticides due to the selection of resistant strains of pathogens and vectors. The vulnerability of communities to the changes in impacts depends on their adaptive capacity, which requires both appropriate technology and responsive public health systems. The availability of resources in turn depends on social stability, economic wealth, and priority allocation of resources to public health. PMID:14726459

The relative contribution of the precipitation and evapotranspiration on total terrestrial water storage change

NASA Astrophysics Data System (ADS)

Zhang, Y.

2017-12-01

Changes of global terrestrial water storage (TWS) retrieved from the Gravity Recovery and Climate Experiment (GRACE) satellite mission has been extensively evaluated by previous studies. However, attributions of global TWS changes are still poorly understood. In this study, the responses TWS to two most important surface water fluxes, precipitation (P) and evapotranspiration (ET), were comprehensively examined based on 3 global P datasets and 3 global ET datasets. In addition, the relative contribution of P and ET to TWS changes were quantified using the hierarchical partitioning analysis. Results show that, over the period of Apr. 2002 to July. 2016, more than 40.5% global continent experienced significant TWS decrease, while significant TWS increases were observed over 36% of global continent. A general positive effect of P on TWS was observed over almost all land, but a contrasting response of TWS to ET were identified between arid or cold areas and humid areas with positive and negative TWS-ET relationship, respectively. Global as a whole, precipitation from GPCC and ET simulated by the Noah model forcing by Global land Data Assimilation System (GLDAS) has the highest performance in explaining global TWS change. HP analysis suggests that the independent contribution of ET to TWS change is apparently higher than that of P. Furthermore, with the decrease of climate humidity, the contribution of P is decreasing, while the contribution of ET is increasing. Spatially speaking, ET has higher impacts on TWS than P in arid areas, while the opposite function was identified for very humid and cold areas. Knowledge from this study is crucial for the understanding of the response of global TWS change to climate change.

Pseudo-global warming controls on the intensity and morphology of extreme convective storm events

NASA Astrophysics Data System (ADS)

Trapp, R. J.

2015-12-01

This research seeks to answer the basic question of how current-day extreme convective storm events might be represented under future anthropogenic climate change. We adapt the "pseudo-global warming" (PGW) methodology employed by Lackmann (2013, 2015) and others, who have investigated flooding and tropical cyclone events under climate change. Here, we exploit coupled atmosphere-ocean GCM data contributed to the CMIP5 archive, and take the mean 3D atmospheric state simulated during May 1990-1999 and subtract it from that simulated during May 2090-2099. Such 3D changes in temperature, humidity, geopotential height, and winds are added to synoptic/meso-scale analyses (NAM-ANL) of specific events, and this modified atmospheric state is then used for initial and boundary conditions for real-data WRF model simulations of the events at high resolution. Comparison of an ensemble of these simulations with control (CTRL) simulations facilitates assessment of PGW effects. In contrast to the robust development of supercellular convection in our CTRL simulations, the combined effects of increased CIN and decreased forcing under PGW led to a failure of convection initiation in many of our ensemble members. Those members that had sufficient matching between the CIN and forcing tended to generate stronger convective updrafts than in the CTRL simulations, because of the relatively higher CAPE under PGW. And, the members with enhanced updrafts also tended to have enhanced vertical rotation. In fact, such mesocyclonic rotation and attendant supercellular morphology were even found in simulations that were driven with PGW-reduced environmental wind shear.

Increased future ice discharge from Antarctica owing to higher snowfall

NASA Astrophysics Data System (ADS)

Winkelmann, Ricarda; Levermann, Anders; Martin, Maria A.; Frieler, Katja

2013-04-01

Anthropogenic climate change is likely to cause continuing global sea-level rise, but some processes within the Earth system may mitigate the magnitude of the projected effect. Regional and global climate models simulate enhanced snowfall over Antarctica, which would provide a direct offset of the future contribution to global sea level rise from cryospheric mass loss and ocean expansion. Uncertainties exist in modelled snowfall, but even larger uncertainties exist in the potential changes of dynamic ice discharge from Antarctica. Here we show that snowfall and discharge are not independent, but that future ice discharge will increase by up to three times as a result of additional snowfall under global warming. Our results, based on an ice-sheet model forced by climate simulations through to the end of 2500, show that the enhanced discharge effect exceeds the effect of surface warming as well as that of basal ice-shelf melting, and is due to the difference in surface elevation change caused by snowfall on grounded versus floating ice. Although different underlying forcings drive ice loss from basal melting versus increased snowfall, similar ice dynamical processes are nonetheless at work in both; therefore results are relatively independent of the specific representation of the transition zone. In an ensemble of simulations designed to capture ice-physics uncertainty, the additional dynamic ice loss along the coastline compensates between 30 and 65 per cent of the ice gain due to enhanced snowfall over the entire continent. This results in a dynamic ice loss of up to 1.25 metres in the year 2500 for the strongest warming scenario.

Impacts of deforestation and afforestation in the Mediterranean region as simulated by the MPI atmospheric GCM

NASA Astrophysics Data System (ADS)

Dümenil Gates, Lydia; Ließ, Stefan

2001-10-01

For two reasons it is important to study the sensitivity of the global climate to changes in the vegetation cover over land. First, in the real world, changes in the vegetation cover may have regional and global implications. Second, in numerical simulations, the sensitivity of the simulated climate may depend on the specific parameterization schemes employed in the model and on the model's large-scale systematic errors. The Max-Planck-Institute's global general circulation model ECHAM4 has been used to study the sensitivity of the local and global climate during a full annual cycle to deforestation and afforestation in the Mediterranean region. The deforestation represents an extreme desertification scenario for this region. The changes in the afforestation experiment are based on the pattern of the vegetation cover 2000 years before present when the climate in the Mediterranean was more humid. The comparison of the deforestation integration to the control shows a slight cooling at the surface and reduced precipitation during the summer as a result of less evapotranspiration of plants and less evaporation from the assumption of eroded soils. There is no significant signal during the winter season due to the stronger influence of the mid-latitude baroclinic disturbances. In general, the results of the afforestation experiment are opposite to those of the deforestation case. A significant response was found in the vicinity of grid points where the land surface characteristics were modified. The response in the Sahara in the afforestation experiment is in agreement with the results from other general circulation model studies.

Estimates of the long-term U.S. economic impacts of global climate change-induced drought.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ehlen, Mark Andrew; Loose, Verne W.; Warren, Drake E.

2010-01-01

While climate-change models have done a reasonable job of forecasting changes in global climate conditions over the past decades, recent data indicate that actual climate change may be much more severe. To better understand some of the potential economic impacts of these severe climate changes, Sandia economists estimated the impacts to the U.S. economy of climate change-induced impacts to U.S. precipitation over the 2010 to 2050 time period. The economists developed an impact methodology that converts changes in precipitation and water availability to changes in economic activity, and conducted simulations of economic impacts using a large-scale macroeconomic model of themore » U.S. economy.« less

Tropical cyclone rainfall area controlled by relative sea surface temperature

PubMed Central

Lin, Yanluan; Zhao, Ming; Zhang, Minghua

2015-01-01

Tropical cyclone rainfall rates have been projected to increase in a warmer climate. The area coverage of tropical cyclones influences their impact on human lives, yet little is known about how tropical cyclone rainfall area will change in the future. Here, using satellite data and global atmospheric model simulations, we show that tropical cyclone rainfall area is controlled primarily by its environmental sea surface temperature (SST) relative to the tropical mean SST (that is, the relative SST), while rainfall rate increases with increasing absolute SST. Our result is consistent with previous numerical simulations that indicated tight relationships between tropical cyclone size and mid-tropospheric relative humidity. Global statistics of tropical cyclone rainfall area are not expected to change markedly under a warmer climate provided that SST change is relatively uniform, implying that increases in total rainfall will be confined to similar size domains with higher rainfall rates. PMID:25761457

Fifty Years of Water Cycle Change expressed in Ocean Salinity

NASA Astrophysics Data System (ADS)

Durack, P. J.; Wijffels, S.

2010-12-01

Using over 1.6 million profiles of salinity, potential temperature and density from historical archives and Argo, we derive the global field of linear change for ocean state properties over the period 1950-2008, taking care to minimise aliasing associated with seasonal and El Nino Southern Oscillation modes. We find large, robust and spatially coherent multi-decadal linear trends in ocean surface salinities. Increases are found in evaporation-dominated regions and freshening in precipitation-dominated regions. The spatial patterns of surface change strongly resemble the climatological mean surface salinity field, consistent with an amplification of the global water cycle. A robust amplification of the mean salinity pattern of 8% (to 200m depth) is found globally and 5-9% is found in each of the 3 key ocean basins. 20th century runs from the CMIP3 model suite support the relationship between amplified patterns of freshwater flux driving an amplified pattern of ocean surface salinity only in models that warm substantially. Models with volcanic aerosols show a diminished warming response and a corresponding weak response in ocean surface salinity change, which implies dampened changes to the global water cycle. The warming response represented in realistic (when compared to observations) 20th century simulations appear quite similar in their broad zonal patterns to those of the projected 21st century simulations, these projected runs being strongly forced by greenhouse gases. This pattern amplification is mostly absent from 20th century simulations which include volcanic forcing. While we confirm that global mean precipitation only weakly change with surface warming (2-3% K-1), the pattern amplification rate in both the freshwater flux and ocean salinity fields indicate larger responses. Our new observed salinity estimates suggest a change of between 8-16% K-1, close to, or greater than, the theoretical response described by the Clausius-Clapeyron relation. The underestimation of change patterns by the CMIP3 model suite is well documented in recent literature describing changes to the atmospheric and terrestrial arms of the global water cycle. These new observational ocean results add emphasis to the conclusion that the rate of observed changes in the 20th century are larger than CMIP3 models, and simplified physical theories predict. A) The 50-year linear surface salinity trend (pss/50-years). Contours every 0.25 pss are plotted in white. B) Ocean-atmosphere freshwater flux (m3 yr-1) averaged over 1980-1993 (Josey et al., 1998). Contours every 1 m3 yr-1 are in white. On both panels, the 1975 surface mean salinity is contoured black (contour interval 0.5 pss for thin lines, 1 for thick lines).

Greenhouse gas policy influences climate via direct effects of land-use change

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, Andrew D.; Collins, William D.; Edmonds, James A.

2013-06-01

Proposed climate mitigation measures do not account for direct biophysical climate impacts of land-use change (LUC), nor do the stabilization targets modeled for the 5th Climate Model Intercomparison Project (CMIP5) Representative Concentration Pathways (RCPs). To examine the significance of such effects on global and regional patterns of climate change, a baseline and alternative scenario of future anthropogenic activity are simulated within the Integrated Earth System Model, which couples the Global Change Assessment Model, Global Land-use Model, and Community Earth System Model. The alternative scenario has high biofuel utilization and approximately 50% less global forest cover compared to the baseline, standardmore » RCP4.5 scenario. Both scenarios stabilize radiative forcing from atmospheric constituents at 4.5 W/m2 by 2100. Thus, differences between their climate predictions quantify the biophysical effects of LUC. Offline radiative transfer and land model simulations are also utilized to identify forcing and feedback mechanisms driving the coupled response. Boreal deforestation is found to strongly influence climate due to increased albedo coupled with a regional-scale water vapor feedback. Globally, the alternative scenario yields a 21st century warming trend that is 0.5 °C cooler than baseline, driven by a 1 W/m2 mean decrease in radiative forcing that is distributed unevenly around the globe. Some regions are cooler in the alternative scenario than in 2005. These results demonstrate that neither climate change nor actual radiative forcing are uniquely related to atmospheric forcing targets such as those found in the RCP’s, but rather depend on particulars of the socioeconomic pathways followed to meet each target.« less

Assessment of NASA GISS E2 CMIP5 and Post-CMIP5 Simulated Clouds and TOA Radiation Budgets Using Satellite Observations: Cloud fraction and properties

NASA Astrophysics Data System (ADS)

Stanfield, R.; Dong, X.; Xi, B.; Kennedy, A. D.; Del Genio, A. D.; Minnis, P.; Jiang, J. H.

2013-12-01

Recent changes to boundary layer turbulence and convection parameterizations of the NASA GISS E2 GCM have led to drastic improvements in the newest Post-CMIP5 (P5) model simulations. A study has been performed to evaluate these changes. Variables including Cloud Fraction (CF), Liquid Water Path (LWP), Ice Water Path (IWP), Cloud Water Path (LWP+IWP, CWP), Precipitable Water Vapor (PWV), and Relative Humidity (RH), from P5 and its CMIP5 (C5) predecessor have been compared to multiple satellite observations including CERES-MODIS (CM), CloudSat/CALIPSO (CC), AIRS, and AMSR-E. P5 simulations show drastic improvements for regional CFs, resulting in better correlations with observations. The largest improvements were found over the Southern Mid-Latitudes (SMLs), where newly implemented changes to the boundary layer turbulence parameterization increased low-level CF by ~20% while generating less optically thick clouds. The double InterTropical Convergence Zone (ITCZ) issue that plagues many GCMs, including previous GISS C5 simulations, is also removed with the new changes to convection parameterizations when decoupled from the ocean. P5 simulations show a decrease in global CWP, more closely resembling CC and CM observations. Globally, P5 simulated PWV is in better agreement with AMSR-R and AIRS, particularly over the SML oceans. RH comparisons show improvement when compared with AIRS. Spatial and variability analyses using Taylor diagrams indicate overall better correlations and smaller standard deviations in PWV and RH comparisons between P5/C5 simulations and AMSR-R/AIRS observations than CF and CWP/LWP/IWP comparisons.

Simulating Climate Change in Ireland

NASA Astrophysics Data System (ADS)

Nolan, P.; Lynch, P.

2012-04-01

At the Meteorology & Climate Centre at University College Dublin, we are using the CLM-Community's COSMO-CLM Regional Climate Model (RCM) and the WRF RCM (developed at NCAR) to simulate the climate of Ireland at high spatial resolution. To address the issue of model uncertainty, a Multi-Model Ensemble (MME) approach is used. The ensemble method uses different RCMs, driven by several Global Climate Models (GCMs), to simulate climate change. Through the MME approach, the uncertainty in the RCM projections is quantified, enabling us to estimate the probability density function of predicted changes, and providing a measure of confidence in the predictions. The RCMs were validated by performing a 20-year simulation of the Irish climate (1981-2000), driven by ECMWF ERA-40 global re-analysis data, and comparing the output to observations. Results confirm that the output of the RCMs exhibit reasonable and realistic features as documented in the historical data record. Projections for the future Irish climate were generated by downscaling the Max Planck Institute's ECHAM5 GCM, the UK Met Office HadGEM2-ES GCM and the CGCM3.1 GCM from the Canadian Centre for Climate Modelling. Simulations were run for a reference period 1961-2000 and future period 2021-2060. The future climate was simulated using the A1B, A2, B1, RCP 4.5 & RCP 8.5 greenhouse gas emission scenarios. Results for the downscaled simulations show a substantial overall increase in precipitation and wind speed for the future winter months and a decrease during the summer months. The predicted annual change in temperature is approximately 1.1°C over Ireland. To date, all RCM projections are in general agreement, thus increasing our confidence in the robustness of the results.

Development of the GEOS-5 Atmospheric General Circulation Model: Evolution from MERRA to MERRA2.

NASA Technical Reports Server (NTRS)

Molod, Andrea; Takacs, Lawrence; Suarez, Max; Bacmeister, Julio

2014-01-01

The Modern-Era Retrospective Analysis for Research and Applications-2 (MERRA2) version of the GEOS-5 (Goddard Earth Observing System Model - 5) Atmospheric General Circulation Model (AGCM) is currently in use in the NASA Global Modeling and Assimilation Office (GMAO) at a wide range of resolutions for a variety of applications. Details of the changes in parameterizations subsequent to the version in the original MERRA reanalysis are presented here. Results of a series of atmosphere-only sensitivity studies are shown to demonstrate changes in simulated climate associated with specific changes in physical parameterizations, and the impact of the newly implemented resolution-aware behavior on simulations at different resolutions is demonstrated. The GEOS-5 AGCM presented here is the model used as part of the GMAO's MERRA2 reanalysis, the global mesoscale "nature run", the real-time numerical weather prediction system, and for atmosphere-only, coupled ocean-atmosphere and coupled atmosphere-chemistry simulations. The seasonal mean climate of the MERRA2 version of the GEOS-5 AGCM represents a substantial improvement over the simulated climate of the MERRA version at all resolutions and for all applications. Fundamental improvements in simulated climate are associated with the increased re-evaporation of frozen precipitation and cloud condensate, resulting in a wetter atmosphere. Improvements in simulated climate are also shown to be attributable to changes in the background gravity wave drag, and to upgrades in the relationship between the ocean surface stress and the ocean roughness. The series of "resolution aware" parameters related to the moist physics were shown to result in improvements at higher resolutions, and result in AGCM simulations that exhibit seamless behavior across different resolutions and applications.

Multimodel Uncertainty Changes in Simulated River Flows Induced by Human Impact Parameterizations

NASA Technical Reports Server (NTRS)

Liu, Xingcai; Tang, Qiuhong; Cui, Huijuan; Mu, Mengfei; Gerten Dieter; Gosling, Simon; Masaki, Yoshimitsu; Satoh, Yusuke; Wada, Yoshihide

2017-01-01

Human impacts increasingly affect the global hydrological cycle and indeed dominate hydrological changes in some regions. Hydrologists have sought to identify the human-impact-induced hydrological variations via parameterizing anthropogenic water uses in global hydrological models (GHMs). The consequently increased model complexity is likely to introduce additional uncertainty among GHMs. Here, using four GHMs, between-model uncertainties are quantified in terms of the ratio of signal to noise (SNR) for average river flow during 1971-2000 simulated in two experiments, with representation of human impacts (VARSOC) and without (NOSOC). It is the first quantitative investigation of between-model uncertainty resulted from the inclusion of human impact parameterizations. Results show that the between-model uncertainties in terms of SNRs in the VARSOC annual flow are larger (about 2 for global and varied magnitude for different basins) than those in the NOSOC, which are particularly significant in most areas of Asia and northern areas to the Mediterranean Sea. The SNR differences are mostly negative (-20 to 5, indicating higher uncertainty) for basin-averaged annual flow. The VARSOC high flow shows slightly lower uncertainties than NOSOC simulations, with SNR differences mostly ranging from -20 to 20. The uncertainty differences between the two experiments are significantly related to the fraction of irrigation areas of basins. The large additional uncertainties in VARSOC simulations introduced by the inclusion of parameterizations of human impacts raise the urgent need of GHMs development regarding a better understanding of human impacts. Differences in the parameterizations of irrigation, reservoir regulation and water withdrawals are discussed towards potential directions of improvements for future GHM development. We also discuss the advantages of statistical approaches to reduce the between-model uncertainties, and the importance of calibration of GHMs for not only better performances of historical simulations but also more robust and confidential future projections of hydrological changes under a changing environment.

Influences of Regional Climate Change on Air Quality across the Continental U.S. Projected from Downscaling IPCC ARS Simulations

EPA Science Inventory

Projecting climate change scenarios to local scales is important for understanding, mitigating, and adapting to the effects of climate change on society and the environment. Many of the global climate models (GCMs) that are participating in the Intergovernmental Panel on Climate ...

Rising temperatures reduce global wheat production

NASA Astrophysics Data System (ADS)

Asseng, S.; Ewert, F.; Martre, P.; Rötter, R. P.; Lobell, D. B.; Cammarano, D.; Kimball, B. A.; Ottman, M. J.; Wall, G. W.; White, J. W.; Reynolds, M. P.; Alderman, P. D.; Prasad, P. V. V.; Aggarwal, P. K.; Anothai, J.; Basso, B.; Biernath, C.; Challinor, A. J.; de Sanctis, G.; Doltra, J.; Fereres, E.; Garcia-Vila, M.; Gayler, S.; Hoogenboom, G.; Hunt, L. A.; Izaurralde, R. C.; Jabloun, M.; Jones, C. D.; Kersebaum, K. C.; Koehler, A.-K.; Müller, C.; Naresh Kumar, S.; Nendel, C.; O'Leary, G.; Olesen, J. E.; Palosuo, T.; Priesack, E.; Eyshi Rezaei, E.; Ruane, A. C.; Semenov, M. A.; Shcherbak, I.; Stöckle, C.; Stratonovitch, P.; Streck, T.; Supit, I.; Tao, F.; Thorburn, P. J.; Waha, K.; Wang, E.; Wallach, D.; Wolf, J.; Zhao, Z.; Zhu, Y.

2015-02-01

Crop models are essential tools for assessing the threat of climate change to local and global food production. Present models used to predict wheat grain yield are highly uncertain when simulating how crops respond to temperature. Here we systematically tested 30 different wheat crop models of the Agricultural Model Intercomparison and Improvement Project against field experiments in which growing season mean temperatures ranged from 15 °C to 32 °C, including experiments with artificial heating. Many models simulated yields well, but were less accurate at higher temperatures. The model ensemble median was consistently more accurate in simulating the crop temperature response than any single model, regardless of the input information used. Extrapolating the model ensemble temperature response indicates that warming is already slowing yield gains at a majority of wheat-growing locations. Global wheat production is estimated to fall by 6% for each °C of further temperature increase and become more variable over space and time.

Machine Learning Predictions of a Multiresolution Climate Model Ensemble

NASA Astrophysics Data System (ADS)

Anderson, Gemma J.; Lucas, Donald D.

2018-05-01

Statistical models of high-resolution climate models are useful for many purposes, including sensitivity and uncertainty analyses, but building them can be computationally prohibitive. We generated a unique multiresolution perturbed parameter ensemble of a global climate model. We use a novel application of a machine learning technique known as random forests to train a statistical model on the ensemble to make high-resolution model predictions of two important quantities: global mean top-of-atmosphere energy flux and precipitation. The random forests leverage cheaper low-resolution simulations, greatly reducing the number of high-resolution simulations required to train the statistical model. We demonstrate that high-resolution predictions of these quantities can be obtained by training on an ensemble that includes only a small number of high-resolution simulations. We also find that global annually averaged precipitation is more sensitive to resolution changes than to any of the model parameters considered.

Impacts of Canadian and global black carbon shipping emissions on Arctic climate

NASA Astrophysics Data System (ADS)

Shrestha, R.; von Salzen, K.

2017-12-01

Shipping activities have increased across the Arctic and are projected to continue to increase in the future. In this study we compare the climate impacts of Canadian and global shipping black carbon (BC) emissions on the Arctic using the Canadian Center for Climate Modelling and Analysis Earth System Model (CanESM4.1). The model simulations are performed with and without shipping emissions at T63 (128 x 64) spectral resolution. Results indicate that shipping activities enhance BC concentrations across the area close to the shipping emissions, which causes increased absorption of solar radiation (direct effect). An impact of shipping on temperatures is simulated across the entire Arctic, with maximum warming in fall and winter seasons. Although global mean temperature changes are very similar between the two simulations, increase in Canadian BC shipping emissions cause warmer Arctic land surface temperature in summer due to the direct radiative effects of aerosol.

Rising Temperatures Reduce Global Wheat Production

NASA Technical Reports Server (NTRS)

Asseng, S.; Ewert, F.; Martre, P.; Rötter, R. P.; Lobell, D. B.; Cammarano, D.; Kimball, B. A.; Ottman, M. J.; Wall, G. W.; White, J. W.;

Will surface winds weaken in response to global warming?

NASA Astrophysics Data System (ADS)

Ma, Jian; Foltz, Gregory R.; Soden, Brian J.; Huang, Gang; He, Jie; Dong, Changming

2016-12-01

The surface Walker and tropical tropospheric circulations have been inferred to slow down from historical observations and model projections, yet analysis of large-scale surface wind predictions is lacking. Satellite measurements of surface wind speed indicate strengthening trends averaged over the global and tropical oceans that are supported by precipitation and evaporation changes. Here we use corrected anemometer-based observations to show that the surface wind speed has not decreased in the averaged tropical oceans, despite its reduction in the region of the Walker circulation. Historical simulations and future projections for climate change also suggest a near-zero wind speed trend averaged in space, regardless of the Walker cell change. In the tropics, the sea surface temperature pattern effect acts against the large-scale circulation slow-down. For higher latitudes, the surface winds shift poleward along with the eddy-driven mid-latitude westerlies, resulting in a very small contribution to the global change in surface wind speed. Despite its importance for surface wind speed change, the influence of the SST pattern change on global-mean rainfall is insignificant since it cannot substantially alter the global energy balance. As a result, the precipitation response to global warming remains ‘muted’ relative to atmospheric moisture increase. Our results therefore show consistency between projections and observations of surface winds and precipitation.

Impact of large-scale circulation changes in the North Atlantic sector on the current and future Mediterranean winter hydroclimate

NASA Astrophysics Data System (ADS)

Barcikowska, Monika J.; Kapnick, Sarah B.; Feser, Frauke

2018-03-01

The Mediterranean region, located in the transition zone between the dry subtropical and wet European mid-latitude climate, is very sensitive to changes in the global mean climate state. Projecting future changes of the Mediterranean hydroclimate under global warming therefore requires dynamic climate models to reproduce the main mechanisms controlling regional hydroclimate with sufficiently high resolution to realistically simulate climate extremes. To assess future winter precipitation changes in the Mediterranean region we use the Geophysical Fluid Dynamics Laboratory high-resolution general circulation model for control simulations with pre-industrial greenhouse gas and aerosol concentrations which are compared to future scenario simulations. Here we show that the coupled model is able to reliably simulate the large-scale winter circulation, including the North Atlantic Oscillation and Eastern Atlantic patterns of variability, and its associated impacts on the mean Mediterranean hydroclimate. The model also realistically reproduces the regional features of daily heavy rainfall, which are absent in lower-resolution simulations. A five-member future projection ensemble, which assumes comparatively high greenhouse gas emissions (RCP8.5) until 2100, indicates a strong winter decline in Mediterranean precipitation for the coming decades. Consistent with dynamical and thermodynamical consequences of a warming atmosphere, derived changes feature a distinct bipolar behavior, i.e. wetting in the north—and drying in the south. Changes are most pronounced over the northwest African coast, where the projected winter precipitation decline reaches 40% of present values. Despite a decrease in mean precipitation, heavy rainfall indices show drastic increases across most of the Mediterranean, except the North African coast, which is under the strong influence of the cold Canary Current.

Predicting the Responses of Soil Nitrite-Oxidizers to Multi-Factorial Global Change: A Trait-Based Approach

DOE PAGES

Le Roux, Xavier; Bouskill, Nicholas J.; Niboyet, Audrey; ...

2016-05-17

Soil microbial diversity is huge and a few grams of soil contain more bacterial taxa than there are bird species on Earth. This high diversity often makes predicting the responses of soil bacteria to environmental change intractable and restricts our capacity to predict the responses of soil functions to global change. Here, using a long-term field experiment in a California grassland, we studied the main and interactive effects of three global change factors (increased atmospheric CO 2 concentration, precipitation and nitrogen addition, and all their factorial combinations, based on global change scenarios for central California) on the potential activity, abundancemore » and dominant taxa of soil nitrite-oxidizing bacteria (NOB). Using a trait-based model, we then tested whether categorizing NOB into a few functional groups unified by physiological traits enables understanding and predicting how soil NOB respond to global environmental change. Contrasted responses to global change treatments were observed between three main NOB functional types. In particular, putatively mixotrophic Nitrobacter, rare under most treatments, became dominant under the 'High CO 2 +Nitrogen+Precipitation' treatment. The mechanistic trait-based model, which simulated ecological niches of NOB types consistent with previous ecophysiological reports, helped predicting the observed effects of global change on NOB and elucidating the underlying biotic and abiotic controls. Our results are a starting point for representing the overwhelming diversity of soil bacteria by a few functional types that can be incorporated into models of terrestrial ecosystems and biogeochemical processes.« less

Predicting the Responses of Soil Nitrite-Oxidizers to Multi-Factorial Global Change: A Trait-Based Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Roux, Xavier; Bouskill, Nicholas J.; Niboyet, Audrey

Soil microbial diversity is huge and a few grams of soil contain more bacterial taxa than there are bird species on Earth. This high diversity often makes predicting the responses of soil bacteria to environmental change intractable and restricts our capacity to predict the responses of soil functions to global change. Here, using a long-term field experiment in a California grassland, we studied the main and interactive effects of three global change factors (increased atmospheric CO 2 concentration, precipitation and nitrogen addition, and all their factorial combinations, based on global change scenarios for central California) on the potential activity, abundancemore » and dominant taxa of soil nitrite-oxidizing bacteria (NOB). Using a trait-based model, we then tested whether categorizing NOB into a few functional groups unified by physiological traits enables understanding and predicting how soil NOB respond to global environmental change. Contrasted responses to global change treatments were observed between three main NOB functional types. In particular, putatively mixotrophic Nitrobacter, rare under most treatments, became dominant under the 'High CO 2 +Nitrogen+Precipitation' treatment. The mechanistic trait-based model, which simulated ecological niches of NOB types consistent with previous ecophysiological reports, helped predicting the observed effects of global change on NOB and elucidating the underlying biotic and abiotic controls. Our results are a starting point for representing the overwhelming diversity of soil bacteria by a few functional types that can be incorporated into models of terrestrial ecosystems and biogeochemical processes.« less

Role of atmospheric heating over the South China Sea and western Pacific regions in modulating Asian summer climate under the global warming background

NASA Astrophysics Data System (ADS)

He, Bian; Yang, Song; Li, Zhenning

2016-05-01

The response of monsoon precipitation to global warming, which is one of the most significant climate change signals at the earth's surface, exhibits very distinct regional features, especially over the South China Sea (SCS) and adjacent regions in boreal summer. To understand the possible atmospheric dynamics in these specific regions under the global warming background, changes in atmospheric heating and their possible influences on Asian summer climate are investigated by both observational diagnosis and numerical simulations. Results indicate that heating in the middle troposphere has intensified in the SCS and western Pacific regions in boreal summer, accompanied by increased precipitation, cloud cover, and lower-tropospheric convergence and decreased sea level pressure. Sensitivity experiments show that middle and upper tropospheric heating causes an east-west feedback pattern between SCS and western Pacific and continental South Asia, which strengthens the South Asian High in the upper troposphere and moist convergence in the lower troposphere, consequently forcing a descending motion and adiabatic warming over continental South Asia. When air-sea interaction is considered, the simulation results are overall more similar to observations, and in particular the bias of precipitation over the Indian Ocean simulated by AGCMs has been reduced. The result highlights the important role of air-sea interaction in understanding the changes in Asian climate.

Prehistoric land use and Neolithisation in Europe in the context of regional climate events

NASA Astrophysics Data System (ADS)

Lemmen, C.; Wirtz, K. W.; Gronenborn, D.

2009-04-01

We present a simple, adaptation-driven, spatially explicit model of pre-Bronze age socio-technological change, called the Global Land Use and Technological Evolution Simulator (GLUES). The socio-technological realm is described by three characteristic traits: available technology, subsistence style ratio, and economic diversity. Human population and culture develop in the context of global paleoclimate and regional paleoclimate events. Global paleoclimate is derived from CLIMBER-2 Earth System Model anomalies superimposed on the IIASA temperature and precipitation database. Regional a forcing is provided by abrupt climate deteriorations from a compilation of 138 long-term high-resolution climate proxy time series from mostly terrestrial and near-shore archives. The GLUES simulator provides for a novel way to explore the interplay between climate, climate change, and cultural evolution both on the Holocene timescale as well as for short-term extreme event periods. We sucessfully simulate the migration of people and the diffusion of Neolithic technology from the Near East into Europe in the period 12000-4000 a BP. We find good agreement with recent archeological compilations of Western Eurasian Neolithic sites. No causal relationship between climate events and cultural evolution could be identified, but the speed of cultural development is found to be modulated by the frequency of climate events. From the demographic evolution and regional ressource consumption, we estimate regional land use change and prehistoric greenhouse gas emissions.

Towards Direct Simulation of Future Tropical Cyclone Statistics in a High-Resolution Global Atmospheric Model

DOE PAGES

Wehner, Michael F.; Bala, G.; Duffy, Phillip; ...

2010-01-01

We present a set of high-resolution global atmospheric general circulation model (AGCM) simulations focusing on the model's ability to represent tropical storms and their statistics. We find that the model produces storms of hurricane strength with realistic dynamical features. We also find that tropical storm statistics are reasonable, both globally and in the north Atlantic, when compared to recent observations. The sensitivity of simulated tropical storm statistics to increases in sea surface temperature (SST) is also investigated, revealing that a credible late 21st century SST increase produced increases in simulated tropical storm numbers and intensities in all ocean basins. Whilemore » this paper supports previous high-resolution model and theoretical findings that the frequency of very intense storms will increase in a warmer climate, it differs notably from previous medium and high-resolution model studies that show a global reduction in total tropical storm frequency. However, we are quick to point out that this particular model finding remains speculative due to a lack of radiative forcing changes in our time-slice experiments as well as a focus on the Northern hemisphere tropical storm seasons.« less

The Role of Sea Ice in 2 x CO2 Climate Model Sensitivity. Part 2; Hemispheric Dependencies

NASA Technical Reports Server (NTRS)

Rind, D.; Healy, R.; Parkinson, C.; Martinson, D.

1997-01-01

How sensitive are doubled CO2 simulations to GCM control-run sea ice thickness and extent? This issue is examined in a series of 10 control-run simulations with different sea ice and corresponding doubled CO2 simulations. Results show that with increased control-run sea ice coverage in the Southern Hemisphere, temperature sensitivity with climate change is enhanced, while there is little effect on temperature sensitivity of (reasonable) variations in control-run sea ice thickness. In the Northern Hemisphere the situation is reversed: sea ice thickness is the key parameter, while (reasonable) variations in control-run sea ice coverage are of less importance. In both cases, the quantity of sea ice that can be removed in the warmer climate is the determining factor. Overall, the Southern Hemisphere sea ice coverage change had a larger impact on global temperature, because Northern Hemisphere sea ice was sufficiently thick to limit its response to doubled CO2, and sea ice changes generally occurred at higher latitudes, reducing the sea ice-albedo feedback. In both these experiments and earlier ones in which sea ice was not allowed to change, the model displayed a sensitivity of -0.02 C global warming per percent change in Southern Hemisphere sea ice coverage.

The Sensitivity of the North American Monsoon to Deglacial Climate Change in Proxies and Models

NASA Astrophysics Data System (ADS)

Bhattacharya, T.; Tierney, J. E.

2017-12-01

The North American Monsoon (NAM), which brings summer rainfall to the arid US Southwest and northwestern Mexico, remains one of the least understood monsoon systems. Model simulations produce divergent NAM responses to future anthropogenic warming, and many paleoclimatic records from the NAM region are more sensitive to winter rainfall than the summertime circulation. As a result, we have an incomplete understanding of NAM sensitivity to past and future global climate change. Our work seeks to improve understanding of NAM dynamics using new proxy records and model simulations. We have developed quantitative reconstructions of NAM strength since the LGM ( 21 ka BP) using leaf wax biomarkers (e.g. dD of n-acids) from marine sediment cores in the Gulf of California. We contrast these proxy records with idealized GCM simulations (i.e. CESM1.2) to diagnose the mechanisms behind NAM responses to LGM boundary conditions and abrupt deglacial climate events. Our results suggest that ice-sheet induced changes in atmospheric circulation acted in concert with local changes in Gulf of California SSTs to modulate the late glacial NAM. This work has important implications for our understanding of NAM dynamics, its relationship with other monsoon systems, and its sensitivity to past and future global climate change.

Evaluating climate models: Should we use weather or climate observations?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oglesby, Robert J; Erickson III, David J

2009-12-01

Calling the numerical models that we use for simulations of climate change 'climate models' is a bit of a misnomer. These 'general circulation models' (GCMs, AKA global climate models) and their cousins the 'regional climate models' (RCMs) are actually physically-based weather simulators. That is, these models simulate, either globally or locally, daily weather patterns in response to some change in forcing or boundary condition. These simulated weather patterns are then aggregated into climate statistics, very much as we aggregate observations into 'real climate statistics'. Traditionally, the output of GCMs has been evaluated using climate statistics, as opposed to their abilitymore » to simulate realistic daily weather observations. At the coarse global scale this may be a reasonable approach, however, as RCM's downscale to increasingly higher resolutions, the conjunction between weather and climate becomes more problematic. We present results from a series of present-day climate simulations using the WRF ARW for domains that cover North America, much of Latin America, and South Asia. The basic domains are at a 12 km resolution, but several inner domains at 4 km have also been simulated. These include regions of complex topography in Mexico, Colombia, Peru, and Sri Lanka, as well as a region of low topography and fairly homogeneous land surface type (the U.S. Great Plains). Model evaluations are performed using standard climate analyses (e.g., reanalyses; NCDC data) but also using time series of daily station observations. Preliminary results suggest little difference in the assessment of long-term mean quantities, but the variability on seasonal and interannual timescales is better described. Furthermore, the value-added by using daily weather observations as an evaluation tool increases with the model resolution.« less

Simulated climate-warming increases Coleoptera activity-densities and reduces community diversity in a cereal crop

USDA-ARS?s Scientific Manuscript database

To assess one likely effect of global warming, we experimentally increased the temperature and precipitation of a coleopteran community (mainly Carabidae) of an agro-ecosystem. We simulated climate change on a field of spring wheat by experimentally increasing the temperature by 2°C using infrared h...

Impacts of land use/cover classification accuracy on regional climate simulations

NASA Astrophysics Data System (ADS)

Ge, Jianjun; Qi, Jiaguo; Lofgren, Brent M.; Moore, Nathan; Torbick, Nathan; Olson, Jennifer M.

2007-03-01

Land use/cover change has been recognized as a key component in global change. Various land cover data sets, including historically reconstructed, recently observed, and future projected, have been used in numerous climate modeling studies at regional to global scales. However, little attention has been paid to the effect of land cover classification accuracy on climate simulations, though accuracy assessment has become a routine procedure in land cover production community. In this study, we analyzed the behavior of simulated precipitation in the Regional Atmospheric Modeling System (RAMS) over a range of simulated classification accuracies over a 3 month period. This study found that land cover accuracy under 80% had a strong effect on precipitation especially when the land surface had a greater control of the atmosphere. This effect became stronger as the accuracy decreased. As shown in three follow-on experiments, the effect was further influenced by model parameterizations such as convection schemes and interior nudging, which can mitigate the strength of surface boundary forcings. In reality, land cover accuracy rarely obtains the commonly recommended 85% target. Its effect on climate simulations should therefore be considered, especially when historically reconstructed and future projected land covers are employed.

Attribution of Trends and Variability in Surface Ozone over the United States

NASA Technical Reports Server (NTRS)

Strode, Sarah; Cooper, Owen; Damo, Megan; Logan, Jennifer; Rodriquez, Jose; Strahan, Susan; Witte, Jacquie

2013-01-01

Concentrations of tropospheric ozone, a greenhouse gas and air pollutant, are impacted by changes in precursor emissions as well meteorology and influx from the stratosphere. Observations show a decreasing trend in summertime surface ozone at rural stations in the eastern United States, while some western stations show increasing trends, particularly in springtime. We use the Global Modeling Initiative (GMI) global chemical transport model to investigate the roles of precursor emission changes, meteorological variability, and stratosphere-troposphere exchange (STE) in explaining observed trends in surface ozone from rural sites in the United States from 1991-2010. The model's interannual variability shows significant correlations with observations from many of the surface sites. We also compare the simulated ozone to ozonesonde data for several locations with sufficiently long records. We compare a simulation with time-dependent precursor emissions, including emission reductions over the United States and Europe and increases over Asia, to a simulation with fixed emissions to quantify the impact of changing emissions on the surface trends. The simulation with varying emissions reproduces much of the east-west difference in summertime ozone over the U.S., although it generally underestimates the negative trend in the East. In contrast, the fixed-emission simulation shows increasing ozone at both eastern and western sites. We will discuss possible causes of this behavior, including long-range transport and STE.

Use and uncertainty evaluation of a process-based model for assessing the methane budgets of global terrestrial ecosystems

NASA Astrophysics Data System (ADS)

Ito, A.; Inatomi, M.

2011-07-01

We assessed the global terrestrial budget of methane (CH4) using a process-based biogeochemical model (VISIT) and inventory data. Emissions from wetlands, paddy fields, biomass burning, and plants, and oxidative consumption by upland soils, were simulated by the model. Emissions from livestock ruminants and termites were evaluated by an inventory approach. These CH4 flows were estimated for each of the model's 0.5° × 0.5° grid cells from 1901 to 2009, while accounting for atmospheric composition, meteorological factors, and land-use changes. Estimation uncertainties were examined through ensemble simulations using different parameterization schemes and input data (e.g. different wetland maps and emission factors). From 1996 to 2005, the average global terrestrial CH4 budget was estimated on the basis of 576 simulations, and terrestrial ecosystems were found to be a net source of 320.4 ± 18.9 Tg CH4 yr-1. Wetland and ruminant emissions were the primary sources. The results of our simulations indicate that sources and sinks are distributed highly heterogeneously over the Earth's land surface. Seasonal and interannual variability in the terrestrial budget was assessed. The trend of increasing net terrestrial sources and its relationship with temperature variability imply that terrestrial CH4 feedbacks will play an increasingly important role as a result of future climatic change.

