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Sample records for african climate variability

  1. Association between climate variability and malaria epidemics in the East African highlands

    PubMed Central

    Zhou, Guofa; Minakawa, Noboru; Githeko, Andrew K.; Yan, Guiyun

    2004-01-01

    The causes of the recent reemergence of Plasmodium falciparum epidemic malaria in the East African highlands are controversial. Regional climate changes have been invoked as a major factor; however, assessing the impact of climate in malaria resurgence is difficult due to high spatial and temporal climate variability and the lack of long-term data series on malaria cases from different sites. Climate variability, defined as short-term fluctuations around the mean climate state, may be epidemiologically more relevant than mean temperature change, but its effects on malaria epidemics have not been rigorously examined. Here we used nonlinear mixed-regression model to investigate the association between autoregression (number of malaria outpatients during the previous time period), seasonality and climate variability, and the number of monthly malaria outpatients of the past 10–20 years in seven highland sites in East Africa. The model explained 65–81% of the variance in the number of monthly malaria outpatients. Nonlinear and synergistic effects of temperature and rainfall on the number of malaria outpatients were found in all seven sites. The net variance in the number of monthly malaria outpatients caused by autoregression and seasonality varied among sites and ranged from 18 to 63% (mean = 38.6%), whereas 12–63% (mean = 36.1%) of variance is attributed to climate variability. Our results suggest that there was a high spatial variation in the sensitivity of malaria outpatient number to climate fluctuations in the highlands, and that climate variability played an important role in initiating malaria epidemics in the East African highlands. PMID:14983017

  2. Association between climate variability and malaria epidemics in the East African highlands.

    PubMed

    Zhou, Guofa; Minakawa, Noboru; Githeko, Andrew K; Yan, Guiyun

    2004-02-24

    The causes of the recent reemergence of Plasmodium falciparum epidemic malaria in the East African highlands are controversial. Regional climate changes have been invoked as a major factor; however, assessing the impact of climate in malaria resurgence is difficult due to high spatial and temporal climate variability and the lack of long-term data series on malaria cases from different sites. Climate variability, defined as short-term fluctuations around the mean climate state, may be epidemiologically more relevant than mean temperature change, but its effects on malaria epidemics have not been rigorously examined. Here we used nonlinear mixed-regression model to investigate the association between autoregression (number of malaria outpatients during the previous time period), seasonality and climate variability, and the number of monthly malaria outpatients of the past 10-20 years in seven highland sites in East Africa. The model explained 65-81% of the variance in the number of monthly malaria outpatients. Nonlinear and synergistic effects of temperature and rainfall on the number of malaria outpatients were found in all seven sites. The net variance in the number of monthly malaria outpatients caused by autoregression and seasonality varied among sites and ranged from 18 to 63% (mean=38.6%), whereas 12-63% (mean=36.1%) of variance is attributed to climate variability. Our results suggest that there was a high spatial variation in the sensitivity of malaria outpatient number to climate fluctuations in the highlands, and that climate variability played an important role in initiating malaria epidemics in the East African highlands.

  3. North African climate variability. Part 1: Tropical thermocline coupling

    NASA Astrophysics Data System (ADS)

    Yeshanew, A.; Jury, M. R.

    2007-05-01

    Tropical ocean thermocline variability is studied using gridded data assimilated by an ocean model in the period 1950-2000. The dominant patterns and variability are identified using EOF analysis applied to E-W depth slices of sea temperatures averaged over the tropics. After removing the annual cycle, an east-west ‘see-saw’ with an interannual to decadal rhythm is the leading mode in each of the tropical basins. In the case of the leading mode in the Pacific, the thermocline oscillation forms a dipole structure, but in the (east) Atlantic and (southwest) Indian Ocean there is a single center of action. The interaction of the ocean thermocline and atmospheric Walker circulations is studied through cross-modulus analysis of wavelet-filtered EOF time scores. Our study demonstrates how tropical ocean thermocline variability contributes to zonal circulation anomalies in the atmosphere. The equatorial Pacific thermocline oscillation explains 62 and 53% of the variability of the Pacific and Atlantic zonal overturning circulations, the latter driving convective polarity between North Africa and South America. The Pacific sea-saw leads the Atlantic zonal circulation by a few months.

  4. Glacial/interglacial climate controls on east African interannual rainfall variability

    NASA Astrophysics Data System (ADS)

    Timmermann, A.; Wolff, C.; Haug, G. H.; Sinninghe Damsté, J. S.; Brauer, A.; Sigman, D. M.; Cane, M. A.; Verschuren, D.

    2011-12-01

    Interannual rainfall variations in equatorial East Africa are tightly linked to the El Niño Southern Oscillation (ENSO), with more rain and flooding during El Niño and droughts in La Niña years, both having severe impacts on water stress and food security. Here we report evidence from an annually laminated lake-sediment record from southeastern Kenya for inter-annual to centennial-scale changes in ENSO-related rainfall variability during the last three millennia, abrupt changes in variability between the Medieval Climate Anomaly and the Little Ice Age, and an overall reduction in East African rainfall and its variability during the Last Glacial period. A suite of CCSM3 climate model experiments for LGM, present-day and future CO2-doubling conditions supports forward extrapolations from these lake-sediment data that future Indian Ocean warming will intensify East Africa's hydrological cycle during the short rainy season in September to November.

  5. Exploring Pacific Climate Variability and Its Impacts on East African Water Resources and Food Security

    NASA Astrophysics Data System (ADS)

    Funk, C. C.; Hoerling, M. P.; Hoell, A.; Liebmann, B.; Verdin, J. P.; Eilerts, G.

    2014-12-01

    In 8 out the past 15 boreal springs (1999, 2000, 2004, 2008, 2009, 2011, 2012, and 2013), substantial parts of eastern East Africa experienced very low boreal spring rains. These rainfall deficits have triggered widespread food insecurity, and even contributed to the outbreak of famine conditions in Somalia in 2011. At both seasonal and decadal time scales, new science supported by the USAID Famine Early Warning Systems Network seeks to understand the mechanisms producing these droughts. We present research suggesting that the ultimate and proximate causes of these increases in aridity are i) stronger equatorial Pacific SST gradients and ii) associated increases in the strength of the Indo-Pacific Walker circulation. Using observations and new modeling ensembles, we explore the relative contributions of Pacific Decadal Variability (PDV) and global warming under warm and cold east Pacific Ocean states. This question is addressed in two ways: by using atmospheric GCMs forced with full and ENSO-only SSTs, and ii) by decomposing coupled ocean-atmosphere climate simulations into PDV and non-PDV components. These analyses allow us to explore the Walker circulation's sensitivity to climate change under various PDV states, and inform a tentative bracketing of 2030 climate conditions. We conclude by discussing links to East African development. Regions of high rainfall sensitivity are delineated and intersected with recent changes in population and land cover/land use. The interaction of elevation and climate is shown to create climatically secure regions that are likely to remain viable even under drier and warmer conditions; such regions may be logical targets for agricultural intensification. Conversely, arid low elevation regions are likely to experience substantial temperature impacts. Continued expansion into these areas may effectively create more 'drought' even if rainfall increases.

  6. The Freshwater Oyster Etheria elliptica as a Tool to Reconstruct Climate Variability across the African Continent

    NASA Astrophysics Data System (ADS)

    Vanhove, D.; Gillikin, D. P.; Kelemen, Z.; Bouillon, S.

    2015-12-01

    The bivalve Etheria elliptica occurs abundantly in (sub)tropical African river basins. We investigate its potential use for the reconstruction of ambient water chemistry and climate by means of stable oxygen isotope ratios in specimens from the Congo river (Kisangani), the Oubangui river (Bangui) and the Victoria Nile (Jinja). Unlike other common African bivalve species, E. elliptica contains distinct organic-rich growth increments, previously suggested to correlate with lunar periodicity. However, cavities in the shell complicate age reading and little is known about the exact timing and continuity of these growth increments. We set up a comparative study between different techniques to visualize and enhance growth features, and find that staining with Mutvei's solution and confocal fluorescence microscopy perform equally well. Despite the presence of cavities, growth lines can generally be followed from umbo to shell margin. Moreover, preliminary δ18O results of two micro-sampled specimens from the Oubangui river show that 12-13 growth lines occur within one year of growth. This corroborates that these increments can be used as temporal anchor points, providing a moon-monthly time frame for sequential microchemistry. In two Congo river specimens, δ18Oshell values vary between -1.9 and -3.8 ‰ (VPDB), in line with a predicted range of -2.1 to -4.1 ‰ based on fortnightly δ18Owater and T monitoring. Reconstructed intra-annual δ18Owater variability from δ18Oshell values and observed T correlates with discharge, reflecting rainfall and runoff variability in the upstream catchment area. In two Victoria Nile specimens, collected 20 km downstream from Lake Victoria, δ18Oshell values are high and relatively constant, varying between +1.8 and +3.2 ‰. Enrichment of 18Oshell is consistent with isotopically heavy rainfall signatures and elevated surface evaporation in Lake Victoria. These first results suggest that E. elliptica is well-suited for the reconstruction

  7. 300 Years of East African Climate Variability from Oxygen Isotopes in a Kenya Coral

    NASA Astrophysics Data System (ADS)

    Dunbar, R.

    2003-04-01

    Instrumental records of climate variability from the western Indian Ocean are relatively scarce and short. Here I present a monthly resolution stable isotopic record acquired from a large living coral head (Porites) from the Malindi Marine Reserve, Kenya (3^oS, 40^oE). The annual chronology is precise and is based on exceptionally clear high and low density growth band couplets. The record extends from 1696 to 1996 A.D., making it the longest coral climate record from the Indian Ocean and one of the longest available worldwide. We have analyzed the uppermost portion of the coral colony in triplicate, using 3 separate cores. This upper section, used for calibration purposes, also provides estimates of signal fidelity and noise in the climate recording system internal to the colony. Coral δ18O at this site primarily records SST; linear regression of monthly coral δ18O vs. SST yields a slope of -0.26 ppm δ18O per ^oC, and δ18O explains ˜57% of the SST variance. Additional isotopic variability may result from changes in seawater δ18O due to local runoff or regional evaporation/precipitation balance, but these changes are likely to be small because local rainfall δ18O is not strongly depleted relative to seawater and salinity gradients are small. The coral record indicates a clear warming trend of about 1.5^oC that accelerates in the latest 20th century, superimposed on strong decadal variability that persists throughout the record. In fact, δ18O values in the 1990's exceed the 300 year envelope (they are lower) and correspond with apparently unprecedented coral bleaching in coastal East Africa. The decadal component of the Malindi coral record reflects a regional climate signal spanning much of the western equatorial Indian Ocean. In general, East African SST and rainfall are better correlated with Pacific ENSO indicators than with the Indian Monsoon at all periods (inter-annual through multi-decadal) but the correlation weakens after 1975. One dramatic new

  8. Plio-pleistocene African climate

    SciTech Connect

    deMenocal, P.B.

    1995-10-06

    Marine records of African climate variability document a shift toward more arid conditions after 2.8 million years ago (Ma), evidently resulting from remote forcing by cold North Atlantic sea-surface temperatures associated with the onset of Northern Hemisphere glacial cycles. African climate before 2.8 Ma was regulated by low-latitude insolation forcing of monsoonal climate due to Earth orbital precession. Major steps in the evolution of African hominids and other vertebrates are coincident with shifts to more arid, open conditions near 2.8 Ma, 1.7 Ma, and 1.0 Ma, suggesting that some Pliocene (Plio)-Pleistocene speciation events may have been climatically mediated. 65 refs., 6 figs.

  9. Plio-Pleistocene African Climate

    NASA Astrophysics Data System (ADS)

    Demenocal, Peter B.

    1995-10-01

    Marine records of African climate variability document a shift toward more arid conditions after 2.8 million years ago (Ma), evidently resulting from remote forcing by cold North Atlantic sea-surface temperatures associated with the onset of Northern Hemisphere glacial cycles. African climate before 2.8 Ma was regulated by low-latitude insolation forcing of monsoonal climate due to Earth orbital precession. Major steps in the evolution of African hominids and other vertebrates are coincident with shifts to more arid, open conditions near 2.8 Ma, 1.7 Ma, and 1.0 Ma, suggesting that some Pliocene (Plio)-Pleistocene speciation events may have been climatically mediated.

  10. Comparing the effect of modeled climatic variables on the distribution of African horse sickness in South Africa and Namibia.

    PubMed

    Liebenberg, Danica; van Hamburg, Huib; Piketh, Stuart; Burger, Roelof

    2015-12-01

    Africa horse sickness (AHS) is a lethal disease of horses with a seasonal occurrence that is influenced by environmental conditions that favor the development of Culicoides midges (Diptera: Ceratopogonidae). This study compared and evaluated the relationship of various modeled climatic variables with the distribution and abundance of AHS in South Africa and Namibia. A comprehensive literature review of the historical AHS reported data collected from the Windhoek archives as well as annual reports from the Directorate of Veterinary services in Namibia were conducted. South African AHS reported data were collected from the South African Department of Agriculture, Forestry, and Fisheries. Daily climatic data were extracted for the time period 1993-2011 from the ERA-interim re-analysis dataset. The principal component analysis of the complete dataset indicated a significant statistical difference between Namibia and South Africa for the various climate variables and the outbreaks of AHS. The most influential parameters in the distribution of AHS included humidity, precipitation, evaporation, and minimum temperature. In South Africa, temperature had the most significant effect on the outbreaks of AHS, whereas in Namibia, humidity and precipitation were the main drivers. The maximum AHS cases in South Africa occurred at temperatures of 20-22° C and relative humidity between 50-70%. Furthermore, anthropogenic effects must be taken into account when trying to understand the distribution of AHS.

  11. Comparing the effect of modeled climatic variables on the distribution of African horse sickness in South Africa and Namibia.