Revision and application of the LINKAGES model to simulate forest growth in central hardwood landscapes in response to climate change

Treesearch

William D. Dijak; Brice B. Hanberry; Jacob S. Fraser; Hong S. He; Wen J. Wang; Frank R. Thompson

2017-01-01

Context. Global climate change impacts forest growth and methods of modeling those impacts at the landscape scale are needed to forecast future forest species composition change and abundance. Changes in forest landscapes will affect ecosystem processes and services such as succession and disturbance, wildlife habitat, and production of forest...

Farm Simulation: a tool for evaluating the mitigation of greenhouse gas emissions and the adaptation of dairy production to climate change

USDA-ARS?s Scientific Manuscript database

Farms both produce greenhouse gas emissions that drive human-induced climate change and are impacted by that climate change. Whole farm and global climate models provide useful tools for studying the benefits and costs of greenhouse gas mitigation and the adaptation of farms to changing climate. The...

Streamflow response to climate and landuse changes in a coastal watershed in North Carolina

Treesearch

S. Qi; G. Sun; Y. Wang; S.G. McNulty; J.A. Moore Myers

2009-01-01

It is essential to examine the sensitivity of hydrologic responses to climate and landuse change across different physiographic regions in order to formulate sound water management policies for local response to projected global change. This study used the a simulation model to examine the potential impacts of climate and landuse changes on streamflow of the...

Evidence for climate change in the satellite cloud record.

PubMed

Norris, Joel R; Allen, Robert J; Evan, Amato T; Zelinka, Mark D; O'Dell, Christopher W; Klein, Stephen A

2016-08-04

Clouds substantially affect Earth's energy budget by reflecting solar radiation back to space and by restricting emission of thermal radiation to space. They are perhaps the largest uncertainty in our understanding of climate change, owing to disagreement among climate models and observational datasets over what cloud changes have occurred during recent decades and will occur in response to global warming. This is because observational systems originally designed for monitoring weather have lacked sufficient stability to detect cloud changes reliably over decades unless they have been corrected to remove artefacts. Here we show that several independent, empirically corrected satellite records exhibit large-scale patterns of cloud change between the 1980s and the 2000s that are similar to those produced by model simulations of climate with recent historical external radiative forcing. Observed and simulated cloud change patterns are consistent with poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops at all latitudes. The primary drivers of these cloud changes appear to be increasing greenhouse gas concentrations and a recovery from volcanic radiative cooling. These results indicate that the cloud changes most consistently predicted by global climate models are currently occurring in nature.

Evidence for climate change in the satellite cloud record

NASA Astrophysics Data System (ADS)

Norris, Joel R.; Allen, Robert J.; Evan, Amato T.; Zelinka, Mark D.; O'Dell, Christopher W.; Klein, Stephen A.

2016-08-01

Clouds substantially affect Earth’s energy budget by reflecting solar radiation back to space and by restricting emission of thermal radiation to space. They are perhaps the largest uncertainty in our understanding of climate change, owing to disagreement among climate models and observational datasets over what cloud changes have occurred during recent decades and will occur in response to global warming. This is because observational systems originally designed for monitoring weather have lacked sufficient stability to detect cloud changes reliably over decades unless they have been corrected to remove artefacts. Here we show that several independent, empirically corrected satellite records exhibit large-scale patterns of cloud change between the 1980s and the 2000s that are similar to those produced by model simulations of climate with recent historical external radiative forcing. Observed and simulated cloud change patterns are consistent with poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops at all latitudes. The primary drivers of these cloud changes appear to be increasing greenhouse gas concentrations and a recovery from volcanic radiative cooling. These results indicate that the cloud changes most consistently predicted by global climate models are currently occurring in nature.

The Jena Diversity Model: Towards a Richer Representation of the Terrestrial Biosphere for Earth System Modelling

NASA Astrophysics Data System (ADS)

Pavlick, R.; Reu, B.; Bohn, K.; Dyke, J.; Kleidon, A.

2010-12-01

The terrestrial biosphere is a complex, self-organizing system which is continually both adapting to and altering its global environment. It also exhibits a vast diversity of vegetation forms and functioning. However, the terrestrial biosphere components within current state-of-the-art Earth System Models abstract this diversity in to a handful of relatively static plant functional types. These coarse and static representations of functional diversity might contribute to overly pessimistic projections regarding terrestrial ecosystem responses to scenarios of global change (e.g. Amazonian and boreal forest diebacks). In the Jena Diversity (JeDi) model, we introduce a new approach to vegetation modelling with a richer representation of functional diversity, based not on plant functional types, but on unavoidable plant ecophysiological trade-offs, which we hypothesize should be more stable in time. The JeDi model tests a large number of plant growth strategies. Each growth strategy is simulated using a set of randomly generated parameter values, which characterize its functioning in terms of carbon allocation, ecophysiology, and phenology, which are then linked to the growing conditions at the land surface. The model is constructed in such a way that these parameters inherently lead to ecophysiological trade-offs, which determine whether a growth strategy is able to survive and reproduce under the prevalent climatic conditions. Kleidon and Mooney (2000) demonstrated that this approach is capable of reproducing the geographic distribution of species richness. More recently, we have shown the JeDi model can explain other biogeographical phenomena including the present-day global pattern of biomes (Reu et al., accepted), ecosystem evenness (Kleidon et al. 2009), and possible mechanisms for biome shifts and biodiversity changes under scenarios of global warming (Reu et al., submitted). We have also evaluated the simulated biogeochemical fluxes from JeDi against a variety of site, field, and satellite observations (Pavlick et al., submitted) following a protocol established by the Carbon-Land Model Intercomparison Project (Randerson et al. 2009). We found that the global patterns of biogeochemical fluxes and land surface properties are reasonably well simulated using this bottom-up trade-off approach and compare favorably with other state of the art terrestrial biosphere models. Here, we present some results from JeDi simulations, wherein we varied the modelled functional diversity to quantify its impact on terrestrial biogeochemical fluxes under both present-day conditions and projected scenarios of global change. We also present results from a set of simulations wherein we vary the ability of the modelled ecosystems to adapt through changes in functional composition, leading to different projection responses of the carbon cycle to global warming. This plant functional tradeoff approach sets the foundation for many applications, including exploring the emergence and climatic impacts of major vegetation transitions throughout the last 400 million years as well as quantifying the significance of preserving functional diversity to hedge against uncertain climates in the future.

Hydrological and associated biogeochemical consequences of rapid global warming during the Paleocene-Eocene Thermal Maximum

NASA Astrophysics Data System (ADS)

Carmichael, Matthew J.; Inglis, Gordon N.; Badger, Marcus P. S.; Naafs, B. David A.; Behrooz, Leila; Remmelzwaal, Serginio; Monteiro, Fanny M.; Rohrssen, Megan; Farnsworth, Alexander; Buss, Heather L.; Dickson, Alexander J.; Valdes, Paul J.; Lunt, Daniel J.; Pancost, Richard D.

2017-10-01

The Paleocene-Eocene Thermal Maximum (PETM) hyperthermal, 56 million years ago (Ma), is the most dramatic example of abrupt Cenozoic global warming. During the PETM surface temperatures increased between 5 and 9 °C and the onset likely took < 20 kyr. The PETM provides a case study of the impacts of rapid global warming on the Earth system, including both hydrological and associated biogeochemical feedbacks, and proxy data from the PETM can provide constraints on changes in warm climate hydrology simulated by general circulation models (GCMs). In this paper, we provide a critical review of biological and geochemical signatures interpreted as direct or indirect indicators of hydrological change at the PETM, explore the importance of adopting multi-proxy approaches, and present a preliminary model-data comparison. Hydrological records complement those of temperature and indicate that the climatic response at the PETM was complex, with significant regional and temporal variability. This is further illustrated by the biogeochemical consequences of inferred changes in hydrology and, in fact, changes in precipitation and the biogeochemical consequences are often conflated in geochemical signatures. There is also strong evidence in many regions for changes in the episodic and/or intra-annual distribution of precipitation that has not widely been considered when comparing proxy data to GCM output. Crucially, GCM simulations indicate that the response of the hydrological cycle to the PETM was heterogeneous - some regions are associated with increased precipitation - evaporation (P - E), whilst others are characterised by a decrease. Interestingly, the majority of proxy data come from the regions where GCMs predict an increase in PETM precipitation. We propose that comparison of hydrological proxies to GCM output can be an important test of model skill, but this will be enhanced by further data from regions of model-simulated aridity and simulation of extreme precipitation events.

Gap Models as Tools for Sustainable Development under Environmental Changes in Northern Eurasia

NASA Astrophysics Data System (ADS)

Shugart, H. H., Jr.; Wang, B.; Brazhnik, K.; Armstrong, A. H.; Foster, A.

2017-12-01

Agent-based models of complex systems or as used in this review, Individual-based Models (IBMs), emerged in the 1960s and early 1970s, across diverse disciplines from astronomy to zoology. IBMs arose from a deeply embedded ecological tradition of understanding the dynamics of ecosystems from a "bottom-up" accounting of the interactions of the parts. In this case, individual trees are principal among the parts. Because they are computationally demanding, these models have prospered as the power of digital computers has increased exponentially over the decades following the 1970s. Forest IBMs are no longer computationally bound from developing continental- or global-scale simulations of responses of forests to climate and other changes. Gap models simulate the changes in forests by simulating the birth, growth and death of each individual tree on small plots of land that in summation comprise a forest (or set of sample plots on a forested landscape or region). Currently, gap models have grown from continental-scale and even global-scale applications to assess the potential consequences of climate change on natural forests. These predictions are valuable in the planning and anticipatory decision-making needed to sustainably manage a vast region such as Northern Eurasia. Modifications to the models have enabled simulation of disturbances including fire, insect outbreak and harvest. These disturbances have significant exogenous drivers, notably weather variables, but their effects are also a function of the endogenous conditions involving the structure of forest itself. This feedback between the forest and its environment can in some cases produce hysteresis and multiple-stable operating-regimes for forests. Such responses, often characterized as "tipping points" could play a significant role in increasing risk under environmental change, notably global warming. Such dynamics in a management context imply regional systems that could be "unforgiving" of management mistakes.

Global assessment of river flood protection benefits and corresponding residual risks under climate change

NASA Astrophysics Data System (ADS)

Lim, Wee Ho; Yamazaki, Dai; Koirala, Sujan; Hirabayashi, Yukiko; Kanae, Shinjiro; Dadson, Simon J.; Hall, Jim W.

2016-04-01

Global warming increases the water-holding capacity of the atmosphere and this could lead to more intense rainfalls and possibly increasing natural hazards in the form of flooding in some regions. This implies that traditional practice of using historical hydrological records alone is somewhat limited for supporting long-term water infrastructure planning. This has motivated recent global scale studies to evaluate river flood risks (e.g., Hirabayashi et al., 2013, Arnell and Gosling, 2014, Sadoff et al., 2015) and adaptations benefits (e.g., Jongman et al., 2015). To support decision-making in river flood risk reduction, this study takes a further step to examine the benefits and corresponding residual risks for a range of flood protection levels. To do that, we channelled runoff information of a baseline period (forced by observed hydroclimate conditions) and each CMIP5 model (historic and future periods) into a global river routing model called CaMa-Flood (Yamazaki et al., 2011). We incorporated the latest global river width data (Yamazaki et al., 2014) into CaMa-Flood and simulate the river water depth at a spatial resolution of 15 min x 15 min. From the simulated results of baseline period, we use the annual maxima river water depth to fit the Gumbel distribution and prepare the return period-flood risk relationship (involving population and GDP). From the simulated results of CMIP5 model, we also used the annual maxima river water depth to obtain the Gumbel distribution and then estimate the exceedance probability (historic and future periods). We apply the return period-flood risk relationship (above) to the exceedance probability and evaluate the flood protection benefits. We quantify the corresponding residual risks using a mathematical approach that is consistent with the modelling structure of CaMa-Flood. Globally and regionally, we find that the benefits of flood protection level peak somewhere between 20 and 500 years; residual risks diminish substantially when flood protection level exceeds 20 years. These findings might be useful for decision-makers to weight the size of water infrastructure investment and emergency response capacity under climate change. References: Arnell, N.W, Gosling, S.N., 2014. The impact of climate change on river flood risk at the global scale. Climatic Change 122: 127-140, doi: 10.1007/s10584-014-1084-5. Hirabayashi et al., 2013. Global flood risk under climate change. Nature Climate Change 3: 816-821, doi: 10.1038/nclimate1911. Jongman et al., 2015. Declining vulnerability to river floods and the global benefits of adaptation. Proceedings of National Academy of the United States of America 112, E2271-E2280, doi: 10.1073/pnas.1414439112. Sadoff et al., 2015. Securing Water, Sustaining Growth: Report of the GWP/OECD Task Force on Water Security and Sustainable Growth, University of Oxford, UK, 180 pp. Yamazaki et al., 2011. A physically based description of floodplain inundation dynamics in a global river routing model. Water Resources Research 47, W04501, doi: 10.1029/2010wr009726. Yamazaki et al., 2014. Development of the Global Width Database for Large Rivers. Water Resources Research 50, 3467-3480, doi: 10.1002/2013WR014664.

Current and future background ozone simulations for Mexico using a multi-scale regional climate modeling system

NASA Astrophysics Data System (ADS)

Lamb, B. K.; Gonzalez Abraham, R.; Avise, J. C.; Chung, S. H.; Salathe, E. P.; Zhang, Y.; Guenther, A. B.; Wiedinmyer, C.; Duhl, T.; Streets, D. G.

2013-05-01

Global change will clearly have a significant impact on the environment. Among the concerns for future air quality in North America, intercontinental transport of pollution has become increasingly important. In this study, we examined the effect of projected changes in Asian emissions and emissions from lightning and wildfires to produce ozone background concentrations within Mexico and the continental US. This provides a basis for developing an understanding of North American background levels and how they may change in the future. Meteorological fields were downscaled from the results of the ECHAM5 global climate model using the Weather Research Forecast (WRF) model. Two nested domains were employed, one covering most of the Northern Hemisphere from eastern Asia to North America using 220 km grid cells (semi-hemispheric domain) and one covering the continental US and northern Mexico using 36 km grid cells. Meteorological results from WRF were used to drive the MEGAN biogenic emissions model, the SMOKE emissions processing tool, and the CMAQ chemical transport model to predict ozone concentrations for current (1995-2004) and future (2045-2054) summertime conditions. The MEGAN model was used to calculate biogenic emissions for all simulations. For the semi-hemispheric domain, year 2000 global emissions of gases (ozone precursors) from anthropogenic (outside of North America), natural, and biomass burning sources from the POET and EDGAR emission inventories were used. The global tabulation for black and organic carbon (BC and OC respectively) was obtained from Bond et al. (2004) For the future decade, the current emissions were projected to the year 2050 following the Intergovernmental Panel for Climate Change (IPCC) A1B emission scenario. Anthropogenic emissions from the US, Canada, and Mexico were omitted so that only global background concentrations, and local biogenic, wildfire, and lightning emissions were treated. In this paper, we focus on background ozone levels in Mexico due to changes in future climate, local biogenic emissions and global emissions.

Global warming preceded by increasing carbon dioxide concentrations during the last deglaciation.

PubMed

Shakun, Jeremy D; Clark, Peter U; He, Feng; Marcott, Shaun A; Mix, Alan C; Liu, Zhengyu; Otto-Bliesner, Bette; Schmittner, Andreas; Bard, Edouard

2012-04-04

The covariation of carbon dioxide (CO(2)) concentration and temperature in Antarctic ice-core records suggests a close link between CO(2) and climate during the Pleistocene ice ages. The role and relative importance of CO(2) in producing these climate changes remains unclear, however, in part because the ice-core deuterium record reflects local rather than global temperature. Here we construct a record of global surface temperature from 80 proxy records and show that temperature is correlated with and generally lags CO(2) during the last (that is, the most recent) deglaciation. Differences between the respective temperature changes of the Northern Hemisphere and Southern Hemisphere parallel variations in the strength of the Atlantic meridional overturning circulation recorded in marine sediments. These observations, together with transient global climate model simulations, support the conclusion that an antiphased hemispheric temperature response to ocean circulation changes superimposed on globally in-phase warming driven by increasing CO(2) concentrations is an explanation for much of the temperature change at the end of the most recent ice age.

Chapman Conference on the Hydrologic Aspects of Global Climate Change, Lake Chelan, WA, June 12-14, 1990, Selected Papers

NASA Technical Reports Server (NTRS)

Lettenmaier, Dennis P. (Editor); Rind, D. (Editor)

1992-01-01

The present conference on the hydrological aspects of global climate change discusses land-surface schemes for future climate models, modeling of the land-surface boundary in climate models as a composite of independent vegetation, a land-surface hydrology parameterizaton with subgrid variability for general circulation models, and conceptual aspects of a statistical-dynamical approach to represent landscape subgrid-scale heterogeneities in atmospheric models. Attention is given to the impact of global warming on river runoff, the influence of atmospheric moisture transport on the fresh water balance of the Atlantic drainage basin, a comparison of observations and model simulations of tropospheric water vapor, and the use of weather types to disaggregate the prediction of general circulation models. Topics addressed include the potential response of an Arctic watershed during a period of global warming and the sensitivity of groundwater recharge estimates to climate variability and change.

Tropical Tree Trait Diversity Enhances Forest Biomass Resilience in a Dynamic Global Vegetation Model

NASA Astrophysics Data System (ADS)

Sakschewski, B.; Kirsten, T.; von Bloh, W.; Poorter, L.; Pena-Claros, M.; Boit, A.

2016-12-01

Functional diversity of ecosystems has been found to increase ecosystem functions and therefore enhance ecosystem resilience against environmental stressors. However, global carbon-cycle and biosphere models still classify the global vegetation into a relatively small number of distinct plant functional types (PFT) with constant features over space and time. Therefore, those models might underestimate the resilience and adaptive capacity of natural vegetation under climate change by ignoring positive effects that functional diversity might bring about. We diversified a set a of selected tree traits in a dynamic global vegetation model (LPJmL). In the new subversion, called LPJmL-FIT, Amazon region biomass stocks and forest structure appear significantly more resilient against climate change. Enhanced tree trait diversity enables the simulated rainforests to adjust to new environmental conditions via ecological sorting. These results may stimulate a new debate on the value of biodiversity for climate change mitigation.

Understanding Decreases in Land Relative Humidity with Global Warming: Conceptual Model and GCM Simulations

NASA Astrophysics Data System (ADS)

Byrne, Michael P.; O'Gorman, Paul A.

2016-12-01

Climate models simulate a strong land-ocean contrast in the response of near-surface relative humidity to global warming: relative humidity tends to increase slightly over oceans but decrease substantially over land. Surface energy balance arguments have been used to understand the response over ocean but are difficult to apply over more complex land surfaces. Here, a conceptual box model is introduced, involving moisture transport between the land and ocean boundary layers and evapotranspiration, to investigate the decreases in land relative humidity as the climate warms. The box model is applied to idealized and full-complexity (CMIP5) general circulation model simulations, and it is found to capture many of the features of the simulated changes in land relative humidity. The box model suggests there is a strong link between fractional changes in specific humidity over land and ocean, and the greater warming over land than ocean then implies a decrease in land relative humidity. Evapotranspiration is of secondary importance for the increase in specific humidity over land, but it matters more for the decrease in relative humidity. Further analysis shows there is a strong feedback between changes in surface-air temperature and relative humidity, and this can amplify the influence on relative humidity of factors such as stomatal conductance and soil moisture.

Variability in Global Top-of-Atmosphere Shortwave Radiation Between 2000 and 2005

NASA Technical Reports Server (NTRS)

Loebe, Norman G.; Wielicki, Bruce A.; Rose, Fred G.; Doelling, David R.

2007-01-01

Measurements from various instruments and analysis techniques are used to directly compare changes in Earth-atmosphere shortwave (SW) top-of-atmosphere (TOA) radiation between 2000 and 2005. Included in the comparison are estimates of TOA reflectance variability from published ground-based Earthshine observations and from new satellite-based CERES, MODIS and ISCCP results. The ground-based Earthshine data show an order-of-magnitude more variability in annual mean SW TOA flux than either CERES or ISCCP, while ISCCP and CERES SW TOA flux variability is consistent to 40%. Most of the variability in CERES TOA flux is shown to be dominated by variations global cloud fraction, as observed using coincident CERES and MODIS data. Idealized Earthshine simulations of TOA SW radiation variability for a lunar-based observer show far less variability than the ground-based Earthshine observations, but are still a factor of 4-5 times more variable than global CERES SW TOA flux results. Furthermore, while CERES global albedos exhibit a well-defined seasonal cycle each year, the seasonal cycle in the lunar Earthshine reflectance simulations is highly variable and out-of-phase from one year to the next. Radiative transfer model (RTM) approaches that use imager cloud and aerosol retrievals reproduce most of the change in SW TOA radiation observed in broadband CERES data. However, assumptions used to represent the spectral properties of the atmosphere, clouds, aerosols and surface in the RTM calculations can introduce significant uncertainties in annual mean changes in regional and global SW TOA flux.

Variability in global top-of-atmosphere shortwave radiation between 2000 and 2005

NASA Astrophysics Data System (ADS)

Loeb, Norman G.; Wielicki, Bruce A.; Rose, Fred G.; Doelling, David R.

2007-02-01

Measurements from various instruments and analysis techniques are used to directly compare changes in Earth-atmosphere shortwave (SW) top-of-atmosphere (TOA) radiation between 2000 and 2005. Included in the comparison are estimates of TOA reflectance variability from published ground-based Earthshine observations and from new satellite-based CERES, MODIS and ISCCP results. The ground-based Earthshine data show an order-of-magnitude more variability in annual mean SW TOA flux than either CERES or ISCCP, while ISCCP and CERES SW TOA flux variability is consistent to 40%. Most of the variability in CERES TOA flux is shown to be dominated by variations global cloud fraction, as observed using coincident CERES and MODIS data. Idealized Earthshine simulations of TOA SW radiation variability for a lunar-based observer show far less variability than the ground-based Earthshine observations, but are still a factor of 4-5 times more variable than global CERES SW TOA flux results. Furthermore, while CERES global albedos exhibit a well-defined seasonal cycle each year, the seasonal cycle in the lunar Earthshine reflectance simulations is highly variable and out-of-phase from one year to the next. Radiative transfer model (RTM) approaches that use imager cloud and aerosol retrievals reproduce most of the change in SW TOA radiation observed in broadband CERES data. However, assumptions used to represent the spectral properties of the atmosphere, clouds, aerosols and surface in the RTM calculations can introduce significant uncertainties in annual mean changes in regional and global SW TOA flux.

Vegetation-induced warming of high-latitude regions during the Late Cretaceous period

NASA Astrophysics Data System (ADS)

Otto-Bliesner, Bette L.; Upchurch, Garland R.

1997-02-01

Modelling studies of pre-Quaternary (>2 million years ago) climate implicate atmospheric carbon dioxide concentrations1, land elevation2 and land-sea distribution3-5 as important factors influencing global climate change over geological timescales. But during times of global warmth, such as the Cretaceous period and Eocene epoch, there are large discrepancies between model simulations of high-latitude and continental-interior temperatures and those indicated by palaeotemperature records6,7. Here we use a global climate model for the latest Cretaceous (66 million years ago) to examine the role played by high- and middle-latitude forests in surface temperature regulation. In our simulations, this forest vegetation warms the global climate by 2.2 °C. The low-albedo deciduous forests cause high-latitude land areas to warm, which then transfer more heat to adjacent oceans, thus delaying sea-ice formation and increasing winter temperatures over coastal land. Overall, the inclusion of some of the physical and physiological climate feedback effects of high-latitude forest vegetation in our simulations reduces the existing discrepancies between observed and modelled climates of the latest Cretaceous, suggesting that these forests may have made an important contribution to climate regulation during periods of global warmth.

The effects of variable biome distribution on global climate.

PubMed

Noever, D A; Brittain, A; Matsos, H C; Baskaran, S; Obenhuber, D

1996-01-01

In projecting climatic adjustments to anthropogenically elevated atmospheric carbon dioxide, most global climate models fix biome distribution to current geographic conditions. Previous biome maps either remain unchanging or shift without taking into account climatic feedbacks such as radiation and temperature. We develop a model that examines the albedo-related effects of biome distribution on global temperature. The model was tested on historical biome changes since 1860 and the results fit both the observed temperature trend and order of magnitude change. The model is then used to generate an optimized future biome distribution that minimizes projected greenhouse effects on global temperature. Because of the complexity of this combinatorial search, an artificial intelligence method, the genetic algorithm, was employed. The method is to adjust biome areas subject to a constant global temperature and total surface area constraint. For regulating global temperature, oceans are found to dominate continental biomes. Algal beds are significant radiative levers as are other carbon intensive biomes including estuaries and tropical deciduous forests. To hold global temperature constant over the next 70 years this simulation requires that deserts decrease and forested areas increase. The effect of biome change on global temperature is revealed as a significant forecasting factor.

A reduction in the asymmetry of ENSO amplitude due to global warming: The role of atmospheric feedback

NASA Astrophysics Data System (ADS)

Ham, Yoo-Geun

2017-08-01

This study analyzes a reduction in the asymmetry of El Niño Southern-Oscillation (ENSO) amplitude due to global warming in Coupled Model Intercomparison Project Phase 5 models. The multimodel-averaged Niño3 skewness during December-February season decreased approximately 40% in the RCP4.5 scenario compared to that in the historical simulation. The change in the nonlinear relationship between sea surface temperature (SST) and precipitation is a key factor for understanding the reduction in ENSO asymmetry due to global warming. In the historical simulations, the background SST leading to the greatest precipitation sensitivity (SST for Maximum Precipitation Sensitivity, SST_MPS) occurs when the positive SST anomaly is located over the equatorial central Pacific. Therefore, an increase in climatological SST due to global warming weakens the atmospheric response during El Niño over the central Pacific. However, the climatological SST over this region in the historical simulation is still lower than the SST_MPS for the negative SST anomaly; therefore, a background SST increase due to global warming can further increase precipitation sensitivity. The atmospheric feedbacks during La Niña are enhanced and increase the La Niña amplitude due to global warming.

The Impact of Anthropogenic Land Cover Change on Continental River Flow

NASA Astrophysics Data System (ADS)

Sterling, S. M.; Ducharne, A.; Polcher, J.

2006-12-01

The 2003 World Water Forum highlighted a water crisis that forces over one billion people to drink contaminated water and leaves countless millions with insufficient supplies for agriculture industry. This crisis has spurred numerous recent calls for improved science and understanding of how we alter the water cycle. Here we investigate how this global water crisis is affected by human-caused land cover change. We examine the impact of the present extent of land cover change on the water cycle, in particular on evapotranspiration and streamflow, through numerical experiments with the ORCHIDEE land surface model. Using Geographic Information Systems, we characterise land cover change by assembling and modifying existing global-scale maps of land cover change. To see how the land cover change impacts river runoff streamflow, we input the maps into ORCHIDEE and run 50-year "potential vegetation" and "current land cover" simulations of the land surface and energy fluxes, forced by the 50-year NCC atmospheric forcing data set. We present global maps showing the "hotspot" areas with the largest change in ET and streamflow due to anthropogenic land cover change. The results of this project enhance scientific understanding of the nature of human impact on the global water cycle.

Hydrological Validation of The Lpj Dynamic Global Vegetation Model - First Results and Required Actions

NASA Astrophysics Data System (ADS)

Haberlandt, U.; Gerten, D.; Schaphoff, S.; Lucht, W.

Dynamic global vegetation models are developed with the main purpose to describe the spatio-temporal dynamics of vegetation at the global scale. Increasing concern about climate change impacts has put the focus of recent applications on the sim- ulation of the global carbon cycle. Water is a prime driver of biogeochemical and biophysical processes, thus an appropriate representation of the water cycle is crucial for their proper simulation. However, these models usually lack thorough validation of the water balance they produce. Here we present a hydrological validation of the current version of the LPJ (Lund- Potsdam-Jena) model, a dynamic global vegetation model operating at daily time steps. Long-term simulated runoff and evapotranspiration are compared to literature values, results from three global hydrological models, and discharge observations from various macroscale river basins. It was found that the seasonal and spatial patterns of the LPJ-simulated average values correspond well both with the measurements and the results from the stand-alone hy- drological models. However, a general underestimation of runoff occurs, which may be attributable to the low input dynamics of precipitation (equal distribution within a month), to the simulated vegetation pattern (potential vegetation without anthro- pogenic influence), and to some generalizations of the hydrological components in LPJ. Future research will focus on a better representation of the temporal variability of climate forcing, improved description of hydrological processes, and on the consider- ation of anthropogenic land use.

Simulated responses of terrestrial aridity to black carbon and sulfate aerosols

NASA Astrophysics Data System (ADS)

Lin, L.; Gettelman, A.; Xu, Y.; Fu, Q.

2016-01-01

Aridity index (AI), defined as the ratio of precipitation to potential evapotranspiration (PET), is a measure of the dryness of terrestrial climate. Global climate models generally project future decreases of AI (drying) associated with global warming scenarios driven by increasing greenhouse gas and declining aerosols. Given their different effects in the climate system, scattering and absorbing aerosols may affect AI differently. Here we explore the terrestrial aridity responses to anthropogenic black carbon (BC) and sulfate (SO4) aerosols with Community Earth System Model simulations. Positive BC radiative forcing decreases precipitation averaged over global land at a rate of 0.9%/°C of global mean surface temperature increase (moderate drying), while BC radiative forcing increases PET by 1.0%/°C (also drying). BC leads to a global decrease of 1.9%/°C in AI (drying). SO4 forcing is negative and causes precipitation a decrease at a rate of 6.7%/°C cooling (strong drying). PET also decreases in response to SO4 aerosol cooling by 6.3%/°C cooling (contributing to moistening). Thus, SO4 cooling leads to a small decrease in AI (drying) by 0.4%/°C cooling. Despite the opposite effects on global mean temperature, BC and SO4 both contribute to the twentieth century drying (AI decrease). Sensitivity test indicates that surface temperature and surface available energy changes dominate BC- and SO4-induced PET changes.

Geoengineering by stratospheric SO2 injection: results from the Met Office HadGEM2 climate model and comparison with the Goddard Institute for Space Studies ModelE

NASA Astrophysics Data System (ADS)

Jones, A.; Haywood, J.; Boucher, O.; Kravitz, B.; Robock, A.

2010-03-01

We examine the response of the Met Office Hadley Centre's HadGEM2-AO climate model to simulated geoengineering by continuous injection of SO2 into the lower stratosphere, and compare the results with those from the Goddard Institute for Space Studies ModelE. The HadGEM2 simulations suggest that the SO2 injection rate considered here (5 Tg[SO2] yr-1) could defer the amount of global warming predicted under the Intergovernmental Panel on Climate Change's A1B scenario by approximately 30-35 years, although both models indicate rapid warming if geoengineering is not sustained. We find a broadly similar geographic distribution of the response to geoengineering in both models in terms of near-surface air temperature and mean June-August precipitation. The simulations also suggest that significant changes in regional climate would be experienced even if geoengineering was successful in maintaining global-mean temperature near current values.

Effects of experimental protocol on global vegetation model accuracy: a comparison of simulated and observed vegetation patterns for Asia

USGS Publications Warehouse

Tang, Guoping; Shafer, Sarah L.; Barlein, Patrick J.; Holman, Justin O.

2009-01-01

Prognostic vegetation models have been widely used to study the interactions between environmental change and biological systems. This study examines the sensitivity of vegetation model simulations to: (i) the selection of input climatologies representing different time periods and their associated atmospheric CO2 concentrations, (ii) the choice of observed vegetation data for evaluating the model results, and (iii) the methods used to compare simulated and observed vegetation. We use vegetation simulated for Asia by the equilibrium vegetation model BIOME4 as a typical example of vegetation model output. BIOME4 was run using 19 different climatologies and their associated atmospheric CO2 concentrations. The Kappa statistic, Fuzzy Kappa statistic and a newly developed map-comparison method, the Nomad index, were used to quantify the agreement between the biomes simulated under each scenario and the observed vegetation from three different global land- and tree-cover data sets: the global Potential Natural Vegetation data set (PNV), the Global Land Cover Characteristics data set (GLCC), and the Global Land Cover Facility data set (GLCF). The results indicate that the 30-year mean climatology (and its associated atmospheric CO2 concentration) for the time period immediately preceding the collection date of the observed vegetation data produce the most accurate vegetation simulations when compared with all three observed vegetation data sets. The study also indicates that the BIOME4-simulated vegetation for Asia more closely matches the PNV data than the other two observed vegetation data sets. Given the same observed data, the accuracy assessments of the BIOME4 simulations made using the Kappa, Fuzzy Kappa and Nomad index map-comparison methods agree well when the compared vegetation types consist of a large number of spatially continuous grid cells. The results of this analysis can assist model users in designing experimental protocols for simulating vegetation.

Global Trends and Variability in Integrated Water Vapor from Ground-Based GPS Data and Climate Models

NASA Astrophysics Data System (ADS)

Bock, O.; Parracho, A. C.; Bastin, S.; Hourdin, F.

2016-12-01

A high-quality, consistent, global, long-term dataset of integrated water vapor (IWV) was produced from Global Positioning System (GPS) measurements at more than 400 sites over the globe among which 120 sites have more than 15 years of data. The GPS delay data were converted to IWV using surface pressure and weighted mean temperature estimates from ERA-Interim reanalysis. A two-step screening method was developed to detect and remove outliers in the IWV data. It is based on: 1) GPS data processing information and delay formal errors, and 2) inter-comparison with ERA-Interim reanalysis data. The GPS IWV data are also homogenized to correct for offsets due to instrumental changes and other unknown factors. The differential homogenization method uses ERA-Interim IWV as a reference. The resulting GPS data are used to document the mean distribution, the global trends and the variability of IWV over the period 1995-2010, and to assess global climate model simulations extracted from the IPCC AR5 archive. Large coherent spatial patterns of moistening and drying are evidenced but significant discrepancies are also seen between GPS measurements, reanalysis and climate models in various regions. In terms of variability, the monthly mean anomalies are inter-compared. The temporal correlation between GPS and the climate model simulations is overall quite small but the spatial variation of the magnitude of the anomalies is globally well simulated. GPS IWV data prove to be useful to validate global climate model simulations and highlight deficiencies in their representation of the water cycle.

Combining a Complex Network Approach and a SEIR Compartmental Model to link Fast Spreading of Infectious Diseases with Climate Change

NASA Astrophysics Data System (ADS)

Brenner, F.; Hoffmann, P.; Marwan, N.

2016-12-01

Infectious diseases are a major threat to human health. The spreading of airborne diseases has become fast and hard to predict. Global air travelling created a network which allows a pathogen to migrate worldwide in only a few days. Pandemics of SARS (2002/03) and H1N1 (2009) have impressively shown the epidemiological danger in a strongly connected world. In this study we simulate the outbreak of an airborne infectious disease that is directly transmitted from human to human. We use a regular Susceptible-Infected-Recovered (SIR) model and a modified Susceptible-Exposed-Infected-Recovered (SEIR) compartmental approach with the basis of a complex network built by global air traffic data (from openflights.org). Local Disease propagation is modeled with a global population dataset (from SEDAC and MaxMind) and parameterizations of human behavior regarding mobility, contacts and awareness. As a final component we combine the worldwide outbreak simulation with daily averaged climate data from WATCH-Forcing-Data-ERA-Interim (WFDEI) and Coupled Model Intercomparison Project Phase 5 (CMIP5). Here we focus on Influenza-like illnesses (ILI), whose transmission rate has a dependency on relative humidity and temperature. Even small changes in relative humidity are sufficient to trigger significant differences in the global outbreak behavior. Apart from the direct effect of climate change on the transmission of airborne diseases, there are indirect ramifications that alter spreading patterns. For example seasonal changing human mobility is influenced by climate settings.

Modelling terrestrial nitrous oxide emissions and implications for climate feedback.

PubMed

Xu-Ri; Prentice, I Colin; Spahni, Renato; Niu, Hai Shan

2012-10-01

Ecosystem nitrous oxide (N2O) emissions respond to changes in climate and CO2 concentration as well as anthropogenic nitrogen (N) enhancements. Here, we aimed to quantify the responses of natural ecosystem N2O emissions to multiple environmental drivers using a process-based global vegetation model (DyN-LPJ). We checked that modelled annual N2O emissions from nonagricultural ecosystems could reproduce field measurements worldwide, and experimentally observed responses to step changes in environmental factors. We then simulated global N2O emissions throughout the 20th century and analysed the effects of environmental changes. The model reproduced well the global pattern of N2O emissions and the observed responses of N cycle components to changes in environmental factors. Simulated 20th century global decadal-average soil emissions were c. 8.2-9.5 Tg N yr(-1) (or 8.3-10.3 Tg N yr(-1) with N deposition). Warming and N deposition contributed 0.85±0.41 and 0.80±0.14 Tg N yr(-1), respectively, to an overall upward trend. Rising CO2 also contributed, in part, through a positive interaction with warming. The modelled temperature dependence of N2O emission (c. 1 Tg N yr(-1) K(-1)) implies a positive climate feedback which, over the lifetime of N2O (114 yr), could become as important as the climate-carbon cycle feedback caused by soil CO2 release. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

Dynamical Downscaling of Meteorology from a Global Model by WRF towards Resolving US PM2.5 Distributions for the Mid 21st Century

NASA Astrophysics Data System (ADS)

Kunwar, S.; Bowden, J.; Milly, G.; Previdi, M. J.; Fiore, A. M.; West, J. J.

2017-12-01

In the coming decades, anthropogenically induced climate change will likely impact PM2.5 through both changing meteorology and feedback in natural emissions. A major goal of our project is to assess changes in PM2.5 levels over the continental US due to climate variability and change for the period 2005-2065. We will achieve this by using regional models to dynamically downscale coarse resolution (20 × 20) meteorology and air chemistry from a global model to finer spatial resolution (12 km), improving air quality projections for regions and subregions of the US (NE, SE, SW, NW, Midwest, Intermountain West). We downscale from GFDL CM3 simulations of the RCP8.5 scenario for the years 2006-2100 with aerosol and ozone precursor emissions fixed at 2005 levels. We carefully select model years from the global simulations that sample the range of PM2.5 distributions for different US regions at mid 21st century (2050-2065). Here we will show results for the meteorological downscaling (using WRF version 3.8.1) for this project, including a performance evaluation for meteorological variables with respect to the global model. In the future, the downscaled meteorology presented here will be used to drive air quality downscaling in CMAQ (version 5.2). Analysis of the resulting PM2.5 statistics for US regions, as well as the drivers for PM2.5 changes, will be important in supporting informed policies for air quality (also health and visibility) planning for different US regions for the next five decades.

Aridity under conditions of increased CO2

NASA Astrophysics Data System (ADS)

Greve, Peter; Roderick, Micheal L.; Seneviratne, Sonia I.

2016-04-01

A string of recent of studies led to the wide-held assumption that aridity will increase under conditions of increasing atmospheric CO2 concentrations and associated global warming. Such results generally build upon analyses of changes in the 'aridity index' (the ratio of potential evaporation to precipitation) and can be described as a direct thermodynamic effect on atmospheric water demand due to increasing temperatures. However, there is widespread evidence that contradicts the 'warmer is more arid' interpretation, leading to the 'global aridity paradox' (Roderick et al. 2015, WRR). Here we provide a comprehensive assessment of modeled changes in a broad set of dryness metrics (primarily based on a range of measures of water availability) over a large range of realistic atmospheric CO2 concentrations. We use an ensemble of simulations from of state-of-the-art climate models to analyse both equilibrium climate experiments and transient historical simulations and future projections. Our results show that dryness is, under conditions of increasing atmospheric CO2 concentrations and related global warming, generally decreasing at global scales. At regional scales we do, however, identify areas that undergo changes towards drier conditions, located primarily in subtropical climate regions and the Amazon Basin. Nonetheless, the majority of regions, especially in tropical and mid- to northern high latitudes areas, display wetting conditions in a warming world. Our results contradict previous findings and highlight the need to comprehensively assess all aspects of changes in hydroclimatological conditions at the land surface. Roderick, M. L., P. Greve, and G. D. Farquhar (2015), On the assessment of aridity with changes in atmospheric CO2, Water Resour. Res., 51, 5450-5463

Dust Storm Signatures in Global Ionosphere Map of GPS Total Electron Content

NASA Astrophysics Data System (ADS)

Lin, Fang-Tse; Shih, Ai-Ling; Liu, Jann-Yenq; Kuo, Cheng-Ling; Lin, Tang-Huang; Lien, Wei-Hung

2016-04-01

In this paper both MODIS data and GIM (global ionosphere map) TEC (total electron content) as well as numerical simulations are used to study ionospheric dust storm effects in May 2008. The aerosol optical depth (AOD) and the LTT (latitude-time-TEC) along the Sahara longitude simultaneously reach their maximum values on 28 May 2008. The LLT (latitude-longitude-TEC) map specifically and significantly increases over the Sahara region on 28 May 2008. The simulation suggests that the dust storm may change the atmospheric conductivity, which in turn modifies the GIM TEC over the Sahara area.