    PubMed

    Liebenberg, Danica; van Hamburg, Huib; Piketh, Stuart; Burger, Roelof

    2015-12-01

    Africa horse sickness (AHS) is a lethal disease of horses with a seasonal occurrence that is influenced by environmental conditions that favor the development of Culicoides midges (Diptera: Ceratopogonidae). This study compared and evaluated the relationship of various modeled climatic variables with the distribution and abundance of AHS in South Africa and Namibia. A comprehensive literature review of the historical AHS reported data collected from the Windhoek archives as well as annual reports from the Directorate of Veterinary services in Namibia were conducted. South African AHS reported data were collected from the South African Department of Agriculture, Forestry, and Fisheries. Daily climatic data were extracted for the time period 1993-2011 from the ERA-interim re-analysis dataset. The principal component analysis of the complete dataset indicated a significant statistical difference between Namibia and South Africa for the various climate variables and the outbreaks of AHS. The most influential parameters in the distribution of AHS included humidity, precipitation, evaporation, and minimum temperature. In South Africa, temperature had the most significant effect on the outbreaks of AHS, whereas in Namibia, humidity and precipitation were the main drivers. The maximum AHS cases in South Africa occurred at temperatures of 20-22° C and relative humidity between 50-70%. Furthermore, anthropogenic effects must be taken into account when trying to understand the distribution of AHS. PMID:26611969

  12. Perception, experience, and indigenous knowledge of climate change and variability: the case of Accra, a sub-Saharan African city

    USGS Publications Warehouse

    Codjoe, Samuel N.A.; Owusu, George; Burkett, Virginia

    2014-01-01

    Several recent international assessments have concluded that climate change has the potential to reverse the modest economic gains achieved in many developing countries over the past decade. The phenomenon of climate change threatens to worsen poverty or burden populations with additional hardships, especially in poor societies with weak infrastructure and economic well-being. The importance of the perceptions, experiences, and knowledge of indigenous peoples has gained prominence in discussions of climate change and adaptation in developing countries and among international development organizations. Efforts to evaluate the role of indigenous knowledge in adaptation planning, however, have largely focused on rural people and their agricultural livelihoods. This paper presents the results of a study that examines perceptions, experiences, and indigenous knowledge relating to climate change and variability in three communities of metropolitan Accra, which is the capital of Ghana. The study design is based on a three-part conceptual framework and interview process involving risk mapping, mental models, and individual stressor cognition. Most of the residents interviewed in the three communities of urban Accra attributed climate change to the combination of deforestation and the burning of firewood and rubbish. None of the residents associated climate change with fossil fuel emissions from developed countries. Numerous potential adaptation strategies were suggested by the residents, many of which have been used effectively during past drought and flood events. Results suggest that ethnic residential clustering as well as strong community bonds in metropolitan Accra have allowed various groups and long-settled communities to engage in the sharing and transmission of knowledge of weather patterns and trends. Understanding and building upon indigenous knowledge may enhance the design, acceptance, and implementation of climate change adaptation strategies in Accra and

  13. Divergent pattern of nuclear genetic diversity across the range of the Afromontane Prunus africana mirrors variable climate of African highlands

    PubMed Central

    Kadu, Caroline A. C.; Konrad, Heino; Schueler, Silvio; Muluvi, Geoffrey M.; Eyog-Matig, Oscar; Muchugi, Alice; Williams, Vivienne L.; Ramamonjisoa, Lolona; Kapinga, Consolatha; Foahom, Bernard; Katsvanga, Cuthbert; Hafashimana, David; Obama, Crisantos; Geburek, Thomas

    2013-01-01

    Background and Aims Afromontane forest ecosystems share a high similarity of plant and animal biodiversity, although they occur mainly on isolated mountain massifs throughout the continent. This resemblance has long provoked questions on former wider distribution of Afromontane forests. In this study Prunus africana (one of the character trees of Afromontane forests) is used as a model for understanding the biogeography of this vegetation zone. Methods Thirty natural populations from nine African countries covering a large part of Afromontane regions were analysed using six nuclear microsatellites. Standard population genetic analysis as well as Bayesian and maximum likelihood models were used to infer genetic diversity, population differentiation, barriers to gene flow, and recent and all migration among populations. Key Results Prunus africana exhibits strong divergence among five main Afromontane regions: West Africa, East Africa west of the Eastern Rift Valley (ERV), East Africa east of the ERV, southern Africa and Madagascar. The strongest divergence was evident between Madagascar and continental Africa. Populations from West Africa showed high similarity with East African populations west of the ERV, whereas populations east of the ERV are closely related to populations of southern Africa, respectively. Conclusions The observed patterns indicate divergent population history across the continent most likely associated to Pleistocene changes in climatic conditions. The high genetic similarity between populations of West Africa with population of East Africa west of the ERV is in agreement with faunistic and floristic patterns and provides further evidence for a historical migration route. Contrasting estimates of recent and historical gene flow indicate a shift of the main barrier to gene flow from the Lake Victoria basin to the ERV, highlighting the dynamic environmental and evolutionary history of the region. PMID:23250908

  14. Land Cover Land Use change and soil organic carbon under climate variability in the semi-arid West African Sahel (1960-2050)

    NASA Astrophysics Data System (ADS)

    Dieye, Amadou M.

    Land Cover Land Use (LCLU) change affects land surface processes recognized to influence climate change at local, national and global levels. Soil organic carbon is a key component for the functioning of agro-ecosystems and has a direct effect on the physical, chemical and biological characteristics of the soil. The capacity to model and project LCLU change is of considerable interest for mitigation and adaptation measures in response to climate change. A combination of remote sensing analyses, qualitative social survey techniques, and biogeochemical modeling was used to study the relationships between climate change, LCLU change and soil organic carbon in the semi-arid rural zone of Senegal between 1960 and 2050. For this purpose, four research hypotheses were addressed. This research aims to contribute to an understanding of future land cover land use change in the semi-arid West African Sahel with respect to climate variability and human activities. Its findings may provide insights to enable policy makers at local to national levels to formulate environmentally and economically adapted policy decisions. This dissertation research has to date resulted in two published and one submitted paper.

  15. U-Pb dated Speleothem records of Plio-Pleistocen climate variability from South African hominin bearing caves

    NASA Astrophysics Data System (ADS)

    Pickering, Robyn; Göktürk, Ozan; Badertscher, Seraina; Fleitmann, Dominik; Kramers, Jan

    2010-05-01

    We use stable isotopes of carbon and oxygen to investigate the potential palaeoclimate records from the caves near Johannesburg in South Africa. The sediments in these caves contain early human (hominin) fossils, as well as speleothem material, providing an ideal opportunity to investigate the palaeo-enviroments of our earliest ancestors. These sites are dated via uranium-lead to between 2.8 and 1.5 Ma and provide a window into changing climatic conditions, rare from both this period and region. We micro-drilled stalagmite and flowstone samples from Sterkfontein (2.8 -2.0 Ma), Swartkrans (2.4 -1.7 Ma) and Cooper's Cave (1.5 - 1.4 Ma) at 0.5mm spacing to provide a total of five high resolution records. Oxygen isotope values range from -6.5 to -3‰, clustering around -4.5‰. Carbon isotopes range from -8 to 2‰ and show more variation. Both a Hendy test and a C vs. O plot show that the deposits in question were deposited in equilibrium with their surroundings and the data can be used for environmental interpretations. Care was also taken to examine the petrography of all the speleothem material to access the mineralogy (calcite vs aragonite) and the extent of re-crystallisation. Oxygen isotope values are interpreted as the product of the amount and type of rainfall, with wetter periods represented by enriched excursions. The contribution of the dolomite aquifer above the cave may, however, obscure the δ18O signal. The carbon isotopes reflect changes in the vegetational communities above the cave, with varying amounts of C3 and C4 plants. At present each speleothem piece has only one U-Pb date, the distribution of suitable uranium rich layers limits the spatial resolution of dates. The Cooper's Cave flowstone pieces display visible growth layers; should these be annual layers, then these two records represent as little as 60 years climate variability - specifically in the amount of rainfall. However, this would require very fast speleothem growth rates (0.5mm

  16. Climate Variability Program

    NASA Technical Reports Server (NTRS)

    Halpern, David (Editor)

    2002-01-01

    The Annual Report of the Climate Variability Program briefly describes research activities of Principal Investigators who are funded by NASA's Earth Science Enterprise Research Division. The report is focused on the year 2001. Utilization of satellite observations is a singularity of research on climate science and technology at JPL (Jet Propulsion Laboratory). Research at JPL has two foci: generate new knowledge and develop new technology.

  17. Inter-annual Tropospheric Aerosol Variability in Late Twentieth Century and its Impact on Tropical Atlantic and West African Climate by Direct and Semi-direct Effects

    SciTech Connect

    Evans, Katherine J; Hack, James J; Truesdale, John; Mahajan, Salil; Lamarque, J-F

    2012-01-01

    A new high-resolution (0.9$^{\\circ}$x1.25$^{\\circ}$ in the horizontal) global tropospheric aerosol dataset with monthly resolution is generated using the finite-volume configuration of Community Atmosphere Model (CAM4) coupled to a bulk aerosol model and forced with recent estimates of surface emissions for the latter part of twentieth century. The surface emissions dataset is constructed from Coupled Model Inter-comparison Project (CMIP5) decadal-resolution surface emissions dataset to include REanalysis of TROpospheric chemical composition (RETRO) wildfire monthly emissions dataset. Experiments forced with the new tropospheric aerosol dataset and conducted using the spectral configuration of CAM4 with a T85 truncation (1.4$^{\\circ}$x1.4$^{\\circ}$) with prescribed twentieth century observed sea surface temperature, sea-ice and greenhouse gases reveal that variations in tropospheric aerosol levels can induce significant regional climate variability on the inter-annual timescales. Regression analyses over tropical Atlantic and Africa reveal that increasing dust aerosols can cool the North African landmass and shift convection southwards from West Africa into the Gulf of Guinea in the spring season in the simulations. Further, we find that increasing carbonaceous aerosols emanating from the southwestern African savannas can cool the region significantly and increase the marine stratocumulus cloud cover over the southeast tropical Atlantic ocean by aerosol-induced diabatic heating of the free troposphere above the low clouds. Experiments conducted with CAM4 coupled to a slab ocean model suggest that present day aerosols can shift the ITCZ southwards over the tropical Atlantic and can reduce the ocean mixed layer temperature beneath the increased marine stratocumulus clouds in the southeastern tropical Atlantic.

  18. Current Climate Variability & Change

    NASA Astrophysics Data System (ADS)

    Diem, J.; Criswell, B.; Elliott, W. C.

    2013-12-01

    Current Climate Variability & Change is the ninth among a suite of ten interconnected, sequential labs that address all 39 climate-literacy concepts in the U.S. Global Change Research Program's Climate Literacy: The Essential Principles of Climate Sciences. The labs are as follows: Solar Radiation & Seasons, Stratospheric Ozone, The Troposphere, The Carbon Cycle, Global Surface Temperature, Glacial-Interglacial Cycles, Temperature Changes over the Past Millennium, Climates & Ecosystems, Current Climate Variability & Change, and Future Climate Change. All are inquiry-based, on-line products designed in a way that enables students to construct their own knowledge of a topic. Questions representative of various levels of Webb's depth of knowledge are embedded in each lab. In addition to the embedded questions, each lab has three or four essential questions related to the driving questions for the lab suite. These essential questions are presented as statements at the beginning of the material to represent the lab objectives, and then are asked at the end as questions to function as a summative assessment. For example, the Current Climate Variability & Change is built around these essential questions: (1) What has happened to the global temperature at the Earth's surface, in the middle troposphere, and in the lower stratosphere over the past several decades?; (2) What is the most likely cause of the changes in global temperature over the past several decades and what evidence is there that this is the cause?; and (3) What have been some of the clearly defined effects of the change in global temperature on the atmosphere and other spheres of the Earth system? An introductory Prezi allows the instructor to assess students' prior knowledge in relation to these questions, while also providing 'hooks' to pique their interest related to the topic. The lab begins by presenting examples of and key differences between climate variability (e.g., Mt. Pinatubo eruption) and

  19. Possible Climate Change/Variability and Human Impacts, Vulnerability of African Drought Prone Regions, its Water Resources and Capacity Building

    NASA Astrophysics Data System (ADS)

    Yew Gan, Thian; Huelsmann, Stephen; Qin, XiaoSheng; Lu, Xi Xi; Liong, Shie-Yui; Rutschmann, Peter; Disse, Markus; Koivusalo, Harri

    2016-04-01

    The climate, water resources and historical droughts of Africa, drought indices, vulnerability, impact of global warming and landuse to drought-prone regions in West, Southern, and Greater Horn of Africa, which have suffered recurrent severe droughts in the past are reviewed first. Recent studies detected warming and drying trends in Africa since the mid-20th century. Based on the 4th Assessment Report of the Intergovernmental Panel of Climate Change, and that of the 5th Coupled Model Intercomparison Project (CMIP5), both northern and southern Africa are projected to experience drying such as decreasing precipitation, runoff and soil moisture in the 21st Century and could become more vulnerable to impact of droughts. The daily maximum temperature is projected to increase up to 8oC (RCP8.5 of CMIP5), precipitation indices such as total wet day precipitation (PRCPTOT) and heavy precipitation days (R10mm) could decrease, while warm spell duration (WSDI) and consecutive dry days (CDD) could increase. Uncertainties of the above long-term projections, teleconnections to climate anomalies such as ENSO and Madden Julian Oscillation which could also affect water resources of Africa, and capacity building in terms of physical infrastructure and non-structural solutions, are also discussed. Given traditional climate and hydrologic data observed in Africa are generally limited, satellite data should also be exploited to fill in the data gap for Africa in future.

  20. Natural climate variability and future climate policy

    NASA Astrophysics Data System (ADS)

    Ricke, Katharine L.; Caldeira, Ken

    2014-05-01

    Large ensemble climate modelling experiments demonstrate the large role natural variability plays in local climate on a multi-decadal timescale. Variability in local weather and climate influences individual beliefs about climate change. To the extent that support for climate mitigation policies is determined by citizens' local experiences, natural variability will strongly influence the timescale for implementation of such policies. Under a number of illustrative threshold criteria for both national and international climate action, we show that variability-driven uncertainty about local change, even in the face of a well-constrained estimate of global change, can potentially delay the time to policy implementation by decades. Because several decades of greenhouse gas emissions can have a large impact on long-term climate outcomes, there is substantial risk associated with climate policies driven by consensus among individuals who are strongly influenced by local weather conditions.

  1. Solar Variability and Climate

    NASA Astrophysics Data System (ADS)

    Haigh, Joanna D.

    Solar radiation is the fundamental energy source for the atmosphere and the global average equilibrium temperature of the Earth is determined by a balance between the energy acquired by the solar radiation absorbed and the energy lost to space by the emission of heat radiation. The interaction of this radiation with the climate system is complex but it is clear that any change in total solar irradiance (TSI) has the potential to influence climate. In the past, although many papers were written on relationships between sunspot numbers and the weather, the topic of solar influences on climate was often disregarded by meteorologists. This was due to a combination of factors of which the key was the lack of any robust measurements indicating that solar radiation did indeed vary. There was also mistrust of the statistical validity of the evidence and, importantly, no established scientific mechanisms whereby the apparent changes in the Sun might induce detectable signals near the Earth's surface. Another influence was a desire by the meteorological profession to distance itself from the Astrometeorology movement popular in the 19th century (anderson1999). Nowadays, with improved measurements of solar and climate parameters, evidence for an influence of solar variability on the climate of the lower atmosphere has emerged from the noise. This article provides a brief review of the observational evidence and an outline of the mechanisms whereby rather small changes in solar radiation may induce detectable signals near the Earth's surface is not possible to review here all potential mechanisms for solar-climate links. What is presented offers, necessarily, a personal perspective but, of the areas that are not covered, two may be pertinent: the effects of solar energetic particles on stratospheric composition (see e.g. jackman et al. 2005) and the possible influence of galactic cosmic rays on clouds through ionisation processes (see Marsh, this volume).

  2. Surfing wave climate variability

    NASA Astrophysics Data System (ADS)

    Espejo, Antonio; Losada, Iñigo J.; Méndez, Fernando J.

    2014-10-01

    International surfing destinations are highly dependent on specific combinations of wind-wave formation, thermal conditions and local bathymetry. Surf quality depends on a vast number of geophysical variables, and analyses of surf quality require the consideration of the seasonal, interannual and long-term variability of surf conditions on a global scale. A multivariable standardized index based on expert judgment is proposed for this purpose. This index makes it possible to analyze surf conditions objectively over a global domain. A summary of global surf resources based on a new index integrating existing wave, wind, tides and sea surface temperature databases is presented. According to general atmospheric circulation and swell propagation patterns, results show that west-facing low to middle-latitude coasts are more suitable for surfing, especially those in the Southern Hemisphere. Month-to-month analysis reveals strong seasonal variations in the occurrence of surfable events, enhancing the frequency of such events in the North Atlantic and the North Pacific. Interannual variability was investigated by comparing occurrence values with global and regional modes of low-frequency climate variability such as El Niño and the North Atlantic Oscillation, revealing their strong influence at both the global and the regional scale. Results of the long-term trends demonstrate an increase in the probability of surfable events on west-facing coasts around the world in recent years. The resulting maps provide useful information for surfers, the surf tourism industry and surf-related coastal planners and stakeholders.

  3. Climate change, climate variability and brucellosis.

    PubMed

    Rodríguez-Morales, Alfonso J

    2013-04-01

    In addition to natural climate variability observed over comparable time periods, climate change is attributed directly or indirectly to human activity, altering the composition of global atmosphere. This phenomenon continues to be a significant and global threat for the humankind, and its impact compromises many aspects of the society at different levels, including health. The impact of climate change on zoonotic diseases has been largely ignored, particularly brucellosis. We here review some direct and indirect evidences of the impact of climate change and climate variability on brucellosis.

  4. Trends and variability in East African rainfall and temperature observations

    NASA Astrophysics Data System (ADS)

    Seregina, Larisa; Ermert, Volker; Fink, Andreas H.; Pinto, Joaquim G.

    2014-05-01

    The economy of East Africa is highly dependent on agriculture, leading to a strong vulnerability of local society to fluctuations in seasonal rainfall amounts, including extreme events. Hence, the knowledge about the evolution of seasonal rainfall under future climate conditions is crucial. Rainfall regimes over East Africa are influenced by multiple factors, including two monsoon systems, several convergence zones and the Rift Valley lakes. In addition, local conditions, like topography, modulate the large-scale rainfall pattern. East African rainfall variability is also influenced by various teleconnections like the Indian Ocean Zonal Mode and El Niño Southern Oscillation. Regarding future climate projections, regional and global climate models partly disagree on the increase or decrease of East African rainfall. The specific aim of the present study is the acquirement of historic data from weather stations in East Africa (Kenya, Tanzania, Ruanda and Uganda), the use of gridded satellite (rainfall) products (ARC2 and TRMM), and three-dimensional atmospheric reanalysis (e.g., ERA-Interim) to quantify climate variability in the recent past and to understand its causes. Climate variability and trends, including changes in extreme events, are evaluated using ETCCDI climate change and standardized precipitation indices. These climate indices are determined in order to investigate the variability of temperature and rainfall and their trends with the focus on most recent decades. In the follow-up, statistical and dynamical analyses are conducted to quantify the local impact of pertinent large-scale modes of climate variability (Indian Ocean Zonal Mode, El Niño Southern Oscillation, Sea Surface Temperature of the Indian Ocean).

  5. Climate Impact of Solar Variability

    NASA Technical Reports Server (NTRS)

    Schatten, Kenneth H. (Editor); Arking, Albert (Editor)

    1990-01-01

    The conference on The Climate Impact of Solar Variability, was held at Goddard Space Flight Center from April 24 to 27, 1990. In recent years they developed a renewed interest in the potential effects of increasing greenhouse gases on climate. Carbon dioxide, methane, nitrous oxide, and the chlorofluorocarbons have been increasing at rates that could significantly change climate. There is considerable uncertainty over the magnitude of this anthropogenic change. The climate system is very complex, with feedback processes that are not fully understood. Moreover, there are two sources of natural climate variability (volcanic aerosols and solar variability) added to the anthropogenic changes which may confuse our interpretation of the observed temperature record. Thus, if we could understand the climatic impact of the natural variability, it would aid our interpretation and understanding of man-made climate changes.

  6. Natural Climate Variability and Future Climate Policy

    NASA Astrophysics Data System (ADS)

    Ricke, K.; Caldeira, K.

    2013-12-01

    Individual beliefs about climate change and willingness-to-pay for its mitigation are influenced by local weather and climate. Large ensemble climate modeling experiments have demonstrated the large role natural variability plays in local weather and climate on a multidecadal timescale. Here we illustrate how if support for global climate policies and subsequent implementation of those policies are determined by citizens' local experiences, natural variability could influence the timeline for implementation of emissions reduction policies by decades. The response of complex social systems to local and regional changes in weather and climate cannot be quantitatively predicted with confidence. Both the form and timing of the societal response can be affected by interactions between social systems and the physical climate system. Here, to illustrate one type of influence decadal natural variability can have on climate policy, we consider a simple example in which the only question is when, if ever, the different parties will support emissions reduction. To analyze the potential effect that unpredictable extreme events may have on the time to reach a global agreement on climate policy, we analyzed the output from a 40-member Community Climate System Model version 3 simulation ensemble to illustrate how local experiences might affect the timing of acceptance of strong climate policy measures. We assume that a nation's decision to take strong actions to abate emissions is contingent upon the local experiences of its citizens and then examine how the timelines for policy action may be influenced by variability in local weather. To illustrate, we assume that a social 'tipping point' is reached at the national level occurs when half of the population of a nation has experienced a sufficiently extreme event. If climate policies are driven by democratic consensus then variability in weather could result in significantly disparate times-to-action. For the top six CO2 emitters

  7. Solar Variability and Climate Change

    NASA Astrophysics Data System (ADS)

    Pap, J. M.

    2004-12-01

    One of the most exciting and important challenges in science today is to understand climate variability and to make reliable predictions. The Earth's climate is a complex system driven by external and internal forces. Climate can vary over a large range of time scales as a consequence of natural variability or anthropogenic influence, or both. Observations of steadily increasing concentrations of greenhouse gases --primarily man-made-- in the Earth's atmosphere have led to an expectation of global warming during the coming decades. However, the greenhouse effect competes with other climate forcing mechanisms, such as solar variability, cosmic ray flux changes, desertification, deforestation, and changes in natural and man-made atmospheric aerosols. Indeed, the climate is always changing, and has forever been so, including periods before the industrial era began. Since the dominant driving force of the climate system is the Sun, the accurate knowledge of the solar radiation received by Earth at various wavelengths and from energetic particles with varying intensities, as well as a better knowledge of the solar-terrestrial interactions and their temporal and spatial variability are crucial to quantify the solar influence on climate and to distinguish between natural and anthropogenic influences. In this paper we give an overview on the recent results of solar irradiance measurements over the last three decades and the possible effects of solar variability on climate.

  8. Climate change risks for African agriculture.

    PubMed

    Müller, Christoph; Cramer, Wolfgang; Hare, William L; Lotze-Campen, Hermann

    2011-03-15

    The Intergovernmental Panel on Climate Change (IPCC) assessment of major risks for African agriculture and food security caused by climate change during coming decades is confirmed by a review of more recent climate change impact assessments (14 quantitative, six qualitative). Projected impacts relative to current production levels range from -100% to +168% in econometric, from -84% to +62% in process-based, and from -57% to +30% in statistical assessments. Despite large uncertainty, there are several robust conclusions from published literature for policy makers and research agendas: agriculture everywhere in Africa runs some risk to be negatively affected by climate change; existing cropping systems and infrastructure will have to change to meet future demand. With respect to growing population and the threat of negative climate change impacts, science will now have to show if and how agricultural production in Africa can be significantly improved.

  9. Influence of the African Great Lakes on the regional climate

    NASA Astrophysics Data System (ADS)

    Thiery, Wim; Davin, Edouard; Panitz, Hans-Jürgen; Demuzere, Matthias; Lhermitte, Stef; van Lipzig, Nicole

    2015-04-01

    Although the African Great Lakes are important regulators for the East-African climate, their influence on atmospheric dynamics and the regional hydrological cycle remains poorly understood. We aim to assess this impact by conducting a regional climate model simulation which resolves individual lakes and explicitly computes lake temperatures. The regional climate model COSMO-CLM, coupled to a state-of-the-art lake parameterization scheme and land surface model, is used to dynamically downscale the COSMO-CLM CORDEX-Africa evaluation simulation to 7 km grid spacing for the period 1999-2008. Evaluation of the model reveals good performance compared to both in-situ and satellite observations, especially for spatio-temporal variability of lake surface temperatures and precipitation. Model integrations indicate that the four major African Great Lakes almost double precipitation amounts over their surface relative to a simulation without lakes, but hardly exert any influence on precipitation beyond their shores. The largest lakes also cool their near-surface air, this time with pronounced downwind influence. The lake-induced cooling happens during daytime, when the lakes absorb incoming solar radiation and inhibit upward turbulent heat transport. At night, when this heat is released, the lakes warm the near-surface air. Furthermore, Lake Victoria has profound influence on atmospheric dynamics and stability as it induces cellular motion with over-lake convective inhibition during daytime, and the reversed pattern at night. Overall, this study shows the added value of resolving individual lakes and realistically representing lake surface temperatures for climate studies in this region. Thiery, W., Davin, E., Panitz, H.-J., Demuzere, M., Lhermitte, S., van Lipzig, N.P.M., The impact of the African Great Lakes on the regional climate, J. Climate (in review).

  10. Climate not to blame for African civil wars.

    PubMed

    Buhaug, Halvard

    2010-09-21

    Vocal actors within policy and practice contend that environmental variability and shocks, such as drought and prolonged heat waves, drive civil wars in Africa. Recently, a widely publicized scientific article appears to substantiate this claim. This paper investigates the empirical foundation for the claimed relationship in detail. Using a host of different model specifications and alternative measures of drought, heat, and civil war, the paper concludes that climate variability is a poor predictor of armed conflict. Instead, African civil wars can be explained by generic structural and contextual conditions: prevalent ethno-political exclusion, poor national economy, and the collapse of the Cold War system. PMID:20823241

  11. Evolution and climate variability

    SciTech Connect

    Potts, R.

    1996-08-16

    Variations in organisms are preserved and accrue if there is a consistent bias in selection over many generations. This idea of long-term directional selection has been embraced to explain major adaptive change. It is widely thought that important adaptive shifts in hominids corresponded with directional environmental change. This view, which echoes the savanna scenario of hominid evolution, has strongly been supported by paleontologists and paleoclimatologists over the past decade. The origin of the hominids, bipedality, stone toolmaking, and brain size increase have all been related to cooling, aridification, and savanna expansion. However there appears to be a more prominent signal than the aridity trend: an increase in the range of climatic variation over time. This article discusses the possible reprocussions of this interpertation. 13 refs.

  12. African climate variability and organic carbon accumulation in the Coniacian-Satonian eastern tropical Atlantic: Insights how insolation-cycles in the Cretaceous were transformed to marine black shales

    NASA Astrophysics Data System (ADS)

    Hofmann, P.; Wagner, T.; Beckmann, B.; Floegel, S.