INTRODUCTION: Anticipated changes in the global atmospheric water cycle

NASA Astrophysics Data System (ADS)

Allan, Richard P.; Liepert, Beate G.

2010-06-01

The atmospheric branch of the water cycle, although containing just a tiny fraction of the Earth's total water reserves, presents a crucial interface between the physical climate (such as large-scale rainfall patterns) and the ecosystems upon which human societies ultimately depend. Because of the central importance of water in the Earth system, the question of how the water cycle is changing, and how it may alter in future as a result of anthropogenic changes, present one of the greatest challenges of this century. The recent Intergovernmental Panel on Climate Change report on Climate Change and Water (Bates et al 2008) highlighted the increasingly strong evidence of change in the global water cycle and associated environmental consequences. It is of critical importance to climate prediction and adaptation strategies that key processes in the atmospheric water cycle are precisely understood and determined, from evaporation at the surface of the ocean, transport by the atmosphere, condensation as cloud and eventual precipitation, and run-off through rivers following interaction with the land surface, sub-surface, ice, snow and vegetation. The purpose of this special focus issue of Environmental Research Letters on anticipated changes in the global atmospheric water cycle is to consolidate the recent substantial advances in understanding past, present and future changes in the global water cycle through evidence built upon theoretical understanding, backed up by observations and borne out by climate model simulations. Thermodynamic rises in water vapour provide a central constraint, as discussed in a guest editorial by Bengtsson (2010). Theoretical implications of the Clausius-Clapeyron equation are presented by O'Gorman and Muller (2010) and with reference to a simple model (Sherwood 2010) while observed humidity changes confirm these anticipated responses at the land and ocean surface (Willett et al 2008). Rises in low-level moisture are thought to fuel an intensification of precipitation (O'Gorman and Schneider 2009) and analysis of observed and simulated changes in extreme rainfall for Europe (Lenderink and van Mijgaard 2008) and over tropical oceans by Allan et al (2010) appear to corroborate this. Radiative absorption by water vapour (Previdi 2010, Stephens and Ellis 2008) also provides a thermodynamic feedback on the water cycle, and explains why climate model projections of global precipitation and evaporation of around 1-3% K-1 are muted with respect to the expected 7% K-1 increases in low-level moisture. Climate models achieve dynamical responses through reductions in strength of the Walker circulation (Vecchi et al 2006) and small yet systematic changes in the atmospheric boundary layer over the ocean that modify evaporation (Richter and Xie 2008). A further consequence is anticipated sub-tropical drying (Neelin et al 2006, Chou et al 2007); Allan et al (2010) confirm a decline in dry sub-tropical precipitation while the wet regions become wetter both in model simulations and satellite-based observations. Discrepancies between observed and climate model simulated hydrological response to warming (Wentz et al 2007, Yu and Weller 2007) are of immediate concern in understanding and predicting future responses. Over decadal time-scales it is important to establish whether such discrepancies relate to the observing system, climate modeling deficiencies, or are a statistical artifact of the brevity of the satellite records (Liepert and Previdi 2009). Techniques for extracting information on century-scale changes in precipitation are emerging (Smith et al 2009) but are also subject to severe limitations. Past decadal-scale changes in the water cycle may be further influenced by regionally and temporally varying forcings and resulting feedbacks which must be represented realistically by models (Andrews et al 2009). The radiative impact of aerosols and their indirect effects on clouds and precipitation (Liepert et al 2004) provide an important example. Understanding surface solar 'dimming' and 'brightening' trends in the context of past and current changes in the water cycle are discussed in a guest editorial by Wild and Liepert (2010). The key roles anthropogenic aerosols can play on a regional scale are discussed by Lau et al (2010) through their study of the regional impact of absorbing aerosols on warming and snow melt over the Himalayas. The overarching goal of climate prediction is to provide reliable, probabilistic estimates of future changes. Relating hydrological responses back to a sound physical basis, the motivation for this special focus issue, is paramount in building confidence in anticipated changes, especially in the global water cycle. We are grateful to the reviewers and the journal editorial board for making this focus issue possible. Focus on Anticipated Changes in the Global Atmospheric Water Cycle Contents Editorials The global atmospheric water cycle Lennart Bengtsson The Earth radiation balance as driver of the global hydrological cycle Martin Wild and Beate Liepert Letters Enhanced surface warming and accelerated snow melt in the Himalayas and Tibetan Plateau induced by absorbing aerosols William K M Lau, Maeng-Ki Kim, Kyu-Myong Kim and Woo-Seop Lee Current changes in tropical precipitation Richard P Allan, Brian J Soden, Viju O John, William Ingram and Peter Good Direct versus indirect effects of tropospheric humidity changes on the hydrologic cycle S C Sherwood How closely do changes in surface and column water vapor follow Clausius-Clapeyron scaling in climate change simulations? P A O'Gorman and C J Muller Linking increases in hourly precipitation extremes to atmospheric temperature and moisture changes Geert Lenderink and Erik van Meijgaard Are climate-related changes to the character of global-mean precipitation predictable? Graeme L Stephens and Yongxiang Hu A comparison of large scale changes in surface humidity over land in observations and CMIP3 general circulation models Katharine M Willett, Philip D Jones, Peter W Thorne and Nathan P Gillett Radiative feedbacks on global precipitation Michael Previdi The transient response of global-mean precipitation to increasing carbon dioxide levels Timothy Andrews and Piers M Forster The observed sensitivity of the global hydrological cycle to changes in surface temperature Phillip A Arkin, Thomas M Smith, Mathew R P Sapiano and John Janowiak Precipitation changes within dynamical regimes in a perturbed climate Jonny Williams and Mark A Ringer

Global Change adaptation in water resources management: the Water Change project.

PubMed

Pouget, Laurent; Escaler, Isabel; Guiu, Roger; Mc Ennis, Suzy; Versini, Pierre-Antoine

2012-12-01

In recent years, water resources management has been facing new challenges due to increasing changes and their associated uncertainties, such as changes in climate, water demand or land use, which can be grouped under the term Global Change. The Water Change project (LIFE+ funding) developed a methodology and a tool to assess the Global Change impacts on water resources, thus helping river basin agencies and water companies in their long term planning and in the definition of adaptation measures. The main result of the project was the creation of a step by step methodology to assess Global Change impacts and define strategies of adaptation. This methodology was tested in the Llobregat river basin (Spain) with the objective of being applicable to any water system. It includes several steps such as setting-up the problem with a DPSIR framework, developing Global Change scenarios, running river basin models and performing a cost-benefit analysis to define optimal strategies of adaptation. This methodology was supported by the creation of a flexible modelling system, which can link a wide range of models, such as hydrological, water quality, and water management models. The tool allows users to integrate their own models to the system, which can then exchange information among them automatically. This enables to simulate the interactions among multiple components of the water cycle, and run quickly a large number of Global Change scenarios. The outcomes of this project make possible to define and test different sets of adaptation measures for the basin that can be further evaluated through cost-benefit analysis. The integration of the results contributes to an efficient decision-making on how to adapt to Global Change impacts. Copyright © 2012 Elsevier B.V. All rights reserved.

Global warming: Clouds cooled the Earth

NASA Astrophysics Data System (ADS)

Mauritsen, Thorsten

2016-12-01

The slow instrumental-record warming is consistent with lower-end climate sensitivity. Simulations and observations now show that changing sea surface temperature patterns could have affected cloudiness and thereby dampened the warming.

Estimated global nitrogen deposition using NO2 column density

USGS Publications Warehouse

Lu, Xuehe; Jiang, Hong; Zhang, Xiuying; Liu, Jinxun; Zhang, Zhen; Jin, Jiaxin; Wang, Ying; Xu, Jianhui; Cheng, Miaomiao

2013-01-01

Global nitrogen deposition has increased over the past 100 years. Monitoring and simulation studies of nitrogen deposition have evaluated nitrogen deposition at both the global and regional scale. With the development of remote-sensing instruments, tropospheric NO2 column density retrieved from Global Ozone Monitoring Experiment (GOME) and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) sensors now provides us with a new opportunity to understand changes in reactive nitrogen in the atmosphere. The concentration of NO2 in the atmosphere has a significant effect on atmospheric nitrogen deposition. According to the general nitrogen deposition calculation method, we use the principal component regression method to evaluate global nitrogen deposition based on global NO2 column density and meteorological data. From the accuracy of the simulation, about 70% of the land area of the Earth passed a significance test of regression. In addition, NO2 column density has a significant influence on regression results over 44% of global land. The simulated results show that global average nitrogen deposition was 0.34 g m−2 yr−1 from 1996 to 2009 and is increasing at about 1% per year. Our simulated results show that China, Europe, and the USA are the three hotspots of nitrogen deposition according to previous research findings. In this study, Southern Asia was found to be another hotspot of nitrogen deposition (about 1.58 g m−2 yr−1 and maintaining a high growth rate). As nitrogen deposition increases, the number of regions threatened by high nitrogen deposits is also increasing. With N emissions continuing to increase in the future, areas whose ecosystem is affected by high level nitrogen deposition will increase.

The Impacts of Various Environments Factors and Adaptive Management Strategies on Food Crops in the 21st Century Based on a Land Surface Model

NASA Astrophysics Data System (ADS)

Jain, A. K.; Lin, T. S.; Lawrence, P.; Kheshgi, H. S.

2017-12-01

Environmental factors - characterized by increasing levels of CO2, and changes in temperature and precipitation patterns - present potential risks to global food supply. To date, understanding of environmental factors' effects on crop production remains uncertain due to (1) uncertainties in projected trends of these factors and their spatial and temporal variability; (2) uncertainties in the physiological, genetic and molecular basis of crop adaptation to adaptive management practices (e.g. change in planting time, irrigation and N fertilization etc.) and (3) uncertainties in current land surface models to estimate the response of crop production to changes in environmental factors and management strategies. In this study we apply a process-based land surface model, the Integrated Science Assessment model (ISAM), to assess the impact of various environmental factors and management strategies on the production of row crops (corn, soybean and wheat) at regional and global scales. Results are compared to corresponding simulations performed with the crop model in the Community Land Model (CLM4.5). Each model is driven with historical atmospheric forcing data (1901-2005), and projected atmospheric forcing data under RCP 4.5 or RCP 8.5 (2006-2100) from CESM CMIP5 simulations to estimate the effects of different climate change projections on potential productivity of food crops at a global scale. For each set of atmospheric forcing data, production of each crop is simulated with and without inclusion of adaptive management practices (e.g. application of irrigation, N fertilization, change in planting time and crop cultivars etc.) to assess the effect of adaptation on projected crop production over the 21st century. In detail, three questions are addressed: (1) what is the impact of different climate change projections on global crop production; (2) what is the effect of adaptive management practices on projected crop production; and (3) how do differences in model mechanisms in ISAM and CLM4.5 impact projected global crop production and adaptive management practices (irrigation and N fertilizer) over the 21st century. The major outcomes of this study will help to understand the uncertainties in potential productivity of food crops under different environmental conditions and management practices.

Deriving Scaling Factors Using a Global Hydrological Model to Restore GRACE Total Water Storage Changes for China's Yangtze River Basin

NASA Technical Reports Server (NTRS)

Long, Di; Yang, Yuting; Yoshihide, Wada; Hong, Yang; Liang, Wei; Chen, Yaning; Yong, Bin; Hou, Aizhong; Wei, Jiangfeng; Chen, Lu

2015-01-01

This study used a global hydrological model (GHM), PCR-GLOBWB, which simulates surface water storage changes, natural and human induced groundwater storage changes, and the interactions between surface water and subsurface water, to generate scaling factors by mimicking low-pass filtering of GRACE signals. Signal losses in GRACE data were subsequently restored by the scaling factors from PCR-GLOBWB. Results indicate greater spatial heterogeneity in scaling factor from PCR-GLOBWB and CLM4.0 than that from GLDAS-1 Noah due to comprehensive simulation of surface and subsurface water storage changes for PCR-GLOBWB and CLM4.0. Filtered GRACE total water storage (TWS) changes applied with PCR-GLOBWB scaling factors show closer agreement with water budget estimates of TWS changes than those with scaling factors from other land surface models (LSMs) in China's Yangtze River basin. Results of this study develop a further understanding of the behavior of scaling factors from different LSMs or GHMs over hydrologically complex basins, and could be valuable in providing more accurate TWS changes for hydrological applications (e.g., monitoring drought and groundwater storage depletion) over regions where human-induced interactions between surface water and subsurface water are intensive.

Solar Simulated Ultraviolet Radiation Induces Global Histone Hypoacetylation in Human Keratinocytes.

PubMed

Zhang, Xiaoru; Kluz, Thomas; Gesumaria, Lisa; Matsui, Mary S; Costa, Max; Sun, Hong

2016-01-01

Ultraviolet radiation (UVR) from sunlight is the primary effector of skin DNA damage. Chromatin remodeling and histone post-translational modification (PTM) are critical factors in repairing DNA damage and maintaining genomic integrity, however, the dynamic changes of histone marks in response to solar UVR are not well characterized. Here we report global changes in histone PTMs induced by solar simulated UVR (ssUVR). A decrease in lysine acetylation of histones H3 and H4, particularly at positions of H3 lysine 9, lysine 56, H4 lysine 5, and lysine 16, was found in human keratinocytes exposed to ssUVR. These acetylation changes were highly associated with ssUVR in a dose-dependent and time-specific manner. Interestingly, H4K16ac, a mark that is crucial for higher order chromatin structure, exhibited a persistent reduction by ssUVR that was transmitted through multiple cell divisions. In addition, the enzymatic activities of histone acetyltransferases were significantly reduced in irradiated cells, which may account for decreased global acetylation. Moreover, depletion of histone deacetylase SIRT1 in keratinocytes rescued ssUVR-induced H4K16 hypoacetylation. These results indicate that ssUVR affects both HDAC and HAT activities, leading to reduced histone acetylation.

A large ozone-circulation feedback and its implications for global warming assessments.

PubMed

Nowack, Peer J; Abraham, N Luke; Maycock, Amanda C; Braesicke, Peter; Gregory, Jonathan M; Joshi, Manoj M; Osprey, Annette; Pyle, John A

2015-01-01

State-of-the-art climate models now include more climate processes which are simulated at higher spatial resolution than ever 1 . Nevertheless, some processes, such as atmospheric chemical feedbacks, are still computationally expensive and are often ignored in climate simulations 1,2 . Here we present evidence that how stratospheric ozone is represented in climate models can have a first order impact on estimates of effective climate sensitivity. Using a comprehensive atmosphere-ocean chemistry-climate model, we find an increase in global mean surface warming of around 1°C (~20%) after 75 years when ozone is prescribed at pre-industrial levels compared with when it is allowed to evolve self-consistently in response to an abrupt 4×CO 2 forcing. The difference is primarily attributed to changes in longwave radiative feedbacks associated with circulation-driven decreases in tropical lower stratospheric ozone and related stratospheric water vapour and cirrus cloud changes. This has important implications for global model intercomparison studies 1,2 in which participating models often use simplified treatments of atmospheric composition changes that are neither consistent with the specified greenhouse gas forcing scenario nor with the associated atmospheric circulation feedbacks 3-5 .

Soil and vegetation parameter uncertainty on future terrestrial carbon sinks

NASA Astrophysics Data System (ADS)

Kothavala, Z.; Felzer, B. S.

2013-12-01

We examine the role of the terrestrial carbon cycle in a changing climate at the centennial scale using an intermediate complexity Earth system climate model that includes the effects of dynamic vegetation and the global carbon cycle. We present a series of ensemble simulations to evaluate the sensitivity of simulated terrestrial carbon sinks to three key model parameters: (a) The temperature dependence of soil carbon decomposition, (b) the upper temperature limits on the rate of photosynthesis, and (c) the nitrogen limitation of the maximum rate of carboxylation of Rubisco. We integrated the model in fully coupled mode for a 1200-year spin-up period, followed by a 300-year transient simulation starting at year 1800. Ensemble simulations were conducted varying each parameter individually and in combination with other variables. The results of the transient simulations show that terrestrial carbon uptake is very sensitive to the choice of model parameters. Changes in net primary productivity were most sensitive to the upper temperature limit on the rate of photosynthesis, which also had a dominant effect on overall land carbon trends; this is consistent with previous research that has shown the importance of climatic suppression of photosynthesis as a driver of carbon-climate feedbacks. Soil carbon generally decreased with increasing temperature, though the magnitude of this trend depends on both the net primary productivity changes and the temperature dependence of soil carbon decomposition. Vegetation carbon increased in some simulations, but this was not consistent across all configurations of model parameters. Comparing to global carbon budget observations, we identify the subset of model parameters which are consistent with observed carbon sinks; this serves to narrow considerably the future model projections of terrestrial carbon sink changes in comparison with the full model ensemble.

Global modeling of storm-time thermospheric dynamics and electrodynamics

NASA Astrophysics Data System (ADS)

Fuller-Rowell, T. J.; Richmond, A. D.; Maruyama, N.

Understanding the neutral dynamic and electrodynamic response of the upper atmosphere to geomagnetic storms, and quantifying the balance between prompt penetration and disturbance dynamo effects, are two of the significant challenges facing us today. This paper reviews our understanding of the dynamical and electrodynamic response of the upper atmosphere to storms from a modeling perspective. After injection of momentum and energy at high latitude during a geomagnetic storm, the neutral winds begin to respond almost immediately. The high-latitude wind system evolves quickly by the action of ion drag and the injection of kinetic energy; however, Joule dissipation provides the bulk of the energy source to change the dynamics and electrodynamics globally. Impulsive energy injection at high latitudes drives large-scale gravity waves that propagate globally. The waves transmit pressure gradients initiating a change in the global circulation. Numerical simulations of the coupled thermosphere, ionosphere, plasmasphere, and electrodynamic response to storms indicate that although the wind and waves are dynamic, with significant apparent "sloshing" between the hemispheres, the net effect is for an increased equatorward wind. The dynamic changes during a storm provide the conduit for many of the physical processes that ensue in the upper atmosphere. For instance, the increased meridional winds at mid latitudes push plasma parallel to the magnetic field to regions of different composition. The global circulation carries molecular rich air from the lower thermosphere upward and equatorward, changing the ratio of atomic and molecular neutral species, and changing loss rates for the ionosphere. The storm wind system also drives the disturbance dynamo, which through plasma transport modifies the strength and location of the equatorial ionization anomaly peaks. On a global scale, the increased equatorward meridional winds, and the generation of zonal winds at mid latitudes via the Coriolis effects, produce a current system opposing the normal quiet-time Sq current system. At the equator, the storm-time zonal electric fields reduce or reverse the normal upward and downward plasma drift on the dayside and nightside, respectively. In the numerical simulations, on the dayside, the disturbance dynamo appears fairly uniform, whereas at night a stronger local time dependence is apparent with increased upward drift between midnight and dawn. The simulations also indicate the possibility for a rapid dynamo response at the equator, within 2 h of storm onset, before the arrival of the large-scale gravity waves. All these wind-driven processes can result in dramatic ionospheric changes during storms. The disturbance dynamo can combine and interact with the prompt penetration of magnetospheric electric fields to the equator.

Understanding Evapotranspiration Trends and their Driving Mechanisms: An investigation across CONUS based on numerical modeling

NASA Astrophysics Data System (ADS)

Parr, D.; Wang, G.; Fu, C.

2015-12-01

As shown by climate models, increasing global temperatures and enhanced greenhouse gas concentration such as CO2 have had major effects on the dynamics of the hydrologic cycle and the surface energy budget, in particular, on evapotranspiration (ET). ET has significant decadal variations whether it be regionally or globally and variations of ET have major environmental and socioeconomic impacts. A number of recent studies have found a global increase in annual mean ET around 7mm per year per decade from about 1982 to the late 1990s. These results correspond with what is expected from an intensification of the hydrological cycle. However, the increasing ET trend did not continue after 1998 and from 1998-2008 this global trend was replaced with a decreasing trend of similar magnitude. This study uses numerical modeling to investigate if similar changing ET trends emerge in the continental U.S and part of northern Mexico. After validating model simulated evaporative fluxes and comparing spatial patterns to the aforementioned studies, various changing trends of different signs are identified across the U.S., and specific regions with strong signals of change are chosen for further examination with the purpose of identifying the root causes of these changing trends and which variables are most influential towards change. Experimental simulations conducted to isolate the most influential factors towards ET reveal that precipitation amount as well as its characteristics have the greatest impact on the ET trends discovered, with other factors like wind and air temperatures displaying less influence over inter-annual trends. This study helps better understand terrestrial ET and it's interactions which will help facilitate better predictions of change in surface climate such as heatwaves and droughts as well as impacts on water resources.

An integrated model of soil, hydrology, and vegetation for carbon dynamics in wetland ecosystems

Treesearch

Yu Zhang; Changsheng Li; Carl C. Trettin; Harbin Li; Ge Sun

2002-01-01

Wetland ecosystems are an important component in global carbon (C) cycles and may exert a large influence on global clinlate change. Predictions of C dynamics require us to consider interactions among many critical factors of soil, hydrology, and vegetation. However, few such integrated C models exist for wetland ecosystems. In this paper, we report a simulation model...

The role of sea ice dynamics in global climate change

NASA Technical Reports Server (NTRS)

Hibler, William D., III

1992-01-01

The topics covered include the following: general characteristics of sea ice drift; sea ice rheology; ice thickness distribution; sea ice thermodynamic models; equilibrium thermodynamic models; effect of internal brine pockets and snow cover; model simulations of Arctic Sea ice; and sensitivity of sea ice models to climate change.

Changing Amazon biomass and the role of atmospheric CO2 concentration, climate, and land use

NASA Astrophysics Data System (ADS)

Almeida Castanho, Andrea D.; Galbraith, David; Zhang, Ke; Coe, Michael T.; Costa, Marcos H.; Moorcroft, Paul

2016-01-01

The Amazon tropical evergreen forest is an important component of the global carbon budget. Its forest floristic composition, structure, and function are sensitive to changes in climate, atmospheric composition, and land use. In this study biomass and productivity simulated by three dynamic global vegetation models (Integrated Biosphere Simulator, Ecosystem Demography Biosphere Model, and Joint UK Land Environment Simulator) for the period 1970-2008 are compared with observations from forest plots (Rede Amazónica de Inventarios Forestales). The spatial variability in biomass and productivity simulated by the DGVMs is low in comparison to the field observations in part because of poor representation of the heterogeneity of vegetation traits within the models. We find that over the last four decades the CO2 fertilization effect dominates a long-term increase in simulated biomass in undisturbed Amazonian forests, while land use change in the south and southeastern Amazonia dominates a reduction in Amazon aboveground biomass, of similar magnitude to the CO2 biomass gain. Climate extremes exert a strong effect on the observed biomass on short time scales, but the models are incapable of reproducing the observed impacts of extreme drought on forest biomass. We find that future improvements in the accuracy of DGVM predictions will require improved representation of four key elements: (1) spatially variable plant traits, (2) soil and nutrients mediated processes, (3) extreme event mortality, and (4) sensitivity to climatic variability. Finally, continued long-term observations and ecosystem-scale experiments (e.g. Free-Air CO2 Enrichment experiments) are essential for a better understanding of the changing dynamics of tropical forests.

Future climate change enhances rainfall seasonality in a regional model of western Maritime Continent

NASA Astrophysics Data System (ADS)

Kang, Suchul; Im, Eun-Soon; Eltahir, Elfatih A. B.

2018-03-01

In this study, future changes in rainfall due to global climate change are investigated over the western Maritime Continent based on dynamically downscaled climate projections using the MIT Regional Climate Model (MRCM) with 12 km horizontal resolution. A total of nine 30-year regional climate projections driven by multi-GCMs projections (CCSM4, MPI-ESM-MR and ACCESS1.0) under multi-scenarios of greenhouse gases emissions (Historical: 1976-2005, RCP4.5 and RCP8.5: 2071-2100) from phase 5 of the Coupled Model Inter-comparison Project (CMIP5) are analyzed. Focusing on dynamically downscaled rainfall fields, the associated systematic biases originating from GCM and MRCM are removed based on observations using Parametric Quantile Mapping method in order to enhance the reliability of future projections. The MRCM simulations with bias correction capture the spatial patterns of seasonal rainfall as well as the frequency distribution of daily rainfall. Based on projected rainfall changes under both RCP4.5 and RCP8.5 scenarios, the ensemble of MRCM simulations project a significant decrease in rainfall over the western Maritime Continent during the inter-monsoon periods while the change in rainfall is not relevant during wet season. The main mechanism behind the simulated decrease in rainfall is rooted in asymmetries of the projected changes in seasonal dynamics of the meridional circulation along different latitudes. The sinking motion, which is marginally positioned in the reference simulation, is enhanced and expanded under global climate change, particularly in RCP8.5 scenario during boreal fall season. The projected enhancement of rainfall seasonality over the western Maritime Continent suggests increased risk of water stress for natural ecosystems as well as man-made water resources reservoirs.

European climate change at global mean temperature increases of 1.5 and 2 °C above pre-industrial conditions as simulated by the EURO-CORDEX regional climate models

NASA Astrophysics Data System (ADS)

Kjellström, Erik; Nikulin, Grigory; Strandberg, Gustav; Bøssing Christensen, Ole; Jacob, Daniela; Keuler, Klaus; Lenderink, Geert; van Meijgaard, Erik; Schär, Christoph; Somot, Samuel; Sørland, Silje Lund; Teichmann, Claas; Vautard, Robert

2018-05-01

We investigate European regional climate change for time periods when the global mean temperature has increased by 1.5 and 2 °C compared to pre-industrial conditions. Results are based on regional downscaling of transient climate change simulations for the 21st century with global climate models (GCMs) from the fifth-phase Coupled Model Intercomparison Project (CMIP5). We use an ensemble of EURO-CORDEX high-resolution regional climate model (RCM) simulations undertaken at a computational grid of 12.5 km horizontal resolution covering Europe. The ensemble consists of a range of RCMs that have been used for downscaling different GCMs under the RCP8.5 forcing scenario. The results indicate considerable near-surface warming already at the lower 1.5 °C of warming. Regional warming exceeds that of the global mean in most parts of Europe, being the strongest in the northernmost parts of Europe in winter and in the southernmost parts of Europe together with parts of Scandinavia in summer. Changes in precipitation, which are less robust than the ones in temperature, include increases in the north and decreases in the south with a borderline that migrates from a northerly position in summer to a southerly one in winter. Some of these changes are already seen at 1.5 °C of warming but are larger and more robust at 2 °C. Changes in near-surface wind speed are associated with a large spread among individual ensemble members at both warming levels. Relatively large areas over the North Atlantic and some parts of the continent show decreasing wind speed while some ocean areas in the far north show increasing wind speed. The changes in temperature, precipitation and wind speed are shown to be modified by changes in mean sea level pressure, indicating a strong relationship with the large-scale circulation and its internal variability on decade-long timescales. By comparing to a larger ensemble of CMIP5 GCMs we find that the RCMs can alter the results, leading either to attenuation or amplification of the climate change signal in the underlying GCMs. We find that the RCMs tend to produce less warming and more precipitation (or less drying) in many areas in both winter and summer.

Convection-Permitting Regional Climate Simulations over the Contiguous United States Including Potential Climate Change Scenarios

NASA Astrophysics Data System (ADS)

Liu, Changhai; Rasmussen, Roy; Ikeda, Kyoko; Barlage, Michael; Chen, Fei; Clark, Martyn; Dai, Aiguo; Dudhia, Jimy; Gochis, David; Gutmann, Ethan; Li, Yanping; Newman, Andrew; Thompson, Gregory

2016-04-01

The WRF model with a domain size of 1360x1016x51 points, using a 4 km spacing to encompass most of North America, is employed to investigate the water cycle and climate change impacts over the Contiguous United States (CONUS). Four suites of numerical experiments are being conducted, consisting of a 13-year retrospective simulation forced with ERA-I reanalysis, a 13-year climate sensitivity or Pseudo-Global Warming (PGW) simulation, and two 10-year CMIP5-based historical/future period simulations based on a revised bias-correction method. The major objectives are: 1) to evaluate high-resolution WRF's capability to capture orographic precipitation and snow mass balance over the western CONUS and convective precipitation over the eastern CONUS; 2) to assess future changes of seasonal snowfall and snowpack and associated hydrological cycles along with their regional variability across the different mountain barriers and elevation dependency, in response to the CMIP5 projected 2071-2100 climate warming; 3) to examine the precipitation changes under the projected global warming, with an emphasis on precipitation extremes and the warm-season precipitation corridor in association with MCS tracks in the central US; and 4) to provide a valuable community dataset for regional climate change and impact studies. Preliminary analysis of the retrospective simulation shows both seasonal/sub-seasonal precipitation and temperature are well reproduced, with precipitation bias being within 10% of the observations and temperature bias being below 1 degree C in most seasons and locations. The observed annual cycle of snow water equivalent (SWE), such as peak time and disappearance time, is also realistically replicated, even though the peak value is somewhat underestimated. The PGW simulation shows a large cold-season warming in northeast US and eastern Canada, possibly associated with snow albedo feedback, and a strong summer warming in north central US in association with precipitation reduction. There is an increase in annual rainfall/precipitation, but a sharp reduction in snowfall/snowpack in response to the global warming. A pronounced seasonal feature is the suppressed summertime precipitation in central US for the warmer climate. More detailed analysis of the modeling results is presently under way and will be presented in the meeting.

Performance and Evaluation of the Global Modeling and Assimilation Office Observing System Simulation Experiment

NASA Technical Reports Server (NTRS)

Prive, Nikki; Errico, R. M.; Carvalho, D.

2018-01-01

The National Aeronautics and Space Administration Global Modeling and Assimilation Office (NASA/GMAO) has spent more than a decade developing and implementing a global Observing System Simulation Experiment framework for use in evaluting both new observation types as well as the behavior of data assimilation systems. The NASA/GMAO OSSE has constantly evolved to relect changes in the Gridpoint Statistical Interpolation data assimiation system, the Global Earth Observing System model, version 5 (GEOS-5), and the real world observational network. Software and observational datasets for the GMAO OSSE are publicly available, along with a technical report. Substantial modifications have recently been made to the NASA/GMAO OSSE framework, including the character of synthetic observation errors, new instrument types, and more sophisticated atmospheric wind vectors. These improvements will be described, along with the overall performance of the current OSSE. Lessons learned from investigations into correlated errors and model error will be discussed.

Relative effects of climate change and wildfires on stream temperatures: A simulation modeling approach in a Rocky Mountain watershed

Treesearch

Lisa Holsinger; Robert E. Keane; Daniel J. Isaak; Lisa Eby; Michael K. Young

2014-01-01

Freshwater ecosystems are warming globally from the direct effects of climate change on air temperature and hydrology and the indirect effects on near-stream vegetation. In fire-prone landscapes, vegetative change may be especially rapid and cause significant local stream temperature increases but the importance of these increases relative to broader changes associated...

Global changes alter soil fungal communities and alter rates of organic matter decomposition

NASA Astrophysics Data System (ADS)

Moore, J.; Frey, S. D.

2016-12-01

Global changes - such as warming, more frequent and severe droughts, increasing atmospheric CO2, and increasing nitrogen (N) deposition rates - are altering ecosystem processes. The balance between soil carbon (C) accumulation and decomposition is determined in large part by the activity and biomass of detrital organisms, namely soil fungi, and yet their sensitivity to global changes remains unresolved. We present results from a meta-analysis of 200+ studies spanning manipulative and observational field experiments to quantify fungal responses to global change and expected consequences for ecosystem C dynamics. Warming altered the functional soil microbial community by reducing the ratio of fungi to bacteria (f:b) total fungal biomass. Additionally, warming reduced lignolytic enzyme activity generally by one-third. Simulated N deposition affected f:b differently than warming, but the effect on fungal biomass and activity was similar. The effect of N-enrichment on f:b was contingent upon ecosystem type; f:b increased in alpine meadows and heathlands but decreased in temperate forests following N-enrichment. Across ecosystems, fungal biomass marginally declined by 8% in N-enriched soils. In general, N-enrichment reduced fungal lignolytic enzyme activity, which could explain why soil C accumulates in some ecosystems following warming and N-enrichment. Several global change experiments have reported the surprising result that soil C builds up following increases in temperature and N deposition rates. While site-specific studies have examined the role of soil fungi in ecosystem responses to global change, we present the first meta-analysis documenting general patterns of global change impacts on soil fungal communities, biomass, and activity. In sum, we provide evidence that soil microbial community shifts and activity plays a large part in ecosystem responses to global changes, and have the potential to alter the magnitude of the C-climate feedback.

Potential strong contribution of future anthropogenic land-use and land-cover change to the terrestrial carbon cycle

NASA Astrophysics Data System (ADS)

Quesada, Benjamin; Arneth, Almut; Robertson, Eddy; de Noblet-Ducoudré, Nathalie

2018-06-01

Anthropogenic land-use and land cover changes (LULCC) affect global climate and global terrestrial carbon (C) cycle. However, relatively few studies have quantified the impacts of future LULCC on terrestrial carbon cycle. Here, using Earth system model simulations performed with and without future LULCC, under the RCP8.5 scenario, we find that in response to future LULCC, the carbon cycle is substantially weakened: browning, lower ecosystem C stocks, higher C loss by disturbances and higher C turnover rates are simulated. Projected global greening and land C storage are dampened, in all models, by 22% and 24% on average and projected C loss by disturbances enhanced by ~49% when LULCC are taken into account. By contrast, global net primary productivity is found to be only slightly affected by LULCC (robust +4% relative enhancement compared to all forcings, on average). LULCC is projected to be a predominant driver of future C changes in regions like South America and the southern part of Africa. LULCC even cause some regional reversals of projected increased C sinks and greening, particularly at the edges of the Amazon and African rainforests. Finally, in most carbon cycle responses, direct removal of C dominates over the indirect CO2 fertilization due to LULCC. In consequence, projections of land C sequestration potential and Earth’s greening could be substantially overestimated just because of not fully accounting for LULCC.

Supervising simulations with the Prodiguer Messaging Platform

NASA Astrophysics Data System (ADS)

Greenslade, Mark; Carenton, Nicolas; Denvil, Sebastien

2015-04-01

At any one moment in time, researchers affiliated with the Institut Pierre Simon Laplace (IPSL) climate modeling group, are running hundreds of global climate simulations. These simulations execute upon a heterogeneous set of High Performance Computing (HPC) environments spread throughout France. The IPSL's simulation execution runtime is called libIGCM (library for IPSL Global Climate Modeling group). libIGCM has recently been enhanced so as to support realtime operational use cases. Such use cases include simulation monitoring, data publication, environment metrics collection, automated simulation control … etc. At the core of this enhancement is the Prodiguer messaging platform. libIGCM now emits information, in the form of messages, for remote processing at IPSL servers in Paris. The remote message processing takes several forms, for example: 1. Persisting message content to database(s); 2. Notifying an operator of changes in a simulation's execution status; 3. Launching rollback jobs upon simulation failure; 4. Dynamically updating controlled vocabularies; 5. Notifying downstream applications such as the Prodiguer web portal; We will describe how the messaging platform has been implemented from a technical perspective and demonstrate the Prodiguer web portal receiving realtime notifications.

Challenges in Global Land Use/Land Cover Change Modeling

NASA Astrophysics Data System (ADS)

Clarke, K. C.

2011-12-01

For the purposes of projecting and anticipating human-induced land use change at the global scale, much work remains in the systematic mapping and modeling of world-wide land uses and their related dynamics. In particular, research has focused on tropical deforestation, loss of prime agricultural land, loss of wild land and open space, and the spread of urbanization. Fifteen years of experience in modeling land use and land cover change at the regional and city level with the cellular automata model SLEUTH, including cross city and regional comparisons, has led to an ability to comment on the challenges and constraints that apply to global level land use change modeling. Some issues are common to other modeling domains, such as scaling, earth geometry, and model coupling. Others relate to geographical scaling of human activity, while some are issues of data fusion and international interoperability. Grid computing now offers the prospect of global land use change simulation. This presentation summarizes what barriers face global scale land use modeling, but also highlights the benefits of such modeling activity on global change research. An approach to converting land use maps and forecasts into environmental impact measurements is proposed. Using such an approach means that multitemporal mapping, often using remotely sensed sources, and forecasting can also yield results showing the overall and disaggregated status of the environment.

Using interactive online role-playing simulations to develop global competency and to prepare engineering students for a globalised world

NASA Astrophysics Data System (ADS)

May, Dominik; Wold, Kari; Moore, Stephanie

2015-09-01

The world is changing significantly, and it is becoming increasingly globalised. This means that countries, businesses, and professionals must think and act globally to be successful. Many individuals, however, are not prepared with the global competency skills needed to communicate and perform effectively in a globalised system. To address this need, higher education institutions are looking for ways to instil these skills in their students. This paper explains one promising approach using current learning principles: transnational interactive online environments in engineering education. In 2011, the TU Dortmund and the University of Virginia initiated a collaboration in which engineering students from both universities took part in one online synchronous course and worked together on global topics. This paper describes how the course was designed and discusses specific research results regarding how interactive online role-playing simulations support students in gaining the global competency skills required to actively participate in today's international workforce.

Simulations of Seismic Wave Propagation on Mars

DOE PAGES

Bozdağ, Ebru; Ruan, Youyi; Metthez, Nathan; ...

2017-03-23

In this paper, we present global and regional synthetic seismograms computed for 1D and 3D Mars models based on the spectral-element method. For global simulations, we implemented a radially-symmetric Mars model with a 110 km thick crust. For this 1D model, we successfully benchmarked the 3D seismic wave propagation solver SPECFEM3D_GLOBE against the 2D axisymmetric wave propagation solver AxiSEM at periods down to 10 s. We also present higher-resolution body-wave simulations with AxiSEM down to 1 s in a model with a more complex 1D crust, revealing wave propagation effects that would have been difficult to interpret based on raymore » theory. For 3D global simulations based on SPECFEM3D_GLOBE, we superimposed 3D crustal thickness variations capturing the distinct crustal dichotomy between Mars’ northern and southern hemispheres, as well as topography, ellipticity, gravity, and rotation. The global simulations clearly indicate that the 3D crust speeds up body waves compared to the reference 1D model, whereas it significantly changes surface waveforms and their dispersive character depending on its thickness. We also perform regional simulations with the solver SES3D based on 3D crustal models derived from surface composition, thereby addressing the effects of various distinct crustal features down to 2 s. The regional simulations confirm the strong effects of crustal variations on waveforms. Finally, we conclude that the numerical tools are ready for examining more scenarios, including various other seismic models and sources.« less

Simulations of Seismic Wave Propagation on Mars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bozdağ, Ebru; Ruan, Youyi; Metthez, Nathan

In this paper, we present global and regional synthetic seismograms computed for 1D and 3D Mars models based on the spectral-element method. For global simulations, we implemented a radially-symmetric Mars model with a 110 km thick crust. For this 1D model, we successfully benchmarked the 3D seismic wave propagation solver SPECFEM3D_GLOBE against the 2D axisymmetric wave propagation solver AxiSEM at periods down to 10 s. We also present higher-resolution body-wave simulations with AxiSEM down to 1 s in a model with a more complex 1D crust, revealing wave propagation effects that would have been difficult to interpret based on raymore » theory. For 3D global simulations based on SPECFEM3D_GLOBE, we superimposed 3D crustal thickness variations capturing the distinct crustal dichotomy between Mars’ northern and southern hemispheres, as well as topography, ellipticity, gravity, and rotation. The global simulations clearly indicate that the 3D crust speeds up body waves compared to the reference 1D model, whereas it significantly changes surface waveforms and their dispersive character depending on its thickness. We also perform regional simulations with the solver SES3D based on 3D crustal models derived from surface composition, thereby addressing the effects of various distinct crustal features down to 2 s. The regional simulations confirm the strong effects of crustal variations on waveforms. Finally, we conclude that the numerical tools are ready for examining more scenarios, including various other seismic models and sources.« less

Confronting Future Risks of Global Water Stress and Sustainability: Avoided Changes Versus Adaptive Actions

NASA Astrophysics Data System (ADS)

Schlosser, C. A.; Strzepek, K. M.; Gao, X.; Fant, C.; Paltsev, S.; Monier, E.; Sokolov, A. P.; Winchester, N.; Chen, H.; Kicklighter, D. W.; Ejaz, Q.