    2003-12-01

    There is increasing evidence from marine proxy records that tropical regions during the late Cretaceous were hotter than previously reported and were by far exceeding modern average temperatures. Tropical sea surface temperatures in the range of 32-36° C apparently lasted from the latest Cenomanian to the early Campanian. A fundamental consequence of superheated Cretaceous tropics is a vigorous hydrological cycle operating in equatorial regions. Geological evidence supporting such an enhanced hydrological cycle and a direct link to the formation of marine black shale cycles was recently reported for ODP Site 959 from the Deep Ivorian Basin (DIB) off equatorial West-Africa. Millennial-scale marine and terrigenous proxy records from that site provide a unique opportunity to investigate short-term variability of the ocean-climate system, to discuss the role of orbital forcing and to assess the primary mechanisms how cyclic marine deposits are formed in the geological record. In the Deep Ivorian Basin formation of cyclic OAE3 black shales was favoured by the paleogeographic position of the drill site in the partly sheltered early Ivory Basin south of the paleo-equator and, most important, was directly linked to orbital-driven fluctuations in atmospheric and oceanic circulation. Dramatic changes in redox sensitive trace metal accumulation as well as the occurrence of molecular fossils of green sulfur bacteria provide evidence for extreme variations in redox conditions, with euxinic conditions occasionally even extending into the lower photic zone. The temporal establishment of a continuous euxinic water column about 200 km offshore the West-African coastline supports the conclusion that redox conditions in the Coniacian-Santonian tropical ocean at least occasionally were as extreme as during the Cenomanian-Turonian OAE-2, although much smaller in extent and restricted to short but repetitive periods. It has also been demonstrated that the terrigenous fraction

  13. CLANIMAE: Climatic and Anthropogenic Impacts on African Ecosystems

    NASA Astrophysics Data System (ADS)

    Verschuren, D.; André, L.; Mahy, G.; Cocquyt, C.; Plisnier, P.-D.; Gelorini, V.; Rumes, B.; Lebrun, J.; Bock, L.; Marchant, R.

    2009-04-01

    distribution against lake trophic status and turbidity in the modern-day regional lake gradient. The integrated paleoecological research method of this project addresses the question of past climate-environment-human relationships at the time scale at which the relevant processes have actually occurred. This will allow us to 1) separate the influences of natural climate variability and human activity on East African ecosystems, 2) determine the exact timing and relative magnitude of indigenous (pre-20th century) anthropogenic land clearance compared to recent landscape alteration, 3) determine the severity of lake water-quality losses due to siltation and excess nutrient input directly linked to deforestation and agriculture, compared to those associated with natural ecosystem variability, and 4) assess the resilience of African ecosystems, and prospects for the restoration of disturbed ecosystems if human pressure were to be reversed.

  14. Solar variability, weather, and climate

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Advances in the understanding of possible effects of solar variations on weather and climate are most likely to emerge by addressing the subject in terms of fundamental physical principles of atmospheric sciences and solar-terrestrial physis. The limits of variability of solar inputs to the atmosphere and the depth in the atmosphere to which these variations have significant effects are determined.

  15. Aerosol interactions with African/Atlantic climate dynamics

    NASA Astrophysics Data System (ADS)

    Hosseinpour, F.; Wilcox, E. M.

    2014-07-01

    Mechanistic relationships exist between variability of dust in the oceanic Saharan air layer (OSAL) and transient changes in the dynamics of Western Africa and the tropical Atlantic Ocean. This study provides evidence of possible interactions between dust in the OSAL region and African easterly jet-African easterly wave (AEJ-AEW) system in the climatology of boreal summer, when easterly wave activity peaks. Synoptic-scale changes in instability and precipitation in the African/Atlantic intertropical convergence zone are correlated with enhanced aerosol optical depth (AOD) in the OSAL region in response to anomalous 3D overturning circulations and upstream/downstream thermal anomalies at above and below the mean-AEJ level. Upstream and downstream anomalies are referred to the daily thermal/dynamical changes over the West African monsoon region and the Eastern Atlantic Ocean, respectively. Our hypothesis is that AOD in the OSAL is positively correlated with the downstream AEWs and negatively correlated with the upstream waves from climatological perspective. The similarity between the 3D pattern of thermal/dynamical anomalies correlated with dust outbreaks and those of AEWs provides a mechanism for dust radiative heating in the atmosphere to reinforce AEW activity. We proposed that the interactions of OSAL dust with regional climate mainly occur through coupling of dust with the AEWs.

  16. Extreme events evaluation over African cities with regional climate simulations

    NASA Astrophysics Data System (ADS)

    Bucchignani, Edoardo; Mercogliano, Paola; Simonis, Ingo; Engelbrecht, Francois

    2013-04-01

    The warming of the climate system in recent decades is evident from observations and is mainly related to the increase of anthropogenic greenhouse gas concentrations (IPCC, 2012). Given the expected climate change conditions on the African continent, as underlined in different publications, and their associated socio-economic impacts, an evaluation of the specific effects on some strategic African cities on the medium and long-term is of crucial importance with regard to the development of adaptation strategies. Assessments usually focus on averages climate properties rather than on variability or extremes, but often these last ones have more impacts on the society than averages values. Global Coupled Models (GCM) are generally used to simulate future climate scenarios as they guarantee physical consistency between variables; however, due to the coarse spatial resolution, their output cannot be used for impact studies on local scales, which makes necessary the generation of higher resolution climate change data. Regional Climate Models (RCM) describe better the phenomena forced by orography or by coastal lines, or that are related to convection. Therefore they can provide more detailed information on climate extremes that are hard to study and even harder to predict because they are, by definition, rare and obey different statistical laws. The normal bias of the RCM to represent the local climatology is reduced using adequate statistical techniques based on the comparison of the simulated results with long observational time series. In the framework of the EU-FP7 CLUVA (Climate Change and Urban Vulnerability in Africa) project, regional projections of climate change at high resolution (about 8 km), have been performed for selected areas surrounding five African cities. At CMCC, the regional climate model COSMO-CLM has been employed: it is a non-hydrostatic model. For each domain, two simulations have been performed, considering the RCP4.5 and RCP8.5 emission

  17. Reanalyses and Essential Climate Variables

    NASA Technical Reports Server (NTRS)

    Bosilovich, Michael

    2011-01-01

    Reanalyses are a potentially powerful climate data collection driven by observations but also subjected to model bias. Additionally, reanalyses can produce and use essential climate variables in a consistent method. For example, snow cover and soil moisture (among other variables) will eventually be assimilated into the reanalyses, but also provide crucial validation data. Sea surface temperature can be prescribed or assimilated in a coupled reanalysis. The strength of reanalysis lies in the ancillary data that is produced from the modeling components but not routinely observed thereby providing more complete Earth system information. The weakness in this concept is that the model derived data can be affected by model bias and may also change relative to the available observing system. Here, we will review the status of existing reanalyses and the ECVs being considered for the workshop. Purpose of Michael Bosilovich's contribution to the workshop: Michael Bosilovich will represent US reanalysis community in this international discussion of Essential Climate Variables (ECVs) and the relative nature of reanalyses to ECVs.

  18. West Indian Ocean variability and East African fish catch.

    PubMed

    Jury, M; McClanahan, T; Maina, J

    2010-08-01

    We describe marine climate variability off the east coast of Africa in the context of fish catch statistics for Tanzania and Kenya. The time series exhibits quasi-decadal cycles over the period 1964-2007. Fish catch is up when sea surface temperature (SST) and atmospheric humidity are below normal in the tropical West Indian Ocean. This pattern relates to an ocean Rossby wave in one phase of its east-west oscillation. Coastal-scale analyses indicate that northward currents and uplift on the shelf edge enhance productivity of East African shelf waters. Some of the changes are regulated by the south equatorial current that swings northward from Madagascar. The weather is drier and a salty layer develops in high catch years. While the large-scale West Indian Ocean has some impact on East African fish catch, coastal dynamics play a more significant role. Climatic changes are reviewed using 200 years of past and projected data. The observed warming trend continues to increase such that predicted SST may reach 30 degrees C by 2100 while SW monsoon winds gradually increase, according to a coupled general circulation model simulation with a gradual doubling of CO(2). PMID:20471674

  19. Cloud feedback on climate change and variability

    NASA Astrophysics Data System (ADS)

    Zhou, C.; Dessler, A. E.; Yang, P.

    2014-12-01

    Cloud feedback on climate change and variability follow similar mechanism in climate models, and the magnitude of cloud feedback on climate change and variability are well correlated among models. Therefore, the cloud feedback on short-term climate fluctuations correlates with the equilibrium climate sensitivity in climate models. Using this correlation and the observed short-term climate feedback, we infer a climate sensitivity of ~2.9K. The cloud response to inter-annual surface warming is generally consistent in observations and climate models, except for the tropical boundary-layer low clouds.

  20. Observed Oceanic and Terrestrial Drivers of North African Climate

    NASA Astrophysics Data System (ADS)

    Yu, Y.; Notaro, M.; Wang, F.; Mao, J.; Shi, X.; Wei, Y.

    2015-12-01

    Hydrologic variability can pose a serious threat to the poverty-stricken regions of North Africa. Yet, the current understanding of oceanic versus terrestrial drivers of North African droughts/pluvials is largely model-based, with vast disagreement among models. In order to identify the observed drivers of North African climate and develop a benchmark for model evaluations, the multivariate Generalized Equilibrium Feedback Assessment (GEFA) is applied to observations, remotely sensed data, and reanalysis products. The identified primary oceanic drivers of North African rainfall variability are the Atlantic, tropical Indian, and tropical Pacific Oceans and Mediterranean Sea. During the summer monsoon, positive tropical eastern Atlantic sea-surface temperature (SST) anomalies are associated with a southward shift of the Inter-Tropical Convergence Zone, enhanced ocean evaporation, and greater precipitable water across coastal West Africa, leading to increased West African monsoon (WAM) rainfall and decreased Sahel rainfall. During the short rains, positive SST anomalies in the western tropical Indian Ocean and negative anomalies in the eastern tropical Indian Ocean support greater easterly oceanic flow, evaporation over the western ocean, and moisture advection to East Africa, thereby enhancing rainfall. The sign, magnitude, and timing of observed vegetation forcing on rainfall vary across North Africa. The positive feedback of leaf area index (LAI) on rainfall is greatest during DJF for the Horn of Africa, while it peaks in autumn and is weakest during the summer monsoon for the Sahel. Across the WAM region, a positive LAI anomaly supports an earlier monsoon onset, increased rainfall during the pre-monsoon, and decreased rainfall during the wet season. Through unique mechanisms, positive LAI anomalies favor enhanced transpiration, precipitable water, and rainfall across the Sahel and Horn of Africa, and increased roughness, ascent, and rainfall across the WAM region

  1. Projections of African drought extremes in CORDEX regional climate simulations

    NASA Astrophysics Data System (ADS)

    Gbobaniyi, Emiola; Nikulin, Grigory; Jones, Colin; Kjellström, Erik

    2013-04-01

    We investigate trends in drought extremes for different climate regions of the African continent over a combined historical and future period 1951-2100. Eight CMIP5 coupled atmospheric global climate models (CanESM2, CNRM-CM5, HadGEM2-ES, NorESM1-M, EC-EARTH, MIROC5, GFDL-ESM2M and MPI-ESM-LR) under two forcing scenarios, the relative concentration pathways (RCP) 4.5 and 8.5, with spatial resolution varying from about 1° to 3° are downscaled to 0.44° resolution by the Rossby Centre (SMHI) regional climate model RCA4. We use data from the ensuing ensembles of CORDEX-Africa regional climate simulations to explore three drought indices namely: standardized precipitation index (SPI), moisture index (MI) and difference in precipitation and evaporation (P-E). Meteorological and agricultural drought conditions are assessed in our analyses and a climate change signal is obtained for the SPI by calculating gamma functions for future SPI with respect to a baseline present climate. Results for the RCP4.5 and RCP8.5 scenarios are inter-compared to assess uncertainties in the future projections. We show that there is a pronounced sensitivity to the choice of forcing GCM which indicates that assessments of future drought conditions in Africa would benefit from large model ensembles. We also note that the results are sensitive to the choice of drought index. We discuss both spatial and temporal variability of drought extremes for different climate zones of Africa and the importance of the ensemble mean. Our study highlights the usefulness of CORDEX simulations in identifying possible future impacts of climate at local and regional scales.

  2. Climate Change Projections for African Urban Areas

    NASA Astrophysics Data System (ADS)

    Simonis, Ingo; Engelbrecht, Francois; Bucchignani, Edoardo; Mercogliano, Paola; Naidoo, Mogesh

    2013-04-01

    Africa have been derived (six at CSIR and two at CMCC). That is, a multi-model ensemble of simulations of present-day and future climate has been made available for a number of African regions. This approach is most useful to describe the range of uncertainty associated with future climate. In order to obtain a set of plausible and physically defensible projections that can be used for a broad range of subsequent research questions, the two partners followed two different modelling approaches. The first approach, (by CMCC) uses a single dynamic climate change model: the model gets executed several times using a number of pertubations, e.g. changing initial conditions to account for the non-linear dynamics, perturbations of the boundary conditions to account for the 'imperfect' characterizations of the non-atmospheric components of the climate system or to handle the uncertainty of the driving global model, or perturbations of the model physics to account for the uncertainties inherent in the parameterizations. The second approach, (by CSIR) keeps the boundary conditions static but downscales a number of different global circulation models to account for the uncertainties inherent in the models themselves. In total, CSIR has run six different dynamic models. All runs have been conducted on super computing clusters to be completed within reasonable timeframes. The full data set is currently made available on the web. A number of tools is used to provide maximum user experience for climate change experts, social geographers, city planners and policy decision makers.

  3. Cyclical konzo epidemics and climate variability.

    PubMed

    Oluwole, Olusegun Steven A

    2015-03-01

    Konzo epidemics have occurred during droughts in the Democratic Republic of Congo (DR Congo) for >70 years, but also in Mozambique, Tanzania, and the Central African Republic. The illness is attributed to exposure to cyanide from cassava foods, on which the population depends almost exclusively during droughts. Production of cassava, a drought-resistant crop, has been shown to correlate with cyclical changes in precipitation in konzo-affected countries. Here we review the epidemiology of konzo as well as models of its pathogenesis. A spectral analysis of precipitation and konzo is performed to determine whether konzo epidemics are cyclical and whether there is spectral coherence. Time series of environmental temperature, precipitation, and konzo show cyclical changes. Periodicities of dominant frequencies in the spectra of precipitation and konzo range from 3 to 6 years in DR Congo. There is coherence of the spectra of precipitation and konzo. The magnitude squared coherence of 0.9 indicates a strong relationship between variability of climate and konzo epidemics. Thus, it appears that low precipitation phases of climate variability reduce the yield of food crops except cassava, upon which the population depends for supply of calories during droughts. Presence of very high concentrations of thiocyanate (SCN(-) ), the major metabolite of cyanide, in the bodily fluids of konzo subjects is a consequence of dietary exposure to cyanide, which follows intake of poorly processed cassava roots. Because cyanogens and minor metabolites of cyanide have not induced konzo-like illnesses, SCN(-) remains the most likely neurotoxicant of konzo. Public health control of konzo will require food and water programs during droughts. [Correction added on 26 February 2015, after first online publication: abstract reformatted per journal style

  4. Trends and variability of East African rainfall and its relationship to the Mascarene High pressure system

    NASA Astrophysics Data System (ADS)

    Seregina, Larisa; Pinto, Joaquim G.; Fink, Andreas H.; Ermert, Volker

    2016-04-01

    In the recent decades, East Africa needs to deal with strong fluctuations in seasonal rainfall including precipitation extremes. In context of climate change, such extremes can become more frequent in the future. However, regional climate projections are uncertain about the future development of seasonal precipitation in the region. Rainfall regimes over East Africa are influenced by multiple factors, including two monsoon systems, several convergence zones and the Rift Valley lakes. In addition, local conditions, like topography, modulate the large-scale rainfall pattern. East African rainfall variability is also influenced by various teleconnections like the Indian Ocean Zonal Mode and El Niño Southern Oscillation. The study of past climate variability in East Africa requires sufficient observational data coverage in the region. As East Africa does not have a dense observational network of meteorological stations, satellite rainfall observations gain on importance in studies on climate variability in the region. The specific aim of the present study is the analysis of historic data from weather stations in East Africa (Kenya, Tanzania, Ruanda and Uganda), the use of gridded satellite products, and three-dimensional atmospheric reanalysis (e.g., ERA-Interim) to quantify climate variability in the recent past and to understand its causes. Climate variability and trends, including changes in extreme events, are evaluated using ETCCDI climate change and standardized precipitation indices. These climate indices are determined in order to investigate the variability of rainfall and its trends with the focus on recent decades. For seasonal trend analysis, an independent and non-calendaric rainfall onset criterion is introduced. In the follow-up, statistical and dynamical analyses are conducted to quantify the local impact of Mascarene High as a part of the Subtropical High Pressure Ridge on East African seasonal rainfall. Possible connections to pertinent large

  5. African lessons on climate change risks for agriculture.

    PubMed

    Müller, Christoph

    2013-01-01

    Climate change impact assessments on agriculture are subject to large uncertainties, as demonstrated in the present review of recent studies for Africa. There are multiple reasons for differences in projections, including uncertainties in greenhouse gas emissions and patterns of climate change; assumptions on future management, aggregation, and spatial extent; and methodological differences. Still, all projections agree that climate change poses a significant risk to African agriculture. Most projections also see the possibility of increasing agricultural production under climate change, especially if suitable adaptation measures are assumed. Climate change is not the only projected pressure on African agriculture, which struggles to meet demand today and may need to feed an additional one billion individuals by 2050. Development strategies are urgently needed, but they will need to consider future climate change and its inherent uncertainties. Science needs to show how existing synergies between climate change adaptation and development can be exploited.

  6. Climate variability, climate change, and fisheries

    SciTech Connect

    Glantz, M.H.

    1992-01-01

    This book contains 15 case studies of the ups and downs of fisheries. Each author focuses on the uncertainties of forecasting for fisheries and offers conclusions on the possible impacts of climatic change. Problems of forecasting for fisheries discussed in the book include the following: inadequate models; alterations in industrial structures;climatic events;habitat loss; interrelationships among life history, industry, society, and ecological processes; sociopolitical factors; predatory-parasitic species irruptions;climatic oceanographic factors; international fisheries politics and technology; large scale fluctuations in a coastal fisheries. The book presents the array of problems faced by scientists, fishery managers, and policy makers, and summarizes with general conclusions.

  7. Human Responses to Climate Variability: The Case of South Africa

    NASA Astrophysics Data System (ADS)

    Oppenheimer, M.; Licker, R.; Mastrorillo, M.; Bohra-Mishra, P.; Estes, L. D.; Cai, R.

    2014-12-01

    Climate variability has been associated with a range of societal and individual outcomes including migration, violent conflict, changes in labor productivity, and health impacts. Some of these may be direct responses to changes in mean temperature or precipitation or extreme events, such as displacement of human populations by tropical cyclones. Others may be mediated by a variety of biological, social, or ecological factors such as migration in response to long-term changes in crops yields. Research is beginning to elucidate and distinguish the many channels through which climate variability may influence human behavior (ranging from the individual to the collective, societal level) in order to better understand how to improve resilience in the face of current variability as well as future climate change. Using a variety of data sets from South Africa, we show how climate variability has influenced internal (within country) migration in recent history. We focus on South Africa as it is a country with high levels of internal migration and dramatic temperature and precipitation changes projected for the 21st century. High poverty rates and significant levels of rain-fed, smallholder agriculture leave large portions of South Africa's population base vulnerable to future climate change. In this study, we utilize two complementary statistical models - one micro-level model, driven by individual and household level survey data, and one macro-level model, driven by national census statistics. In both models, we consider the effect of climate on migration both directly (with gridded climate reanalysis data) and indirectly (with agricultural production statistics). With our historical analyses of climate variability, we gain insights into how the migration decisions of South Africans may be influenced by future climate change. We also offer perspective on the utility of micro and macro level approaches in the study of climate change and human migration.

  8. Multidecadal variability in East African hydroclimate controlled by the Indian Ocean.

    PubMed

    Tierney, Jessica E; Smerdon, Jason E; Anchukaitis, Kevin J; Seager, Richard

    2013-01-17

    The recent decades-long decline in East African rainfall suggests that multidecadal variability is an important component of the climate of this vulnerable region. Prior work based on analysing the instrumental record implicates both Indian and Pacific ocean sea surface temperatures (SSTs) as possible drivers of East African multidecadal climate variability, but the short length of the instrumental record precludes a full elucidation of the underlying physical mechanisms. Here we show that on timescales beyond the decadal, the Indian Ocean drives East African rainfall variability by altering the local Walker circulation, whereas the influence of the Pacific Ocean is minimal. Our results, based on proxy indicators of relative moisture balance for the past millennium paired with long control simulations from coupled climate models, reveal that moist conditions in coastal East Africa are associated with cool SSTs (and related descending circulation) in the eastern Indian Ocean and ascending circulation over East Africa. The most prominent event identified in the proxy record--a coastal pluvial from 1680 to 1765--occurred when Indo-Pacific warm pool SSTs reached their minimum values of the past millennium. Taken together, the proxy and model evidence suggests that Indian Ocean SSTs are the primary influence on East African rainfall over multidecadal and perhaps longer timescales.

  9. Multidecadal variability in East African hydroclimate controlled by the Indian Ocean.

    PubMed

    Tierney, Jessica E; Smerdon, Jason E; Anchukaitis, Kevin J; Seager, Richard

    2013-01-17

    The recent decades-long decline in East African rainfall suggests that multidecadal variability is an important component of the climate of this vulnerable region. Prior work based on analysing the instrumental record implicates both Indian and Pacific ocean sea surface temperatures (SSTs) as possible drivers of East African multidecadal climate variability, but the short length of the instrumental record precludes a full elucidation of the underlying physical mechanisms. Here we show that on timescales beyond the decadal, the Indian Ocean drives East African rainfall variability by altering the local Walker circulation, whereas the influence of the Pacific Ocean is minimal. Our results, based on proxy indicators of relative moisture balance for the past millennium paired with long control simulations from coupled climate models, reveal that moist conditions in coastal East Africa are associated with cool SSTs (and related descending circulation) in the eastern Indian Ocean and ascending circulation over East Africa. The most prominent event identified in the proxy record--a coastal pluvial from 1680 to 1765--occurred when Indo-Pacific warm pool SSTs reached their minimum values of the past millennium. Taken together, the proxy and model evidence suggests that Indian Ocean SSTs are the primary influence on East African rainfall over multidecadal and perhaps longer timescales. PMID:23325220

  10. Climatic Variability over the North Atlantic

    NASA Astrophysics Data System (ADS)

    Hurrell, J.; Hoerling, M. P.; Folland, C. K.

    INTRODUCTION WHAT IS THE NORTH ATLANTIC OSCILLATION AND HOW DOES IT IMPACT REGIONAL - CLIMATE? WHAT ARE THE MECHANISMS THAT GOVERN NORTH ATLANTIC OSCILLATION VARIABILITY? Atmospheric Processes Ocean Forcing of the Atmosphere CONCLUDING COMMENTS ON THE OTHER ASPECTS OF NORTH ATLANTIC CLIMATE - VARIABILITY REFERENCES

  11. Climate variability and vulnerability to climate change: a review.

    PubMed

    Thornton, Philip K; Ericksen, Polly J; Herrero, Mario; Challinor, Andrew J

    2014-11-01

    The focus of the great majority of climate change impact studies is on changes in mean climate. In terms of climate model output, these changes are more robust than changes in climate variability. By concentrating on changes in climate means, the full impacts of climate change on biological and human systems are probably being seriously underestimated. Here, we briefly review the possible impacts of changes in climate variability and the frequency of extreme events on biological and food systems, with a focus on the developing world. We present new analysis that tentatively links increases in climate variability with increasing food insecurity in the future. We consider the ways in which people deal with climate variability and extremes and how they may adapt in the future. Key knowledge and data gaps are highlighted. These include the timing and interactions of different climatic stresses on plant growth and development, particularly at higher temperatures, and the impacts on crops, livestock and farming systems of changes in climate variability and extreme events on pest-weed-disease complexes. We highlight the need to reframe research questions in such a way that they can provide decision makers throughout the food system with actionable answers, and the need for investment in climate and environmental monitoring. Improved understanding of the full range of impacts of climate change on biological and food systems is a critical step in being able to address effectively the effects of climate variability and extreme events on human vulnerability and food security, particularly in agriculturally based developing countries facing the challenge of having to feed rapidly growing populations in the coming decades. PMID:24668802

  12. Climate variability and vulnerability to climate change: a review.

    PubMed

    Thornton, Philip K; Ericksen, Polly J; Herrero, Mario; Challinor, Andrew J

    2014-11-01

    The focus of the great majority of climate change impact studies is on changes in mean climate. In terms of climate model output, these changes are more robust than changes in climate variability. By concentrating on changes in climate means, the full impacts of climate change on biological and human systems are probably being seriously underestimated. Here, we briefly review the possible impacts of changes in climate variability and the frequency of extreme events on biological and food systems, with a focus on the developing world. We present new analysis that tentatively links increases in climate variability with increasing food insecurity in the future. We consider the ways in which people deal with climate variability and extremes and how they may adapt in the future. Key knowledge and data gaps are highlighted. These include the timing and interactions of different climatic stresses on plant growth and development, particularly at higher temperatures, and the impacts on crops, livestock and farming systems of changes in climate variability and extreme events on pest-weed-disease complexes. We highlight the need to reframe research questions in such a way that they can provide decision makers throughout the food system with actionable answers, and the need for investment in climate and environmental monitoring. Improved understanding of the full range of impacts of climate change on biological and food systems is a critical step in being able to address effectively the effects of climate variability and extreme events on human vulnerability and food security, particularly in agriculturally based developing countries facing the challenge of having to feed rapidly growing populations in the coming decades.

  13. Climate variability and vulnerability to climate change: a review

    PubMed Central

    Thornton, Philip K; Ericksen, Polly J; Herrero, Mario; Challinor, Andrew J

    2014-01-01

    The focus of the great majority of climate change impact studies is on changes in mean climate. In terms of climate model output, these changes are more robust than changes in climate variability. By concentrating on changes in climate means, the full impacts of climate change on biological and human systems are probably being seriously underestimated. Here, we briefly review the possible impacts of changes in climate variability and the frequency of extreme events on biological and food systems, with a focus on the developing world. We present new analysis that tentatively links increases in climate variability with increasing food insecurity in the future. We consider the ways in which people deal with climate variability and extremes and how they may adapt in the future. Key knowledge and data gaps are highlighted. These include the timing and interactions of different climatic stresses on plant growth and development, particularly at higher temperatures, and the impacts on crops, livestock and farming systems of changes in climate variability and extreme events on pest-weed-disease complexes. We highlight the need to reframe research questions in such a way that they can provide decision makers throughout the food system with actionable answers, and the need for investment in climate and environmental monitoring. Improved understanding of the full range of impacts of climate change on biological and food systems is a critical step in being able to address effectively the effects of climate variability and extreme events on human vulnerability and food security, particularly in agriculturally based developing countries facing the challenge of having to feed rapidly growing populations in the coming decades. PMID:24668802

  14. Plio-Pleistocene climate-driven facial morphology in southern African australopithecines

    NASA Astrophysics Data System (ADS)

    Williams, F. L.; Christensen, B. A.

    2004-12-01

    Intensification of Northern Hemispheric Glaciation (INHG) has been cited as the driving force for climate change in southern Africa, despite the fact that rare and fragmentary continental records for the region allow for only a loose correlation between local faunal events and global climate change. Determining climatic influence from the limited climate history is exacerbated by the difficult chronology for the cave sites. The depositional history of the caves nonetheless reveals a turnover of southern African mammals, and variability, among other forcing factors, have implicated the INHG to explain the evolution of these novel forms. We suggest that evolutionary changes in southern African fauna may have also been driven by a subsequent climate event, the Onset of Walker Circulation (OWC) at ~ 2 Myr. The OWC, with enhanced high frequency climate variability, may have been more dominant than INHG in driving southern African mammalian evolution. For example, Pleistocene Australopithecus robustus, but not Pliocene Australopithecus africanus, exhibits relatively broad palates, postcanine megadonty and deep mandibular corpora that correspond to a dietary niche involving heavy mastication. These adaptations may have been selected for in unstable Pleistocene environments initiated by the OWC. Moreover, the temporal context of Australopithecus robustus, found in the Pleistocene dated caves of Swartkrans, Kromdraai and Drimolen, coincides more closely with the OWC than with the INHG.