2016-12-01

We examine the fate of global water resources under a range of self-consistent socio-economic projections using the MIT Integrated Global System Model (IGSM) under a range of plausible mitigation and adaptation scenarios of development to the water-energy-land systems and against an assessment of the results from the UN COP-21 meeting. We assess the trends of an index of managed water stress as well as unmet water demands as simulated by the Water Resource System within the IGSM framework (IGSM-WRS). The WRS is forced by the simulations of the global climate response, variations in regional climate pattern changes, as well as the socio-economic drivers from the IGSM scenarios. We focus on the changes in water-stress metrics in the coming decades and going into the latter half of this century brought about by our projected climate and socio-economic changes, as well as the total (additional) populations affected by increased stress. We highlight selected basins to demonstrate sensitivities and interplay between supply and demand, the uncertainties in global climate sensitivity as well as regional climate change, and their implications to assessing and reducing water risks and the populations affected by water scarcity. We also evaluate the impact of explicitly representing irrigated land and water scarcity in an economy-wide model on food prices, bioenergy production and deforestation both with and without a global carbon policy. We highlight the importance of adaptive measures that will be required, worldwide, to meet surface-water shortfalls even under more aggressive and certainly under intermediate climate mitigation pathways - and further analyses is presented in this context quantifying risks averted and their associated costs. In addition, we also demonstrate that the explicit representation of irrigated land within this intergrated modeling frameowork has a small impact on food, bioenergy and deforestation outcomes within the scenarios considered. Nevertheless, globally speaking the scenarios indicate that going into the latter half of the twentieth century, approximately one-and-a-half billion additional people will experience at least moderately stressed water conditions worldwide and of that 1 billion will be at least will be living within regions under heavily stressed water conditions.

Possible future changes in extreme events over Northern Eurasia

NASA Astrophysics Data System (ADS)

Monier, Erwan; Sokolov, Andrei; Scott, Jeffery

2013-04-01

In this study, we investigate possible future climate change over Northern Eurasia and its impact on extreme events. Northern Eurasia is a major player in the global carbon budget because of boreal forests and peatlands. Circumpolar boreal forests alone contain more than five times the amount of carbon of temperate forests and almost double the amount of carbon of the world's tropical forests. Furthermore, severe permafrost degradation associated with climate change could result in peatlands releasing large amounts of carbon dioxide and methane. Meanwhile, changes in the frequency and magnitude of extreme events, such as extreme precipitation, heat waves or frost days are likely to have substantial impacts on Northern Eurasia ecosystems. For this reason, it is very important to quantify the possible climate change over Northern Eurasia under different emissions scenarios, while accounting for the uncertainty in the climate response and changes in extreme events. For several decades, the Massachusetts Institute of Technology (MIT) Joint Program on the Science and Policy of Global Change has been investigating uncertainty in climate change using the MIT Integrated Global System Model (IGSM) framework, an integrated assessment model that couples an earth system model of intermediate complexity (with a 2D zonal-mean atmosphere) to a human activity model. In this study, regional change is investigated using the MIT IGSM-CAM framework that links the IGSM to the National Center for Atmospheric Research (NCAR) Community Atmosphere Model (CAM). New modules were developed and implemented in CAM to allow climate parameters to be changed to match those of the IGSM. The simulations presented in this paper were carried out for two emission scenarios, a "business as usual" scenario and a 660 ppm of CO2-equivalent stabilization, which are similar to, respectively, the Representative Concentration Pathways RCP8.5 and RCP4.5 scenarios. Values of climate sensitivity and net aerosol forcing used in the simulations within the IGSM-CAM framework provide a good approximation for the median, and the lower and upper bound of 90% probability distribution of 21st century climate change. Five member ensembles were carried out for each choice of parameters using different initial conditions. With these simulations, we investigate the role of emissions scenarios (climate policies), the global climate response (climate sensitivity) and natural variability (initial conditions) on the uncertainty in future climate changes over Northern Eurasia. A particular emphasis is made on future changes in extreme events, including frost days, extreme summer temperature and extreme summer and winter precipitation.

Resolving the Kinetic Reconnection Length Scale in Global Magnetospheric Simulations with MHD-EPIC

NASA Astrophysics Data System (ADS)

Toth, G.; Chen, Y.; Cassak, P.; Jordanova, V.; Peng, B.; Markidis, S.; Gombosi, T. I.

2016-12-01

We have recently developed a new modeling capability: the Magnetohydrodynamics with Embedded Particle-in-Cell (MHD-EPIC) algorithm with support from Los Alamos SHIELDS and NSF INSPIRE grants. We have implemented MHD-EPIC into the Space Weather Modeling Framework (SWMF) using the implicit Particle-in-Cell (iPIC3D) and the BATS-R-US extended magnetohydrodynamic codes. The MHD-EPIC model allows two-way coupled simulations in two and three dimensions with multiple embedded PIC regions. Both BATS-R-US and iPIC3D are massively parallel codes. The MHD-EPIC approach allows global magnetosphere simulations with embedded kinetic simulations. For small magnetospheres, like Ganymede or Mercury, we can easily resolve the ion scales around the reconnection sites. Modeling the Earth magnetosphere is very challenging even with our efficient MHD-EPIC model due to the large separation between the global and ion scales. On the other hand the large separation of scales may be exploited: the solution may not be sensitive to the ion inertial length as long as it is small relative to the global scales. The ion inertial length can be varied by changing the ion mass while keeping the MHD mass density, the velocity, and pressure the same for the initial and boundary conditions. Our two-dimensional MHD-EPIC simulations for the dayside reconnection region show in fact, that the overall solution is not sensitive to ion inertial length. The shape, size and frequency of flux transfer events are very similar for a wide range of ion masses. Our results mean that 3D MHD-EPIC simulations for the Earth and other large magnetospheres can be made computationally affordable by artificially increasing the ion mass: the required grid resolution and time step in the PIC model are proportional to the ion inertial length. Changing the ion mass by a factor of 4, for example, speeds up the PIC code by a factor of 256. In fact, this approach allowed us to perform an hour-long 3D MHD-EPIC simulations for the Earth magnetosphere.

Going with the flow: the role of ocean circulation in global marine ecosystems under a changing climate.

PubMed

van Gennip, Simon J; Popova, Ekaterina E; Yool, Andrew; Pecl, Gretta T; Hobday, Alistair J; Sorte, Cascade J B

2017-07-01

Ocean warming, acidification, deoxygenation and reduced productivity are widely considered to be the major stressors to ocean ecosystems induced by emissions of CO 2 . However, an overlooked stressor is the change in ocean circulation in response to climate change. Strong changes in the intensity and position of the western boundary currents have already been observed, and the consequences of such changes for ecosystems are beginning to emerge. In this study, we address climatically induced changes in ocean circulation on a global scale but relevant to propagule dispersal for species inhabiting global shelf ecosystems, using a high-resolution global ocean model run under the IPCC RCP 8.5 scenario. The ¼ degree model resolution allows improved regional realism of the ocean circulation beyond that of available CMIP5-class models. We use a Lagrangian approach forced by modelled ocean circulation to simulate the circulation pathways that disperse planktonic life stages. Based on trajectory backtracking, we identify present-day coastal retention, dominant flow and dispersal range for coastal regions at the global scale. Projecting into the future, we identify areas of the strongest projected circulation change and present regional examples with the most significant modifications in their dominant pathways. Climatically induced changes in ocean circulation should be considered as an additional stressor of marine ecosystems in a similar way to ocean warming or acidification. © 2017 John Wiley & Sons Ltd.

A modeling study of coastal inundation induced by storm surge, sea-level rise, and subsidence in the Gulf of Mexico

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Zhaoqing; Wang, Taiping; Leung, Lai-Yung R.

The northern coasts of the Gulf of Mexico are highly vulnerable to the direct threats of climate change, such as hurricane-induced storm surge, and such risks can be potentially exacerbated by land subsidence and global sea level rise. This paper presents an application of a coastal storm surge model to study the coastal inundation process induced by tide and storm surge, and its response to the effects of land subsidence and sea level rise in the northern Gulf coast. An unstructured-grid Finite Volume Coastal Ocean Model was used to simulate tides and hurricane-induced storm surges in the Gulf of Mexico.more » Simulated distributions of co-amplitude and co-phase of semi-diurnal and diurnal tides are in good agreement with previous modeling studies. The storm surges induced by four historical hurricanes (Rita, Katrina, Ivan and Dolly) were simulated and compared to observed water levels at National Oceanic and Atmospheric Administration tide stations. Effects of coastal subsidence and future global sea level rise on coastal inundation in the Louisiana coast were evaluated using a parameter “change of inundation depth” through sensitivity simulations that were based on a projected future subsidence scenario and 1-m global sea level rise by the end of the century. Model results suggested that hurricane-induced storm surge height and coastal inundation could be exacerbated by future global sea level rise and subsidence, and that responses of storm surge and coastal inundation to the effects of sea level rise and subsidence are highly nonlinear and vary on temporal and spatial scales.« less

Present and Future Projections of Habitat Suitability of the Asian Tiger Mosquito, a Vector of Viral Pathogens, from Global Climate Simulations.

NASA Astrophysics Data System (ADS)

Proestos, Y.; Christophides, G.; Erguler, K.; Tanarhte, M.; Waldock, J.; Lelieveld, J.

2014-12-01

Climate change can influence the transmission of vector borne diseases (VBDs) through altering the habitat suitability of insect vectors. Here we present global climate model simulations and evaluate the associated uncertainties in view of the main meteorological factors that may affect the distribution of the Asian Tiger mosquito (Aedes albopictus), which can transmit pathogens that cause Chikungunya, Dengue fever, yellow fever and various encephalitides. Using a general circulation model (GCM) at 50 km horizontal resolution to simulate mosquito survival variables including temperature, precipitation and relative humidity, we present both global and regional projections of the habitat suitability up to the middle of the 21st century. The model resolution of 50 km allows evaluation against previous projections for Europe and provides a basis for comparative analyses with other regions. Model uncertainties and performance are addressed in light of the recent CMIP5 ensemble climate model simulations for the RCP8.5 concentration pathway and using meteorological re-analysis data (ERA-Interim/ECMWF) for the recent past. Uncertainty ranges associated with the thresholds of meteorological variables that may affect the distribution of Ae. albopictus are diagnosed using fuzzy-logic methodology, notably to assess the influence of selected meteorological criteria and combinations of criteria that influence mosquito habitat suitability. From the climate projections for 2050, and adopting a habitat suitability index larger than 70%, we estimate that about 2.4 billion individuals in a land area of nearly 20 million square kilometres will potentially be exposed to Ae. albopictus. The synthesis of fuzzy-logic based on mosquito biology and climate change analysis provides new insights into the regional and global spreading of VBDs to support disease control and policy making.

Influence of Transport on Two-Dimensional Model Simulation: 2. Stratospheric Aircraft Perturbations. 2; Stratospheric Aircraft Perturbations

NASA Technical Reports Server (NTRS)

Fleming, Eric L.; Jackman, Charles H.; Considine, David B.

1999-01-01

We have adopted the transport scenarios used in Part 1 to examine the sensitivity of stratospheric aircraft perturbations to transport changes in our 2-D model. Changes to the strength of the residual circulation in the upper troposphere and stratosphere and changes to the lower stratospheric K(sub zz) had similar effects in that increasing the transport rates decreased the overall stratospheric residence time and reduced the magnitude of the negative perturbation response in total ozone. Increasing the stratospheric K(sub yy) increased the residence time and enhanced the global scale negative total ozone response. However, increasing K(sub yy) along with self-consistent increases in the corresponding planetary wave drive, which leads to a stronger residual circulation, more than compensates for the K(sub yy)-effect, and results in a significantly weaker perturbation response, relative to the base case, throughout the stratosphere. We found a relatively minor model perturbation response sensitivity to the magnitude of K(sub yy) in the tropical stratosphere, and only a very small sensitivity to the magnitude of the horizontal mixing across the tropopause and to the strength of the mesospheric gravity wave drag and diffusion. These transport simulations also revealed a generally strong correlation between passive NO(sub y) accumulation and age of air throughout the stratosphere, such that faster transport rates resulted in a younger mean age and a smaller NO(y) mass accumulation. However, specific variations in K(sub yy) and mesospheric gravity wave strength exhibited very little NO(sub y)-age correlation in the lower stratosphere, similar to 3-D model simulations performed in the recent NASA "Models and Measurements" II analysis. The base model transport, which gives the most favorable overall comparison with inert tracer observations, simulated a global/annual mean total ozone response of -0.59%, with only a slightly larger response in the northern compared to the southern hemisphere. For transport scenarios which gave tracer simulations within some agreement with measurements, the annual/globally averaged total ozone response ranged from -0.45% to -0.70%. Our previous 1995 model exhibited overly fast transport rates, resulting in a global/annually averaged perturbation total ozone response of -0.25%, which is significantly weaker compared to the 1999 model. This illustrates how transport deficiencies can bias model simulations of stratospheric aircraft.

Increasing atmospheric CO2 overrides the historical legacy of multiple stable biome states in Africa.

PubMed

Moncrieff, Glenn R; Scheiter, Simon; Bond, William J; Higgins, Steven I

2014-02-01

The dominant vegetation over much of the global land surface is not predetermined by contemporary climate, but also influenced by past environmental conditions. This confounds attempts to predict current and future biome distributions, because even a perfect model would project multiple possible biomes without knowledge of the historical vegetation state. Here we compare the distribution of tree- and grass-dominated biomes across Africa simulated using a dynamic global vegetation model (DGVM). We explicitly evaluate where and under what conditions multiple stable biome states are possible for current and projected future climates. Our simulation results show that multiple stable biomes states are possible for vast areas of tropical and subtropical Africa under current conditions. Widespread loss of the potential for multiple stable biomes states is projected in the 21st Century, driven by increasing atmospheric CO2 . Many sites where currently both tree-dominated and grass-dominated biomes are possible become deterministically tree-dominated. Regions with multiple stable biome states are widespread and require consideration when attempting to predict future vegetation changes. Testing for behaviour characteristic of systems with multiple stable equilibria, such as hysteresis and dependence on historical conditions, and the resulting uncertainty in simulated vegetation, will lead to improved projections of global change impacts. © 2013 The Authors. New Phytologist © 2013 New Phytologist Trust.

The Hydrological Sensitivity to Global Warming and Solar Geoengineering Derived from Thermodynamic Constraints

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kleidon, Alex; Kravitz, Benjamin S.; Renner, Maik

2015-01-16

We derive analytic expressions of the transient response of the hydrological cycle to surface warming from an extremely simple energy balance model in which turbulent heat fluxes are constrained by the thermodynamic limit of maximum power. For a given magnitude of steady-state temperature change, this approach predicts the transient response as well as the steady-state change in surface energy partitioning and the hydrologic cycle. We show that the transient behavior of the simple model as well as the steady state hydrological sensitivities to greenhouse warming and solar geoengineering are comparable to results from simulations using highly complex models. Many ofmore » the global-scale hydrological cycle changes can be understood from a surface energy balance perspective, and our thermodynamically-constrained approach provides a physically robust way of estimating global hydrological changes in response to altered radiative forcing.« less

Synergistic Ecoclimate Teleconnections from Forest Loss in Different Regions Structure Global Ecological Responses.

PubMed

Garcia, Elizabeth S; Swann, Abigail L S; Villegas, Juan C; Breshears, David D; Law, Darin J; Saleska, Scott R; Stark, Scott C

2016-01-01

Forest loss in hotspots around the world impacts not only local climate where loss occurs, but also influences climate and vegetation in remote parts of the globe through ecoclimate teleconnections. The magnitude and mechanism of remote impacts likely depends on the location and distribution of forest loss hotspots, but the nature of these dependencies has not been investigated. We use global climate model simulations to estimate the distribution of ecologically-relevant climate changes resulting from forest loss in two hotspot regions: western North America (wNA), which is experiencing accelerated dieoff, and the Amazon basin, which is subject to high rates of deforestation. The remote climatic and ecological net effects of simultaneous forest loss in both regions differed from the combined effects of loss from the two regions simulated separately, as evident in three impacted areas. Eastern South American Gross Primary Productivity (GPP) increased due to changes in seasonal rainfall associated with Amazon forest loss and changes in temperature related to wNA forest loss. Eurasia's GPP declined with wNA forest loss due to cooling temperatures increasing soil ice volume. Southeastern North American productivity increased with simultaneous forest loss, but declined with only wNA forest loss due to changes in VPD. Our results illustrate the need for a new generation of local-to-global scale analyses to identify potential ecoclimate teleconnections, their underlying mechanisms, and most importantly, their synergistic interactions, to predict the responses to increasing forest loss under future land use change and climate change.

Elevation-dependent warming in global climate model simulations at high spatial resolution

NASA Astrophysics Data System (ADS)

Palazzi, Elisa; Mortarini, Luca; Terzago, Silvia; von Hardenberg, Jost

2018-06-01

The enhancement of warming rates with elevation, so-called elevation-dependent warming (EDW), is one of the regional, still not completely understood, expressions of global warming. Sentinels of climate and environmental changes, mountains have experienced more rapid and intense warming trends in the recent decades, leading to serious impacts on mountain ecosystems and downstream. In this paper we use a state-of-the-art Global Climate Model (EC-Earth) to investigate the impact of model spatial resolution on the representation of this phenomenon and to highlight possible differences in EDW and its causes in different mountain regions of the Northern Hemisphere. To this end we use EC-Earth climate simulations at five different spatial resolutions, from ˜ 125 to ˜ 16 km, to explore the existence and the driving mechanisms of EDW in the Colorado Rocky Mountains, the Greater Alpine Region and the Tibetan Plateau-Himalayas. Our results show that the more frequent EDW drivers in all regions and seasons are the changes in albedo and in downward thermal radiation and this is reflected in both daytime and nighttime warming. In the Tibetan Plateau-Himalayas and in the Greater Alpine Region, an additional driver is the change in specific humidity. We also find that, while generally the model shows no clear resolution dependence in its ability to simulate the existence of EDW in the different regions, specific EDW characteristics such as its intensity and the relative role of different driving mechanisms may be different in simulations performed at different spatial resolutions. Moreover, we find that the role of internal climate variability can be significant in modulating the EDW signal, as suggested by the spread found in the multi-member ensemble of the EC-Earth experiments which we use.

Input-driven versus turnover-driven controls of simulated changes in soil carbon due to land-use change

NASA Astrophysics Data System (ADS)

Nyawira, S. S.; Nabel, J. E. M. S.; Brovkin, V.; Pongratz, J.

2017-08-01

Historical changes in soil carbon associated with land-use change (LUC) result mainly from the changes in the quantity of litter inputs to the soil and the turnover of carbon in soils. We use a factor separation technique to assess how the input-driven and turnover-driven controls, as well as their synergies, have contributed to historical changes in soil carbon associated with LUC. We apply this approach to equilibrium simulations of present-day and pre-industrial land use performed using the dynamic global vegetation model JSBACH. Our results show that both the input-driven and turnover-driven changes generally contribute to a gain in soil carbon in afforested regions and a loss in deforested regions. However, in regions where grasslands have been converted to croplands, we find an input-driven loss that is partly offset by a turnover-driven gain, which stems from a decrease in the fire-related carbon losses. Omitting land management through crop and wood harvest substantially reduces the global losses through the input-driven changes. Our study thus suggests that the dominating control of soil carbon losses is via the input-driven changes, which are more directly accessible to human management than the turnover-driven ones.

Modelling fast spreading patterns of airborne infectious diseases using complex networks

NASA Astrophysics Data System (ADS)

Brenner, Frank; Marwan, Norbert; Hoffmann, Peter

2017-04-01

The pandemics of SARS (2002/2003) and H1N1 (2009) have impressively shown the potential of epidemic outbreaks of infectious diseases in a world that is strongly connected. Global air travelling established an easy and fast opportunity for pathogens to migrate globally in only a few days. This made epidemiological prediction harder. By understanding this complex development and its link to climate change we can suggest actions to control a part of global human health affairs. In this study we combine the following data components to simulate the outbreak of an airborne infectious disease that is directly transmitted from human to human: em{Global Air Traffic Network (from openflights.org) with information on airports, airport location, direct flight connection, airplane type} em{Global population dataset (from SEDAC, NASA)} em{Susceptible-Infected-Recovered (SIR) compartmental model to simulate disease spreading in the vicinity of airports. A modified Susceptible-Exposed-Infected-Recovered (SEIR) model to analyze the impact of the incubation period.} em{WATCH-Forcing-Data-ERA-Interim (WFDEI) climate data: temperature, specific humidity, surface air pressure, and water vapor pressure} These elements are implemented into a complex network. Nodes inside the network represent airports. Each single node is equipped with its own SIR/SEIR compartmental model with node specific attributes. Edges between those nodes represent direct flight connections that allow infected individuals to move between linked nodes. Therefore the interaction of the set of unique SIR models creates the model dynamics we will analyze. To better figure out the influence on climate change on disease spreading patterns, we focus on Influenza-like-Illnesses (ILI). The transmission rate of ILI has a dependency on climate parameters like humidity and temperature. Even small changes of environmental variables can trigger significant differences in the global outbreak behavior. Apart from the direct effect of climate change on the transmission of airborne diseases, there are indirect ramifications that alter spreading patterns. An example is seasonal human mobility behavior which will change with varied climate conditions. The direct and indirect effects of climate change on disease spreading patterns will be discussed in this study.

CFD simulation of local and global mixing time in an agitated tank

NASA Astrophysics Data System (ADS)

Li, Liangchao; Xu, Bin

2017-01-01

The Issue of mixing efficiency in agitated tanks has drawn serious concern in many industrial processes. The turbulence model is very critical to predicting mixing process in agitated tanks. On the basis of computational fluid dynamics(CFD) software package Fluent 6.2, the mixing characteristics in a tank agitated by dual six-blade-Rushton-turbines(6-DT) are predicted using the detached eddy simulation(DES) method. A sliding mesh(SM) approach is adopted to solve the rotation of the impeller. The simulated flow patterns and liquid velocities in the agitated tank are verified by experimental data in the literature. The simulation results indicate that the DES method can obtain more flow details than Reynolds-averaged Navier-Stokes(RANS) model. Local and global mixing time in the agitated tank is predicted by solving a tracer concentration scalar transport equation. The simulated results show that feeding points have great influence on mixing process and mixing time. Mixing efficiency is the highest for the feeding point at location of midway of the two impellers. Two methods are used to determine global mixing time and get close result. Dimensionless global mixing time remains unchanged with increasing of impeller speed. Parallel, merging and diverging flow pattern form in the agitated tank, respectively, by changing the impeller spacing and clearance of lower impeller from the bottom of the tank. The global mixing time is the shortest for the merging flow, followed by diverging flow, and the longest for parallel flow. The research presents helpful references for design, optimization and scale-up of agitated tanks with multi-impeller.

Xanthos – A Global Hydrologic Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xinya; Vernon, Chris R.; Hejazi, Mohamad I.

Xanthos is an open-source hydrologic model, written in Python, designed to quantify and analyse global water availability. Xanthos simulates historical and future global water availability on a monthly time step at a spatial resolution of 0.5 geographic degrees. Xanthos was designed to be extensible and used by scientists that study global water supply and work with the Global Change Assessment Model (GCAM). Xanthos uses a user-defined configuration file to specify model inputs, outputs and parameters. Xanthos has been tested using actual global data sets and the model is able to provide historical observations and future estimates of renewable freshwater resourcesmore » in the form of total runoff.« less

Xanthos – A Global Hydrologic Model

DOE PAGES

Li, Xinya; Vernon, Chris R.; Hejazi, Mohamad I.; ...

2017-09-11

Xanthos is an open-source hydrologic model, written in Python, designed to quantify and analyse global water availability. Xanthos simulates historical and future global water availability on a monthly time step at a spatial resolution of 0.5 geographic degrees. Xanthos was designed to be extensible and used by scientists that study global water supply and work with the Global Change Assessment Model (GCAM). Xanthos uses a user-defined configuration file to specify model inputs, outputs and parameters. Xanthos has been tested using actual global data sets and the model is able to provide historical observations and future estimates of renewable freshwater resourcesmore » in the form of total runoff.« less

Impacts of climate change on the global forest sector

USGS Publications Warehouse

Perez-Garcia, J.; Joyce, L.A.; McGuire, A.D.; Xiao, X.

2002-01-01

The path and magnitude of future anthropogenic emissions of carbon dioxide will likely influence changes in climate that may impact the global forest sector. These responses in the global forest sector may have implications for international efforts to stabilize the atmospheric concentration of carbon dioxide. This study takes a step toward including the role of global forest sector in integrated assessments of the global carbon cycle by linking global models of climate dynamics, ecosystem processes and forest economics to assess the potential responses of the global forest sector to different levels of greenhouse gas emissions. We utilize three climate scenarios and two economic scenarios to represent a range of greenhouse gas emissions and economic behavior. At the end of the analysis period (2040), the potential responses in regional forest growing stock simulated by the global ecosystem model range from decreases and increases for the low emissions climate scenario to increases in all regions for the high emissions climate scenario. The changes in vegetation are used to adjust timber supply in the softwood and hardwood sectors of the economic model. In general, the global changes in welfare are positive, but small across all scenarios. At the regional level, the changes in welfare can be large and either negative or positive. Markets and trade in forest products play important roles in whether a region realizes any gains associated with climate change. In general, regions with the lowest wood fiber production cost are able to expand harvests. Trade in forest products leads to lower prices elsewhere. The low-cost regions expand market shares and force higher-cost regions to decrease their harvests. Trade produces different economic gains and losses across the globe even though, globally, economic welfare increases. The results of this study indicate that assumptions within alternative climate scenarios and about trade in forest products are important factors that strongly influence the effects of climate change on the global forest sector.

Regional temperature and precipitation changes under high-end (≥4°C) global warming.

PubMed

Sanderson, M G; Hemming, D L; Betts, R A

2011-01-13

Climate models vary widely in their projections of both global mean temperature rise and regional climate changes, but are there any systematic differences in regional changes associated with different levels of global climate sensitivity? This paper examines model projections of climate change over the twenty-first century from the Intergovernmental Panel on Climate Change Fourth Assessment Report which used the A2 scenario from the IPCC Special Report on Emissions Scenarios, assessing whether different regional responses can be seen in models categorized as 'high-end' (those projecting 4°C or more by the end of the twenty-first century relative to the preindustrial). It also identifies regions where the largest climate changes are projected under high-end warming. The mean spatial patterns of change, normalized against the global rate of warming, are generally similar in high-end and 'non-high-end' simulations. The exception is the higher latitudes, where land areas warm relatively faster in boreal summer in high-end models, but sea ice areas show varying differences in boreal winter. Many continental interiors warm approximately twice as fast as the global average, with this being particularly accentuated in boreal summer, and the winter-time Arctic Ocean temperatures rise more than three times faster than the global average. Large temperature increases and precipitation decreases are projected in some of the regions that currently experience water resource pressures, including Mediterranean fringe regions, indicating enhanced pressure on water resources in these areas.

Detection and Attribution of Regional Climate Change

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bala, G; Mirin, A

2007-01-19

We developed a high resolution global coupled modeling capability to perform breakthrough studies of the regional climate change. The atmospheric component in our simulation uses a 1{sup o} latitude x 1.25{sup o} longitude grid which is the finest resolution ever used for the NCAR coupled climate model CCSM3. Substantial testing and slight retuning was required to get an acceptable control simulation. The major accomplishment is the validation of this new high resolution configuration of CCSM3. There are major improvements in our simulation of the surface wind stress and sea ice thickness distribution in the Arctic. Surface wind stress and oceanmore » circulation in the Antarctic Circumpolar Current are also improved. Our results demonstrate that the FV version of the CCSM coupled model is a state of the art climate model whose simulation capabilities are in the class of those used for IPCC assessments. We have also provided 1000 years of model data to Scripps Institution of Oceanography to estimate the natural variability of stream flow in California. In the future, our global model simulations will provide boundary data to high-resolution mesoscale model that will be used at LLNL. The mesoscale model would dynamically downscale the GCM climate to regional scale on climate time scales.« less

Global variability of cloud condensation nuclei concentrations

NASA Astrophysics Data System (ADS)

Makkonen, Risto; Krüger, Olaf

2017-04-01

Atmospheric aerosols can influence cloud optical and dynamical processes by acting as cloud condensation nuclei (CCN). Globally, these indirect aerosol effects are significant to the radiative budget as well as a source of high uncertainty in anthropogenic radiative forcing. While historically many global climate models have fixed CCN concentrations to a certain level, most state-of-the-art models calculate aerosol-cloud interactions with sophisticated methodologies based on interactively simulated aerosol size distributions. However, due to scarcity of atmospheric observations simulated global CCN concentrations remain poorly constrained. Here we assess global CCN variability with a climate model, and attribute potential trends during 2000-2010 to changes in emissions and meteorological fields. Here we have used ECHAM5.5-HAM2 with model M7 microphysical aerosol model. The model has been upgraded with a secondary organic aerosol (SOA) scheme including ELVOCs. Dust and sea salt emissions are calculated online, based on wind speed and hydrology. Each experiment is 11 years, analysed after a 6-month spin-up period. The MODIS CCN product (Terra platform) is used to evaluate model performance throughout 2000-2010. While optical remote observation of CCN column includes several deficiencies, the products serves as a proxy for changes during the simulation period. In our analysis we utilize the observed and simulated vertical column integrated CCN concentration, and limit our analysis only over marine regions. Simulated annual CCN column densities reach 2ṡ108 cm-2 near strong source regions in central Africa, Arabian Sea, Bay of Bengal and China sea. The spatial concentration gradient in CCN(0.2%) is steep, and column densities drop to <50% a few hundred kilometers away from the coasts. While the spatial distribution of CCN at 0.2% supersaturation is closer to that of MODIS proxy, as opposed to 1.0% supersaturation, the overall column integrated CCN are too low. Still, we can compare the relative response of CCN to emission and meteorological variability. Most evident pattern of high temporal correlation is found over North Atlantic ocean, extending throughout Europe and up to Gulf of Mexico. All of these regions show a generally decreasing trend throughout the decade in control simulations and MODIS CCN, and the simulations including the emission trends clearly improve the simulations with climatological emissions. In regions where the observed intra-annual cycle correlates well with sea-spray emissions, the long-term annual correlation usually remains poor. This could indicate that the model is unable to capture the natural variability in marine aerosol emissions.

Rainfall estimation with TFR model using Ensemble Kalman filter

NASA Astrophysics Data System (ADS)

Asyiqotur Rohmah, Nabila; Apriliani, Erna

2018-03-01

Rainfall fluctuation can affect condition of other environment, correlated with economic activity and public health. The increasing of global average temperature is influenced by the increasing of CO2 in the atmosphere, which caused climate change. Meanwhile, the forests as carbon sinks that help keep the carbon cycle and climate change mitigation. Climate change caused by rainfall intensity deviations can affect the economy of a region, and even countries. It encourages research on rainfall associated with an area of forest. In this study, the mathematics model that used is a model which describes the global temperatures, forest cover, and seasonal rainfall called the TFR (temperature, forest cover, and rainfall) model. The model will be discretized first, and then it will be estimated by the method of Ensemble Kalman Filter (EnKF). The result shows that the more ensembles used in estimation, the better the result is. Also, the accurateness of simulation result is influenced by measurement variable. If a variable is measurement data, the result of simulation is better.

Economic implications of climate-driven trends in global hydropower generation

NASA Astrophysics Data System (ADS)

Turner, S. W. D.; Galelli, S.; Hejazi, M. I.; Clarke, L.; Edmonds, J.; Kim, S. H.

2017-12-01

Recent progress in global scale hydrological and dam modeling has allowed for the study of climate change impacts on global hydropower production. Here we explore how these impacts could affect the composition of global electricity supply, and what those changes could mean for power sector emissions and investment needs in the 21st century. Regional hydropower projections are developed for two emissions scenarios by forcing a coupled global hydrological and dam model (1593 major hydropower dams; 54% global installed capacity) with downscaled, bias-corrected climate realizations derived from sixteen General Circulation Models (GCMs). To incorporate possible non-linearity in hydropower response to climate change, dam simulations incorporate plant specifications (e.g., maximum turbine flow), reservoir storage dynamics, reservoir bathymetry, evaporation losses and bespoke, site specific operations. Consequent impacts on regional and global-level electricity generation and associated emissions and investment costs are examined using the Global Change Assessment Model (GCAM). We show that changes in hydropower generation resulting from climate change can shift power demands onto and away from carbon intensive technologies, resulting in significant impacts on CO2 emissions for several regions. Many of these countries are also highly vulnerable to investment impacts (costs of new electricity generating facilities to make up for shortfalls in hydro), which in some cases amount to tens of billions of dollars by 2100. The Balkans region—typified by weak economies in a drying region that relies heavily on hydropower—emerges as the most vulnerable. Reduced impacts of climate change on hydropower production under a low emissions scenario coincide with increased costs of marginal power generating capacity (low emissions requires greater uptake of clean generating technologies, which are more expensive). This means impacts on power sector investment costs are similar for high and low emissions scenarios.

Investigating Dry Deposition of Ozone to Vegetation

NASA Astrophysics Data System (ADS)

Silva, Sam J.; Heald, Colette L.

2018-01-01

Atmospheric ozone loss through dry deposition to vegetation is a critically important process for both air quality and ecosystem health. The majority of atmospheric chemistry models calculate dry deposition using a resistance-in-series parameterization by Wesely (1989), which is dependent on many environmental variables and lookup table values. The uncertainties contained within this parameterization have not been fully explored, ultimately challenging our ability to understand global scale biosphere-atmosphere interactions. In this work, we evaluate the GEOS-Chem model simulation of ozone dry deposition using a globally distributed suite of observations. We find that simulated daytime deposition velocities generally reproduce the magnitude of observations to within a factor of 1.4. When correctly accounting for differences in land class between the observations and model, these biases improve, most substantially over the grasses and shrubs land class. These biases do not impact the global ozone burden substantially; however, they do lead to local absolute changes of up to 4 ppbv and relative changes of 15% in summer surface concentrations. We use MERRA meteorology from 1979 to 2008 to assess that the interannual variability in simulated annual mean ozone dry deposition due to model input meteorology is small (generally less than 5% over vegetated surfaces). Sensitivity experiments indicate that the simulation is most sensitive to the stomatal and ground surface resistances, as well as leaf area index. To improve ozone dry deposition models, more measurements are necessary over rainforests and various crop types, alongside constraints on individual depositional pathways and other in-canopy ozone loss processes.

Use of a process-based model for assessing the methane budgets of global terrestrial ecosystems and evaluation of uncertainty

NASA Astrophysics Data System (ADS)

Ito, A.; Inatomi, M.

2012-02-01

We assessed the global terrestrial budget of methane (CH4) by using a process-based biogeochemical model (VISIT) and inventory data for components of the budget that were not included in the model. Emissions from wetlands, paddy fields, biomass burning, and plants, as well as oxidative consumption by upland soils, were simulated by the model. Emissions from ruminant livestock and termites were evaluated by using an inventory approach. These CH4 flows were estimated for each of the model's 0.5° × 0.5° grid cells from 1901 to 2009, while accounting for atmospheric composition, meteorological factors, and land-use changes. Estimation uncertainties were examined through ensemble simulations using different parameterization schemes and input data (e.g., different wetland maps and emission factors). From 1996 to 2005, the average global terrestrial CH4 budget was estimated on the basis of 1152 simulations, and terrestrial ecosystems were found to be a net source of 308.3 ± 20.7 Tg CH4 yr-1. Wetland and livestock ruminant emissions were the primary sources. The results of our simulations indicate that sources and sinks are distributed highly heterogeneously over the Earth's land surface. Seasonal and interannual variability in the terrestrial budget was also assessed. The trend of increasing net emission from terrestrial sources and its relationship with temperature variability imply that terrestrial CH4 feedbacks will play an increasingly important role as a result of future climatic change.

Evaluating simulated functional trait patterns and quantifying modelled trait diversity effects on simulated ecosystem fluxes

NASA Astrophysics Data System (ADS)

Pavlick, R.; Schimel, D.

2014-12-01

Dynamic Global Vegetation Models (DGVMs) typically employ only a small set of Plant Functional Types (PFTs) to represent the vast diversity of observed vegetation forms and functioning. There is growing evidence, however, that this abstraction may not adequately represent the observed variation in plant functional traits, which is thought to play an important role for many ecosystem functions and for ecosystem resilience to environmental change. The geographic distribution of PFTs in these models is also often based on empirical relationships between present-day climate and vegetation patterns. Projections of future climate change, however, point toward the possibility of novel regional climates, which could lead to no-analog vegetation compositions incompatible with the PFT paradigm. Here, we present results from the Jena Diversity-DGVM (JeDi-DGVM), a novel traits-based vegetation model, which simulates a large number of hypothetical plant growth strategies constrained by functional tradeoffs, thereby allowing for a more flexible temporal and spatial representation of the terrestrial biosphere. First, we compare simulated present-day geographical patterns of functional traits with empirical trait observations (in-situ and from airborne imaging spectroscopy). The observed trait patterns are then used to improve the tradeoff parameterizations of JeDi-DGVM. Finally, focusing primarily on the simulated leaf traits, we run the model with various amounts of trait diversity. We quantify the effects of these modeled biodiversity manipulations on simulated ecosystem fluxes and stocks for both present-day conditions and transient climate change scenarios. The simulation results reveal that the coarse treatment of plant functional traits by current PFT-based vegetation models may contribute substantial uncertainty regarding carbon-climate feedbacks. Further development of trait-based models and further investment in global in-situ and spectroscopic plant trait observations are needed.

Driving Solar Giant Cells through the Self-organization of Near-surface Plumes

NASA Astrophysics Data System (ADS)

Nelson, Nicholas J.; Featherstone, Nicholas A.; Miesch, Mark S.; Toomre, Juri

2018-06-01

Global 3D simulations of solar giant-cell convection have provided significant insight into the processes which yield the Sun’s observed differential rotation and cyclic dynamo action. However, as we move to higher-resolution simulations a variety of codes have encountered what has been termed the convection conundrum. As these simulations increase in resolution and hence the level of turbulence achieved, they tend to produce weak or even anti-solar differential rotation patterns associated with a weak rotational influence (high Rossby number) due to large convective velocities. One potential culprit for this convection conundrum is the upper boundary condition applied in most simulations, which is generally impenetrable. Here we present an alternative stochastic plume boundary condition which imposes small-scale convective plumes designed to mimic near-surface convective downflows, thus allowing convection to carry the majority of the outward solar energy flux up to and through our simulated upper boundary. The use of a plume boundary condition leads to significant changes in the convective driving realized in the simulated domain and thus to the convective energy transport, the dominant scale of the convective enthalpy flux, and the relative strength of the strongest downflows, the downflow network, and the convective upflows. These changes are present even far from the upper boundary layer. Additionally, we demonstrate that, in spite of significant changes, giant cell morphology in the convective patterns is still achieved with self-organization of the imposed boundary plumes into downflow lanes, cellular patterns, and even rotationally aligned banana cells in equatorial regions. This plume boundary presents an alternative pathway for 3D global convection simulations where driving is non-local and may provide a new approach toward addressing the convection conundrum.

Global vegetation-fire pattern under different land use and climate conditions

NASA Astrophysics Data System (ADS)

Thonicke, K.; Poulter, B.; Heyder, U.; Gumpenberger, M.; Cramer, W.

2008-12-01

Fire is a process of global significance in the Earth System influencing vegetation dynamics, biogeochemical cycling and biophysical feedbacks. Naturally ignited wildfires have long history in the Earth System. Humans have been using fire to shape the landscape for their purposes for many millenia, sometimes influencing the status of the vegetation remarkably as for example in Mediterranean-type ecosystems. Processes and drivers describing fire danger, ignitions, fire spread and effects are relatively well-known for many fire-prone ecosystems. Modeling these has a long tradition in fire-affected regions to predict fire risk and behavior for fire-fighting purposes. On the other hand, the global vegetation community realized the importance of disturbances to be recognized in their global vegetation models with fire being globally most important and so-far best studied. First attempts to simulate fire globally considered a minimal set of drivers, whereas recent developments attempt to consider each fire process separately. The process-based fire model SPITFIRE (SPread and InTensity of FIRE) simulates these processes embedded in the LPJ DGVM. Uncertainties still arise from missing measurements for some parameters in less-studied fire regimes, or from broad PFT classifications which subsume different fire-ecological adaptations and tolerances. Some earth observation data sets as well as fire emission models help to evaluate seasonality and spatial distribution of simulated fire ignitions, area burnt and fire emissions within SPITFIRE. Deforestation fires are a major source of carbon released to the atmosphere in the tropics; in the Amazon basin it is the second-largest contributor to Brazils GHG emissions. How ongoing deforestation affects fire regimes, forest stability and biogeochemical cycling in the Amazon basin under present climate conditions will be presented. Relative importance of fire vs. climate and land use change is analyzed. Emissions resulting from wildfires, agricultural and woodfuel burning will be quantified and drivers identified. Future projections of climate and land use change are applied to the model to investigate joint effects on future changes in fire, deforestation and vegetation dynamics in the Amazon basin.

The potential impact of global warming on the efficacy of field margins sown for the conservation of bumble-bees.

PubMed

Memmott, Jane; Carvell, Claire; Pywell, Richard F; Craze, Paul G

2010-07-12

Climate change is expected to drive species extinct by reducing their survival, reproduction and habitat. Less well appreciated is the possibility that climate change could cause extinction by changing the ecological interactions between species. If ecologists, land managers and policy makers are to manage farmland biodiversity sustainably under global climate change, they need to understand the ways in which species interact with each other as this will affect the way they respond to climate change. Here, we consider the ability of nectar flower mixtures used in field margins to provide sufficient forage for bumble-bees under future climate change. We simulated the effect of global warming on the network of plant-pollinator interactions in two types of field margin: a four-species pollen and nectar mix and a six-species wildflower mix. While periods without flowering resources and periods with no food were rare, curtailment of the field season was very common for the bumble-bees in both mixtures. The effect of this, however, could be ameliorated by adding extra species at the start and end of the flowering season. The plant species that could be used to future-proof margins against global warming are discussed.