  15. Environmental variability and the evolution of the glucocorticoid receptor (Nr3c1) in African starlings.

    PubMed

    Hofmeister, Natalie R; Rubenstein, Dustin R

    2016-10-01

    One of the primary ways that organisms cope with environmental change is through regulation of the hypothalamo-pituitary-adrenal (HPA) axis, the neuroendocrine system that controls reactions to stress. Variation in genes regulating the HPA axis - particularly the glucocorticoid receptor - may facilitate adaptation to changing climatic conditions by altering expression. Here we examine signatures of selection on the glucocorticoid receptor gene (Nr3c1) in African starlings that inhabit a range of environments, including those with variable climatic conditions. To investigate potential adaptive mechanisms underlying the vertebrate stress response, we sequence the Nr3c1 gene in 27 species of African starlings. Although we find some evidence of positive selection, substitution rate is negatively correlated with variance in precipitation. This suggests climatic cycling in sub-Saharan Africa may have resulted in lower substitution rates to maintain a successful coping strategy. When environmental conditions fluctuate rapidly, variation in the strength of purifying selection can explain evolutionary rate variation. PMID:27500971

  16. Timing of climate variability and grassland productivity

    PubMed Central

    Craine, Joseph M.; Nippert, Jesse B.; Elmore, Andrew J.; Skibbe, Adam M.; Hutchinson, Stacy L.; Brunsell, Nathaniel A.

    2012-01-01

    Future climates are forecast to include greater precipitation variability and more frequent heat waves, but the degree to which the timing of climate variability impacts ecosystems is uncertain. In a temperate, humid grassland, we examined the seasonal impacts of climate variability on 27 y of grass productivity. Drought and high-intensity precipitation reduced grass productivity only during a 110-d period, whereas high temperatures reduced productivity only during 25 d in July. The effects of drought and heat waves declined over the season and had no detectable impact on grass productivity in August. If these patterns are general across ecosystems, predictions of ecosystem response to climate change will have to account not only for the magnitude of climate variability but also for its timing. PMID:22331914

  17. Processes Understanding of Decadal Climate Variability

    NASA Astrophysics Data System (ADS)

    Prömmel, Kerstin; Cubasch, Ulrich

    2016-04-01

    The realistic representation of decadal climate variability in the models is essential for the quality of decadal climate predictions. Therefore, the understanding of those processes leading to decadal climate variability needs to be improved. Several of these processes are already included in climate models but their importance has not yet completely been clarified. The simulation of other processes requires sometimes a higher resolution of the model or an extension by additional subsystems. This is addressed within one module of the German research program "MiKlip II - Decadal Climate Predictions" (http://www.fona-miklip.de/en/) with a focus on the following processes. Stratospheric processes and their impact on the troposphere are analysed regarding the climate response to aerosol perturbations caused by volcanic eruptions and the stratospheric decadal variability due to solar forcing, climate change and ozone recovery. To account for the interaction between changing ozone concentrations and climate a computationally efficient ozone chemistry module is developed and implemented in the MiKlip prediction system. The ocean variability and air-sea interaction are analysed with a special focus on the reduction of the North Atlantic cold bias. In addition, the predictability of the oceanic carbon uptake with a special emphasis on the underlying mechanism is investigated. This addresses a combination of physical, biological and chemical processes.

  18. Creating a Learning Climate: A South African Study

    ERIC Educational Resources Information Center

    Carrim, Nasima Mohamed Hoosen; Basson, Johan Schutte

    2013-01-01

    Purpose: The purpose of this study is to ascertain whether there were differences in how one public and two private South African organizations created a learning climate. Design/methodology/approach: This article is based on a survey and comparative analysis of specific departments in a chemical and gas company, an insurance company, and a…

  19. The income-climate trap of health development: a comparative analysis of African and Non-African countries.

    PubMed

    Tang, Kam Ki; Petrie, Dennis; Rao, D S Prasada

    2009-10-01

    This article conducts a comparative analysis of the interrelationship between climate, life expectancy and income between African and non-African countries. To put the analysis in a broader context of development, the paper develops an income-climate trap model that explains the multi-directional interaction between income, climate and life expectancy. It is suggested that the interaction can give rise to either a virtuous cycle of prosperity or a vicious cycle of poverty. Applying the model to a data set of 158 countries, we find that climate is a more important determinant of life expectancy in African countries than in non-African countries. We provide further empirical evidence that while climate is important in determining both life expectancy and income, income can in turn moderate the adverse effects of climate on life expectancy. In the past two decades, the income level of non-African countries has grown significantly while that of African countries has largely been stagnant, implying that the future development of African countries remains highly vulnerable to adverse climatic conditions. These findings have important implications in the context of climate change, as global warming is likely to create worsening climatic conditions that could see many less developed countries sinking deeper into an income-climate trap of underdevelopment in health.

  20. Climate Variability and Sugarcane Yield in Louisiana.

    NASA Astrophysics Data System (ADS)

    Greenland, David

    2005-11-01

    This paper seeks to understand the role that climate variability has on annual yield of sugarcane in Louisiana. Unique features of sugarcane growth in Louisiana and nonclimatic, yield-influencing factors make this goal an interesting and challenging one. Several methods of seeking and establishing the relations between yield and climate variables are employed. First, yield climate relations were investigated at a single research station where crop variety and growing conditions could be held constant and yield relations could be established between a predominant older crop variety and a newer one. Interviews with crop experts and a literature survey were used to identify potential climatic factors that control yield. A statistical analysis was performed using statewide yield data from the American Sugar Cane League from 1963 to 2002 and a climate database. Yield values for later years were adjusted downward to form an adjusted yield dataset. The climate database was principally constructed from daily and monthly values of maximum and minimum temperature and daily and monthly total precipitation for six cooperative weather-reporting stations representative of the area of sugarcane production. The influence of 74 different, though not independent, climate-related variables on sugarcane yield was investigated. The fact that a climate signal exists is demonstrated by comparing mean values of the climate variables corresponding to the upper and lower third of adjusted yield values. Most of these mean-value differences show an intuitively plausible difference between the high- and low-yield years. The difference between means of the climate variables for years corresponding to the upper and lower third of annual yield values for 13 of the variables is statistically significant at or above the 90% level. A correlation matrix was used to identify the variables that had the largest influence on annual yield. Four variables [called here critical climatic variables (CCV

  1. Recent climatological trend of the Saharan heat low and its impact on the West African climate

    NASA Astrophysics Data System (ADS)

    Lavaysse, Christophe; Flamant, Cyrille; Evan, Amato; Janicot, Serge; Gaetani, Marco

    2015-10-01

    The Saharan heat low (SHL) plays a pivotal role in the West African monsoon system in spring and summer. The recent trend in SHL activity has been analysed using two sets of numerical weather prediction (NWP) model reanalyses and Atmospheric Models Intercomparison Project simulations from 15 climate models performed in the framework of the 5th Coupled Models Intercomparison Project (CMIP5) exercise. A local increase of temperature in the Sahara during the 90s is found in the two sets of NWP models temperature. This increase is stronger within the SHL region than over the surrounding areas. Using different temporal filters (under 25 days, 25-100 days and above 300 days), we show that this is accompanied by a slight but widespread increase of temperature, and a change in the filtered signal under 25 days during the transition period of the 90s. We also show that SHL pulsations occurring at different time scales impact the West Africa climate on a variety of spatial scales, from the regional scale (for the high band pass) to the synoptic scale (for the low band pass signal). Despite a large variability in the temporal trends for 15 climate models from the CMIP5 project, the warming trend in the 90s is observed in the models ensemble mean. Nevertheless, large discrepancies are found between the NWP models reanalyses and the climate model simulations regarding the spatial and temporal evolutions of the SHL as well as its impact on West African climate at the different time scales. These comparisons also reveal that climate models represent the West African monsoon interactions with SHL pulsations quite differently. We provide recommendations to use some of them depending on the time scales of the processes at play (synoptic, seasonal, interannual) and based on key SHL metrics (location, mean intensity, global trend, interaction with the West African monsoon dynamics).

  2. Modification of the southern African rainfall variability/ENSO relationship since the late 1960s

    NASA Astrophysics Data System (ADS)

    Richard, Y.; Trzaska, S.; Roucou, P.; Rouault, M.

    Analysis of 149 raingauge series (1946-1988) shows a weak positive correlation between late summer rainfalls (January-March) in tropical southern Africa and the Southern Oscillation Index (SOI). The correlation coefficients have been unstable since World War II. They were close to zero before 1970 and significant thereafter. Before 1970, southern African late summer rainfalls were more specifically correlated with regional patterns of sea surface temperature (SST), mainly over the southwestern Indian Ocean. After 1970, teleconnections with near global SST anomaly patterns, i.e. over the central Pacific and Indian oceans, dominate the regional connections. The increase in the sensitivity of the southern African rainfall to the global SO-related circulation anomalies is simultaneous with the correlation between SOI and more extensive SST anomalies, particularly over the southern Indian Ocean. This feature is part of longer term (decadal), global SST variability, as inferred from statistical analyses. Numerical experiments, using the Météo-France general circulation model ARPEGE-Climat, are performed to test the impact of the observed SST warming in the southern Indian and extratropical oceans during El Niño Southern Oscillation (ENSO) events on southern African rainfall. Simulated results show that ENSO events, which occurred in the relatively cold background of the pre-1970 period in the southern oceans, had a little effect on southern Africa climatic conditions and atmospheric circulation. By contrast, more recent ENSO events, with warmer SST over the southern oceans, lead to a climatic bipolar pattern between continental southern African and the western Indian Ocean, which is characterized by reduced (enhanced) deep convection and rainfall over the subcontinent (the western Indian Ocean). A weaker subtropical high-pressure belt in the southwestern Indian Ocean is also simulated, along with a reduced penetration of the moist southern Indian Ocean trade winds

  3. Temporal and climatic variables in naturalistic observation.

    PubMed

    Russell, M B; Bernal, M E

    1977-01-01

    Home-observation data on 5- to 7-yr-old boys collected over 2 yr were examined for systematic variations in rates of desirable and undesirable behaviors associated with several temporal and climatic variables. Significant effects associated with time of day, day of the week, precipitation, and temperature were found. No significant effects on the naturalistic observation data were found for environmental factors associated with lunar phase. It was noted that the correlational nature of the findings did not obviate the necessity for control of the influence of temporal and climatic variables. Several methodological strategies for such control were discussed.

  4. Rainfall variability over the East African coast

    NASA Astrophysics Data System (ADS)

    Gamoyo, Majambo; Reason, Chris; Obura, David

    2015-04-01

    The coastal region of Kenya and Tanzania experiences two rainy seasons per year (October-November-December (OND) and March-April-May (MAM)) and has an economy that is highly dependent on and vulnerable to the amounts and timing of rainfall during these seasons. Most of the interannual variability in OND seasonal rainfall totals relate to El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events. While these relationships are fairly well documented and understood, there is a relatively poor understanding of the timing and intensity of the rainfall during ENSO/IOD seasons. In an attempt to improve understanding on this topic, daily rainfall station data, dekad and seasonal satellite rainfall estimates and Normalized Difference Vegetation Index (NDVI) imagery are analyzed for two recent OND seasons with El Niño conditions. These are OND 2006 which was characterized by devastating floods over the region and 2009 when the magnitude and spatial extent of the above average rainfall patterns were smaller. Daily rainfall data for the Tanzanian coastal stations showed that Tanga and Dar es Salaam (north and central coast) experienced few dry spells and several relatively intense wet spells during OND 2006 whereas at Mtwara, on the south coast, there were two very intense wet spells and a number of dry spells during the season. In OND 2009, only the north coast (Tanga) experienced above average rainfall, comprised of three wet spells with the one about a month after the beginning of the season being very intense. These data highlight the complexity of the rainfall distributions in the coastal region. A shift of the Walker circulation over coastal East Africa with strong uplift there seemed to be responsible for the very wet conditions during OND 2006. The marine air mass being advected from the western tropical Indian Ocean towards East Africa contained more moisture than average. Similar, but weaker, horizontal circulation anomalies occurred in OND 2009

  5. Persistence of African American Men in Science: Exploring the Influence of Scientist Identity, Mentoring, and Campus Climate

    NASA Astrophysics Data System (ADS)

    Guy, Breonte Stephan

    The scant literature on persistence of African American males in science typically takes a deficits-based approach to encapsulate the myriad reasons this population is so often underrepresented. Scientist Identity, Mentoring, and Campus Climate have, individually, been found to be related to the persistence of African American students. However, the unified impact of these three variables on the persistence of African American students with science interests has not been evaluated, and the relationship between the variables, the students' gender, and markers of academic achievement have not been previously investigated. The current study takes a strengths-based approach to evaluating the relationship between Scientist Identity, Mentoring, and Campus climate with a population of African American students with science interests who were studying at six Minority Serving Institutions and Predominantly White Institutions in the Southern United States. Multiple regression analyses were conducted to determine the impact of Scientist Identity, Mentoring, and Campus Climate on Intention to Persist of African American males. The results indicate that Scientist Identity predicts Intention to Persist, and that gender, academic performance, and institution type moderate the relationship between Scientist Identity and Intention to Persist. These results lend credence to the emerging notion that, for African American men studying science, generating a greater depth and breadth of understanding of the factors that lead to persistence will aid in the development of best practices for supporting persistence among this perpetually underrepresented population.

  6. Prediction of climate variability and projection of climate change

    SciTech Connect

    Grassl, H.

    1996-12-31

    The years since 1985 have seen rapid progress in climate research. By the implementation of a new observing system in the Tropical Pacific Ocean combined with the development of adapted coupled ocean-atmosphere models the Tropical Ocean-Global Atmosphere (TOGA) project of the World Climate Research Programme (WCRP) led to the breakthrough to physically-based climate predictions. For most of the tropics and partly extending to mid-latitudes, climate anomalies can now be predicted for the next season and in some places even for the next year. On the other hand, global coupled ocean-atmosphere-land models have recently approached natural climate variability on time-scales to several decades to such an extent, that these models, partly validated with data from the past, became useful for answering the following two questions: Has mankind already changed global climate? Is anthropogenic global climate change, in the coming century, surmounting at least all variability observed during the last 10,000 years? Both questions are answered by yes. For the first question, the observed patterns of warming and cooling with respect to geographical, seasonal and vertical dependence can only be explained by a combined action of global greenhouse gas increase, regional sulfate aerosol load and stratospheric ozone depletion. For the second, even low climate sensitivity and low economic growth, will lead, if no measures are taken, to a mean global warming of 1.0 C, thus surmounting the warmest phase of the holocene. Implications of these findings for the implementation of the UN Framework Convention on Climate Change will also be discussed.

  7. Climatic Variability In Tropical Countries

    NASA Astrophysics Data System (ADS)

    Seneviratne, L. W.

    2003-04-01

    atmospheric condition and hence reduces rainfall for about 1.5 years in tropical countries. This was proved in 2001. This forecast was presented as a paper in 1998 Stockholm Water Symposium. The results were true for Brazil as well. The danger is now over when the episode is relaxed. Second half of 2002 was heavily wet and all the tanks in Sri Lanka except Kirindioya complex in Hambanthoa area got filled. This condition was seen in 1997 where all tanks got filled. El Nino analysts declared 1997 as a drought year as the previous year had experienced warming in Pacific Ocean. Southern Oscillation events are now dissociating to conformity. Discussion Hambanthoa District remained in the dry zone of Sri Lanka for 2000 years as the soil forms expressed as reddish brown earths. Original kingdoms had its base in Anuradhapura in Northcentral Province and Magama in Hambanthota district. Tools used by contemporary farmers were not powerful to use enormous water resources in wet zone. A system of diversion dams and use of run of the river irrigation has proved as the main criteria of that era. Diversion dams and canal projects were in existence. The diversion dams with special shape was mistaken by british surveyors and marked as broken dams in plans. DLOMendis later identified these as effective deflecting dams. The purpose was to wet the area to do cultivation. This system of wetting the land was suitable for dry climates with low rainfall. High technology was introduced by Irrigation Department to construct several reservoirs in Hambanthota. This was planned after the insufficient water use of Ellagala anicut from Kirindi Oya. Next step was to plan a reservoir project at Lunugamvehera dam site. Precipitation data available for 50 years were studied and a reservoir was designed for 20 000acres of paddy. It was planned to cultivate rice for Maha season and other field crops for Yala season. Cultivation commenced in 1985 and the farmers had enough water for 20000acres including

  8. Weather variability, climatic change, and soybean production

    SciTech Connect

    Thompson, L.M.

    1985-01-01

    A crop/weather model was used to determine the effect of changing climate and weather variability on soybean production in the Corn Belt. A cooling trend from the 1930s to the 1970s was accompanied by an upward trend in July plus August rainfall. There was decreased weather variability from the 1930s to 1973 and greatly increased weather variability after 1973. Improved weather from 1930 to 1972 increased soybean yields 3 bushels/acre. Higher intensity rainfalls increased in Illinois and Iowa after 1970.

  9. Patterns of interannual climate variability in large marine ecosystems

    NASA Astrophysics Data System (ADS)

    Soares, Helena Cachanhuk; Gherardi, Douglas Francisco Marcolino; Pezzi, Luciano Ponzi; Kayano, Mary Toshie; Paes, Eduardo Tavares

    2014-06-01

    The purpose of this study is to investigate the vulnerability of the Brazilian and western African Large Marine Ecosystems (LMEs) to local and remote forcing, including the Pacific Decadal Oscillation (PDO) regime shift. The analyses are based on the total and partial correlation between climate indices (Niño3, tropical South Atlantic (TSA), tropical North Atlantic (TNA) and Antarctic oscillation (AAO) and oceanic and atmospheric variables (sea surface temperature (SST), wind stress, Ekman transport, sea level pressure and outgoing longwave radiation). Differences in the correlation fields between the cold and warm PDO indicate that this mode exerts a significant impact on the thermodynamic balance of the ocean-atmosphere system on the South Atlantic ocean, mainly in the South Brazil and Benguela LMEs. The PDO regime shift also resulted in an increase in the spatial variability of SST and wind stress anomalies, mainly along the western African LMEs. Another important finding is the strong AAO influence on the SST anomalies (SSTA) in the South Brazil LME. It is also striking that TSA modulates the relation between El Niño-Southern Oscillation (ENSO) and SSTA, by reducing the influence of ENSO on SSTA during the warm PDO period in the North and East Brazil LMEs and in the Guinea Current LME. The relation between AAO and SSTA on the tropical area is also influenced by the TSA. The results shown here give a clear indication that future ecosystem-based management actions aimed at the conservation of marine resources under climate change need to consider the high complexity of basin-scale interactions between local and remote climate forcings, including their effects on the ocean-atmosphere system of the South Atlantic ocean.

  10. Environment, Health and Climate: Impact of African aerosols

    NASA Astrophysics Data System (ADS)

    Liousse, C.; Doumbia, T.; Assamoi, E.; Galy-Lacaux, C.; Baeza, A.; Penner, J. E.; Val, S.; Cachier, H.; Xu, L.; Criqui, P.

    2012-12-01

    Fossil fuel and biofuel emissions of particles in Africa are expected to significantly increase in the near future, particularly due to rapid growth of African cities. In addition to biomass burning emissions prevailing in these areas, air quality degradation is then expected with important consequences on population health and climatic/radiative impact. In our group, we are constructing a new integrated methodology to study the relations between emissions, air quality and their impacts. This approach includes: (1) African combustion emission characterizations; (2) joint experimental determination of aerosol chemistry from ultrafine to coarse fractions and health issues (toxicology and epidemiology). (3) integrated environmental, health and radiative modeling. In this work, we show some results illustrating our first estimates of African anthropogenic emission impacts: - a new African anthropogenic emission inventory adapted to regional specificities on traffic, biofuel and industrial emissions has been constructed for the years 2005 and 2030. Biomass burning inventories were also improved in the frame of AMMA (African Monsoon) program. - carbonaceous aerosol radiative impact in Africa has been modeled with TM5 model and Penner et al. (2011) radiative code for these inventories for 2005 and 2030 and for two scenarios of emissions : a reference scenario, with no further emission controls beyond those achieved in 2003 and a ccc* scenario including planned policies in Kyoto protocol and regulations as applied to African emission specificities. In this study we will show that enhanced heating is expected with the ccc* scenarios emissions in which the OC fraction is relatively lower than in the reference scenario. - results of short term POLCA intensive campaigns in Bamako and Dakar in terms of aerosol chemical characterization linked to specific emissions sources and their inflammatory impacts on the respiratory tract through in vitro studies. In this study, organic

  11. Inferring climate variability from skewed proxy records

    NASA Astrophysics Data System (ADS)

    Emile-Geay, J.; Tingley, M.

    2013-12-01

    Many paleoclimate analyses assume a linear relationship between the proxy and the target climate variable, and that both the climate quantity and the errors follow normal distributions. An ever-increasing number of proxy records, however, are better modeled using distributions that are heavy-tailed, skewed, or otherwise non-normal, on account of the proxies reflecting non-normally distributed climate variables, or having non-linear relationships with a normally distributed climate variable. The analysis of such proxies requires a different set of tools, and this work serves as a cautionary tale on the danger of making conclusions about the underlying climate from applications of classic statistical procedures to heavily skewed proxy records. Inspired by runoff proxies, we consider an idealized proxy characterized by a nonlinear, thresholded relationship with climate, and describe three approaches to using such a record to infer past climate: (i) applying standard methods commonly used in the paleoclimate literature, without considering the non-linearities inherent to the proxy record; (ii) applying a power transform prior to using these standard methods; (iii) constructing a Bayesian model to invert the mechanistic relationship between the climate and the proxy. We find that neglecting the skewness in the proxy leads to erroneous conclusions and often exaggerates changes in climate variability between different time intervals. In contrast, an explicit treatment of the skewness, using either power transforms or a Bayesian inversion of the mechanistic model for the proxy, yields significantly better estimates of past climate variations. We apply these insights in two paleoclimate settings: (1) a classical sedimentary record from Laguna Pallcacocha, Ecuador (Moy et al., 2002). Our results agree with the qualitative aspects of previous analyses of this record, but quantitative departures are evident and hold implications for how such records are interpreted, and

  12. Climate variation explains a third of global crop yield variability

    PubMed Central

    Ray, Deepak K.; Gerber, James S.; MacDonald, Graham K.; West, Paul C.

    2015-01-01

    Many studies have examined the role of mean climate change in agriculture, but an understanding of the influence of inter-annual climate variations on crop yields in different regions remains elusive. We use detailed crop statistics time series for ~13,500 political units to examine how recent climate variability led to variations in maize, rice, wheat and soybean crop yields worldwide. While some areas show no significant influence of climate variability, in substantial areas of the global breadbaskets, >60% of the yield variability can be explained by climate variability. Globally, climate variability accounts for roughly a third (~32–39%) of the observed yield variability. Our study uniquely illustrates spatial patterns in the relationship between climate variability and crop yield variability, highlighting where variations in temperature, precipitation or their interaction explain yield variability. We discuss key drivers for the observed variations to target further research and policy interventions geared towards buffering future crop production from climate variability. PMID:25609225

  13. Climate variation explains a third of global crop yield variability.

    PubMed

    Ray, Deepak K; Gerber, James S; MacDonald, Graham K; West, Paul C

    2015-01-22

    Many studies have examined the role of mean climate change in agriculture, but an understanding of the influence of inter-annual climate variations on crop yields in different regions remains elusive. We use detailed crop statistics time series for ~13,500 political units to examine how recent climate variability led to variations in maize, rice, wheat and soybean crop yields worldwide. While some areas show no significant influence of climate variability, in substantial areas of the global breadbaskets, >60% of the yield variability can be explained by climate variability. Globally, climate variability accounts for roughly a third (~32-39%) of the observed yield variability. Our study uniquely illustrates spatial patterns in the relationship between climate variability and crop yield variability, highlighting where variations in temperature, precipitation or their interaction explain yield variability. We discuss key drivers for the observed variations to target further research and policy interventions geared towards buffering future crop production from climate variability.

  14. Prioritizing Global Observations Along Essential Climate Variables

    NASA Astrophysics Data System (ADS)

    Bojinski, Stephan; Richter, Carolin

    2010-12-01

    The Global Climate Observing System (GCOS) Secretariat, housed within the World Meteorological Organization, released in August 2010 updated guidance for priority actions worldwide in support of observations of GCOS Essential Climate Variables (ECVs). This guidance states that full achievement of the recommendations in the 2010 Implementation Plan for the Global Observing System for Climate in Support of the UNFCCC (http://www.wmo.int/pages/prog/gcos/Publications/gcos­138.pdf) is required to ensure that countries are able to understand and predict climate change and its impacts and manage their response throughout the 21st century and beyond. GCOS is sponsored by the United Nations and the International Council for Science (ICSU) and is an internationally coordinated network of observing systems and a program of activities that support and improve the network, which is designed to meet evolving national and international requirements for climate observations. One of the main objectives of GCOS is to sustain observations into the future to allow evaluation of how climate is changing, so that informed decisions can be made on prevention, mitigation, and adaptation strategies. GCOS priorities are based on the belief that observations are crucial to supporting the research needed to refine understanding of the climate system and its changes, to initialize predictions on time scales out to decades, and to develop the models used to make these predictions and longer­term scenario-based projections. Observations are also needed to assess social and economic vulnerabilities and to support related actions needed across a broad range of societal sectors by underpinning emerging climate services.

  15. Space-time structure of climate variability

    NASA Astrophysics Data System (ADS)

    Laepple, Thomas; Reschke, Maria; Huybers, Peter; Rehfeld, Kira

    2016-04-01

    The spatial scale of climate variability is closely linked to the temporal scale. Whereas fast variations such as weather are regional, glacial-interglacial cycles appear to be globally coherent. Quantifying the relationship between local and large-scale climate variations is essential for mapping the extent of past climate changes. Larger spatial scales of climate variations on longer time scales are expected if one views the atmosphere and oceans as primarily diffusive with respect to heat. On the other hand, the interaction of a dynamical system with spatially variable boundary conditions --- for example: topography, gradients in insolation, and variations in rotational effects --- will lead to spatially heterogeneous structures that are largely independent of time scale. It has been argued that the increase in spatial scales continues across all time scales [Mitchell, 1976], but up to now, the space-time structure of variations beyond the decadal scale is basically unexplored. Here, we attempt to estimate the spatial extent of temperature changes up to millennial time-scales using instrumental observations, paleo-observations and climate model simulations. Although instrumental and climate model data show an increase in spatial scale towards slower variations, paleo-proxy data, if interpreted as temperature signals, lead to ambiguous results. An analysis of a global Holocene stack [Marcott et al., 2013], for example, suggests a jump towards more localized patterns when leaving the instrumental time scale. Localization contradicts physical expectations and may instead reflect the presence of various types of noise. Turning the problem around, and imposing a consistent space-time structure across instruments and proxy records allows us to constrain the interpretation of the climate signal in proxy records. In the case of the Holocene stack, preliminary results suggest that the time-uncertainty on the Holocene records would have to be much larger than published in

  16. Monitoring and Predicting the African Climate for Food Security

    NASA Astrophysics Data System (ADS)

    Thiaw, W. M.

    2015-12-01

    Drought is one of the greatest challenges in Africa due to its impact on access to sanitary water and food. In response to this challenge, the international community has mobilized to develop famine early warning systems (FEWS) to bring safe food and water to populations in need. Over the past several decades, much attention has focused on advance risk planning in agriculture and water. This requires frequent updates of weather and climate outlooks. This paper describes the active role of NOAA's African Desk in FEWS. Emphasis is on the operational products from short and medium range weather forecasts to subseasonal and seasonal outlooks in support of humanitarian relief programs. Tools to provide access to real time weather and climate information to the public are described. These include the downscaling of the U.S. National Multi-model Ensemble (NMME) to improve seasonal forecasts in support of Regional Climate Outlook Forums (RCOFs). The subseasonal time scale has emerged as extremely important to many socio-economic sectors. Drawing from advances in numerical models that can now provide a better representation of the MJO, operational subseasonal forecasts are included in the African Desk product suite. These along with forecasts skill assessment and verifications are discussed. The presentation will also highlight regional hazards outlooks basis for FEWSNET food security outlooks.