Global trends and variability in integrated water vapour from ground-based GPS data and atmospheric models

NASA Astrophysics Data System (ADS)

Bock, Olivier; Parracho, Ana; Bastin, Sophie; Hourdin, Frededic; Mellul, Lidia

2016-04-01

A high-quality, consistent, global, long-term dataset of integrated water vapour (IWV) was produced from Global Positioning System (GPS) measurements at more than 400 sites over the globe among which 120 sites have more than 15 years of data. The GPS delay data were converted to IWV using surface pressure and weighted mean temperature estimates from ERA-Interim reanalysis. A two-step screening method was developed to detect and remove outliers in the IWV data. It is based on: 1) GPS data processing information and delay formal errors, and 2) intercomparison with ERA-Interim reanalysis data. The GPS IWV data are also homogenized to correct for offsets due to instrumental changes and other unknown factors. The differential homogenization method uses ERA-Interim IWV as a reference. The resulting GPS data are used to document the mean distribution, the global trends and the variability of IWV over the period 1995-2010, and are analysed in coherence with precipitation and surface temperature data (from observations and ERA-Interim reanalysis). These data are also used to assess global climate model simulations extracted from the IPCC AR5 archive. Large coherent spatial patterns of moistening and drying are evidenced but significant discrepancies are also seen between GPS measurements, reanalysis and climate models in various regions. In terms of variability, the monthly mean anomalies are intercompared. The temporal correlation between GPS and the climate model simulations is overall quite small but the spatial variation of the magnitude of the anomalies is globally well simulated. GPS IWV data prove to be useful to validate global climate model simulations and highlight deficiencies in their representation of the water cycle.

Numerical simulation of the radiation environment on Martian surface

NASA Astrophysics Data System (ADS)

Zhao, L.

2015-12-01

The radiation environment on the Martian surface is significantly different from that on earth. Existing observation and studies reveal that the radiation environment on the Martian surface is highly variable regarding to both short- and long-term time scales. For example, its dose rate presents diurnal and seasonal variations associated with atmospheric pressure changes. Moreover, dose rate is also strongly influenced by the modulation from GCR flux. Numerical simulation and theoretical explanations are required to understand the mechanisms behind these features, and to predict the time variation of radiation environment on the Martian surface if aircraft is supposed to land on it in near future. The high energy galactic cosmic rays (GCRs) which are ubiquitous throughout the solar system are highly penetrating and extremely difficult to shield against beyond the Earth's protective atmosphere and magnetosphere. The goal of this article is to evaluate the long term radiation risk on the Martian surface. Therefore, we need to develop a realistic time-dependent GCR model, which will be integrated with Geant4 transport code subsequently to reproduce the observed variation of surface dose rate associated with the changing heliospheric conditions. In general, the propagation of cosmic rays in the interplanetary medium can be described by a Fokker-Planck equation (or Parker equation). In last decade,we witnessed a fast development of GCR transport models within the heliosphere based on accurate gas-dynamic and MHD backgrounds from global models of the heliosphere. The global MHD simulation produces a more realistic pattern of the 3-D heliospheric structure, as well as the interface between the solar system and the surrounding interstellar space. As a consequence, integrating plasma background obtained from global-dependent 3-D MHD simulation and stochastic Parker transport simulation, we expect to produce an accurate global physical-based GCR modulation model. Combined with the Geant4 transport code, this GCR model will provide valuable insight into the long-term dose rates variation on the Martian surface.

Climatic Consequences and Agricultural Impact of Regional Nuclear Conflict

NASA Astrophysics Data System (ADS)

Toon, O. B.; Robock, A.; Mills, M. J.; Xia, L.

2013-05-01

A nuclear war between India and Pakistan, with each country using 50 Hiroshima-sized atom bombs as airbursts on urban areas, would inject smoke from the resulting fires into the stratosphere.This could produce climate change unprecedented in recorded human history and global-scale ozone depletion, with enhanced ultraviolet (UV) radiation reaching the surface.Simulations with the Whole Atmosphere Community Climate Model (WACCM), run at higher vertical and horizontal resolution than a previous simulation with the NASA Goddard Institute for Space Studies ModelE, and incorporating ozone chemistry for the first time, show a longer stratospheric residence time for smoke and hence a longer-lasting climate response, with global average surface air temperatures still 1.1 K below normal and global average precipitation 4% below normal after a decade.The erythemal dose from the enhanced UV radiation would greatly increase, in spite of enhanced absorption by the remaining smoke, with the UV index more than 3 units higher in the summer midlatitudes, even after a decade. Scenarios of changes in temperature, precipitation, and downward shortwave radiation from the ModelE and WACCM simulations, applied to the Decision Support System for Agrotechnology Transfer crop model for winter wheat, rice, soybeans, and maize by perturbing observed time series with anomalies from the regional nuclear war simulations, produce decreases of 10-50% in yield averaged over a decade, with larger decreases in the first several years, over the midlatitudes of the Northern Hemisphere. The impact of the nuclear war simulated here, using much less than 1% of the global nuclear arsenal, would be devastating to world agricultural production and trade, possibly sentencing a billion people now living marginal existences to starvation.The continued environmental threat of the use of even a small number of nuclear weapons must be considered in nuclear policy deliberations in Russia, the U.S., and the rest of the world.

Climatic Consequences and Agricultural Impact of Regional Nuclear Conflict

NASA Astrophysics Data System (ADS)

Robock, Alan; Mills, Michael; Toon, Owen Brian; Xia, Lili

2013-04-01

A nuclear war between India and Pakistan, with each country using 50 Hiroshima-sized atom bombs as airbursts on urban areas, would inject smoke from the resulting fires into the stratosphere. This could produce climate change unprecedented in recorded human history and global-scale ozone depletion, with enhanced ultraviolet (UV) radiation reaching the surface. Simulations with the NCAR Whole Atmosphere Community Climate Model (WACCM), run at higher vertical and horizontal resolution than a previous simulation with the NASA Goddard Institute for Space Studies ModelE, and incorporating ozone chemistry for the first time, show a longer stratospheric residence time for smoke and hence a longer-lasting climate response, with global average surface air temperatures still 1.1 K below normal and global average precipitation 4% below normal after a decade. The erythemal dose from the enhanced UV radiation would greatly increase, in spite of enhanced absorption by the remaining smoke, with the UV index more than 3 units higher in the summer midlatitudes, even after a decade. Scenarios of changes in temperature, precipitation, and downward shortwave radiation from the ModelE and WACCM simulations, applied to the Decision Support System for Agrotechnology Transfer crop model for winter wheat, rice, soybeans, and maize by perturbing observed time series with anomalies from the regional nuclear war simulations, produce decreases of 10-50% in yield averaged over a decade, with larger decreases in the first several years, over several regions in the midlatitudes of the Northern Hemisphere. The impact of the nuclear war simulated here, using much less than 1% of the global nuclear arsenal, would be devastating to world agricultural production and trade, possibly sentencing a billion people now living marginal existences to starvation. The continued environmental threat of the use of even a small number of nuclear weapons must be considered in nuclear policy deliberations in Russia, the U.S., and the rest of the world

Predicting the variation in Echinogammarus marinus at its southernmost limits under global warming scenarios: can the sex-ratio make a difference?

PubMed

Guerra, Alexandra; Leite, Nuno; Marques, João Carlos; Ford, Alex T; Martins, Irene

2014-01-01

Understanding the environmental parameters that constrain the distribution of a species at its latitudinal extremes is critical for predicting how ecosystems react to climate change. Our first aim was to predict the variation in the amphipod populations of Echinogammarus marinus from the southernmost limit of its distribution under global warming scenarios. Our second aim was to test whether sex-ratio fluctuations - a mechanism frequently displayed by amphipods - respond to the variations in populations under altered climate conditions. To achieve these aims, scenarios were run with a validated model of E. marinus populations. Simulations were divided into: phase I - simulation of the effect of climate change on amphipod populations, and phase II - simulation of the effect of climate change on populations with male and female proportions. In both phases, temperature (T), salinity (S) and temperature and salinity (T-S) were tested. Results showed that E. marinus populations are highly sensitive to increases in temperature (>2 °C), which has adverse effects on amphipod recruitment and growth. Results from the climate change scenarios coupled with the sex-ratio fluctuations depended largely on the degree of female bias within population. Temperature increase of 2 °C had less impact on female-biased populations, particularly when conjugated with increases in salinity. Male-biased populations were highly sensitive to any variation in temperature and/or salinity; these populations exhibited a long-term decline in density. Simulations in which temperature increased more than 4 °C led to a continuous decline in the E. marinus population. According to this work, E. marinus populations at their southernmost limit are vulnerable to global warming. We anticipate that in Europe, temperature increases of 2 °C will incite a withdrawal of the population of 5°N from the amphipod species located at southernmost geographical borders. This effect is discussed in relation to the distribution of E. marinus along the Atlantic coast. © 2013 Elsevier B.V. All rights reserved.

Assessing the impact of late Pleistocene megafaunal extinctions on global vegetation and climate

NASA Astrophysics Data System (ADS)

Brault, M.-O.; Mysak, L. A.; Matthews, H. D.; Simmons, C. T.

2013-08-01

The end of the Pleistocene was a turning point for the Earth system as climate gradually emerged from millennia of severe glaciation in the Northern Hemisphere. The deglacial climate change coincided with an unprecedented decline in many species of Pleistocene megafauna, including the near-total eradication of the woolly mammoth. Due to an herbivorous diet that presumably involved large-scale tree grazing, the mammoth extinction has been associated with the rapid expansion of dwarf deciduous trees in Siberia and Beringia, thus potentially contributing to the changing climate of the period. In this study, we use the University of Victoria Earth System Climate Model (UVic ESCM) to simulate the possible effects of these extinctions on climate during the latest deglacial period. We have explored various hypothetical scenarios of forest expansion in the northern high latitudes, quantifying the biogeophysical effects in terms of changes in surface albedo and air temperature. These scenarios include a Maximum Impact Scenario (MIS) which simulates the greatest possible post-extinction reforestation in the model, and sensitivity tests which investigate the timing of extinction, the fraction of trees grazed by mammoths, and the southern extent of mammoth habitats. We also show the results of a simulation with free atmospheric CO2-carbon cycle interactions. For the MIS, we obtained a surface albedo increase and global warming of 0.006 and 0.175 °C, respectively. Less extreme scenarios produced smaller global mean temperature changes, though local warming in some locations exceeded 0.3 °C even in the more realistic extinction scenarios. In the free CO2 simulation, the biogeophysical-induced warming was amplified by a biogeochemical effect, whereby the replacement of high-latitude tundra with shrub forest led to a release of soil carbon to the atmosphere and a small atmospheric CO2 increase. Overall, our results suggest the potential for a small, though non-trivial, effect of megafaunal extinctions on Pleistocene climate.

Changes in future air quality, deposition, and aerosol-cloud interactions under future climate and emission scenarios

NASA Astrophysics Data System (ADS)

Glotfelty, Timothy; Zhang, Yang; Karamchandani, Prakash; Streets, David G.

2016-08-01

The prospect of global climate change will have wide scale impacts, such as ecological stress and human health hazards. One aspect of concern is future changes in air quality that will result from changes in both meteorological forcing and air pollutant emissions. In this study, the GU-WRF/Chem model is employed to simulate the impact of changing climate and emissions following the IPCC AR4 SRES A1B scenario. An average of 4 future years (2020, 2030, 2040, and 2050) is compared against an average of 2 current years (2001 and 2010). Under this scenario, by the Mid-21st century global air quality is projected to degrade with a global average increase of 2.5 ppb in the maximum 8-hr O3 level and of 0.3 μg m-3 in 24-hr average PM2.5. However, PM2.5 changes are more regional due to regional variations in primary aerosol emissions and emissions of gaseous precursor for secondary PM2.5. Increasing NOx emissions in this scenario combines with a wetter climate elevating levels of OH, HO2, H2O2, and the nitrate radical and increasing the atmosphere's near surface oxidation state. This differs from findings under the RCP scenarios that experience declines in OH from reduced NOx emissions, stratospheric recovery of O3, and increases in CH4 and VOCs. Increasing NOx and O3 levels enhances the nitrogen and O3 deposition, indicating potentially enhanced crop damage and ecosystem stress under this scenario. The enhanced global aerosol level results in enhancements in aerosol optical depth, cloud droplet number concentration, and cloud optical thickness. This leads to dimming at the Earth's surface with a global average reduction in shortwave radiation of 1.2 W m-2. This enhanced dimming leads to a more moderate warming trend and different trends in radiation than those found in NCAR's CCSM simulation, which does not include the advanced chemistry and aerosol treatment of GU-WRF/Chem and cannot simulate the impacts of changing climate and emissions with the same level of detailed treatments. This study indicates that effective climate mitigation and emission control strategies are needed to prevent future health impact and ecosystem stress. Further, studies that are used to develop these strategies should use fully coupled models with sophisticated chemical and aerosol-interaction treatments that can provide a more realistic representation of the atmosphere.

Role of Climate Change in Global Predictions of Future Tropospheric Ozone and Aerosols

NASA Technical Reports Server (NTRS)

Liao, Hong; Chen, Wei-Ting; Seinfeld, John H.

2006-01-01

A unified tropospheric chemistry-aerosol model within the Goddard Institute for Space Studies general circulation model II is applied to simulate an equilibrium CO2-forced climate in the year 2100 to examine the effects of climate change on global distributions of tropospheric ozone and sulfate, nitrate, ammonium, black carbon, primary organic carbon, secondary organic carbon, sea salt, and mineral dust aerosols. The year 2100 CO2 concentration as well as the anthropogenic emissions of ozone precursors and aerosols/aerosol precursors are based on the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (SRES) A2. Year 2100 global O3 and aerosol burdens predicted with changes in both climate and emissions are generally 5-20% lower than those simulated with changes in emissions alone; as exceptions, the nitrate burden is 38% lower, and the secondary organic aerosol burden is 17% higher. Although the CO2-driven climate change alone is predicted to reduce the global O3 concentrations over or near populated and biomass burning areas because of slower transport, enhanced biogenic hydrocarbon emissions, decomposition of peroxyacetyl nitrate at higher temperatures, and the increase of O3 production by increased water vapor at high NOx levels. The warmer climate influences aerosol burdens by increasing aerosol wet deposition, altering climate-sensitive emissions, and shifting aerosol thermodynamic equilibrium. Climate change affects the estimates of the year 2100 direct radiative forcing as a result of the climate-induced changes in burdens and different climatological conditions; with full gas-aerosol coupling and accounting for ozone and direct radiative forcings by the O2, sulfate, nitrate, black carbon, and organic carbon are predicted to be +0.93, -0.72, -1.0, +1.26, and -0.56 W m(exp -2), respectively, using present-day climate and year 2100 emissions, while they are predicted to be +0.76, -0.72, 0.74, +0.97, and -0.58 W m(exp -2), respectively, with year 2100 climate and emissions.

Application of MODFLOW’s farm process to California’s Central Valley

USGS Publications Warehouse

Faunt, Claudia; Hanson, Randall T.; Schmid, Wolfgang; Belitz, Kenneth

2008-01-01

landscape processes. The FMP provides coupled simulation of the ground-water and surface-water components of the hydrologic cycle for irrigated and non-irrigated areas. A dynamic allocation of ground-water recharge and ground-water pumping is simulated on the basis of residual crop-water demand after surface-water deliveries and root uptake from shallow ground water. The FMP links with the Streamflow Routing Package SFR1) to facilitate the simulated conveyance of surface-water deliveries. Ground-water Pumpage through both single-aquifer and multi-node wells, irrigation return flow, and variable irrigation efficiencies also are simulated by the FMP. The simulated deliveries and ground-water pumpage in the updated model reflect climatic differences, differences among defined water-balance regions, and changes in the waterdelivery system, during the 1961–2003 simulation period. The model is designed to accept forecasts from Global Climate Models (GCMs) to simulate the potential effects on surface-water delivery, ground-water pumpage, and ground-water storage in response to climate change. The model provides a detailed transient analysis of changes in ground-water availability in relation to climatic variability, urbanization, and changes in irrigated agriculture.

ASSESSING THE WATER QUALITY IMPACTS OF GLOBAL CLIMATE CHANGE IN SOUTHWESTERN OHIO, U.S.A

EPA Science Inventory

This paper uses a watershed-scale hydrologic model (Soil and Water Assessment Tool) to simulate the water quality impacts of future climate change in the Little Miami River (LMR) watershed in southwestern Ohio. The LMR watershed, the principal source of drinking water for 1.6 mi...

Simulation of climate change impacts on grain sorghum production grown under free air CO2 enrichment

USDA-ARS?s Scientific Manuscript database

Potential impacts of global climate change on crop productivity have drawn much attention in recent years. To investigate these impacts on grain sorghum [Sorghum bicolor (L.) Möench] productivity, we calibrated the CERES-Sorghum model in the Decision Support System for Agrotechnology Transfer (DSSAT...

Evaluating the effects of climate change on summertime ozone using a relative reduction factor approach for policymakers

EPA Science Inventory

The impact of climate change on surface-level ozone is examined through a multiscale modeling effort that linked global and regional climate models to drive air quality model simulations. Results are quantified in terms of the relative response factor (RRFE), which estimates the ...

Improvement of Mars surface snow albedo modeling in LMD Mars GCM with SNICAR

NASA Astrophysics Data System (ADS)

Singh, D.; Flanner, M.; Millour, E.

2017-12-01

The current version of Laboratoire de Météorologie Dynamique (LMD) Mars GCM (original-MGCM) uses annually repeating (prescribed) albedo values from the Thermal Emission Spectrometer observations. We integrate the Snow, Ice, and Aerosol Radiation (SNICAR) model with MGCM (SNICAR-MGCM) to prognostically determine H2O and CO2 ice cap albedos interactively in the model. Over snow-covered regions mean SNICAR-MGCM albedo is higher by about 0.034 than original-MGCM. Changes in albedo and surface dust content also impact the shortwave energy flux at the surface. SNICAR-MGCM model simulates a change of -1.26 W/m2 shortwave flux on a global scale. Globally, net CO2 ice deposition increases by about 4% over one Martian annual cycle as compared to original-MGCM simulations. SNICAR integration reduces the net mean global surface temperature, and the global surface pressure of Mars by about 0.87% and 2.5% respectively. Changes in albedo also show a similar distribution as dust deposition over the globe. The SNICAR-MGCM model generates albedos with higher sensitivity to surface dust content as compared to original-MGCM. For snow-covered regions, we improve the correlation between albedo and optical depth of dust from -0.91 to -0.97 with SNICAR-MGCM as compared to original-MGCM. Using new diagnostic capabilities with this model, we find that cryospheric surfaces (with dust) increase the global surface albedo of Mars by 0.022. The cryospheric effect is severely muted by dust in snow, however, which acts to decrease the planet-mean surface albedo by 0.06.

Energetic-particle-modified global Alfvén eigenmodes

NASA Astrophysics Data System (ADS)

Lestz, J. B.; Belova, E. V.; Gorelenkov, N. N.

2018-04-01

Fully self-consistent hybrid MHD/particle simulations reveal strong energetic particle modifications to sub-cyclotron global Alfvén eigenmodes (GAEs) in low-aspect ratio, NSTX-like conditions. Key parameters defining the fast ion distribution function—the normalized injection velocity v0/vA and central pitch—are varied in order to study their influence on the characteristics of the excited modes. It is found that the frequency of the most unstable mode changes significantly and continuously with beam parameters, in accordance with the Doppler-shifted cyclotron resonances which drive the modes, and depending most substantially on v0/vA . This unexpected result is present for both counter-propagating GAEs, which are routinely excited in NSTX, and high frequency co-GAEs, which have not been previously studied. Large changes in frequency without clear corresponding changes in the mode structure are signatures of an energetic particle mode, referred to here as an energetic-particle-modified GAE. Additional simulations conducted for a fixed MHD equilibrium demonstrate that the GAE frequency shift cannot be explained by the equilibrium changes due to energetic particle effects.

Energetic-particle-modified global Alfven eigenmodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lestz, J. B.; Belova, E. V.; Gorelenkov, N. N.

Fully self-consistent hybrid MHD/particle simulations reveal strong energetic particle modifications to sub-cyclotron global Alfvén eigenmodes (GAEs) in low-aspect ratio, NSTX-like conditions. Key parameters defining the fast ion distribution function—the normalized injection velocity v 0/v A and central pitch—are varied in order to study their influence on the characteristics of the excited modes. It is found that the frequency of the most unstable mode changes significantly and continuously with beam parameters, in accordance with the Doppler-shifted cyclotron resonances which drive the modes, and depending most substantially on v 0/v A. This unexpected result is present for both counter-propagating GAEs, which aremore » routinely excited in NSTX, and high frequency co-GAEs, which have not been previously studied. Large changes in frequency without clear corresponding changes in the mode structure are signatures of an energetic particle mode, referred to here as an energetic-particle-modified GAE. In conclusion, additional simulations conducted for a fixed MHD equilibrium demonstrate that the GAE frequency shift cannot be explained by the equilibrium changes due to energetic particle effects.« less

Energetic-particle-modified global Alfven eigenmodes

DOE PAGES

Lestz, J. B.; Belova, E. V.; Gorelenkov, N. N.

2018-04-30

Fully self-consistent hybrid MHD/particle simulations reveal strong energetic particle modifications to sub-cyclotron global Alfvén eigenmodes (GAEs) in low-aspect ratio, NSTX-like conditions. Key parameters defining the fast ion distribution function—the normalized injection velocity v 0/v A and central pitch—are varied in order to study their influence on the characteristics of the excited modes. It is found that the frequency of the most unstable mode changes significantly and continuously with beam parameters, in accordance with the Doppler-shifted cyclotron resonances which drive the modes, and depending most substantially on v 0/v A. This unexpected result is present for both counter-propagating GAEs, which aremore » routinely excited in NSTX, and high frequency co-GAEs, which have not been previously studied. Large changes in frequency without clear corresponding changes in the mode structure are signatures of an energetic particle mode, referred to here as an energetic-particle-modified GAE. In conclusion, additional simulations conducted for a fixed MHD equilibrium demonstrate that the GAE frequency shift cannot be explained by the equilibrium changes due to energetic particle effects.« less

The recent increase of atmospheric methane from 10 years of ground-based NDACC FTIR observations since 2005

DOE PAGES

Bader, Whitney; Bovy, Benoît; Conway, Stephanie; ...

2017-02-14

Changes of atmospheric methane total columns (CH 4) since 2005 have been evaluated using Fourier transform infrared (FTIR) solar observations carried out at 10 ground-based sites, affiliated to the Network for Detection of Atmospheric Composition Change (NDACC). From this, we find an increase of atmospheric methane total columns of 0.31 ± 0.03 % year –1 (2 σ level of uncertainty) for the 2005–2014 period. Comparisons with in situ methane measurements at both local and global scales show good agreement. We used the GEOS-Chem chemical transport model tagged simulation, which accounts for the contribution of each emission source and one sinkmore » in the total methane, simulated over 2005–2012. After regridding according to NDACC vertical layering using a conservative regridding scheme and smoothing by convolving with respective FTIR seasonal averaging kernels, the GEOS-Chem simulation shows an increase of atmospheric methane total columns of 0.35 ± 0.03 % year –1 between 2005 and 2012, which is in agreement with NDACC measurements over the same time period (0.30 ± 0.04 % year –1, averaged over 10 stations). Analysis of the GEOS-Chem-tagged simulation allows us to quantify the contribution of each tracer to the global methane change since 2005. We find that natural sources such as wetlands and biomass burning contribute to the interannual variability of methane. However, anthropogenic emissions, such as coal mining, and gas and oil transport and exploration, which are mainly emitted in the Northern Hemisphere and act as secondary contributors to the global budget of methane, have played a major role in the increase of atmospheric methane observed since 2005. Furthermore based on the GEOS-Chem-tagged simulation, we discuss possible cause(s) for the increase of methane since 2005, which is still unexplained.« less

The recent increase of atmospheric methane from 10 years of ground-based NDACC FTIR observations since 2005

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bader, Whitney; Bovy, Benoît; Conway, Stephanie

Changes of atmospheric methane total columns (CH 4) since 2005 have been evaluated using Fourier transform infrared (FTIR) solar observations carried out at 10 ground-based sites, affiliated to the Network for Detection of Atmospheric Composition Change (NDACC). From this, we find an increase of atmospheric methane total columns of 0.31 ± 0.03 % year –1 (2 σ level of uncertainty) for the 2005–2014 period. Comparisons with in situ methane measurements at both local and global scales show good agreement. We used the GEOS-Chem chemical transport model tagged simulation, which accounts for the contribution of each emission source and one sinkmore » in the total methane, simulated over 2005–2012. After regridding according to NDACC vertical layering using a conservative regridding scheme and smoothing by convolving with respective FTIR seasonal averaging kernels, the GEOS-Chem simulation shows an increase of atmospheric methane total columns of 0.35 ± 0.03 % year –1 between 2005 and 2012, which is in agreement with NDACC measurements over the same time period (0.30 ± 0.04 % year –1, averaged over 10 stations). Analysis of the GEOS-Chem-tagged simulation allows us to quantify the contribution of each tracer to the global methane change since 2005. We find that natural sources such as wetlands and biomass burning contribute to the interannual variability of methane. However, anthropogenic emissions, such as coal mining, and gas and oil transport and exploration, which are mainly emitted in the Northern Hemisphere and act as secondary contributors to the global budget of methane, have played a major role in the increase of atmospheric methane observed since 2005. Furthermore based on the GEOS-Chem-tagged simulation, we discuss possible cause(s) for the increase of methane since 2005, which is still unexplained.« less

Evidence for climate change in the satellite cloud record

DOE PAGES

Norris, Joel R.; Allen, Robert J.; Evan, Amato T.; ...

2016-07-11

Clouds substantially affect Earth’s energy budget by reflecting solar radiation back to space and by restricting emission of thermal radiation to space 1. They are perhaps the largest uncertainty in our understanding of climate change, owing to disagreement among climate models and observational datasets over what cloud changes have occurred during recent decades and will occur in response to global warming 2, 3. This is because observational systems originally designed for monitoring weather have lacked sufficient stability to detect cloud changes reliably over decades unless they have been corrected to remove artefacts 4, 5. Here we show that several independent,more » empirically corrected satellite records exhibit large-scale patterns of cloud change between the 1980s and the 2000s that are similar to those produced by model simulations of climate with recent historical external radiative forcing. Observed and simulated cloud change patterns are consistent with poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops at all latitudes. The primary drivers of these cloud changes appear to be increasing greenhouse gas concentrations and a recovery from volcanic radiative cooling. Here, these results indicate that the cloud changes most consistently predicted by global climate models are currently occurring in nature.« less

Evidence for climate change in the satellite cloud record

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norris, Joel R.; Allen, Robert J.; Evan, Amato T.

Clouds substantially affect Earth’s energy budget by reflecting solar radiation back to space and by restricting emission of thermal radiation to space 1. They are perhaps the largest uncertainty in our understanding of climate change, owing to disagreement among climate models and observational datasets over what cloud changes have occurred during recent decades and will occur in response to global warming 2, 3. This is because observational systems originally designed for monitoring weather have lacked sufficient stability to detect cloud changes reliably over decades unless they have been corrected to remove artefacts 4, 5. Here we show that several independent,more » empirically corrected satellite records exhibit large-scale patterns of cloud change between the 1980s and the 2000s that are similar to those produced by model simulations of climate with recent historical external radiative forcing. Observed and simulated cloud change patterns are consistent with poleward retreat of mid-latitude storm tracks, expansion of subtropical dry zones, and increasing height of the highest cloud tops at all latitudes. The primary drivers of these cloud changes appear to be increasing greenhouse gas concentrations and a recovery from volcanic radiative cooling. Here, these results indicate that the cloud changes most consistently predicted by global climate models are currently occurring in nature.« less

Integrated modelling of anthropogenic land-use and land-cover change on the global scale

NASA Astrophysics Data System (ADS)

Schaldach, R.; Koch, J.; Alcamo, J.

2009-04-01

In many cases land-use activities go hand in hand with substantial modifications of the physical and biological cover of the Earth's surface, resulting in direct effects on energy and matter fluxes between terrestrial ecosystems and the atmosphere. For instance, the conversion of forest to cropland is changing climate relevant surface parameters (e.g. albedo) as well as evapotranspiration processes and carbon flows. In turn, human land-use decisions are also influenced by environmental processes. Changing temperature and precipitation patterns for example are important determinants for location and intensity of agriculture. Due to these close linkages, processes of land-use and related land-cover change should be considered as important components in the construction of Earth System models. A major challenge in modelling land-use change on the global scale is the integration of socio-economic aspects and human decision making with environmental processes. One of the few global approaches that integrates functional components to represent both anthropogenic and environmental aspects of land-use change, is the LandSHIFT model. It simulates the spatial and temporal dynamics of the human land-use activities settlement, cultivation of food crops and grazing management, which compete for the available land resources. The rational of the model is to regionalize the demands for area intensive commodities (e.g. crop production) and services (e.g. space for housing) from the country-level to a global grid with the spatial resolution of 5 arc-minutes. The modelled land-use decisions within the agricultural sector are influenced by changing climate and the resulting effects on biomass productivity. Currently, this causal chain is modelled by integrating results from the process-based vegetation model LPJmL model for changing crop yields and net primary productivity of grazing land. Model output of LandSHIFT is a time series of grid maps with land-use/land-cover information that can serve as basis for further impact analysis. An exemplary simulation study with LandSHIFT is presented, based on scenario assumptions from the UNEP Global Environmental Outlook 4. Time horizon of the analysis is the year 2050. Changes of future food production on country level are computed by the agro-economy model IMPACT as a function of demography, economic development and global trade pattern. Together with scenario assumptions on climatic change and population growth, this data serves as model input to compute the changing land-use und land-cover. The continental and global scale model results are then analysed with respect to changes in the spatial pattern of natural vegetation as well as the resulting effects on evapotranspiration processes and land surface parameters. Furthermore, possible linkages of LandSHIFT to the different components of Earth System models (e.g. climate and natural vegetation) are discussed.

Open Source Tools for Assessment of Global Water Availability, Demands, and Scarcity

NASA Astrophysics Data System (ADS)

Li, X.; Vernon, C. R.; Hejazi, M. I.; Link, R. P.; Liu, Y.; Feng, L.; Huang, Z.; Liu, L.

2017-12-01

Water availability and water demands are essential factors for estimating water scarcity conditions. To reproduce historical observations and to quantify future changes in water availability and water demand, two open source tools have been developed by the JGCRI (Joint Global Change Research Institute): Xanthos and GCAM-STWD. Xanthos is a gridded global hydrologic model, designed to quantify and analyze water availability in 235 river basins. Xanthos uses a runoff generation and a river routing modules to simulate both historical and future estimates of total runoff and streamflows on a monthly time step at a spatial resolution of 0.5 degrees. GCAM-STWD is a spatiotemporal water disaggregation model used with the Global Change Assessment Model (GCAM) to spatially downscale global water demands for six major enduse sectors (irrigation, domestic, electricity generation, mining, and manufacturing) from the region scale to the scale of 0.5 degrees. GCAM-STWD then temporally downscales the gridded annual global water demands to monthly results. These two tools, written in Python, can be integrated to assess global, regional or basin-scale water scarcity or water stress. Both of the tools are extensible to ensure flexibility and promote contribution from researchers that utilize GCAM and study global water use and supply.

N2O Source Strength of Tropical Rain Forests: From the Site to the Global Scale

NASA Astrophysics Data System (ADS)

Kiese, R.; Werner, C.; Butterbach-Bahl, K.

2006-12-01

In contrast to the significant importance of tropical rain forest ecosystems as one of the major single sources within the global atmospheric N2O budget (2.2 3.7 Tg N y-1, regional and global estimates of their N2O source strength are still limited and highly uncertain. However, accurate quantification of sources and sinks of greenhouse gases like CO2, N2O and CH4 for natural, agricultural and forest ecosystems is crucial to our understanding of land use change effects on global climate change. At present, up-scaling approaches which link detailed geographic information systems (GIS) to mechanistic biochemical models are seen as a promising tool to contribute towards more reliable estimates of biogenic sources of N2O, e.g. tropical rain forest ecosystems. In our study we further developed and tested the PnET-N-DNDC model using Bayesian calibration techniques based on detailed N2O emission data of two recently conducted field campaigns in African (Kenya) and Asian (SE-China) tropical forest ecosystems and additional datasets from earlier own field campaigns or the literature. For global upscaling of N2O emissions an extensive GIS database was constructed holding all necessary parameters (climate ECWMF ERA 40; soil: FAO, vegetation: LPJ-DGVM simulation) in spatial and temporal resolution for initializing and driving the further developed biogeochemical model at a grid size of 0.25°x0.25°. We calculated global N2O emissions inventories for the years 1991 to 2001, and found a general agreement of the simulated flux ranges with reported N2O emissions from tropical forest ecosystems worldwide. According to our simulations, tropical rainforest soils are indeed a significant source of atmospheric N2O ranging from 1.1 2.2 Tg in dependence from the simulated year. Notably, related to differences in environmental conditions, N2O emissions varied considerably within the tropical belt. Furthermore, our simulations revealed a pronounced inter-annual variability of N2O emissions mainly driven by differences in weather conditions (e.g. distribution and total amount of rainfall) across years, which may be mirrored in atmospheric N2O concentrations.

Water resources sensitivity to the isolated effects of land use, water demand and climate change under 2 degree global warming

NASA Astrophysics Data System (ADS)

Bisselink, Berny; Bernhard, Jeroen; de Roo, Ad

2017-04-01

One of the key impacts of global change are the future water resources. These water resources are influenced by changes in land use (LU), water demand (WD) and climate change. Recent developments in scenario modelling opened new opportunities for an integrated assessment. However, for identifying water resource management strategies it is helpful to focus on the isolated effects of possible changes in LU, WD and climate that may occur in the near future. In this work, we quantify the isolated contribution of LU, WD and climate to the integrated total water resources assuming a linear model behavior. An ensemble of five EURO-CORDEX RCP8.5 climate projections for the 31-year periods centered on the year of exceeding the global-mean temperature of 2 degree is used to drive the fully distributed hydrological model LISFLOOD for multiple river catchments in Europe. The JRC's Land Use Modelling Platform LUISA was used to obtain a detailed pan-European reference land use scenario until 2050. Water demand is estimated based on socio-economic (GDP, population estimates etc.), land use and climate projections as well. For each climate projection, four model runs have been performed including an integrated (LU, WD and climate) simulation and other three simulations to isolate the effect of LU, WD and climate. Changes relative to the baseline in terms of water resources indicators of the ensemble means of the 2 degree warming period and their associated uncertainties will reveal the integrated and isolated effect of LU, WD and climate change on water resources.

Decline of the marine ecosystem caused by a reduction in the Atlantic overturning circulation.

PubMed

Schmittner, Andreas

2005-03-31

Reorganizations of the Atlantic meridional overturning circulation were associated with large and abrupt climatic changes in the North Atlantic region during the last glacial period. Projections with climate models suggest that similar reorganizations may also occur in response to anthropogenic global warming. Here I use ensemble simulations with a coupled climate-ecosystem model of intermediate complexity to investigate the possible consequences of such disturbances to the marine ecosystem. In the simulations, a disruption of the Atlantic meridional overturning circulation leads to a collapse of the North Atlantic plankton stocks to less than half of their initial biomass, owing to rapid shoaling of winter mixed layers and their associated separation from the deep ocean nutrient reservoir. Globally integrated export production declines by more than 20 per cent owing to reduced upwelling of nutrient-rich deep water and gradual depletion of upper ocean nutrient concentrations. These model results are consistent with the available high-resolution palaeorecord, and suggest that global ocean productivity is sensitive to changes in the Atlantic meridional overturning circulation.

Simulated responses of terrestrial aridity to black carbon and sulfate aerosols

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, L.; Gettelman, A.; Xu, Y.

Aridity index (AI), defined as the ratio of precipitation to potential evapotranspiration (PET), is a measure of the dryness of terrestrial climate. Global climate models generally project future decreases of AI (drying) associated with global warming scenarios driven by increasing greenhouse gas and declining aerosols. Given their different effects in the climate system, scattering and absorbing aerosols may affect AI differently. In this work, we explore the terrestrial aridity responses to anthropogenic black carbon (BC) and sulfate (SO 4) aerosols with Community Earth System Model simulations. Positive BC radiative forcing decreases precipitation averaged over global land at a rate ofmore » 0.9%/°C of global mean surface temperature increase (moderate drying), while BC radiative forcing increases PET by 1.0%/°C (also drying). BC leads to a global decrease of 1.9%/°C in AI (drying). SO 4 forcing is negative and causes precipitation a decrease at a rate of 6.7%/°C cooling (strong drying). PET also decreases in response to SO 4 aerosol cooling by 6.3%/°C cooling (contributing to moistening). Thus, SO 4 cooling leads to a small decrease in AI (drying) by 0.4%/°C cooling. Despite the opposite effects on global mean temperature, BC and SO 4 both contribute to the twentieth century drying (AI decrease). Sensitivity test indicates that surface temperature and surface available energy changes dominate BC- and SO 4-induced PET changes.« less

Simulated responses of terrestrial aridity to black carbon and sulfate aerosols

DOE PAGES

Lin, L.; Gettelman, A.; Xu, Y.; ...

2016-01-27

Aridity index (AI), defined as the ratio of precipitation to potential evapotranspiration (PET), is a measure of the dryness of terrestrial climate. Global climate models generally project future decreases of AI (drying) associated with global warming scenarios driven by increasing greenhouse gas and declining aerosols. Given their different effects in the climate system, scattering and absorbing aerosols may affect AI differently. In this work, we explore the terrestrial aridity responses to anthropogenic black carbon (BC) and sulfate (SO 4) aerosols with Community Earth System Model simulations. Positive BC radiative forcing decreases precipitation averaged over global land at a rate ofmore » 0.9%/°C of global mean surface temperature increase (moderate drying), while BC radiative forcing increases PET by 1.0%/°C (also drying). BC leads to a global decrease of 1.9%/°C in AI (drying). SO 4 forcing is negative and causes precipitation a decrease at a rate of 6.7%/°C cooling (strong drying). PET also decreases in response to SO 4 aerosol cooling by 6.3%/°C cooling (contributing to moistening). Thus, SO 4 cooling leads to a small decrease in AI (drying) by 0.4%/°C cooling. Despite the opposite effects on global mean temperature, BC and SO 4 both contribute to the twentieth century drying (AI decrease). Sensitivity test indicates that surface temperature and surface available energy changes dominate BC- and SO 4-induced PET changes.« less

The asymmetric impact of global warming on US drought types and distributions in a large ensemble of 97 hydro-climatic simulations.

PubMed

Huang, Shengzhi; Leng, Guoyong; Huang, Qiang; Xie, Yangyang; Liu, Saiyan; Meng, Erhao; Li, Pei

2017-07-19

Projection of future drought is often involved large uncertainties from climate models, emission scenarios as well as drought definitions. In this study, we investigate changes in future droughts in the conterminous United States based on 97 1/8 degree hydro-climate model projections. Instead of focusing on a specific drought type, we investigate changes in meteorological, agricultural, and hydrological drought as well as the concurrences. Agricultural and hydrological droughts are projected to become more frequent with increase in global mean temperature, while less meteorological drought is expected. Changes in drought intensity scale linearly with global temperature rises under RCP8.5 scenario, indicating the potential feasibility to derive future drought severity given certain global warming amount under this scenario. Changing pattern of concurrent droughts generally follows that of agricultural and hydrological droughts. Under the 1.5 °C warming target as advocated in recent Paris agreement, several hot spot regions experiencing highest droughts are identified. Extreme droughts show similar patterns but with much larger magnitude than the climatology. This study highlights the distinct response of droughts of various types to global warming and the asymmetric impact of global warming on drought distribution resulting in a much stronger influence on extreme drought than on mean drought.

Global Pyrogeography: the Current and Future Distribution of Wildfire

PubMed Central

Krawchuk, Meg A.; Moritz, Max A.; Parisien, Marc-André; Van Dorn, Jeff; Hayhoe, Katharine

2009-01-01

Climate change is expected to alter the geographic distribution of wildfire, a complex abiotic process that responds to a variety of spatial and environmental gradients. How future climate change may alter global wildfire activity, however, is still largely unknown. As a first step to quantifying potential change in global wildfire, we present a multivariate quantification of environmental drivers for the observed, current distribution of vegetation fires using statistical models of the relationship between fire activity and resources to burn, climate conditions, human influence, and lightning flash rates at a coarse spatiotemporal resolution (100 km, over one decade). We then demonstrate how these statistical models can be used to project future changes in global fire patterns, highlighting regional hotspots of change in fire probabilities under future climate conditions as simulated by a global climate model. Based on current conditions, our results illustrate how the availability of resources to burn and climate conditions conducive to combustion jointly determine why some parts of the world are fire-prone and others are fire-free. In contrast to any expectation that global warming should necessarily result in more fire, we find that regional increases in fire probabilities may be counter-balanced by decreases at other locations, due to the interplay of temperature and precipitation variables. Despite this net balance, our models predict substantial invasion and retreat of fire across large portions of the globe. These changes could have important effects on terrestrial ecosystems since alteration in fire activity may occur quite rapidly, generating ever more complex environmental challenges for species dispersing and adjusting to new climate conditions. Our findings highlight the potential for widespread impacts of climate change on wildfire, suggesting severely altered fire regimes and the need for more explicit inclusion of fire in research on global vegetation-climate change dynamics and conservation planning. PMID:19352494

Climate Change, Globalization and Geopolitics in the New Maritime Arctic

NASA Astrophysics Data System (ADS)

Brigham, L. W.

2011-12-01

Early in the 21st century a confluence of climate change, globalization and geopolitics is shaping the future of the maritime Arctic. This nexus is also fostering greater linkage of the Arctic to the rest of the planet. Arctic sea ice is undergoing a historic transformation of thinning, extent reduction in all seasons, and reduction in the area of multiyear ice in the central Arctic Ocean. Global Climate Model simulations of Arctic sea ice indicate multiyear ice could disappear by 2030 for a short period of time each summer. These physical changes invite greater marine access, longer seasons of navigation, and potential, summer trans-Arctic voyages. As a result, enhanced marine safety, environmental protection, and maritime security measures are under development. Coupled with climate change as a key driver of regional change is the current and future integration of the Arctic's natural wealth with global markets (oil, gas and hard minerals). Abundant freshwater in the Arctic could also be a future commodity of value. Recent events such as drilling for hydrocarbons off Greenland's west coast and the summer marine transport of natural resources from the Russian Arctic to China across the top of Eurasia are indicators of greater global economic ties to the Arctic. Plausible Arctic futures indicate continued integration with global issues and increased complexity of a range of regional economic, security and environmental challenges.

Feasibility study of aerosol retrieval for GCOM-C/SGLI with simulated data

NASA Astrophysics Data System (ADS)

Mukai, S.; Sano, I.; Yasumoto, M.; Nakata, M.; Nishi, N.

2016-12-01

The Japan Aerospace Exploration Agency (JAXA) has been developing the new Earth observing system, GCOM (Global Change Observation Mission) project, which consists of two satellite series of GCOM-W1 and GCOM-C1. The 1st GCOM-C satellite will board the SGLI (second generation global imager) to be launched in early of 2017. The SGLI has multi (19)-channels including near ultra violet (NUV) channels (380, 412 nm) and two polarization channels at red and near-infrared wavelengths of 670 and 870 nm. Global aerosol retrieval is achieved with both polarization and total radiance. It is noted that NUV measurements are available for detection of the carbonaceous aerosols. The biomass burning aerosols (BBA) generated by forest fire and/or burn agriculture have influenced on the severe air pollutions. It is known that the forest fire increases due to global warming and a climate change, and has influences on them vice versa. It is well known that this negative cycle decreases the quality of global environment and human health. In this work, we use both radiance and polarization measurements observed by GLI and POLDER-2 on Japanese ADEOS-2 satellite in 2003 as a simulated data set for coming GCOM-C/SGLI sensor. As a result the possibility of GCOM-C1/SGLI related to remote sensing for aerosols, especially in the hazardous aerosol episodes including biomass burning case, can be examined.

Regional-Scale Forcing and Feedbacks from Alternative Scenarios of Global-Scale Land Use Change

NASA Astrophysics Data System (ADS)

Jones, A. D.; Chini, L. P.; Collins, W.; Janetos, A. C.; Mao, J.; Shi, X.; Thomson, A. M.; Torn, M. S.

2011-12-01

Future patterns of land use change depend critically on the degree to which terrestrial carbon management strategies, such as biological carbon sequestration and biofuels, are utilized in order to mitigate global climate change. Furthermore, land use change associated with terrestrial carbon management induces biogeophysical changes to surface energy budgets that perturb climate at regional and possibly global scales, activating different feedback processes depending on the nature and location of the land use change. As a first step in a broader effort to create an integrated earth system model, we examine two scenarios of future anthropogenic activity generated by the Global Change Assessment Model (GCAM) within the full-coupled Community Earth System Model (CESM). Each scenario stabilizes radiative forcing from greenhouse gases and aerosols at 4.5 W/m^2. In the first, stabilization is achieved through a universal carbon tax that values terrestrial carbon equally with fossil carbon, leading to modest afforestation globally and low biofuel utilization. In the second scenario, stabilization is achieved with a tax on fossil fuel and industrial carbon alone. In this case, biofuel utilization increases dramatically and crop area expands to claim approximately 50% of forest cover globally. By design, these scenarios exhibit identical climate forcing from atmospheric constituents. Thus, differences among them can be attributed to the biogeophysical effects of land use change. In addition, we utilize offline radiative transfer and offline land model simulations to identify forcing and feedback mechanisms operating in different regions. We find that boreal deforestation has a strong climatic signature due to significant albedo change coupled with a regional-scale water vapor feedback. Tropical deforestation, on the other hand, has more subtle effects on climate. Globally, the two scenarios yield warming trends over the 21st century that differ by 0.5 degrees Celsius. This work demonstrates the importance of land use in shaping future patterns of climate change, both globally and regionally.

What are the effects of Agro-Ecological Zones and land use region boundaries on land resource projection using the Global Change Assessment Model?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Di Vittorio, Alan V.; Kyle, Page; Collins, William D.

Understanding the potential impacts of climate change is complicated by mismatched spatial representations between gridded Earth System Models (ESMs) and Integrated Assessment Models (IAMs), whose regions are typically larger and defined by geopolitical and biophysical criteria. In this study we address uncertainty stemming from the construction of land use regions in an IAM, the Global Change Assessment Model (GCAM), whose regions are currently based on historical climatic conditions (1961-1990). We re-define GCAM’s regions according to projected climatic conditions (2070-2099), and investigate how this changes model outcomes for land use, agriculture, and forestry. By 2100, we find potentially large differences inmore » projected global and regional area of biomass energy crops, fodder crops, harvested forest, and intensive pasture. These land area differences correspond with changes in agricultural commodity prices and production. These results have broader implications for understanding policy scenarios and potential impacts, and for evaluating and comparing IAM and ESM simulations.« less

Benchmarking carbon-nitrogen interactions in Earth System Models to observations: An inter-comparison of nitrogen limitation in global land surface models with carbon and nitrogen cycles (CLM-CN and O-CN)

NASA Astrophysics Data System (ADS)

Thomas, R. Q.; Zaehle, S.; Templer, P. H.; Goodale, C. L.

2011-12-01

Predictions of climate change depend on accurately modeling the feedbacks among the carbon cycle, nitrogen cycle, and climate system. Several global land surface models have shown that nitrogen limitation determines how land carbon fluxes respond to rising CO2, nitrogen deposition, and climate change, thereby influencing predictions of climate change. However, the magnitude of the carbon-nitrogen-climate feedbacks varies considerably by model, leading to critical and timely questions of why they differ and how they compare to field observations. To address these questions, we initiated a model inter-comparison of spatial patterns and drivers of nitrogen limitation. The experiment assessed the regional consequences of sustained nitrogen additions in a set of 25-year global nitrogen fertilization simulations. The model experiments were designed to cover effects from small changes in nitrogen inputs associated with plausible increases in nitrogen deposition to large changes associated with field-based nitrogen fertilization experiments. The analyses of model simulations included assessing the geographically varying degree of nitrogen limitation on plant and soil carbon cycling and the mechanisms underlying model differences. Here, we present results from two global land-surface models (CLM-CN and O-CN) with differing approaches to modeling carbon-nitrogen interactions. The predictions from each model were compared to a set of globally distributed observational data that includes nitrogen fertilization experiments, 15N tracer studies, small catchment nitrogen input-output studies, and syntheses across nitrogen deposition gradients. Together these datasets test many aspects of carbon-nitrogen coupling and are able to differentiate between the two models. Overall, this study is the first to explicitly benchmark carbon and nitrogen interactions in Earth System Models using a range of observations and is a foundation for future inter-comparisons.

The Great Plains low-level jet in 1.5C and 2C HAPPI simulations: Implications for changes in extreme climate events

NASA Astrophysics Data System (ADS)

Weaver, S. J.; Barcikowska, M. J.

2017-12-01

Global temperature targets have become the cornerstone for global climate policy discussions. Given the goal of the Paris Accord to limit the rise in global mean temperature to well below 2.0oC above pre-industrial levels, and pursue efforts toward the more ambitious 1.5oC goal, there is increasing focus in the climate science community on what the relative changes in regional climate extremes may be for these two scenarios. Despite the successes of major climate science modeling efforts, there is still a significant information gap regarding the regional and seasonal changes in some climate extremes over the U.S. as a function of these global mean temperature targets.During the spring and summer, large amounts of heat and moisture are transported northward into the central and eastern U.S. by the Great Plains Low-Level Jet (GPLLJ) - an atmospheric river which dominates the subcontinental scale climate variability during the warm half of the year. Accordingly, the GPLLJ and its vast spatiotemporal variability is highly influential over several types of extreme climate anomalies east of the Rocky Mountains, including, drought and pluvial events, tornadic activity, and the evolution of central U.S warming hole. Changes in the GPLLJ and its variability are probed from the perspective of several hundred climate realizations afforded by the availability of climate model experiments from the Half a degree additional warming, Prognosis, and Projected Impacts (HAPPI) effort - a suite of multi-model ensemble AMIP simulations forced by 1.5oC and 2oC levels of global warming. The multimodel analysis focuses on the variable magnitude of the seasonal changes in the mean GPLLJ and shifts in the extremes of the prominent modes of GPLLJ variability - both of which have implications for the future shifts in extreme climate events over the Great Plains, Midwest, and southeast regions of the U.S.

Integration of Linear Dynamic Emission and Climate Models with Air Traffic Simulations

NASA Technical Reports Server (NTRS)

Sridhar, Banavar; Ng, Hok K.; Chen, Neil Y.

2012-01-01

Future air traffic management systems are required to balance the conflicting objectives of maximizing safety and efficiency of traffic flows while minimizing the climate impact of aviation emissions and contrails. Integrating emission and climate models together with air traffic simulations improve the understanding of the complex interaction between the physical climate system, carbon and other greenhouse gas emissions and aviation activity. This paper integrates a national-level air traffic simulation and optimization capability with simple climate models and carbon cycle models, and climate metrics to assess the impact of aviation on climate. The capability can be used to make trade-offs between extra fuel cost and reduction in global surface temperature change. The parameters in the simulation can be used to evaluate the effect of various uncertainties in emission models and contrails and the impact of different decision horizons. Alternatively, the optimization results from the simulation can be used as inputs to other tools that monetize global climate impacts like the FAA s Aviation Environmental Portfolio Management Tool for Impacts.

Ecosystem service impacts of future changes in CO2, climate, and land use as simulated by a coupled vegetation/land-use model system

NASA Astrophysics Data System (ADS)

Rabin, S. S.; Alexander, P.; Henry, R.; Anthoni, P.; Pugh, T.; Rounsevell, M.; Arneth, A.

2017-12-01

In a future of increasing atmospheric carbon dioxide (CO2) concentrations, changing climate, increasing human populations, and changing socioeconomic dynamics, the global agricultural system will need to adapt in order to feed the world. Global modeling can help to explore what these adaptations will look like, and their potential impacts on ecosystem services. To do so, however, the complex interconnections among the atmosphere, terrestrial ecosystems, and society mean that these various parts of the Earth system must be examined as an interconnected whole. With the goal of answering these questions, a model system has been developed that couples a biologically-representative global vegetation model, LPJ-GUESS, with the PLUMv2 land use model. LPJ-GUESS first simulates—at 0.5º resolution across the world—the potential yield of various crops and pasture under a range of management intensities for a time step given its atmospheric CO2 level and climatic forcings. These potential yield simulations are fed into PLUMv2, which uses them in conjunction with endogenous agricultural commodity demand and prices to produce land use and management inputs (fertilizer and irrigation water) at a sub-national level for the next time step. This process is performed through 2100 for a range of future climate and societal scenarios—the Representative Concentration Pathways (RCPs) and the Shared Socioeconomic Pathways (SSPs), respectively—providing a thorough exploration of possible trajectories of land use and land cover change. The land use projections produced by PLUMv2 are fed back into LPJ-GUESS to simulate the future impacts of land use change, along with increasing CO2 and climate change, on terrestrial ecosystems. This integrated analysis examines the resulting impacts on regulating and provisioning ecosystem services affecting biophysics (albedo); carbon, nitrogen, and water cycling; and the emission of biogenic volatile organic compounds (BVOCs).

Trends in simulated chemical composition of global and regional population-weighted fine particulate matter over the recent 25 years

NASA Astrophysics Data System (ADS)

Li, C.; Martin, R.; van Donkelaar, A.; Boys, B.; Hammer, M. S.; Xu, J.; Marais, E. A.; Reff, A.; Strum, M.; Ridley, D. A.; Crippa, M.; Zhang, Q.

2017-12-01

We interpret in situ and satellite observations with a chemical transport model (GEOS-Chem) to understand global trends in population-weighted mean chemical composition of fine particulate matter (PM2.5) over 1989-2013. Simulated PM2.5 composition concentrations at 2˚ × 2.5˚ resolution are downscaled to 0.1˚ × 0.1˚ with satellite-based estimates of PM2.5 to better represent population exposure. Trends in simulated and observed population-weighted mean PM2.5 composition over 1989-2013 exhibit a high degree of consistency for (in situ vs. downscaled simulation) PM2.5 (-2.4 vs. -2.4 % yr-1), secondary inorganic aerosols (-4.3 vs. -4.1% yr-1), organic aerosols (OA, -3.6 vs. -3.0 % yr-1) and black carbon (-4.3 vs. -3.9 % yr-1) over North America, as well as sulfate (-4.7 vs. -5.8 % yr-1) over Europe. The downscaled simulation also has overlapping 95% confidence intervals with satellite-derived trends in population-weighted mean PM2.5 for 20 of the 21 Global Burden of Disease Study (GBD) regions over 1998-2013. Over 1989-2013, most (79%) of the simulated increase in global population-weighted mean PM2.5 of 0.28 μg m-3yr-1 is explained by significantly (p < 0.05) increasing OA (0.10 μg m-3yr-1), nitrate (0.05 μg m-3yr-1), sulfate (0.04 μg m-3yr-1) and ammonium (0.03 μg m-3yr-1). These species predominantly drive trends in population-weighted mean PM2.5 over populous regions of South Asia (0.94 μg m-3yr-1), East Asia (0.66 μg m-3yr-1), Western Europe (-0.47 μg m-3yr-1) and North America (-0.32 μg m-3yr-1), primarily due to changes in anthropogenic emissions. Mineral dust from deserts and OA over open burning regions usually cause weak, insignificant trends in population-weighted mean PM2.5, despite strong inter-annual variation. Global trends in area-weighted mean PM2.5 differ significantly from population-weighted trends in both the magnitude and sign, indicating the importance of population weighting for relevance to human exposure studies. This study provides new insights into global changes in PM2.5 exposure through the recent 25 years, with particular attention given to the evolution of PM2.5 composition.

Smaller global and regional carbon emissions from gross land use change when considering sub-grid secondary land cohorts in a global dynamic vegetation model

NASA Astrophysics Data System (ADS)

Yue, Chao; Ciais, Philippe; Li, Wei

2018-02-01

Several modelling studies reported elevated carbon emissions from historical land use change (ELUC) by including bidirectional transitions on the sub-grid scale (termed gross land use change), dominated by shifting cultivation and other land turnover processes. However, most dynamic global vegetation models (DGVMs) that have implemented gross land use change either do not account for sub-grid secondary lands, or often have only one single secondary land tile over a model grid cell and thus cannot account for various rotation lengths in shifting cultivation and associated secondary forest age dynamics. Therefore, it remains uncertain how realistic the past ELUC estimations are and how estimated ELUC will differ between the two modelling approaches with and without multiple sub-grid secondary land cohorts - in particular secondary forest cohorts. Here we investigated historical ELUC over 1501-2005 by including sub-grid forest age dynamics in a DGVM. We run two simulations, one with no secondary forests (Sageless) and the other with sub-grid secondary forests of six age classes whose demography is driven by historical land use change (Sage). Estimated global ELUC for 1501-2005 is 176 Pg C in Sage compared to 197 Pg C in Sageless. The lower ELUC values in Sage arise mainly from shifting cultivation in the tropics under an assumed constant rotation length of 15 years, being 27 Pg C in Sage in contrast to 46 Pg C in Sageless. Estimated cumulative ELUC values from wood harvest in the Sage simulation (31 Pg C) are however slightly higher than Sageless (27 Pg C) when the model is forced by reconstructed harvested areas because secondary forests targeted in Sage for harvest priority are insufficient to meet the prescribed harvest area, leading to wood harvest being dominated by old primary forests. An alternative approach to quantify wood harvest ELUC, i.e. always harvesting the close-to-mature forests in both Sageless and Sage, yields similar values of 33 Pg C by both simulations. The lower ELUC from shifting cultivation in Sage simulations depends on the predefined forest clearing priority rules in the model and the assumed rotation length. A set of sensitivity model runs over Africa reveal that a longer rotation length over the historical period likely results in higher emissions. Our results highlight that although gross land use change as a former missing emission component is included by a growing number of DGVMs, its contribution to overall ELUC remains uncertain and tends to be overestimated when models ignore sub-grid secondary forests.

Tropospheric Ozone Change from 1980 to 2010 Dominated by Equatorward Redistribution of Emissions

NASA Technical Reports Server (NTRS)

Zhang, Yuqiang; Cooper, Owen R.; Gaudel, Audrey; Thompson, Anne M.; Nedelec, Philippe; Ogino, Shin-Ya; West, J. Jason

2016-01-01

Ozone is an important air pollutant at the surface, and the third most important anthropogenic greenhouse gas in the troposphere. Since 1980, anthropogenic emissions of ozone precursors methane, non-methane volatile organic compounds, carbon monoxide and nitrogen oxides (NOx) have shifted from developed to developing regions. Emissions have thereby been redistributed equatorwards, where they are expected to have a stronger effect on the tropospheric ozone burden due to greater convection, reaction rates and NOx sensitivity. Here we use a global chemical transport model to simulate changes in tropospheric ozone concentrations from 1980 to 2010, and to separate the influences of changes in the spatial distribution of global anthropogenic emissions of short-lived pollutants, the magnitude of these emissions, and the global atmospheric methane concentration. We estimate that the increase in ozone burden due to the spatial distribution change slightly exceeds the combined influences of the increased emission magnitude and global methane. Emission increases in Southeast, East and South Asia may be most important for the ozone change, supported by an analysis of statistically significant increases in observed ozone above these regions. The spatial distribution of emissions dominates global tropospheric ozone, suggesting that the future ozone burden will be determined mainly by emissions from low latitudes.

Estimating the Response of Mid-latitude Orographic Precipitation to Global Warming

NASA Astrophysics Data System (ADS)

Shi, Xiaoming

The possible change in orographic precipitation in response to global warming is a rising concern under climate change, which could potentially cause significant societal impact. A general circulation model was employed to simulate the climate on an aquaplanet which has idealized mountains at its mid-latitudes. It was found that orographic precipitation at northern mid-latitudes could increase by rates faster than the Clausius-Clapeyron scaling, ˜7%/K of surface warming, in doubling CO2 simulations, while at southern mid-latitudes orographic precipitation decreased. The frequency of extreme events increased at all latitudes of the idealized mountains. Through a simple diagnostic model it was revealed that the changes in the climatological means of orographic precipitation rates were mostly determined by the changes in three variables: the speed of the wind component perpendicular to a mountain, the vertical displacement of saturated parcels, and the moist adiabatic lapse rate of saturation specific humidity. The last variable had relatively uniform contribution to the total changes in orographic precipitation across different latitudes, about 4 -- 5%/K. But contributions from the changes in wind speed and saturated vertical displacement were found to have strong north-south asymmetry, which were linked to the poleward shift of storm tracks. The changes in wind speed had positive contributions in general, with larger contributions at higher mid-latitudes. While the changes in saturated vertical displacement had negative contributions at all latitudes, but larger negative contributions were located at lower mid-latitudes. Although the poleward shift of storm tracks greatly affects regional precipitation, following the poleward shift of storm tracks the cumulative distribution function (CDF) of precipitation at the latitudes of maximum precipitation in the control simulation is very similar to that in the warm climate simulation, except that precipitation intensity was positively shifted by a constant factor --- mainly due to changes in the moist adiabatic lapse rate of saturation specific humidity.

Assessment of the Ability of Contemporary Climate Models to Assess Adequately the Risk of Possible Regional Anomalies and Trends

NASA Astrophysics Data System (ADS)

Mokhov, I. I.

2018-04-01

The results describing the ability of contemporary global and regional climate models not only to assess the risk of general trends of changes but also to predict qualitatively new regional effects are presented. In particular, model simulations predicted spatially inhomogeneous changes in the wind and wave conditions in the Arctic basins, which have been confirmed in recent years. According to satellite and reanalysis data, a qualitative transition to the regime predicted by model simulations occurred about a decade ago.

Constant pH simulations of pH responsive polymers

NASA Astrophysics Data System (ADS)

Sharma, Arjun; Smith, J. D.; Walters, Keisha B.; Rick, Steven W.

2016-12-01

Polyacidic polymers can change structure over a narrow range of pH in a competition between the hydrophobic effect, which favors a compact state, and electrostatic repulsion, which favors an extended state. Constant pH molecular dynamics computer simulations of poly(methacrylic acid) reveal that there are two types of structural changes, one local and one global, which make up the overall response. The local structural response depends on the tacticity of the polymer and leads to different cooperative effects for polymers with different stereochemistries, demonstrating both positive and negative cooperativities.

Alanine and proline content modulate global sensitivity to discrete perturbations in disordered proteins.

PubMed

Perez, Romel B; Tischer, Alexander; Auton, Matthew; Whitten, Steven T

2014-12-01

Molecular transduction of biological signals is understood primarily in terms of the cooperative structural transitions of protein macromolecules, providing a mechanism through which discrete local structure perturbations affect global macromolecular properties. The recognition that proteins lacking tertiary stability, commonly referred to as intrinsically disordered proteins (IDPs), mediate key signaling pathways suggests that protein structures without cooperative intramolecular interactions may also have the ability to couple local and global structure changes. Presented here are results from experiments that measured and tested the ability of disordered proteins to couple local changes in structure to global changes in structure. Using the intrinsically disordered N-terminal region of the p53 protein as an experimental model, a set of proline (PRO) and alanine (ALA) to glycine (GLY) substitution variants were designed to modulate backbone conformational propensities without introducing non-native intramolecular interactions. The hydrodynamic radius (R(h)) was used to monitor changes in global structure. Circular dichroism spectroscopy showed that the GLY substitutions decreased polyproline II (PP(II)) propensities relative to the wild type, as expected, and fluorescence methods indicated that substitution-induced changes in R(h) were not associated with folding. The experiments showed that changes in local PP(II) structure cause changes in R(h) that are variable and that depend on the intrinsic chain propensities of PRO and ALA residues, demonstrating a mechanism for coupling local and global structure changes. Molecular simulations that model our results were used to extend the analysis to other proteins and illustrate the generality of the observed PRO and alanine effects on the structures of IDPs. © 2014 Wiley Periodicals, Inc.

Alanine and proline content modulate global sensitivity to discrete perturbations in disordered proteins

PubMed Central

Perez, Romel B.; Tischer, Alexander; Auton, Matthew; Whitten, Steven T.

2014-01-01

Molecular transduction of biological signals is understood primarily in terms of the cooperative structural transitions of protein macromolecules, providing a mechanism through which discrete local structure perturbations affect global macromolecular properties. The recognition that proteins lacking tertiary stability, commonly referred to as intrinsically disordered proteins, mediate key signaling pathways suggests that protein structures without cooperative intramolecular interactions may also have the ability to couple local and global structure changes. Presented here are results from experiments that measured and tested the ability of disordered proteins to couple local changes in structure to global changes in structure. Using the intrinsically disordered N-terminal region of the p53 protein as an experimental model, a set of proline and alanine to glycine substitution variants were designed to modulate backbone conformational propensities without introducing non-native intramolecular interactions. The hydrodynamic radius (Rh) was used to monitor changes in global structure. Circular dichroism spectroscopy showed that the glycine substitutions decreased polyproline II (PPII) propensities relative to the wild type, as expected, and fluorescence methods indicated that substitution-induced changes in Rh were not associated with folding. The experiments showed that changes in local PPII structure cause changes in Rh that are variable and that depend on the intrinsic chain propensities of proline and alanine residues, demonstrating a mechanism for coupling local and global structure changes. Molecular simulations that model our results were used to extend the analysis to other proteins and illustrate the generality of the observed proline and alanine effects on the structures of intrinsically disordered proteins. PMID:25244701

A modelling approach to estimate carbon emissions from D.R.C. deforestation

NASA Astrophysics Data System (ADS)

Najdovski, Nicolas; Poulter, Benjamin; Defourny, Pierre; Moreau, Inès; Maignan, Fabienne; Ciais, Philippe; Verhegghen, Astrid; Kibambe Lubamba, Jean-Paul; Jungers, Quentin; De Weirdt, Marjolein; Verbeeck, Hans; MacBean, Natasha; Peylin, Philippe

2014-05-01

With its 1.8 million squared kilometres, the Congo basin dense forest represents the second largest contiguous forest of the world. These extensive forest ecosystems play a significant role in the regulation of global climate by their potential carbon dioxide emissions and carbon storage. Under a stable climate, the vegetation, assumed to be at the equilibrium, is known to present neutral emissions over a year with seasonal variations. However, modifications in temperatures, precipitations, CO2 atmospheric concentrations have the potential to modify this balance leading to higher or lower biomass storage. In addition, deforestation and forest degradation have played a significant role over the past several decades and are expected to become increasingly important in the future. Here, we quantify the relative effects of deforestation and 21st century climate change on carbon emissions in Congo Basin over the next three decades (2005-2035). Carbon dioxide emissions are estimated using a series of moderate resolution (10 km) vegetation maps merged with spatially explicit deforestation projections and developed to work with a prognostic carbon cycle model. The inversion of the deforestation model allowed hindcast land-use patterns back to 1800 by using land cover change rates based on the HYDE database. Simulations were made over the Democratic Republic of Congo (DRC) using the ORCHIDEE dynamic global vegetation model with climate forcing from the CMIP5 Representative Concentration Pathway 8.5 scenario for the HadGEM2. Two simulations were made, a reference simulation with land cover fixed at 2005 and a land cover change simulation with changing climate and CO2, to quantify the net land cover change emissions and climate emissions directly. Because of the relatively high resolution of the model simulations, the spatial patterns of human-driven carbon losses can be tracked in the context of climate change, providing information for mitigation and vulnerability activities.

Assessing recent and near-future changes in Southern California's groundwater storage from the perspective of regional climate modeling

NASA Astrophysics Data System (ADS)

De Sales, F.; Rother, D.

2017-12-01

Current climate change assessments project an increase in temperature throughout the western U.S. over the next century, while precipitation is projected to decrease in the Southwest. These assessments are based mainly on coarse spatial resolution general circulation model (GCM) simulations, which do not include groundwater (soil and aquifer) storage projections. However, water availability is a regionally variable resource and climate change impacts on groundwater distribution will probably differ regionally across the southwestern U.S. We have implemented a coupled atmosphere-biosphere-aquifer regional modelling system (WRF/SSiB2/SIMGM) to generate recent (2005-2017) and near-future (2018-2030) high-resolution groundwater projections for Southern California. These projections are obtained by dynamic downscaling data from the Global Operation Analysis (recent) and the NCAR Community Earth System Model CMIP5 global projections (near future), which supported the Intergovernmental Panel on Climate Change 5th Assessment Report. Near-future simulations include three representative concentration pathway (RCP) scenarios namely, RCP4.5, RCP6, and RCP8.5. The model can reasonably simulate the recent changes in Southern California's groundwater as indicated by a comparison to terrestrial water storage obtained from the Gravity Recovery and Climate Experiment dataset. In particular, the 2011-2017 drought is simulated well with total groundwater storages declining throughout the period, especially along the western portion of the domain, which includes the high-populated areas of western Los Angeles, San Diego, Ventura and Orange counties. In general, the near-future simulations show a decline in groundwater storage for the region. The largest changes are observed with the RCP8.5 emission pathway, towards to southeastern tier of the study area. In addition to groundwater, this downscaling experiment also generates high-resolution precipitation and temperature estimates, which can help policy makers in the development of strategies to alleviate potential water resource deficiencies in California in the near future.

Climate Change Response of Ocean Net Primary Production (NPP) and Export Production (EP) Regulated by Stratification Increases in The CMIP5 models

NASA Astrophysics Data System (ADS)

Fu, W.; Randerson, J. T.; Moore, J. K.

2014-12-01

Ocean warming due to rising atmospheric CO2 has increasing impacts on ocean ecosystems by modifying the ecophysiology and distribution of marine organisms, and by altering ocean circulation and stratification. We explore ocean NPP and EP changes at the global scale with simulations performed in the framework of the fifth Coupled Model Inter-comparison Project (CMIP5). Global NPP and EP are reduced considerably by the end of the century for the representative concentration pathway (RCP) 8.5 scenario, although models differ in their significantly in their direct temperature impacts on production and remineralization. The Earth system models used here project similar NPP trends albeit the magnitudes vary substantially. In general, projected changes in the 2090s for NPP range between -2.3 to -16.2% while export production reach -7 to -18% relative to 1990s. This is accompanied by increased stratification by 17-30%. Results indicate that globally reduced NPP is closely related to increased ocean stratification (R2=0.78). This is especially the case for global export production, that seems to be mostly controlled by the increased stratification (R2=0.95). We also identify phytoplankton community impacts on these patterns, that vary across the models. The negative response of NPP to climate change may be through bottom-up control, leading to a reduced capacity of oceans to regulate climate through the biological carbon pump. There are large disagreements among the CMIP5 models in terms of simulated nutrient and oxygen concentrations for the 1990s, and their trends over time with climate change. In addition, potentially important marine biogeochemical feedbacks on the climate system were not well represented in the CMIP5 models, including important feedbacks with aerosol deposition and the marine iron cycle, and feedbacks involving the oxygen minimum zones and the marine nitrogen cycle. Thus, these substantial reductions in primary productivity and export production over the 21st century simulated under the RCP 8.5 scenario were likely conservative estimates, and may need to be revised as marine biogeochemistry in Earth System Models (ESMs) continues to be developed.

Global temperature change

PubMed Central

Hansen, James; Sato, Makiko; Ruedy, Reto; Lo, Ken; Lea, David W.; Medina-Elizade, Martin

2006-01-01

Global surface temperature has increased ≈0.2°C per decade in the past 30 years, similar to the warming rate predicted in the 1980s in initial global climate model simulations with transient greenhouse gas changes. Warming is larger in the Western Equatorial Pacific than in the Eastern Equatorial Pacific over the past century, and we suggest that the increased West–East temperature gradient may have increased the likelihood of strong El Niños, such as those of 1983 and 1998. Comparison of measured sea surface temperatures in the Western Pacific with paleoclimate data suggests that this critical ocean region, and probably the planet as a whole, is approximately as warm now as at the Holocene maximum and within ≈1°C of the maximum temperature of the past million years. We conclude that global warming of more than ≈1°C, relative to 2000, will constitute “dangerous” climate change as judged from likely effects on sea level and extermination of species. PMID:17001018

High resolution simulations of aerosol microphysics in a global and regionally nested chemical transport model

NASA Astrophysics Data System (ADS)

Adams, P. J.; Marks, M.

2015-12-01

The aerosol indirect effect is the largest source of forcing uncertainty in current climate models. This effect arises from the influence of aerosols on the reflective properties and lifetimes of clouds, and its magnitude depends on how many particles can serve as cloud droplet formation sites. Assessing levels of this subset of particles (cloud condensation nuclei, or CCN) requires knowledge of aerosol levels and their global distribution, size distributions, and composition. A key tool necessary to advance our understanding of CCN is the use of global aerosol microphysical models, which simulate the processes that control aerosol size distributions: nucleation, condensation/evaporation, and coagulation. Previous studies have found important differences in CO (Chen, D. et al., 2009) and ozone (Jang, J., 1995) modeled at different spatial resolutions, and it is reasonable to believe that short-lived, spatially-variable aerosol species will be similarly - or more - susceptible to model resolution effects. The goal of this study is to determine how CCN levels and spatial distributions change as simulations are run at higher spatial resolution - specifically, to evaluate how sensitive the model is to grid size, and how this affects comparisons against observations. Higher resolution simulations are necessary supports for model/measurement synergy. Simulations were performed using the global chemical transport model GEOS-Chem (v9-02). The years 2008 and 2009 were simulated at 4ox5o and 2ox2.5o globally and at 0.5ox0.667o over Europe and North America. Results were evaluated against surface-based particle size distribution measurements from the European Supersites for Atmospheric Aerosol Research project. The fine-resolution model simulates more spatial and temporal variability in ultrafine levels, and better resolves topography. Results suggest that the coarse model predicts systematically lower ultrafine levels than does the fine-resolution model. Significant differences are also evident with respect to model-measurement comparisons, and will be discussed.

The Ozone Budget in the Upper Troposphere from Global Modeling Initiative (GMI)Simulations

NASA Technical Reports Server (NTRS)

Rodriquez, J.; Duncan, Bryan N.; Logan, Jennifer A.

2006-01-01

Ozone concentrations in the upper troposphere are influenced by in-situ production, long-range tropospheric transport, and influx of stratospheric ozone, as well as by photochemical removal. Since ozone is an important greenhouse gas in this region, it is particularly important to understand how it will respond to changes in anthropogenic emissions and changes in stratospheric ozone fluxes.. This response will be determined by the relative balance of the different production, loss and transport processes. Ozone concentrations calculated by models will differ depending on the adopted meteorological fields, their chemical scheme, anthropogenic emissions, and treatment of the stratospheric influx. We performed simulations using the chemical-transport model from the Global Modeling Initiative (GMI) with meteorological fields from (It)h e NASA Goddard Institute for Space Studies (GISS) general circulation model (GCM), (2) the atmospheric GCM from NASA's Global Modeling and Assimilation Office(GMAO), and (3) assimilated winds from GMAO . These simulations adopt the same chemical mechanism and emissions, and adopt the Synthetic Ozone (SYNOZ) approach for treating the influx of stratospheric ozone -. In addition, we also performed simulations for a coupled troposphere-stratosphere model with a subset of the same winds. Simulations were done for both 4degx5deg and 2degx2.5deg resolution. Model results are being tested through comparison with a suite of atmospheric observations. In this presentation, we diagnose the ozone budget in the upper troposphere utilizing the suite of GMI simulations, to address the sensitivity of this budget to: a) the different meteorological fields used; b) the adoption of the SYNOZ boundary condition versus inclusion of a full stratosphere; c) model horizontal resolution. Model results are compared to observations to determine biases in particular simulations; by examining these comparisons in conjunction with the derived budgets, we may pinpoint deficiencies in the representation of chemical/dynamical processes.

Tracking the global maximum power point of PV arrays under partial shading conditions

NASA Astrophysics Data System (ADS)

Fennich, Meryem

This thesis presents the theoretical and simulation studies of the global maximum power point tracking (MPPT) for photovoltaic systems under partial shading. The main goal is to track the maximum power point of the photovoltaic module so that the maximum possible power can be extracted from the photovoltaic panels. When several panels are connected in series with some of them shaded partially either due to clouds or shadows from neighboring buildings, several local maxima appear in the power vs. voltage curve. A power increment based MPPT algorithm is effective in identifying the global maximum from the several local maxima. Several existing MPPT algorithms are explored and the state-of-the-art power increment method is simulated and tested for various partial shading conditions. The current-voltage and power-voltage characteristics of the PV model are studied under different partial shading conditions, along with five different cases demonstrating how the MPPT algorithm performs when shading switches from one state to another. Each case is supplemented with simulation results. The method of tracking the Global MPP is based on controlling the DC-DC converter connected to the output of the PV array. A complete system simulation including the PV array, the direct current to direct current (DC-DC) converter and the MPPT is presented and tested using MATLAB software. The simulation results show that the MPPT algorithm works very well with the buck converter, while the boost converter needs further changes and implementation.

Preindustrial to Present-Day Changes in Tropospheric Hydroxyl Radical and Methane Lifetime from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)

NASA Technical Reports Server (NTRS)

Naik, V.; Voulgarakis, A.; Fiore, A. M.; Horowitz, L. W.; Lamarque, J.-F.; Lin, M.; Prather, M. J.; Young, P. J.; Bergmann, D.; Cameron-Smith, P. J.;

Global isoprene and monoterpene emissions under changing climate, vegetation, CO2 and land use

NASA Astrophysics Data System (ADS)

Hantson, Stijn; Knorr, Wolfgang; Schurgers, Guy; Pugh, Thomas A. M.; Arneth, Almut

2017-04-01

Plants emit large quantities of isoprene and monoterpenes, the main components of global biogenic volatile organic compound (BVOC) emissions. BVOCs have an important impact on the atmospheric composition of methane, and of short-lived radiative forcing agents (e.g. ozone, aerosols etc.). It is therefore necessary to know how isoprene and monoterpene emissions have changed over the past and how future changes in climate, land-use and other factors will impact them. Here we present emission estimates of isoprene and monoterpenes over the period 1901-2 100 based on the dynamic global vegetation model LPJ-GUESS, including the effects of all known important drivers. We find that both isoprene and monoterpene emissions at the beginning of the 20th century were higher than at present. While anthropogenic land-use change largely drives the global decreasing trend for isoprene over the 20th century, changes in natural vegetation composition caused a decreasing trend for monoterpene emissions. Future global isoprene and monoterpene emissions depend strongly on the climate and land-use scenarios considered. Over the 21st century, global isoprene emissions are simulated to either remain stable (RCP 4.5), or decrease further (RCP 8.5), with important differences depending on the underlying land-use scenario. Future monoterpene emissions are expected to continue their present decreasing trend for all scenarios, possibly stabilizing from 2050 onwards (RCP 4.5). These results demonstrate the importance to take both natural vegetation dynamics and anthropogenic changes in land-use into account when estimating past and future BVOC emissions. They also indicate that a future global increase in BVOC emissions is improbable.

Impact of Geoengineering Schemes on the Global Hydrological Cycle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bala, G; Duffy, P; Taylor, K

2007-12-07

The rapidly rising CO{sub 2} level in the atmosphere has led to proposals of climate stabilization via 'Geoengineering' schemes that would mitigate climate change by intentionally reducing the solar radiation incident on earth's surface. In this paper, we address the impact of these climate stabilization schemes on the global hydrological cycle, using equilibrium simulations from an atmospheric general circulation model coupled to a slab ocean model. We show that insolation reductions sufficient to offset global-scale temperature increases lead to a decrease in the intensity of the global hydrologic cycle. This occurs because solar forcing is more effective in driving changesmore » in global mean evaporation than is CO{sub 2} forcing of a similar magnitude. In the model used here, the hydrologic sensitivity, defined as the percentage change in global mean precipitation per degree warming, is 2.4% for solar forcing, but only 1.5% for CO{sub 2} forcing. Although other models and the climate system itself may differ quantitatively from this result, the conclusion can be understood based on simple considerations of the surface energy budget and thus is likely to be robust. Compared to changing temperature by altering greenhouse gas concentrations, changing temperature by varying insolation results in larger changes in net radiative fluxes at the surface; these are compensated by larger changes in latent and sensible heat fluxes. Hence the hydrological cycle is more sensitive to temperature adjustment via changes in insolation than changes in greenhouse gases. This implies that an alteration in solar forcing might offset temperature changes or hydrological changes from greenhouse warming, but could not cancel both at once.« less

Global upper ocean heat storage response to radiative forcing from changing solar irradiance and increasing greenhouse gas/aerosol concentrations

NASA Astrophysics Data System (ADS)

White, Warren B.; Cayan, Daniel R.; Lean, Judith

1998-09-01

We constructed gridded fields of diabatic heat storage changes in the upper ocean from 20°S to 60°N from historical temperature profiles collected from 1955 to 1996. We filtered these 42 year records for periods of 8 to 15 years and 15 to 30 years, producing depth-weighted vertical average temperature (DVT) changes from the sea surface to the top of the main pycnocline. Basin and global averages of these DVT changes reveal decadal and interdecadal variability in phase across the Indian, Pacific, Atlantic, and Global Oceans, each significantly correlated with changing surface solar radiative forcing at a lag of 0+/-2 years. Decadal and interdecadal changes in global average DVT are 0.06°+/-0.01°K and 0.04°K+/-0.01°K, respectively, the same as those expected from consideration of the Stefan-Boltzmann radiation balance (i.e., 0.3°K per Wm-2) in response to 0.1% changes in surface solar radiative forcing of 0.2 Wm-2 and 0.15 Wm-2, respectively. Global spatial patterns of DVT changes are similar to temperature changes simulated in coupled ocean-atmosphere models, suggesting that natural modes of Earth's variability are phase-locked to the solar irradiance cycle. A trend in global average DVT of 0.15°K over this 42 year record cannot be explained by changing surface solar radiative forcing. But when we consider the 0.5 Wm-2 increase in surface radiative forcing estimated from the increase in atmospheric greenhouse gas and aerosol (GGA) concentrations over this period [Intergovernmental Panel on Climate Change, 1995], the Stefan-Boltzmann radiation balance yields this observed change. Moreover, the sum of solar and GGA surface radiative forcing can explain the relatively sharp increase in global and basin average DVT in the late 1970's.

Linking global-change induced shifts in soil nitrogen cycling with the abundance of key microorganisms

NASA Astrophysics Data System (ADS)

Carey, C.; Eviner, V.; Beman, M.; Hart, S. C.

2013-12-01

Since western colonization, the ecology of California has seen marked transformations. In particular, invasion of terrestrial ecosystems by exotic plants has altered plant community composition, disturbances, soil hydrologic regimes, and nutrient cycling. In addition, as a result of fertilization and combustion of fossil fuels, California experiences some of the highest nitrogen (N) deposition rates in the country. Land use has also changed with the introduction of domestic livestock grazing about 250 years ago. Currently, approximately 32% of land in California experiences grazing pressure. These ecological changes likely affect the ecosystems of California simultaneously. However, with multifactor global change experiments in their infancy, little is known about potential interactive effects on ecosystem structure and function. Our study measured the response of soil N dynamics to a unique combination of treatments: invasion by exotic plants (Aegilops triuncialis and Taeniatherum caput-medusae), elevated N additions, and simulated cattle grazing (aboveground vegetation removal). In addition, we quantified the abundance of key functional genes involved in nitrification (amoA) and denitrification (nirS/nirK) in order to gain a mechanistic insight into changes in ecosystem functioning. We found that, while responses of soil N pools and processes to global change factors tend to be dominated by main effects, interactions among factors can substantially alter the overall response of the ecosystem. For instance, N additions increased potential nitrification and pools of total inorganic N (TIN; NH4+ and NO3-); when N additions and grazing were combined, however, nitrification potentials and TIN decreased to those of ambient N (control) levels. Additionally, neither N additions nor simulated grazing independently affected soil microbial biomass of invaded plots; yet, when combined, the microbial biomass increased significantly. Our results help to provide a better understanding of the regulatory role of the soil microbial community in terrestrial N cycling and also help to improve our understanding of the controls on global change-induced shifts in ecosystem functioning.

Downscaling CESM1 climate change projections for the MENA-CORDEX domain using WRF

NASA Astrophysics Data System (ADS)

Zittis, George; Hadjinicolaou, Panos; Lelieveld, Jos

2017-04-01

According to analysis of observations and global climate model projections, the broader Middle East, North Africa and Mediterranean region is found to be a climate change hotspot. Substantial changes in precipitation amounts and patterns and strong summer warming (including an intensification of heat extremes) is a likely future scenario for the region, but a recent uncertainty analysis indicated good model agreement for temperature but much less for precipitation. Although the horizontal resolution of global models has increased over the last years, it is still not adequate for impact and adaptation assessments of regional or national level and further downscaling of the climate information is required. The region is now studied within the CORDEX initiative (Coordinated Regional Climate Downscaling Experiment) with the establishment of a domain covering the Middle East - North Africa (MENA-CORDEX) region (http://mena-cordex.cyi.ac.cy/). In this study, we present the first climate change projections for the MENA produced by dynamically downscaling a bias-corrected output of the CESM1 global earth system model. For the downscaling, we use a climate configuration of the Weather, Research and Forecasting model (WRF). Our simulations use a standard CORDEX Phase I 50-km grid in three simulations, a historical (1950-2005) and two scenario runs (2006-2100) with the greenhouse gas forcing following the RCP 4.5 and 8.5. We evaluate precipitation, temperature and other surface meteorological variables from the historical using gridded and station observational datasets. Maps of projected changes are constructed for different periods in the future as differences of the two scenarios model output against the data from the historical run. The main spatial and temporal patterns of change are discussed, especially in the context of the United Nations Framework Convention on Climate Change agreement in Paris to limit the global average temperature increase to 1.5 degrees above pre-industrial levels.

The Double ITCZ Syndrome in GCMs: A Coupled Problem among Convection, Atmospheric and Ocean Circulations

NASA Astrophysics Data System (ADS)

Zhang, G. J.; Song, X.

2017-12-01

The double ITCZ bias has been a long-standing problem in coupled atmosphere-ocean models. A previous study indicates that uncertainty in the projection of global warming due to doubling of CO2 is closely related to the double ITCZ biases in global climate models. Thus, reducing the double ITCZ biases is not only important to getting the current climate features right, but also important to narrowing the uncertainty in future climate projection. In this work, we will first review the possible factors contributing to the ITCZ problem. Then, we will focus on atmospheric convection, presenting recent progress in alleviating the double ITCZ problem and its sensitivity to details of convective parameterization, including trigger conditions for convection onset, convective memory, entrainment rate, updraft model and closure in the NCAR CESM1. These changes together can result in dramatic improvements in the simulation of ITCZ. Results based on both atmospheric only and coupled simulations with incremental changes of convection scheme will be shown to demonstrate the roles of convection parameterization and coupled interaction between convection, atmospheric circulation and ocean circulation in the simulation of ITCZ.

An ensemble approach to simulate CO2 emissions from natural fires

NASA Astrophysics Data System (ADS)

Eliseev, A. V.; Mokhov, I. I.; Chernokulsky, A. V.

2014-01-01

This paper presents ensemble simulations with the global climate model developed at the A. M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS CM). These simulations were forced by historical reconstruction of external forcings for 850-2005 AD and by the Representative Concentration Pathways (RCP) scenarios till year 2300. Different ensemble members were constructed by varying the governing parameters of the IAP RAS CM module to simulate natural fires. These members are constrained by the GFED-3.1 observational data set and further subjected to Bayesian averaging. This approach allows to select only changes in fire characteristics which are robust within the constrained ensemble. In our simulations, the present-day (1998-2011 AD) global area burnt due to natural fires is (2.1 ± 0.4) × 106 km2 yr-1 (ensemble means and intra-ensemble standard deviations are presented), and the respective CO2 emissions in the atmosphere are (1.4 ± 0.2) PgC yr-1. The latter value is in agreement with the corresponding observational estimates. Regionally, the model underestimates CO2 emissions in the tropics; in the extra-tropics, it underestimates these emissions in north-east Eurasia and overestimates them in Europe. In the 21st century, the ensemble mean global burnt area is increased by 13% (28%, 36%, 51%) under scenario RCP 2.6 (RCP 4.5, RCP 6.0, RCP 8.5). The corresponding global emissions increase is 14% (29%, 37%, 42%). In the 22nd-23rd centuries, under the mitigation scenario RCP 2.6 the ensemble mean global burnt area and respective CO2 emissions slightly decrease, both by 5% relative to their values in year 2100. Under other RCP scenarios, these variables continue to increase. Under scenario RCP 8.5 (RCP 6.0, RCP 4.5) the ensemble mean burnt area in year 2300 is higher by 83% (44%, 15%) than its value in year 2100, and the ensemble mean CO2 emissions are correspondingly higher by 31% (19%, 9%). All changes of natural fire characteristics in the 21st-23rd centuries are associated mostly with the corresponding changes in boreal regions of Eurasia and North America. However, under the RCP 8.5 scenario, increase of the burnt area and CO2 emissions in boreal regions during the 22nd-23rd centuries are accompanied by the respective decreases in the tropics and subtropics.

Assessing modeled Greenland surface mass balance in the GISS Model E2 and its sensitivity to surface albedo

NASA Astrophysics Data System (ADS)

Alexander, Patrick; LeGrande, Allegra N.; Koenig, Lora S.; Tedesco, Marco; Moustafa, Samiah E.; Ivanoff, Alvaro; Fischer, Robert P.; Fettweis, Xavier

2016-04-01

The surface mass balance (SMB) of the Greenland Ice Sheet (GrIS) plays an important role in global sea level change. Regional Climate Models (RCMs) such as the Modèle Atmosphérique Régionale (MAR) have been employed at high spatial resolution with relatively complex physics to simulate ice sheet SMB. Global climate models (GCMs) incorporate less sophisticated physical schemes and provide outputs at a lower spatial resolution, but have the advantage of modeling the interaction between different components of the earth's oceans, climate, and land surface at a global scale. Improving the ability of GCMs to represent ice sheet SMB is important for making predictions of future changes in global sea level. With the ultimate goal of improving SMB simulated by the Goddard Institute for Space Studies (GISS) Model E2 GCM, we compare simulated GrIS SMB against the outputs of the MAR model and radar-derived estimates of snow accumulation. In order to reproduce present-day climate variability in the Model E2 simulation, winds are constrained to match the reanalysis datasets used to force MAR at the lateral boundaries. We conduct a preliminary assessment of the sensitivity of the simulated Model E2 SMB to surface albedo, a parameter that is known to strongly influence SMB. Model E2 albedo is set to a fixed value of 0.8 over the entire ice sheet in the initial configuration of the model (control case). We adjust this fixed value in an ensemble of simulations over a range of 0.4 to 0.8 (roughly the range of observed summer GrIS albedo values) to examine the sensitivity of ice-sheet-wide SMB to albedo. We prescribe albedo from the Moderate Resolution Imaging Spectroradiometer (MODIS) MCD43A3 v6 to examine the impact of a more realistic spatial and temporal variations in albedo. An age-dependent snow albedo parameterization is applied, and its impact on SMB relative to observations and the RCM is assessed.

Solar Simulated Ultraviolet Radiation Induces Global Histone Hypoacetylation in Human Keratinocytes

PubMed Central

Zhang, Xiaoru; Kluz, Thomas; Gesumaria, Lisa; Matsui, Mary S.; Costa, Max; Sun, Hong

2016-01-01

Ultraviolet radiation (UVR) from sunlight is the primary effector of skin DNA damage. Chromatin remodeling and histone post-translational modification (PTM) are critical factors in repairing DNA damage and maintaining genomic integrity, however, the dynamic changes of histone marks in response to solar UVR are not well characterized. Here we report global changes in histone PTMs induced by solar simulated UVR (ssUVR). A decrease in lysine acetylation of histones H3 and H4, particularly at positions of H3 lysine 9, lysine 56, H4 lysine 5, and lysine 16, was found in human keratinocytes exposed to ssUVR. These acetylation changes were highly associated with ssUVR in a dose-dependent and time-specific manner. Interestingly, H4K16ac, a mark that is crucial for higher order chromatin structure, exhibited a persistent reduction by ssUVR that was transmitted through multiple cell divisions. In addition, the enzymatic activities of histone acetyltransferases were significantly reduced in irradiated cells, which may account for decreased global acetylation. Moreover, depletion of histone deacetylase SIRT1 in keratinocytes rescued ssUVR-induced H4K16 hypoacetylation. These results indicate that ssUVR affects both HDAC and HAT activities, leading to reduced histone acetylation. PMID:26918332

Modeling the imprint of Milankovitch cycles on early Pleistocene ice volume

NASA Astrophysics Data System (ADS)

Roychowdhury, R.; DeConto, R.; Pollard, D.

2017-12-01

Global climate during Quaternary and Late Pliocene (present-3.1 Ma) is characterized by alternating glacial and interglacial conditions. Several proposed theories associate these cycles with variations in the Earth's orbital configuration. In this study, we attempt to address the anomalously strong obliquity forcing in the Late Pliocene/Early Pleistocene ice volume records (41 kyr world), which stands in sharp contrast to the primary cyclicity of insolation, which is at precessional periods (23 kyr). Model results from GCM simulations show that at low eccentricities (e<0.015), the effect of precession is minimal, and the integrated insolation metrics (such as summer metric, PDD, etc.) vary in-phase between the two hemispheres. At higher eccentricities (e>0.015), precessional response is important, and the insolation metrics vary out-of-phase between the two hemispheres. Using simulations from a GCM-driven ice sheet model, we simulate time continuous ice volume changes from Northern and Southern Hemispheres. Under eccentricities lower than 0.015, ice sheets in both hemispheres respond only to obliquity cycle, and grow and melt together (in-phase). If the ice sheet is simulated with eccentricity higher than 0.015, both hemispheres become more sensitive to precessional variation, and vary out-of-phase with each other, which is consistent with proxy observations from the late Pleistocene glaciations. We use the simulated ice volumes from 2.0 to 1.0 ma to empirically calculate global benthic δ18O variations based on the assumption that relationships between collapse and growth of ice-sheets and sea level is linear and symmetric and that the isotopic signature of the individual ice-sheets has not changed with time. Our modeled global benthic δ18O values are broadly consistent with the paleoclimate proxy records such as the LR04 stack.

JULES-crop: a parametrisation of crops in the Joint UK Land Environment Simulator

NASA Astrophysics Data System (ADS)

Osborne, T.; Gornall, J.; Hooker, J.; Williams, K.; Wiltshire, A.; Betts, R.; Wheeler, T.

2014-10-01

Studies of climate change impacts on the terrestrial biosphere have been completed without recognition of the integrated nature of the biosphere. Improved assessment of the impacts of climate change on food and water security requires the development and use of models not only representing each component but also their interactions. To meet this requirement the Joint UK Land Environment Simulator (JULES) land surface model has been modified to include a generic parametrisation of annual crops. The new model, JULES-crop, is described and evaluation at global and site levels for the four globally important crops; wheat, soy bean, maize and rice is presented. JULES-crop demonstrates skill in simulating the inter-annual variations of yield for maize and soy bean at the global level, and for wheat for major spring wheat producing countries. The impact of the new parametrisation, compared to the standard configuration, on the simulation of surface heat fluxes is largely an alteration of the partitioning between latent and sensible heat fluxes during the later part of the growing season. Further evaluation at the site level shows the model captures the seasonality of leaf area index and canopy height better than in standard JULES. However, this does not lead to an improvement in the simulation of sensible and latent heat fluxes. The performance of JULES-crop from both an earth system and crop yield model perspective is encouraging however, more effort is needed to develop the parameterisation of the model for specific applications. Key future model developments identified include the specification of the yield gap to enable better representation of the spatial variability in yield.

Global climate simulations with the A1F1 scenario for 2000-2100: Meltwater, temperature and river flow impacts in India

NASA Astrophysics Data System (ADS)

Erickson, D. J.; Branstetter, M. L.; Wilbanks, T. J.; Ganguly, A. R.; Hoffman, F. M.; King, A. W.; Buja, L.; Panwar, T. S.

2008-05-01

Climate simulations based on the assumptions implicit in the SRES A1F1 scenario for the period 2000-2100 using CCSM3 are analyzed. We find temperature increases of 3-9oC over Northern India by the end of this century. We will discuss the implications and resulting alterations of the hydrologic cycle as the climate evolves from 2000-2100. In particular, we will assess the changes in the surface latent and sensible heat energy budget, the Indian regional water budgets including trends in the timing and duration of the Indian monsoon and the resulting impacts on mean river flow and hydroelectric power generation potential. These analyses will also be examined within the context of heat index, droughts, floods and related estimates of societal robustness and resiliency. We will compare our new insights with the existing literature. Climate simulations based on the SRES A2 and B1 scenarios forced with land cover have indicated increased cloud cover and precipitation, resulting in decreased incident radiation and higher latent heat fluxes, in India during June, July and August by 2050 (Feddema et al., 2005). Analyses of historical records in the context of the Indian Monsoon Rainfall (IMR) have suggested an evolving relation of IMR with natural climate variability caused by El Nino events (Krishna Kumar et al., 2006), studied the combined effects of natural climate variability and global warming (Kripalini et al., 2003) on IMR, as well as demonstrated an increasing trend of extreme rain events in a warming environment (Goswami et al., 2006). In addition, the vulnerability of the Indian agriculture sector to climate change was analyzed and mapped at district-levels by combining with multiple global stressors (O'Brien et al., 2004). [[References::: (1) Feddema, J.J., Oleson, K.W., Bonan, G.B., Mearns, L.O., Buja, L.E., Meehl, G.A., and W.M. Washington (2005): The importance of land-cover change in simulating future climates, Science, 310 (5754): 1674-1678, 9 December.... (2) Goswami, B.N., Venugopal, V., Sengupta, D., Madhusoodanan, and P.K. Xavier (2006): Increasing trend of extreme rain events over India in a warming environment, Science, 314 (5804): 1442-1445, 1 December.... (3) Kripalini, R.H., Kulkarni, A., Sabade, S.S., and M.L. Khandekar (2003): Indian monsoon variability in a global warming scenario, Natural Hazards, 29: 189-206.... (4) Krishna Kumar, M., Rajagolapan, B., Hoerling, M., Bates, G., and M. Cane (2006): Unraveling the mystery of Indian Monsoon failure during El Nino, Science, 314 (5796): 115-119, 6 October.... (5) O'Brien, K., Leichenko, R., Kelkar, U., Venema, H., Aandhal, G., Tompkins, H., Javed, A., Bhadwal, S., Barg, S., Nygaard, L., and J. West (2004): Mapping vulnerability to multiple stressors: climate change and globalization in India, Global Environmental Change, 14: 303-313.

Does extreme precipitation intensity depend on the emissions scenario?

NASA Astrophysics Data System (ADS)

Pendergrass, Angeline; Lehner, Flavio; Sanderson, Benjamin; Xu, Yangyang

2016-04-01

The rate of increase of global-mean precipitation per degree surface temperature increase differs for greenhouse gas and aerosol forcings, and therefore depends on the change in composition of the emissions scenario used to drive climate model simulations for the remainder of the century. We investigate whether or not this is also the case for extreme precipitation simulated by a multi-model ensemble driven by four realistic emissions scenarios. In most models, the rate of increase of maximum annual daily rainfall per degree global warming in the multi-model ensemble is statistically indistinguishable across the four scenarios, whether this extreme precipitation is calculated globally, over all land, or over extra-tropical land. These results indicate that, in most models, extreme precipitation depends on the total amount of warming and does not depend on emissions scenario, in contrast to mean precipitation.

Projected change in global fisheries revenues under climate change

PubMed Central

Lam, Vicky W. Y.; Cheung, William W. L.; Reygondeau, Gabriel; Sumaila, U. Rashid

2016-01-01

Previous studies highlight the winners and losers in fisheries under climate change based on shifts in biomass, species composition and potential catches. Understanding how climate change is likely to alter the fisheries revenues of maritime countries is a crucial next step towards the development of effective socio-economic policy and food sustainability strategies to mitigate and adapt to climate change. Particularly, fish prices and cross-oceans connections through distant water fishing operations may largely modify the projected climate change impacts on fisheries revenues. However, these factors have not formally been considered in global studies. Here, using climate-living marine resources simulation models, we show that global fisheries revenues could drop by 35% more than the projected decrease in catches by the 2050 s under high CO2 emission scenarios. Regionally, the projected increases in fish catch in high latitudes may not translate into increases in revenues because of the increasing dominance of low value fish, and the decrease in catches by these countries’ vessels operating in more severely impacted distant waters. Also, we find that developing countries with high fisheries dependency are negatively impacted. Our results suggest the need to conduct full-fledged economic analyses of the potential economic effects of climate change on global marine fisheries. PMID:27600330

Statistical emulators of maize, rice, soybean and wheat yields from global gridded crop models

DOE PAGES

Blanc, Élodie

2017-01-26

This study provides statistical emulators of crop yields based on global gridded crop model simulations from the Inter-Sectoral Impact Model Intercomparison Project Fast Track project. The ensemble of simulations is used to build a panel of annual crop yields from five crop models and corresponding monthly summer weather variables for over a century at the grid cell level globally. This dataset is then used to estimate, for each crop and gridded crop model, the statistical relationship between yields, temperature, precipitation and carbon dioxide. This study considers a new functional form to better capture the non-linear response of yields to weather,more » especially for extreme temperature and precipitation events, and now accounts for the effect of soil type. In- and out-of-sample validations show that the statistical emulators are able to replicate spatial patterns of yields crop levels and changes overtime projected by crop models reasonably well, although the accuracy of the emulators varies by model and by region. This study therefore provides a reliable and accessible alternative to global gridded crop yield models. By emulating crop yields for several models using parsimonious equations, the tools provide a computationally efficient method to account for uncertainty in climate change impact assessments.« less

Pliocene oceanic seaways and global climate.

PubMed

Karas, Cyrus; Nürnberg, Dirk; Bahr, André; Groeneveld, Jeroen; Herrle, Jens O; Tiedemann, Ralf; deMenocal, Peter B

2017-01-05

Tectonically induced changes in oceanic seaways had profound effects on global and regional climate during the Late Neogene. The constriction of the Central American Seaway reached a critical threshold during the early Pliocene ~4.8-4 million years (Ma) ago. Model simulations indicate the strengthening of the Atlantic Meridional Overturning Circulation (AMOC) with a signature warming response in the Northern Hemisphere and cooling in the Southern Hemisphere. Subsequently, between ~4-3 Ma, the constriction of the Indonesian Seaway impacted regional climate and might have accelerated the Northern Hemisphere Glaciation. We here present Pliocene Atlantic interhemispheric sea surface temperature and salinity gradients (deduced from foraminiferal Mg/Ca and stable oxygen isotopes, δ 18 O) in combination with a recently published benthic stable carbon isotope (δ 13 C) record from the southernmost extent of North Atlantic Deep Water to reconstruct gateway-related changes in the AMOC mode. After an early reduction of the AMOC at ~5.3 Ma, we show in agreement with model simulations of the impacts of Central American Seaway closure a strengthened AMOC with a global climate signature. During ~3.8-3 Ma, we suggest a weakening of the AMOC in line with the global cooling trend, with possible contributions from the constriction of the Indonesian Seaway.

Statistical emulators of maize, rice, soybean and wheat yields from global gridded crop models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blanc, Élodie

This study provides statistical emulators of crop yields based on global gridded crop model simulations from the Inter-Sectoral Impact Model Intercomparison Project Fast Track project. The ensemble of simulations is used to build a panel of annual crop yields from five crop models and corresponding monthly summer weather variables for over a century at the grid cell level globally. This dataset is then used to estimate, for each crop and gridded crop model, the statistical relationship between yields, temperature, precipitation and carbon dioxide. This study considers a new functional form to better capture the non-linear response of yields to weather,more » especially for extreme temperature and precipitation events, and now accounts for the effect of soil type. In- and out-of-sample validations show that the statistical emulators are able to replicate spatial patterns of yields crop levels and changes overtime projected by crop models reasonably well, although the accuracy of the emulators varies by model and by region. This study therefore provides a reliable and accessible alternative to global gridded crop yield models. By emulating crop yields for several models using parsimonious equations, the tools provide a computationally efficient method to account for uncertainty in climate change impact assessments.« less

Impacts on Global Agriculture of Stratospheric Sulfate Injection

NASA Astrophysics Data System (ADS)

Robock, A.; Xia, L.

2014-12-01

Impacts on global food supply are one of the most important concerns in the discussion of stratospheric sulfate geoengineering. Stratospheric sulfate injection could reduce surface temperature, precipitation, and insolation, which could affect agricultural production. We use output from climate model simulations using the two most "realistic" scenarios from the Geoengineering Model Intercomparison Project, G3 and G4. G3 posits balancing the increasing radiative forcing from the RCP4.5 business-as-usual scenario with stratospheric sulfate aerosols from 2020 through 2070. The G4 scenario also uses RCP4.5, but models simulate the stratospheric injection of 5 Tg SO2 per year from 2020 to 2070. In total, there are three modeling groups which have completed G3 and four for G4. We use two crop models, the global gridded Decision Support System for Agrotechnology Transfer (gDSSAT) crop model and the crop model in the NCAR Community Land Model (CLM-crop), to predict global maize yield changes. Without changing agricultural technology, we find that compared to the reference run forced by the RCP4.5 scenario, maize yields could increase in both G3 and G4 due to both the cooling effect of stratospheric sulfate injection and the CO2 fertilization effect, with the cooling effect contributing more to the increased productivity. However, the maize yield changes are not much larger than natural variability under G3, since the temperature reduction is smaller in G3 than in G4. Both crop models show similar results.

Germination shifts of C3 and C4 species under simulated global warming scenario.

PubMed

Zhang, Hongxiang; Yu, Qiang; Huang, Yingxin; Zheng, Wei; Tian, Yu; Song, Yantao; Li, Guangdi; Zhou, Daowei

2014-01-01

Research efforts around the world have been increasingly devoted to investigating changes in C3 and C4 species' abundance or distribution with global warming, as they provide important insight into carbon fluxes and linked biogeochemical cycles. However, changes in the early life stage (e.g. germination) of C3 and C4 species in response to global warming, particularly with respect to asymmetric warming, have received less attention. We investigated germination percentage and rate of C3 and C4 species under asymmetric (+3/+6°C at day/night) and symmetric warming (+5/+5°C at day/night), simulated by alternating temperatures. A thermal time model was used to calculate germination base temperature and thermal time constant. Two additional alternating temperature regimes were used to test temperature metrics effect. The germination percentage and rate increased continuously for C4 species, but increased and then decreased with temperature for C3 species under both symmetric and asymmetric warming. Compared to asymmetric warming, symmetric warming significantly overestimated the speed of germination percentage change with temperature for C4 species. Among the temperature metrics (minimum, maximum, diurnal temperature range and average temperature), maximum temperature was most correlated with germination of C4 species. Our results indicate that global warming may favour germination of C4 species, at least for the C4 species studied in this work. The divergent effects of asymmetric and symmetric warming on plant germination also deserve more attention in future studies.

Trend of surface solar radiation over Asia simulated by aerosol transport-climate model

NASA Astrophysics Data System (ADS)

Takemura, T.; Ohmura, A.

2009-12-01

Long-term records of surface radiation measurements indicate a decrease in the solar radiation between the 1950s and 1980s (“global dimming”), then its recovery afterward (“global brightening”) at many locations all over the globe [Wild, 2009]. On the other hand, the global brightening is delayed over the Asian region [Ohmura, 2009]. It is suggested that these trends of the global dimming and brightening are strongly related with a change in aerosol loading in the atmosphere which affect the climate change through the direct, semi-direct, and indirect effects. In this study, causes of the trend of the surface solar radiation over Asia during last several decades are analyzed with an aerosol transport-climate model, SPRINTARS. SPRINTARS is coupled with MIROC which is a general circulation model (GCM) developed by Center for Climate System Research (CCSR)/University of Tokyo, National Institute for Environmental Studies (NIES), and Frontier Research Center for Global Change (FRCGC) [Takemura et al., 2000, 2002, 2005, 2009]. The horizontal and vertical resolutions are T106 (approximately 1.1° by 1.1°) and 56 layers, respectively. SPRINTARS includes the transport, radiation, cloud, and precipitation processes of all main tropospheric aerosols (black and organic carbons, sulfate, soil dust, and sea salt). The model treats not only the aerosol mass mixing ratios but also the cloud droplet and ice crystal number concentrations as prognostic variables, and the nucleation processes of cloud droplets and ice crystals depend on the number concentrations of each aerosol species. Changes in the cloud droplet and ice crystal number concentrations affect the cloud radiation and precipitation processes in the model. Historical emissions, that is consumption of fossil fuel and biofuel, biomass burning, aircraft emissions, and volcanic eruptions are prescribed from database provided by the Aerosol Model Intercomparison Project (AeroCom) and the latest IPCC inventories. Continuous hindcast simulation during the last several decades is done to compare with surface radiation measurements. Cause of the global dimming and brightening is separated into the aerosol direct and indirect effects from the simulation. Acknowledgments. The simulation in this study was performed on the NIES supercomputer system (NEC SX-8R). This study is partly supported by the Global Environment Research Fund (RF-091) by the Ministry of the Environment of Japan, Grant-in-Aid for Young Scientist (21681001) by the Ministry of Education, Culture, Sports, Science, and Technology of Japan, and Mitsui & Co., Ltd. Environment Fund (R08-D035). References Ohmura, A. (2009), J. Geophys. Res., 114, doi:10.1029/2008JD011290. Takemura, T., et al. (2000), J. Geophys. Res., 105, 17853-17873. Takemura, T., et al. (2002), J. Climate, 15, 333-352. Takemura, T., et al. (2005), J. Geophys. Res., 110, doi:10.1029/2004JD005029. Takemura, T., et al. (2009), Atmos. Chem. Phys., 9, 3061-3073. Wild, M. (2009), J. Geophys. Res., 114, doi:10.1029/2008JD011470.

Global terrestrial N2O budget for present and future

NASA Astrophysics Data System (ADS)

Olin, Stefan; Xing, Xu-Ri; Wårlind, David; Eliasson, Peter; Smith, Ben; Arneth, Almut

2017-04-01

Nitrogen (N) plays an important role in plant productivity and physiology and is the main limiting nutrient in a majority of the terrestrial ecosystems. The enhanced input of anthropogenic reactive nitrogen (Nr) in agriculture have enhanced global food production, but with adverse effects on biodiversity and water quality, and substantially increased emissions of N trace gases that affect air quality and climate. Emissions of N gases affects the climate, either through cloud forming nitrogen oxides (NOx) gases or as greenhouse gases, where nitrous oxide (N2O) is the most important being approximately 300 times more potent than carbon dioxide (CO2). In this study we use the process-based global vegetation model Lund-Potsdam-Jena General Ecosystem Simulator (LPJ-GUESS) (Olin et al. 2015) that recently have incorporated a new soil N transformation scheme, adopted from Xu-Ri and Prentice (2008), which makes it possible to study the N2O emission respond to changes in climate and CO2 concentration as well as anthropogenic N enhancements on a global scale. We present here results from the validation of the new model against site-scale N2O measurements from agricultural and non-agricultural ecosystems. We will also present results from a study to examine how land use, land use change and anthropogenic N fertilisation influence historical and future global N2O emissions. This new development represents a key component within future projects in CMIP6 (LUMIP) and in EC-Earth for the EU Horizon 2020 project CRESCENDO. Olin, S., Lindeskog, M., Pugh, T., Schurgers, G., Mischurow, M., Wårlind, D., Zaehle, S., Stocker, B., Smith, B. and Arneth, A. 2015. Soil carbon management in large-scale Earth system modelling: implications for crop yields and nitrogen leaching. Earth System Dynamics, 6, 745-768. Xu-Ri and Prentice IC. 2008. Terrestrial nitrogen cycle simulation with a dynamic global vegetation model. Global Change Biology, 14, 1745-1764.

Risk Assessment in Relation to the Effect of Climate Change on Water Shortage in the Taichung Area

NASA Astrophysics Data System (ADS)

Hsiao, J.; Chang, L.; Ho, C.; Niu, M.

2010-12-01

Rapid economic development has stimulated a worldwide greenhouse effect and induced global climate change. Global climate change has increased the range of variation in the quantity of regional river flows between wet and dry seasons, which effects the management of regional water resources. Consequently, the influence of climate change has become an important issue in the management of regional water resources. In this study, the Monte Carlo simulation method was applied to risk analysis of shortage of water supply in the Taichung area. This study proposed a simulation model that integrated three models: weather generator model, surface runoff model, and water distribution model. The proposed model was used to evaluate the efficiency of the current water supply system and the potential effectiveness of two additional plans for water supply: the “artificial lakes” plan and the “cross-basin water transport” plan. A first-order Markov Chain method and two probability distribution models, exponential distribution and normal distribution, were used in the weather generator model. In the surface runoff model, researchers selected the Generalized Watershed Loading Function model (GWLF) to simulate the relationship between quantity of rainfall and basin outflow. A system dynamics model (SD) was applied to the water distribution model. Results of the simulation indicated that climate change could increase the annual quantity of river flow in the Dachia River and Daan River basins. However, climate change could also increase the difference in the quantity of river flow between wet and dry seasons. Simulation results showed that in current system case or in the additional plan cases, shortage status of water for both public and agricultural uses with conditions of climate change will be mostly worse than that without conditions of climate change except for the shortage status for the public use in the current system case. With or without considering the effect of climate change, the additional plans, especially the “cross-basin water transport” plan, for water supply could significantly increase the supply of water for public use. The proposed simulation model and results of analysis in this study could provide valuable reference for decision-makers in regards to risk analysis of regional water supply.

Modulation of Heavy Rainfall in the Middle East and North Africa by Madden-Julian Oscillation Using High Resolution Atmospheric General Circulation Model

NASA Astrophysics Data System (ADS)

Deng, L.; Stenchikov, G. L.; McCabe, M. F.; Bangalath, H. K.

2014-12-01

Recently, the modulation of subtropical rainfall by the dominant tropical intraseasonal signal of the Madden-Julian Oscillation (MJO), has been explored through the discussion of the MJO-convection-induced Kelvin and Rossby wave related teleconnection patterns. Our study focuses on characterizing the modulation of heavy rainfall in the Middle East and North Africa (MENA) region by the MJO, using the Geophysical Fluid Dynamics Laboratory (GFDL) global High Resolution Atmospheric Model (HIRAM) simulations (25-km; 1979-2012) and a combination of available atmospheric products from satellite, in-situ and reanalysis data. The observed Hadley Centre Global Sea Ice and Sea Surface Temperature (HadISST) and the simulated SST from GFDL's global coupled carbon-climate Earth System Models (ESM2M) are employed in HIRAM to investigate the sensitivity of the simulated heavy rainfall and MJO to SST. The future trend of the extreme rainfalls and their links to the MJO response to climate change are examined using HIRAM simulations of 2012-2050 with the RCP4.5 and RCP 8.5 scenarios to advance the possibility of characterization and forecasting of future extreme rainfall events in the MENA region.

Synergistic Ecoclimate Teleconnections from Forest Loss in Different Regions Structure Global Ecological Responses

PubMed Central

Garcia, Elizabeth S.; Swann, Abigail L. S.; Villegas, Juan C.; Breshears, David D.; Law, Darin J.; Saleska, Scott R.; Stark, Scott C.

2016-01-01

Forest loss in hotspots around the world impacts not only local climate where loss occurs, but also influences climate and vegetation in remote parts of the globe through ecoclimate teleconnections. The magnitude and mechanism of remote impacts likely depends on the location and distribution of forest loss hotspots, but the nature of these dependencies has not been investigated. We use global climate model simulations to estimate the distribution of ecologically-relevant climate changes resulting from forest loss in two hotspot regions: western North America (wNA), which is experiencing accelerated dieoff, and the Amazon basin, which is subject to high rates of deforestation. The remote climatic and ecological net effects of simultaneous forest loss in both regions differed from the combined effects of loss from the two regions simulated separately, as evident in three impacted areas. Eastern South American Gross Primary Productivity (GPP) increased due to changes in seasonal rainfall associated with Amazon forest loss and changes in temperature related to wNA forest loss. Eurasia’s GPP declined with wNA forest loss due to cooling temperatures increasing soil ice volume. Southeastern North American productivity increased with simultaneous forest loss, but declined with only wNA forest loss due to changes in VPD. Our results illustrate the need for a new generation of local-to-global scale analyses to identify potential ecoclimate teleconnections, their underlying mechanisms, and most importantly, their synergistic interactions, to predict the responses to increasing forest loss under future land use change and climate change. PMID:27851740

Synergistic Ecoclimate Teleconnections from Forest Loss in Different Regions Structure Global Ecological Responses

DOE PAGES

Garcia, Elizabeth S.; Swann, Abigail L. S.; Villegas, Juan C.; ...

2016-11-16

Forest loss in hotspots around the world impacts not only local climate where loss occurs, but also influences climate and vegetation in remote parts of the globe through ecoclimate teleconnections. The magnitude and mechanism of remote impacts likely depends on the location and distribution of forest loss hotspots, but the nature of these dependencies has not been investigated. We use global climate model simulations to estimate the distribution of ecologically-relevant climate changes resulting from forest loss in two hotspot regions: western North America (wNA), which is experiencing accelerated dieoff, and the Amazon basin, which is subject to high rates ofmore » deforestation. The remote climatic and ecological net effects of simultaneous forest loss in both regions differed from the combined effects of loss from the two regions simulated separately, as evident in three impacted areas. Eastern South American Gross Primary Productivity (GPP) increased due to changes in seasonal rainfall associated with Amazon forest loss and changes in temperature related to wNA forest loss. Eurasia's GPP declined with wNA forest loss due to cooling temperatures increasing soil ice volume. Southeastern North American productivity increased with simultaneous forest loss, but declined with only wNA forest loss due to changes in VPD. In conclusion, our results illustrate the need for a new generation of local-to-global scale analyses to identify potential ecoclimate teleconnections, their underlying mechanisms, and most importantly, their synergistic interactions, to predict the responses to increasing forest loss under future land use change and climate change.« less

A Web-Based Modelling Platform for Interactive Exploration of Regional Responses to Global Change

NASA Astrophysics Data System (ADS)

Holman, I.

2014-12-01

Climate change adaptation is a complex human-environmental problem that is framed by the uncertainty in impacts and the adaptation choices available, but is also bounded by real-world constraints such as future resource availability and environmental and institutional capacities. Educating the next generation of informed decision-makers that will be able to make knowledgeable responses to global climate change impacts requires them to have access to information that is credible, accurate, easy to understand, and appropriate. However, available resources are too often produced by inaccessible models for scenario simulations chosen by researchers hindering exploration and enquiry. This paper describes the interactive exploratory web-based CLIMSAVE Integrated Assessment (IA) Platform (www.climsave.eu/iap) that aims to democratise climate change impacts, adaptation and vulnerability modelling. The regional version of the Platform contain linked simulation models (of the urban, agriculture, forestry, water and biodiversity sectors), probabilistic climate scenarios and socio-economic scenarios, that enable users to select their inputs (climate and socioeconomic), rapidly run the models using their input variable settings and view their chosen outputs. The interface of the CLIMSAVE IA Platform is designed to facilitate a two-way iterative process of dialogue and exploration of "what if's" to enable a wide range of users to improve their understanding surrounding impacts, adaptation responses and vulnerability of natural resources and ecosystem services under uncertain futures. This paper will describe the evolution of the Platform and demonstrate how using its holistic framework (multi sector / ecosystem service; cross-sectoral, climate and socio-economic change) will help to assist learning around the challenging concepts of responding to global change.

Synergistic Ecoclimate Teleconnections from Forest Loss in Different Regions Structure Global Ecological Responses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcia, Elizabeth S.; Swann, Abigail L. S.; Villegas, Juan C.

Forest loss in hotspots around the world impacts not only local climate where loss occurs, but also influences climate and vegetation in remote parts of the globe through ecoclimate teleconnections. The magnitude and mechanism of remote impacts likely depends on the location and distribution of forest loss hotspots, but the nature of these dependencies has not been investigated. We use global climate model simulations to estimate the distribution of ecologically-relevant climate changes resulting from forest loss in two hotspot regions: western North America (wNA), which is experiencing accelerated dieoff, and the Amazon basin, which is subject to high rates ofmore » deforestation. The remote climatic and ecological net effects of simultaneous forest loss in both regions differed from the combined effects of loss from the two regions simulated separately, as evident in three impacted areas. Eastern South American Gross Primary Productivity (GPP) increased due to changes in seasonal rainfall associated with Amazon forest loss and changes in temperature related to wNA forest loss. Eurasia's GPP declined with wNA forest loss due to cooling temperatures increasing soil ice volume. Southeastern North American productivity increased with simultaneous forest loss, but declined with only wNA forest loss due to changes in VPD. In conclusion, our results illustrate the need for a new generation of local-to-global scale analyses to identify potential ecoclimate teleconnections, their underlying mechanisms, and most importantly, their synergistic interactions, to predict the responses to increasing forest loss under future land use change and climate change.« less

Evaluating the Effects of Climate Change on Summertime Ozone using a Relative Response Factor approach for Policy Makers

EPA Science Inventory

The impact of climate change on surface level ozone is examined through a multi-scale modeling effort that linked global and regional climate models to drive air quality model simulations. Results are quantified in terms of the Relative Response Factor (RRF_E), which es...

A new climate dataset for systematic assessments of climate change impacts as a function of global warming

NASA Astrophysics Data System (ADS)

Heinke, J.; Ostberg, S.; Schaphoff, S.; Frieler, K.; Müller, C.; Gerten, D.; Meinshausen, M.; Lucht, W.

2013-10-01

In the ongoing political debate on climate change, global mean temperature change (ΔTglob) has become the yardstick by which mitigation costs, impacts from unavoided climate change, and adaptation requirements are discussed. For a scientifically informed discourse along these lines, systematic assessments of climate change impacts as a function of ΔTglob are required. The current availability of climate change scenarios constrains this type of assessment to a narrow range of temperature change and/or a reduced ensemble of climate models. Here, a newly composed dataset of climate change scenarios is presented that addresses the specific requirements for global assessments of climate change impacts as a function of ΔTglob. A pattern-scaling approach is applied to extract generalised patterns of spatially explicit change in temperature, precipitation and cloudiness from 19 Atmosphere-Ocean General Circulation Models (AOGCMs). The patterns are combined with scenarios of global mean temperature increase obtained from the reduced-complexity climate model MAGICC6 to create climate scenarios covering warming levels from 1.5 to 5 degrees above pre-industrial levels around the year 2100. The patterns are shown to sufficiently maintain the original AOGCMs' climate change properties, even though they, necessarily, utilise a simplified relationships between ΔTglob and changes in local climate properties. The dataset (made available online upon final publication of this paper) facilitates systematic analyses of climate change impacts as it covers a wider and finer-spaced range of climate change scenarios than the original AOGCM simulations.

A new dataset for systematic assessments of climate change impacts as a function of global warming

NASA Astrophysics Data System (ADS)

Heinke, J.; Ostberg, S.; Schaphoff, S.; Frieler, K.; M{ü}ller, C.; Gerten, D.; Meinshausen, M.; Lucht, W.

2012-11-01

In the ongoing political debate on climate change, global mean temperature change (ΔTglob) has become the yardstick by which mitigation costs, impacts from unavoided climate change, and adaptation requirements are discussed. For a scientifically informed discourse along these lines systematic assessments of climate change impacts as a function of ΔTglob are required. The current availability of climate change scenarios constrains this type of assessment to a~narrow range of temperature change and/or a reduced ensemble of climate models. Here, a newly composed dataset of climate change scenarios is presented that addresses the specific requirements for global assessments of climate change impacts as a function of ΔTglob. A pattern-scaling approach is applied to extract generalized patterns of spatially explicit change in temperature, precipitation and cloudiness from 19 AOGCMs. The patterns are combined with scenarios of global mean temperature increase obtained from the reduced-complexity climate model MAGICC6 to create climate scenarios covering warming levels from 1.5 to 5 degrees above pre-industrial levels around the year 2100. The patterns are shown to sufficiently maintain the original AOGCMs' climate change properties, even though they, necessarily, utilize a simplified relationships betweenΔTglob and changes in local climate properties. The dataset (made available online upon final publication of this paper) facilitates systematic analyses of climate change impacts as it covers a wider and finer-spaced range of climate change scenarios than the original AOGCM simulations.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Glotfelty, Timothy; Zhang, Yang; Karamchandani, Prakash

The prospect of global climate change will have wide scale impacts, such as ecological stress and human health hazards. One aspect of concern is future changes in air quality that will result from changes in both meteorological forcing and air pollutant emissions. In this study, the GU-WRF/Chem model is employed to simulate the impact of changing climate and emissions following the IPCC AR4 SRES A1B scenario. An average of 4 future years (2020, 2030, 2040, and 2050) is compared against an average of 2 current years (2001 and 2010). Under this scenario, by the Mid-21st century global air quality ismore » projected to degrade with a global average increase of 2.5 ppb in the maximum 8-hr O 3 level and of 0.3 mg m 3 in 24-hr average PM2.5. However, PM2.5 changes are more regional due to regional variations in primary aerosol emissions and emissions of gaseous precursor for secondary PM2.5. Increasing NOx emissions in this scenario combines with a wetter climate elevating levels of OH, HO 2, H 2O 2, and the nitrate radical and increasing the atmosphere’s near surface oxidation state. This differs from findings under the RCP scenarios that experience declines in OH from reduced NOx emissions, stratospheric recovery of O 3, and increases in CH 4 and VOCs. Increasing NO x and O 3 levels enhances the nitrogen and O 3 deposition, indicating potentially enhanced crop damage and ecosystem stress under this scenario. The enhanced global aerosol level results in enhancements in aerosol optical depth, cloud droplet number concentration, and cloud optical thickness. This leads to dimming at the Earth’s surface with a global average reduction in shortwave radiation of 1.2 W m 2 . This enhanced dimming leads to a more moderate warming trend and different trends in radiation than those found in NCAR’s CCSM simulation, which does not include the advanced chemistry and aerosol treatment of GU-WRF/Chem and cannot simulate the impacts of changing climate and emissions with the same level of detailed treatments. This study indicates that effective climate mitigation and emission control strategies are needed to prevent future health impact and ecosystem stress. Further, studies that are used to develop these strategies should use fully coupled models with sophisticated chemical and aerosol-interaction treatments that can provide a more realistic representation of the atmosphere.« less

A Semi-empirical Model of the Stratosphere in the Climate System

NASA Astrophysics Data System (ADS)

Sodergren, A. H.; Bodeker, G. E.; Kremser, S.; Meinshausen, M.; McDonald, A.

2014-12-01

Chemistry climate models (CCMs) currently used to project changes in Antarctic ozone are extremely computationally demanding. CCM projections are uncertain due to lack of knowledge of future emissions of greenhouse gases (GHGs) and ozone depleting substances (ODSs), as well as parameterizations within the CCMs that have weakly constrained tuning parameters. While projections should be based on an ensemble of simulations, this is not currently possible due to the complexity of the CCMs. An inexpensive but realistic approach to simulate changes in stratospheric ozone, and its coupling to the climate system, is needed as a complement to CCMs. A simple climate model (SCM) can be used as a fast emulator of complex atmospheric-ocean climate models. If such an SCM includes a representation of stratospheric ozone, the evolution of the global ozone layer can be simulated for a wide range of GHG and ODS emissions scenarios. MAGICC is an SCM used in previous IPCC reports. In the current version of the MAGICC SCM, stratospheric ozone changes depend only on equivalent effective stratospheric chlorine (EESC). In this work, MAGICC is extended to include an interactive stratospheric ozone layer using a semi-empirical model of ozone responses to CO2and EESC, with changes in ozone affecting the radiative forcing in the SCM. To demonstrate the ability of our new, extended SCM to generate projections of global changes in ozone, tuning parameters from 19 coupled atmosphere-ocean general circulation models (AOGCMs) and 10 carbon cycle models (to create an ensemble of 190 simulations) have been used to generate probability density functions of the dates of return of stratospheric column ozone to 1960 and 1980 levels for different latitudes.

Dynamic Biological Functioning Important for Simulating and Stabilizing Ocean Biogeochemistry

NASA Astrophysics Data System (ADS)

Buchanan, P. J.; Matear, R. J.; Chase, Z.; Phipps, S. J.; Bindoff, N. L.

2018-04-01

The biogeochemistry of the ocean exerts a strong influence on the climate by modulating atmospheric greenhouse gases. In turn, ocean biogeochemistry depends on numerous physical and biological processes that change over space and time. Accurately simulating these processes is fundamental for accurately simulating the ocean's role within the climate. However, our simulation of these processes is often simplistic, despite a growing understanding of underlying biological dynamics. Here we explore how new parameterizations of biological processes affect simulated biogeochemical properties in a global ocean model. We combine 6 different physical realizations with 6 different biogeochemical parameterizations (36 unique ocean states). The biogeochemical parameterizations, all previously published, aim to more accurately represent the response of ocean biology to changing physical conditions. We make three major findings. First, oxygen, carbon, alkalinity, and phosphate fields are more sensitive to changes in the ocean's physical state. Only nitrate is more sensitive to changes in biological processes, and we suggest that assessment protocols for ocean biogeochemical models formally include the marine nitrogen cycle to assess their performance. Second, we show that dynamic variations in the production, remineralization, and stoichiometry of organic matter in response to changing environmental conditions benefit the simulation of ocean biogeochemistry. Third, dynamic biological functioning reduces the sensitivity of biogeochemical properties to physical change. Carbon and nitrogen inventories were 50% and 20% less sensitive to physical changes, respectively, in simulations that incorporated dynamic biological functioning. These results highlight the importance of a dynamic biology for ocean properties and climate.

The biogeophysical climatic impacts of anthropogenic land use change during the Holocene

NASA Astrophysics Data System (ADS)

Smith, M. C.; Singarayer, J. S.; Valdes, P. J.; Kaplan, J. O.; Branch, N. P.

2015-10-01

The first agricultural societies were established around 10 ka BP and had spread across much of Europe and southern Asia by 5.5 ka BP with resultant anthropogenic deforestation for crop and pasture land. Various studies have attempted to assess the biogeochemical implications for Holocene climate in terms of increased carbon dioxide and methane emissions. However, less work has been done to examine the biogeophysical impacts of this early land use change. In this study, global climate model simulations with HadCM3 were used to examine the biogeophysical effects of Holocene land cover change on climate, both globally and regionally, from the early Holocene (8 ka BP) to the early industrial era (1850 CE). Two experiments were performed with alternative descriptions of past vegetation: (i) potential natural vegetation simulated by TRIFFID but no land-use changes, and (ii) where the anthropogenic land use model, KK10 (Kaplan et al., 2009, 2011) has been used to set the HadCM3 crop regions. Snapshot simulations have been run at 1000 year intervals to examine when the first signature of anthropogenic climate change can be detected both regionally, in the areas of land use change, and globally. Results indicate that in regions of early land disturbance such as Europe and S.E. Asia detectable temperature changes, outside the normal range of variability, are encountered in the model as early as 7 ka BP in the June/July/August (JJA) season and throughout the entire annual cycle by 2-3 ka BP. Areas outside the regions of land disturbance are also affected, with virtually the whole globe experiencing significant temperature changes (predominantly cooling) by the early industrial period. Large-scale precipitation features such as the Indian monsoon, the intertropical convergence zone (ITCZ), and the North Atlantic storm track are also impacted by local land use and remote teleconnections. We investigated how advection by surface winds, mean sea level pressure (MSLP) anomalies, and tropospheric stationary wave train disturbances in the mid- to high-latitudes led to remote teleconnections.

RCP4.5: A Pathway for Stabilization of Radiative Forcing by 2100

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomson, Allison M.; Calvin, Katherine V.; Smith, Steven J.

2011-07-29

Representative Concentration Pathway (RCP) 4.5 is a scenario that stabilizes radiative forcing at 4.5 W m{sup -2} in the year 2100 without ever exceeding that value. Simulated with the Global Change Assessment Model (GCAM), RCP4.5 includes long-term, global emissions of greenhouse gases, short-lived species, and land-use-land-cover in a global economic framework. RCP4.5 was updated from earlier GCAM scenarios to incorporate historical emissions and land cover information common to the RCP process and follows a cost-minimizing pathway to reach the target radiative forcing. The imperative to limit emissions in order to reach this target drives changes in the energy system, includingmore » shifts to electricity, to lower emissions energy technologies and to the deployment of carbon capture and geologic storage technology. In addition, the RCP4.5 emissions price also applies to land use emissions; as a result, forest lands expand from their present day extent. The simulated future emissions and land use were downscaled from the regional simulation to a grid to facilitate transfer to climate models. While there are many alternative pathways to achieve a radiative forcing level of 4.5 W m{sup -2}, the application of the RCP4.5 provides a common platform for climate models to explore the climate system response to stabilizing the anthropogenic components of radiative forcing.« less

Rapid Ice-Sheet Changes and Mechanical Coupling to Solid-Earth/Sea-Level and Space Geodetic Observation

NASA Astrophysics Data System (ADS)

Adhikari, S.; Ivins, E. R.; Larour, E. Y.

2015-12-01

Perturbations in gravitational and rotational potentials caused by climate driven mass redistribution on the earth's surface, such as ice sheet melting and terrestrial water storage, affect the spatiotemporal variability in global and regional sea level. Here we present a numerically accurate, computationally efficient, high-resolution model for sea level. Unlike contemporary models that are based on spherical-harmonic formulation, the model can operate efficiently in a flexible embedded finite-element mesh system, thus capturing the physics operating at km-scale yet capable of simulating geophysical quantities that are inherently of global scale with minimal computational cost. One obvious application is to compute evolution of sea level fingerprints and associated geodetic and astronomical observables (e.g., geoid height, gravity anomaly, solid-earth deformation, polar motion, and geocentric motion) as a companion to a numerical 3-D thermo-mechanical ice sheet simulation, thus capturing global signatures of climate driven mass redistribution. We evaluate some important time-varying signatures of GRACE inferred ice sheet mass balance and continental hydrological budget; for example, we identify dominant sources of ongoing sea-level change at the selected tide gauge stations, and explain the relative contribution of different sources to the observed polar drift. We also report our progress on ice-sheet/solid-earth/sea-level model coupling efforts toward realistic simulation of Pine Island Glacier over the past several hundred years.

The Pilot Phase of the Global Soil Wetness Project Phase 3

NASA Astrophysics Data System (ADS)

Kim, H.; Oki, T.

2015-12-01

After the second phase of the Global Soil Wetness Project (GSWP2) as an early global continuous gridded multi-model analysis, a comprehensive set of land surface fluxes and state variables became available. It has been broadly utilized in the hydrology community, and its success has evolved to take advantages of recent scientific progress and to extend the relatively short time span (1986-1995) of the previous project. In the third phase proposed here (GSWP3), an extensive set of quantities for hydro-energy-eco systems will be produced to investigate their long-term (1901-2010) changes. The energy-water-carbon cycles and their interactions are also examined subcomponent-wise with appropriate model verifications in ensemble land simulations. In this study, the preliminary results and problems found from the first round analysis of the GSWP3 pilot study are shown. Also, it is discussed how the global offline simulation activity contributes to wider communities and a bigger scope such as Climate Model Intercomparison Project Phase 6 (CMIP6).

Impacts of Stratospheric Sulfate Geoengineering on PM2.5

NASA Astrophysics Data System (ADS)

Robock, A.; Xia, L.; Tilmes, S.; Mills, M. J.; Richter, J.; Kravitz, B.; MacMartin, D.

2017-12-01

Particulate matter (PM) includes sulfate, nitrate, organic carbon, elemental carbon, soil dust, and sea salt. The first four components are mostly present near the ground as fine particulate matter with a diameter less than 2.5 µm (PM2.5), and these are of the most concern for human health. PM is efficiently scavenged by precipitation, which is its main atmospheric sink. Here we examine the impact of stratospheric climate engineering on this important pollutant and health risk, taking advantage of two sets of climate model simulations conducted at the National Center for Atmospheric Research. We use the full tropospheric and stratospheric chemistry version of the Community Earth System Model - Community Atmospheric Model 4 (CESM CAM4-chem) with a horizontal resolution of 0.9° x 1.25° lat-lon to simulate a stratospheric sulfate injection climate intervention of 8 Tg SO2 yr-1 combined with an RCP6.0 global warming forcing, the G4 Specified Stratospheric Aerosol (G4SSA) scenario. We also analyze the output from a 20-member ensemble of Community Earth System Model, version 1 with the Whole Atmosphere Community Climate Model as its atmospheric component (CESM1(WACCM)) simulations, also at 0.9° x 1.25° lat-lon resolution, with sulfur dioxide injection at 15°N, 15°S, 30°N, and 30°S varying in time to balance RCP8.5 forcing. While the CESM CAM4-chem model has full tropospheric and stratospheric chemistry, CESM1(WACCM) has an internally generated quasi-biennial oscillation and a comprehensive tropospheric and stratospheric sulfate aerosol treatment, but only stratospheric chemistry. For G4SSA, there are a global temperature reduction of 0.8 K and global averaged precipitation decrease of 3% relative to RCP6.0. The global averaged surface PM2.5 reduces about 1% compared with RCP6.0, mainly over Eurasian and East Asian regions in Northern Hemisphere winter. The PM2.5 concentration change is a combination of effects from tropospheric chemistry and precipitation changes. We compare those changes to the impacts from the CESM1(WACCM) simulations.

A Randomized Trial Evaluating Child Dog-Bite Prevention in Rural China through Video-Based Testimonials

PubMed Central

Shen, Jiabin; Pang, Shulan; Schwebel, David C.

2015-01-01

Objective Dog-bite injuries pose significant threat to children globally. School-aged children are especially at risk because of their cognitively immature tendency toward low perceived vulnerability to bites, and this risk is elevated further for school-aged children living in rural China due to the large number of stray dogs, all potential rabies carriers, present in their communities. Methods This randomized controlled trial evaluated whether viewing an educational video of testimonials would change safety knowledge, perceived vulnerability, and simulated behaviors with dogs among a sample of 280 third and fourth graders living in rural China. Participants were randomly assigned to view either an educational video of testimonials on dog-bite prevention (treatment) or an educational video of testimonials on drowning prevention (comparison). Safety knowledge, perceived vulnerability to dog bites, and simulated behavior with dogs using a dollhouse model were assessed both before and after exposure to the video of testimonials. Results Children who watched the educational video of testimonials on dog-bite prevention had increased safety knowledge, higher perceived vulnerability, and less risky simulated behaviors with dogs compared to the comparison group. Mediation analysis revealed that the intervention successfully changed children's simulated behaviors with dogs through greater safety knowledge and increased perceived vulnerability. Conclusions Results suggest the incorporation of testimonials into injury prevention programs has potential for broad global dissemination. The fact that both increased knowledge and heightened perceived vulnerability mediated changes in simulated behavior suggests the dual roles of knowledge and appraisal on children's injury-risk behavior. PMID:26523353

A randomized trial evaluating child dog-bite prevention in rural China through video-based testimonials.

PubMed

Shen, Jiabin; Pang, Shulan; Schwebel, David C

2016-05-01

Dog-bite injuries pose significant threat to children globally. School-age children are especially at risk because of their insufficient safety knowledge and cognitively immature tendency toward low perceived vulnerability to bites, and this risk is elevated further for school-age children living in rural China due to the large number of stray dogs, all potential rabies carriers, present in their communities. This randomized controlled trial evaluated whether viewing an educational video of testimonials would change safety knowledge, perceived vulnerability, and simulated behaviors with dogs among a sample of 280 third and fourth graders living in rural China. Participants were randomly assigned to view either an educational video of testimonials on dog-bite prevention (treatment) or an educational video of testimonials on drowning prevention (comparison). Safety knowledge, perceived vulnerability to dog bites, and simulated behavior with dogs using a dollhouse model were assessed both before and after exposure to the video of testimonials. Children who watched the educational video of testimonials on dog-bite prevention had increased safety knowledge, higher perceived vulnerability, and less risky simulated behaviors with dogs compared with the comparison group. Mediation analysis revealed that the intervention successfully changed children's simulated behaviors with dogs through greater safety knowledge and increased perceived vulnerability. Results suggest the incorporation of testimonials into injury prevention programs has potential for broad global dissemination. The fact that both increased knowledge and heightened perceived vulnerability mediated changes in simulated behavior suggests the dual roles of knowledge and appraisal on children's injury-risk behavior. (c) 2016 APA, all rights reserved).

Human-experienced temperature changes exceed global average climate changes for all income groups

NASA Astrophysics Data System (ADS)

Hsiang, S. M.; Parshall, L.

2009-12-01

Global climate change alters local climates everywhere. Many climate change impacts, such as those affecting health, agriculture and labor productivity, depend on these local climatic changes, not global mean change. Traditional, spatially averaged climate change estimates are strongly influenced by the response of icecaps and oceans, providing limited information on human-experienced climatic changes. If used improperly by decision-makers, these estimates distort estimated costs of climate change. We overlay the IPCC’s 20 GCM simulations on the global population distribution to estimate local climatic changes experienced by the world population in the 21st century. The A1B scenario leads to a well-known rise in global average surface temperature of +2.0°C between the periods 2011-2030 and 2080-2099. Projected on the global population distribution in 2000, the median human will experience an annual average rise of +2.3°C (4.1°F) and the average human will experience a rise of +2.4°C (4.3°F). Less than 1% of the population will experience changes smaller than +1.0°C (1.8°F), while 25% and 10% of the population will experience changes greater than +2.9°C (5.2°F) and +3.5°C (6.2°F) respectively. 67% of the world population experiences temperature changes greater than the area-weighted average change of +2.0°C (3.6°F). Using two approaches to characterize the spatial distribution of income, we show that the wealthiest, middle and poorest thirds of the global population experience similar changes, with no group dominating the global average. Calculations for precipitation indicate that there is little change in average precipitation, but redistributions of precipitation occur in all income groups. These results suggest that economists and policy-makers using spatially averaged estimates of climate change to approximate local changes will systematically and significantly underestimate the impacts of climate change on the 21st century population. Top: The distribution of temperature changes experienced by the world population between 2011-2030 and 2080-2099. Lower 3 panels: Temperatures experienced 2011-2030 (dashed, circle = mean) and 2080-2099 (solid, cross = mean) by income tercile. The poor do not experience larger changes than the wealthy. However, the poor begin the 21st century at higher temperatures.

Stoichiometric homeostasis predicts plant species dominance, temporal stability, and responses to global change.

PubMed

Yu, Qiang; Wilcox, Kevin; La Pierre, Kimberly; Knapp, Alan K; Han, Xingguo; Smith, Melinda D

2015-09-01

Why some species are consistently more abundant than others, and predicting how species will respond to global change, are fundamental questions in ecology. Long-term observations indicate that plant species with high stoichiometric homeostasis for nitrogen (HN), i.e., the ability to decouple foliar N levels from variation in soil N availability, were more common and stable through time than low-HN species in a central U.S. grassland. However, with nine years of nitrogen addition, species with high H(N) decreased in abundance, while those with low H(N) increased in abundance. In contrast, in climate change experiments simulating a range of forecast hydrologic changes, e.g., extreme drought (two years), increased rainfall variability (14 years), and chronic increases in rainfall (21 years), plant species with the highest H(N) were least responsive to changes in soil water availability. These results suggest that H(N) may be predictive of plant species success and stability, and how plant species and ecosystems will respond to global-change-driven alterations in resource availability.

The impacts of climate, land use, and demography on fires during the 21st century simulated by CLM-CN

NASA Astrophysics Data System (ADS)

Kloster, S.; Mahowald, N. M.; Randerson, J. T.; Lawrence, P. J.

2012-01-01

Landscape fires during the 21st century are expected to change in response to multiple agents of global change. Important controlling factors include climate controls on the length and intensity of the fire season, fuel availability, and fire management, which are already anthropogenically perturbed today and are predicted to change further in the future. An improved understanding of future fires will contribute to an improved ability to project future anthropogenic climate change, as changes in fire activity will in turn impact climate. In the present study we used a coupled-carbon-fire model to investigate how changes in climate, demography, and land use may alter fire emissions. We used climate projections following the SRES A1B scenario from two different climate models (ECHAM5/MPI-OM and CCSM) and changes in population. Land use and harvest rates were prescribed according to the RCP 45 scenario. In response to the combined effect of all these drivers, our model estimated, depending on our choice of climate projection, an increase in future (2075-2099) fire carbon emissions by 17 and 62% compared to present day (1985-2009). The largest increase in fire emissions was predicted for Southern Hemisphere South America for both climate projections. For Northern Hemisphere Africa, a region that contributed significantly to the global total fire carbon emissions, the response varied between a decrease and an increase depending on the climate projection. We disentangled the contribution of the single forcing factors to the overall response by conducting an additional set of simulations in which each factor was individually held constant at pre-industrial levels. The two different projections of future climate change evaluated in this study led to increases in global fire carbon emissions by 22% (CCSM) and 66% (ECHAM5/MPI-OM). The RCP 45 projection of harvest and land use led to a decrease in fire carbon emissions by -5%. The RCP 26 and RCP 60 harvest and landuse projections caused decreases around -20%. Changes in human ignition led to an increase of 20%. When we also included changes in fire management efforts to suppress fires in densely populated areas, global fire carbon emission decreased by -6% in response to changes in population density. We concluded from this study that changes in fire emissions in the future are controlled by multiple interacting factors. Although changes in climate led to an increase in future fire emissions this could be globally counterbalanced by coupled changes in land use, harvest, and demography.

A review on vegetation models and applicability to climate simulations at regional scale

NASA Astrophysics Data System (ADS)

Myoung, Boksoon; Choi, Yong-Sang; Park, Seon Ki

2011-11-01

The lack of accurate representations of biospheric components and their biophysical and biogeochemical processes is a great source of uncertainty in current climate models. The interactions between terrestrial ecosystems and the climate include exchanges not only of energy, water and momentum, but also of carbon and nitrogen. Reliable simulations of these interactions are crucial for predicting the potential impacts of future climate change and anthropogenic intervention on terrestrial ecosystems. In this paper, two biogeographical (Neilson's rule-based model and BIOME), two biogeochemical (BIOME-BGC and PnET-BGC), and three dynamic global vegetation models (Hybrid, LPJ, and MC1) were reviewed and compared in terms of their biophysical and physiological processes. The advantages and limitations of the models were also addressed. Lastly, the applications of the dynamic global vegetation models to regional climate simulations have been discussed.

Updates on Modeling the Water Cycle with the NASA Ames Mars Global Climate Model

NASA Technical Reports Server (NTRS)

Kahre, M. A.; Haberle, R. M.; Hollingsworth, J. L.; Montmessin, F.; Brecht, A. S.; Urata, R.; Klassen, D. R.; Wolff, M. J.

2017-01-01

Global Circulation Models (GCMs) have made steady progress in simulating the current Mars water cycle. It is now widely recognized that clouds are a critical component that can significantly affect the nature of the simulated water cycle. Two processes in particular are key to implementing clouds in a GCM: the microphysical processes of formation and dissipation, and their radiative effects on heating/ cooling rates. Together, these processes alter the thermal structure, change the dynamics, and regulate inter-hemispheric transport. We have made considerable progress representing these processes in the NASA Ames GCM, particularly in the presence of radiatively active water ice clouds. We present the current state of our group's water cycle modeling efforts, show results from selected simulations, highlight some of the issues, and discuss avenues for further investigation.­

Statistical structure of intrinsic climate variability under global warming

NASA Astrophysics Data System (ADS)

Zhu, Xiuhua; Bye, John; Fraedrich, Klaus

2017-04-01

Climate variability is often studied in terms of fluctuations with respect to the mean state, whereas the dependence between the mean and variability is rarely discussed. We propose a new climate metric to measure the relationship between means and standard deviations of annual surface temperature computed over non-overlapping 100-year segments. This metric is analyzed based on equilibrium simulations of the Max Planck Institute-Earth System Model (MPI-ESM): the last millennium climate (800-1799), the future climate projection following the A1B scenario (2100-2199), and the 3100-year unforced control simulation. A linear relationship is globally observed in the control simulation and thus termed intrinsic climate variability, which is most pronounced in the tropical region with negative regression slopes over the Pacific warm pool and positive slopes in the eastern tropical Pacific. It relates to asymmetric changes in temperature extremes and associates fluctuating climate means with increase or decrease in intensity and occurrence of both El Niño and La Niña events. In the future scenario period, the linear regression slopes largely retain their spatial structure with appreciable changes in intensity and geographical locations. Since intrinsic climate variability describes the internal rhythm of the climate system, it may serve as guidance for interpreting climate variability and climate change signals in the past and the future.

Shifts in nitrogen acquisition strategies enable enhanced terrestrial carbon storage under elevated CO2 in a global model

NASA Astrophysics Data System (ADS)

Sulman, B. N.; Brzostek, E. R.; Menge, D.; Malyshev, S.; Shevliakova, E.

2017-12-01

Earth System Model (ESM) projections of terrestrial carbon (C) uptake are critical to understanding the future of the global C cycle. Current ESMs include intricate representations of photosynthetic C fixation in plants, allowing them to simulate the stimulatory effect of increasing atmospheric CO2 levels on photosynthesis. However, they lack sophisticated representations of plant nutrient acquisition, calling into question their ability to project the future land C sink. We conducted simulations using a new model of terrestrial C and nitrogen (N) cycling within the Geophysical Fluid Dynamics Laboratory (GFDL) global land model LM4 that uses a return on investment framework to simulate global patterns of N acquisition via fixation of N2 from the atmosphere, scavenging of inorganic N from soil solution, and mining of organic N from soil organic matter (SOM). We show that these strategies drive divergent C cycle responses to elevated CO2 at the ecosystem scale, with the scavenging strategy leading to N limitation of plant growth and the mining strategy facilitating stimulation of plant biomass accumulation over decadal time scales. In global simulations, shifts in N acquisition from inorganic N scavenging to organic N mining along with increases in N fixation supported long-term acceleration of C uptake under elevated CO2. Our results indicate that the ability of the land C sink to mitigate atmospheric CO2 levels is tightly coupled to the functional diversity of ecosystems and their capacity to change their N acquisition strategies over time. Incorporation of these mechanisms into ESMs is necessary to improve confidence in model projections of the global C cycle.

The Implications of Future Food Demand on Global Land Use, Land-Use Change Emissions, and Climate

NASA Astrophysics Data System (ADS)

Calvin, K. V.; Wise, M.; Kyle, P.; Luckow, P.; Clarke, L.; Edmonds, J.; Eom, J.; Kim, S.; Moss, R.; Patel, P.

2011-12-01

In 2005, cropland accounted for approximately 10% of global land area. The amount of cropland needed in the future depends on a number of factors including global population, dietary preferences, and agricultural crop yields. In this paper, we explore the effect of various assumptions about global food demand and agricultural productivity between now and 2100 on global land use, land-use change emissions, and climate using the GCAM model. GCAM is a global integrated assessment model, linking submodules of the regionally disaggregated, global economy, energy system, agriculture and land-use, terrestrial carbon cycle, oceans and climate. GCAM simulates supply, demand, and prices for energy and agricultural goods from 2005 to 2100 in 5-year increments. In each time period, the model computes the allocation of land across a variety of land cover types in 151 different regions, assuming that farmers maximize profits and that food demand is relatively inelastic. For this analysis, we look at the effect of alternative socioeconomic pathways, crop yield improvement assumptions, and future meat demand scenarios on the demand for agricultural land. The three socioeconomic pathways explore worlds where global population in 2100 ranges from 6 billion people to 14 billion people. The crop yield improvement assumptions range from a world where yields do not improve beyond today's levels to a world with significantly higher crop productivity. The meat demand scenarios range from a vegetarian world to a world where meat is a dominant source of calories in the global diet. For each of these scenarios, we find that sufficient land exists to feed the global economy. However, rates of deforestation, bioenergy potential, land-use change emissions, and climate change differ across the scenarios. Under less favorable scenarios, deforestation rates, land-use change emissions, and the rate of climate change can be adversely affected.

Projected changes, climate change signal, and uncertainties in the CMIP5-based projections of ocean surface wave heights

NASA Astrophysics Data System (ADS)

Wang, Xiaolan; Feng, Yang; Swail, Val R.

2016-04-01

Ocean surface waves can be major hazards in coastal and offshore activities. However, wave observations are available only at limited locations and cover only the recent few decades. Also, there exists very limited information on ocean wave behavior in response to climate change, because such information is not simulated in current global climate models. In a recent study, we used a multivariate regression model with lagged dependent variable to make statistical global projections of changes in significant wave heights (Hs) using mean sea level pressure (SLP) information from 20 CMIP5 climate models for the twenty-first century. The statistical model was calibrated and validated using the ERA-Interim reanalysis of Hs and SLP for the period 1981-2010. The results show Hs increases in the tropics (especially in the eastern tropical Pacific) and in southern hemisphere high-latitudes. Under the projected 2070-2099 climate condition of the RCP8.5 scenario, the occurrence frequency of the present-day one-in-10-year extreme wave heights is likely to double or triple in several coastal regions around the world (e.g., the Chilean coast, Gulf of Oman, Gulf of Bengal, Gulf of Mexico). More recently, we used the analysis of variance approaches to quantify the climate change signal and uncertainty in multi-model ensembles of statistical Hs simulations globally, which are based on the CMIP5 historical, RCP4.5 and RCP8.5 forcing scenario simulations of SLP. In a 4-model 3-run ensemble, the 4-model common signal of climate change is found to strengthen over time, as would be expected. For the historical followed by RCP8.5 scenario, the common signal in annual mean Hs is found to be significant over 16.6%, 55.0% and 82.2% of the area by year 2005, 2050 and 2099, respectively. For the annual maximum, the signal is much weaker. The signal is strongest in the eastern tropical Pacific, featuring significant increases in both the annual mean and maximum of Hs in this region. The climate model uncertainty (i.e., inter-model variability) is significant over 99.9% of the area; its magnitude is comparable to or greater than the climate change signal by 2099 over most areas, except in the eastern tropical Pacific where the signal is much larger. In a 20-model 2-scenario single-run ensemble of statistical Hs simulations for the period 2006-2099, the model uncertainty is found to be significant globally; it is about 10 times as large as the scenario uncertainty between RCP4.5 and RCP8.5 scenarios.

Global lake evaporation accelerated by changes in surface energy allocation in a warmer climate

NASA Astrophysics Data System (ADS)

Wang, Wei; Lee, Xuhui; Xiao, Wei; Liu, Shoudong; Schultz, Natalie; Wang, Yongwei; Zhang, Mi; Zhao, Lei

2018-06-01

Lake evaporation is a sensitive indicator of the hydrological response to climate change. Variability in annual lake evaporation has been assumed to be controlled primarily by the incoming surface solar radiation. Here we report simulations with a numerical model of lake surface fluxes, with input data based on a high-emissions climate change scenario (Representative Concentration Pathway 8.5). In our simulations, the global annual lake evaporation increases by 16% by the end of the century, despite little change in incoming solar radiation at the surface. We attribute about half of this projected increase to two effects: periods of ice cover are shorter in a warmer climate and the ratio of sensible to latent heat flux decreases, thus channelling more energy into evaporation. At low latitudes, annual lake evaporation is further enhanced because the lake surface warms more slowly than the air, leading to more long-wave radiation energy available for evaporation. We suggest that an analogous change in the ratio of sensible to latent heat fluxes in the open ocean can help to explain some of the spread among climate models in terms of their sensitivity of precipitation to warming. We conclude that an accurate prediction of the energy balance at the Earth's surface is crucial for evaluating the hydrological response to climate change.

Multicriteria evaluation of discharge simulation in Dynamic Global Vegetation Models

NASA Astrophysics Data System (ADS)

Yang, Hui; Piao, Shilong; Zeng, Zhenzhong; Ciais, Philippe; Yin, Yi; Friedlingstein, Pierre; Sitch, Stephen; Ahlström, Anders; Guimberteau, Matthieu; Huntingford, Chris; Levis, Sam; Levy, Peter E.; Huang, Mengtian; Li, Yue; Li, Xiran; Lomas, Mark R.; Peylin, Philippe; Poulter, Ben; Viovy, Nicolas; Zaehle, Soenke; Zeng, Ning; Zhao, Fang; Wang, Lei

2015-08-01

In this study, we assessed the performance of discharge simulations by coupling the runoff from seven Dynamic Global Vegetation Models (DGVMs; LPJ, ORCHIDEE, Sheffield-DGVM, TRIFFID, LPJ-GUESS, CLM4CN, and OCN) to one river routing model for 16 large river basins. The results show that the seasonal cycle of river discharge is generally modeled well in the low and middle latitudes but not in the high latitudes, where the peak discharge (due to snow and ice melting) is underestimated. For the annual mean discharge, the DGVMs chained with the routing model show an underestimation. Furthermore, the 30 year trend of discharge is also underestimated. For the interannual variability of discharge, a skill score based on overlapping of probability density functions (PDFs) suggests that most models correctly reproduce the observed variability (correlation coefficient higher than 0.5; i.e., models account for 50% of observed interannual variability) except for the Lena, Yenisei, Yukon, and the Congo river basins. In addition, we compared the simulated runoff from different simulations where models were forced with either fixed or varying land use. This suggests that both seasonal and annual mean runoff has been little affected by land use change but that the trend itself of runoff is sensitive to land use change. None of the models when considered individually show significantly better performances than any other and in all basins. This suggests that based on current modeling capability, a regional-weighted average of multimodel ensemble projections might be appropriate to reduce the bias in future projection of global river discharge.

Multi-criteria Evaluation of Discharge Simulation in Dynamic Global Vegetation Models

NASA Astrophysics Data System (ADS)

Yang, H.; Piao, S.; Zeng, Z.; Ciais, P.; Yin, Y.; Friedlingstein, P.; Sitch, S.; Ahlström, A.; Guimberteau, M.; Huntingford, C.; Levis, S.; Levy, P. E.; Huang, M.; Li, Y.; Li, X.; Lomas, M.; Peylin, P. P.; Poulter, B.; Viovy, N.; Zaehle, S.; Zeng, N.; Zhao, F.; Wang, L.

2015-12-01

In this study, we assessed the performance of discharge simulations by coupling the runoff from seven Dynamic Global Vegetation Models (DGVMs; LPJ, ORCHIDEE, Sheffield-DGVM, TRIFFID, LPJ-GUESS, CLM4CN, and OCN) to one river routing model for 16 large river basins. The results show that the seasonal cycle of river discharge is generally modelled well in the low and mid latitudes, but not in the high latitudes, where the peak discharge (due to snow and ice melting) is underestimated. For the annual mean discharge, the DGVMs chained with the routing model show an underestimation. Furthermore the 30-year trend of discharge is also under-estimated. For the inter-annual variability of discharge, a skill score based on overlapping of probability density functions (PDFs) suggests that most models correctly reproduce the observed variability (correlation coefficient higher than 0.5; i.e. models account for 50% of observed inter-annual variability) except for the Lena, Yenisei, Yukon, and the Congo river basins. In addition, we compared the simulated runoff from different simulations where models were forced with either fixed or varying land use. This suggests that both seasonal and annual mean runoff has been little affected by land use change, but that the trend itself of runoff is sensitive to land use change. None of the models when considered individually show significantly better performances than any other and in all basins. This suggests that based on current modelling capability, a regional-weighted average of multi-model ensemble projections might be appropriate to reduce the bias in future projection of global river discharge.

Development of a global aerosol model using a two-dimensional sectional method: 1. Model design

NASA Astrophysics Data System (ADS)

Matsui, H.

2017-08-01

This study develops an aerosol module, the Aerosol Two-dimensional bin module for foRmation and Aging Simulation version 2 (ATRAS2), and implements the module into a global climate model, Community Atmosphere Model. The ATRAS2 module uses a two-dimensional (2-D) sectional representation with 12 size bins for particles from 1 nm to 10 μm in dry diameter and 8 black carbon (BC) mixing state bins. The module can explicitly calculate the enhancement of absorption and cloud condensation nuclei activity of BC-containing particles by aging processes. The ATRAS2 module is an extension of a 2-D sectional aerosol module ATRAS used in our previous studies within a framework of a regional three-dimensional model. Compared with ATRAS, the computational cost of the aerosol module is reduced by more than a factor of 10 by simplifying the treatment of aerosol processes and 2-D sectional representation, while maintaining good accuracy of aerosol parameters in the simulations. Aerosol processes are simplified for condensation of sulfate, ammonium, and nitrate, organic aerosol formation, coagulation, and new particle formation processes, and box model simulations show that these simplifications do not substantially change the predicted aerosol number and mass concentrations and their mixing states. The 2-D sectional representation is simplified (the number of advected species is reduced) primarily by the treatment of chemical compositions using two interactive bin representations. The simplifications do not change the accuracy of global aerosol simulations. In part 2, comparisons with measurements and the results focused on aerosol processes such as BC aging processes are shown.

Test of High-resolution Global and Regional Climate Model Projections

NASA Astrophysics Data System (ADS)

Stenchikov, Georgiy; Nikulin, Grigory; Hansson, Ulf; Kjellström, Erik; Raj, Jerry; Bangalath, Hamza; Osipov, Sergey

2014-05-01

In scope of CORDEX project we have simulated the past (1975-2005) and future (2006-2050) climates using the GFDL global high-resolution atmospheric model (HIRAM) and the Rossby Center nested regional model RCA4 for the Middle East and North Africa (MENA) region. Both global and nested runs were performed with roughly the same spatial resolution of 25 km in latitude and longitude, and were driven by the 2°x2.5°-resolution fields from GFDL ESM2M IPCC AR5 runs. The global HIRAM simulations could naturally account for interaction of regional processes with the larger-scale circulation features like Indian Summer Monsoon, which is lacking from regional model setup. Therefore in this study we specifically address the consistency of "global" and "regional" downscalings. The performance of RCA4, HIRAM, and ESM2M is tested based on mean, extreme, trends, seasonal and inter-annual variability of surface temperature, precipitation, and winds. The impact of climate change on dust storm activity, extreme precipitation and water resources is specifically addressed. We found that the global and regional climate projections appear to be quite consistent for the modeled period and differ more significantly from ESM2M than between each other.

Uncertain soil moisture feedbacks in model projections of Sahel precipitation

NASA Astrophysics Data System (ADS)

Berg, Alexis; Lintner, Benjamin R.; Findell, Kirsten; Giannini, Alessandra

2017-06-01

Given the uncertainties in climate model projections of Sahel precipitation, at the northern edge of the West African Monsoon, understanding the factors governing projected precipitation changes in this semiarid region is crucial. This study investigates how long-term soil moisture changes projected under climate change may feedback on projected changes of Sahel rainfall, using simulations with and without soil moisture change from five climate models participating in the Global Land Atmosphere Coupling Experiment-Coupled Model Intercomparison Project phase 5 experiment. In four out of five models analyzed, soil moisture feedbacks significantly influence the projected West African precipitation response to warming; however, the sign of these feedbacks differs across the models. These results demonstrate that reducing uncertainties across model projections of the West African Monsoon requires, among other factors, improved mechanistic understanding and constraint of simulated land-atmosphere feedbacks, even at the large spatial scales considered here.