  17. Advances in Understanding Decadal Climate Variability

    NASA Technical Reports Server (NTRS)

    Busalaacchi, Antonio J.

    1998-01-01

    Recently, a joint Brazil-France-U.S. program, known as PIRATA (Pilot Research moored Array in the Tropical Atlantic), was proposed to begin the deployment of moored measurement platforms in the tropical Atlantic in order to enhance the existing observational data base and subsequent understanding of the processes by which the ocean and atmosphere couple in key regions of the tropical Atlantic Ocean. Empirical studies have suggested that there are strong relationships between tropical Atlantic upper ocean variability, SST, ocean-atmosphere coupling and regional climate variability. During the early 1980's a coordinated set of surface wind, subsurface thermal structure, and subsurface current observations were obtained as part of the U.S.-France SEQUAL- FOCAL process experiment designed to observe the seasonal response of the tropical Atlantic Ocean to surface forcing. Since that time, however, the observational data base for the tropical Atlantic Ocean has disintegrated to a few shiptracks measuring ocean temperatures and a small collection of tide gauge stations measuring sea level. A more comprehensive set of observations, modeling and empirical studies is now in order to make progress on understanding the regional climate variability. The proposed PIRATA program will use mooring platforms similar to the tropical Pacific Ocean TAO array to measure surface fluxes of momentum and heat and the corresponding changes in the upper ocean thermal structure. It is anticipated that the oceanic data from this monitoring array will also be used in a predictive mode for initialization studies of regional coupled climate models. Of particular interest are zonal and meridional modes of ocean-atmosphere variability within the tropical Atlantic basin that have significant impacts on the regional climate of the bordering continents.

  18. Advances in Understanding Decadal Climate Variability

    NASA Technical Reports Server (NTRS)

    Busalacchi, Antonio J.

    1999-01-01

    Recently, a joint Brazil-France-U.S. program, known as PIRATA (Pilot Research moored Array in the Tropical Atlantic), was proposed to begin the deployment of moored measurement platforms in the tropical Atlantic in order to enhance the existing observational data base and subsequent understanding of the processes by which the ocean and atmosphere couple in key regions of the tropical Atlantic Ocean. Empirical studies have suggested that there are strong relationships between tropical Atlantic upper ocean variability, SST, ocean-atmosphere coupling and regional climate variability. During the early 1980's a coordinated set of surface wind, subsurface thermal structure, and subsurface current observations were obtained as part of the U.S.-France SEQUAL-FOCAL process experiment designed to observe the seasonal response of the tropical Atlantic Ocean to surface forcing. Since that time, however, the observational data base for the tropical Atlantic Ocean has disintegrated to a few ship-tracks measuring ocean temperatures and a small collection of tide gauge stations measuring sea level. A more comprehensive set of observations, modeling and empirical studies is now in order to make progress on understanding the regional climate variability. The proposed PIRATA program will use mooring platforms similar to the tropical Pacific Ocean TAO array to measure surface fluxes of momentum and heat and the corresponding changes in the upper ocean thermal structure. It is anticipated that the oceanic data from this monitoring array will also be used in a predictive mode for initialization studies of regional coupled climate models. Of particular interest are zonal and meridional modes of ocean-atmosphere variability within the tropical Atlantic basin that have significant impacts on the regional climate of the bordering continents.

  19. Tree Density and Species Decline in the African Sahel Attributable to Climate

    NASA Technical Reports Server (NTRS)

    Gonzalez, Patrick; Tucker, Compton J.; Sy, H.

    2012-01-01

    Increased aridity and human population have reduced tree cover in parts of the African Sahel and degraded resources for local people. Yet, tree cover trends and the relative importance of climate and population remain unresolved. From field measurements, aerial photos, and Ikonos satellite images, we detected significant 1954-2002 tree density declines in the western Sahel of 18 +/- 14% (P = 0.014, n = 204) and 17 +/- 13% (P = 0.0009, n = 187). From field observations, we detected a significant 1960-2000 species richness decline of 21 +/- 11% (P = 0.0028, n = 14) across the Sahel and a southward shift of the Sahel, Sudan, and Guinea zones. Multivariate analyses of climate, soil, and population showed that temperature most significantly (P < 0.001) explained tree cover changes. Multivariate and bivariate tests and field observations indicated the dominance of temperature and precipitation, supporting attribution of tree cover changes to climate variability. Climate change forcing of Sahel climate variability, particularly the significant (P < 0.05) 1901-2002 temperature increases and precipitation decreases in the research areas, connects Sahel tree cover changes to global climate change. This suggests roles for global action and local adaptation to address ecological change in the Sahel.

  20. Precipitation extremes with climate variability and change

    NASA Astrophysics Data System (ADS)

    Ganguly, A. R.

    2011-12-01

    Significant gaps exist in our understanding of hydro-meteorological processes in the context of climate variability or change. However, despite the uncertainties, developing relatively credible insights for precipitation extremes at scales relevant for hydrology is necessary and may be possible. Statistical analyses of observed and model-simulated precipitation data, particularly methods based on extreme value theory, have demonstrated the potential to yield new insights. Specifically, a delineation of the impacts of global climate change versus regional changes in land use or urbanization may be possible and could be important for policy-makers. Precipitation extremes have known dependence on variables like sea surface temperatures, atmospheric temperature profiles and wind velocities, some of which may be better predicted than precipitation from models, exhibit less variability in observations and may not be as subject to thresholds and intermittences in either models or observations. Thus, leveraging the information content in these auxiliary variables through data mining or network science based approaches, especially if the techniques are informed by process understanding at multiple scales, may help improve regional projections of precipitation and corresponding extremes. Enhanced regional projections of precipitation and their extremes can help drive models of hydrology and hence better inform water managers, especially at scales that matter for water resources planning or managing hydraulic infrastructures. A combination of physics-based models, data-guided mathematical approaches, and quantitative techniques informed by conceptual process understanding, may be a way forward to understand the possible consequences of climate variability and global or regional change on precipitation extremes. Examples and case studies are presented from the published literature and from ongoing research.

  1. Interpolation of climate variables and temperature modeling

    NASA Astrophysics Data System (ADS)

    Samanta, Sailesh; Pal, Dilip Kumar; Lohar, Debasish; Pal, Babita

    2012-01-01

    Geographic Information Systems (GIS) and modeling are becoming powerful tools in agricultural research and natural resource management. This study proposes an empirical methodology for modeling and mapping of the monthly and annual air temperature using remote sensing and GIS techniques. The study area is Gangetic West Bengal and its neighborhood in the eastern India, where a number of weather systems occur throughout the year. Gangetic West Bengal is a region of strong heterogeneous surface with several weather disturbances. This paper also examines statistical approaches for interpolating climatic data over large regions, providing different interpolation techniques for climate variables' use in agricultural research. Three interpolation approaches, like inverse distance weighted averaging, thin-plate smoothing splines, and co-kriging are evaluated for 4° × 4° area, covering the eastern part of India. The land use/land cover, soil texture, and digital elevation model are used as the independent variables for temperature modeling. Multiple regression analysis with standard method is used to add dependent variables into regression equation. Prediction of mean temperature for monsoon season is better than winter season. Finally standard deviation errors are evaluated after comparing the predicted temperature and observed temperature of the area. For better improvement, distance from the coastline and seasonal wind pattern are stressed to be included as independent variables.

  2. Influence of 21st century atmospheric and sea surface temperature forcing on West African climate

    SciTech Connect

    Skinner, Chris B; Ashfaq, Moetasim; Diffenbaugh, Noah

    2011-01-01

    he persistence of extended drought events throughout West Africa during the 20th century has motivated a substantial effort to understand the mechanisms driving African climate variability, as well as the possible response to elevated greenhouse gas (GHG) forcing. We use an ensemble of global climate model experiments to examine the relative roles of future direct atmospheric radiative forcing and SST forcing in shaping potential future changes in boreal summer precipitation over West Africa. We find that projected increases in precipitation throughout the Western Sahel result primarily from direct atmospheric radiative forcing. The changes in atmospheric forcing generate a slight northward displacement and weakening of the African easterly jet (AEJ), a strengthening of westward monsoon flow onto West Africa and an intensification of the tropical easterly jet (TEJ). Alternatively, we find that the projected decreases in precipitation over much of the Guinea Coast region are caused by SST changes that are induced by the atmospheric radiative forcing. The changes in SSTs generate a weakening of the monsoon westerlies and the TEJ, as well as a decrease in low-level convergence and resultant rising air throughout the mid levels of the troposphere. Our experiments suggest a potential shift in the regional moisture balance of West Africa should global radiative forcing continue to increase, highlighting the importance of climate system feedbacks in shaping the response of regional-scale climate to global-scale changes in radiative forcing.

  3. Challenges in probabilistic event attribution in African climates (Invited)

    NASA Astrophysics Data System (ADS)

    Otto, F. E.; Allen, M. R.; Massey, N.

    2013-12-01

    Global climate change is almost certainly affecting the magnitude and frequency of extreme weather and hydrological events around the world. However, whether and to what extent the occurrence of an extreme weather event or the impacts of such an event on, agriculture, infrastructure, and livelihoods can be attributed to climate change remains a challenging question. With the introduction of the work programme on loss and damage associated with the impacts of climate change in developing countries on the UNFCCC agenda finding answers to this question has become even more important. Probabilistic event attribution (PEA) provides a method of evaluating the extent to which human-induced climate change is affecting localised weather events and impacts of such events that relies on good observations as well as climate modelling. The overall approach is to simulate, with as realistic a model as possible and accounting as far as possible for modelling uncertainties, both the statistics of observed weather and the statistics of the weather that would have occurred had specific external drivers of climate change been absent. The majority of studies applying PEA have focused on quantifying attributable risk, with changes in risk depending on an assumption of 'all other things being equal', including natural drivers of climate change and vulnerability. The fraction of attributable risk (FAR) to human-induced climate change is defined as the change in the probability of an event occurring due to human influence on the climate compared to the corresponding probability in a world not influenced by humans. We will present first results of a recently started project on 'Attributing the impacts of external climate drivers on extreme weather in Africa' applying PEA, which will provide an important step towards quantifying the link between climate change and extreme weather in Africa. However, especially in an African context, with the strong influence of global sea surface

  4. Use of Machine Learning Techniques for Iidentification of Robust Teleconnections to East African Rainfall Variability in Observations and Models

    NASA Technical Reports Server (NTRS)

    Roberts, J. Brent; Robertson, Franklin R.; Funk, Chris

    2014-01-01

    Providing advance warning of East African rainfall variations is a particular focus of several groups including those participating in the Famine Early Warming Systems Network. Both seasonal and long-term model projections of climate variability are being used to examine the societal impacts of hydrometeorological variability on seasonal to interannual and longer time scales. The NASA / USAID SERVIR project, which leverages satellite and modeling-based resources for environmental decision making in developing nations, is focusing on the evaluation of both seasonal and climate model projections to develop downscaled scenarios for using in impact modeling. The utility of these projections is reliant on the ability of current models to capture the embedded relationships between East African rainfall and evolving forcing within the coupled ocean-atmosphere-land climate system. Previous studies have posited relationships between variations in El Niño, the Walker circulation, Pacific decadal variability (PDV), and anthropogenic forcing. This study applies machine learning methods (e.g. clustering, probabilistic graphical model, nonlinear PCA) to observational datasets in an attempt to expose the importance of local and remote forcing mechanisms of East African rainfall variability. The ability of the NASA Goddard Earth Observing System (GEOS5) coupled model to capture the associated relationships will be evaluated using Coupled Model Intercomparison Project Phase 5 (CMIP5) simulations.

  5. Robust negative impacts of climate change on African agriculture

    NASA Astrophysics Data System (ADS)

    Schlenker, Wolfram; Lobell, David B.

    2010-01-01

    There is widespread interest in the impacts of climate change on agriculture in Sub-Saharan Africa (SSA), and on the most effective investments to assist adaptation to these changes, yet the scientific basis for estimating production risks and prioritizing investments has been quite limited. Here we show that by combining historical crop production and weather data into a panel analysis, a robust model of yield response to climate change emerges for several key African crops. By mid-century, the mean estimates of aggregate production changes in SSA under our preferred model specification are - 22, - 17, - 17, - 18, and - 8% for maize, sorghum, millet, groundnut, and cassava, respectively. In all cases except cassava, there is a 95% probability that damages exceed 7%, and a 5% probability that they exceed 27%. Moreover, countries with the highest average yields have the largest projected yield losses, suggesting that well-fertilized modern seed varieties are more susceptible to heat related losses.

  6. Solar Variability in the Context of Other Climate Forcing Mechanisms

    NASA Technical Reports Server (NTRS)

    Hansen, James E.

    1999-01-01

    I compare and contrast climate forcings due to solar variability with climate forcings due to other mechanisms of climate change, interpretation of the role of the sun in climate change depends upon climate sensitivity and upon the net forcing by other climate change mechanisms. Among the potential indirect climate forcings due to solar variability, only that due to solar cycle induced ozone changes has been well quantified. There is evidence that the sun has been a significant player in past climate change on decadal to century time scales, and that it has the potential to contribute to climate change in the 21st century.

  7. Variable temperature seat climate control system

    DOEpatents

    Karunasiri, Tissa R.; Gallup, David F.; Noles, David R.; Gregory, Christian T.

    1997-05-06

    A temperature climate control system comprises a variable temperature seat, at least one heat pump, at least one heat pump temperature sensor, and a controller. Each heat pump comprises a number of Peltier thermoelectric modules for temperature conditioning the air in a main heat exchanger and a main exchanger fan for passing the conditioned air from the main exchanger to the variable temperature seat. The Peltier modules and each main fan may be manually adjusted via a control switch or a control signal. Additionally, the temperature climate control system may comprise a number of additional temperature sensors to monitor the temperature of the ambient air surrounding the occupant as well as the temperature of the conditioned air directed to the occupant. The controller is configured to automatically regulate the operation of the Peltier modules and/or each main fan according to a temperature climate control logic designed both to maximize occupant comfort during normal operation, and minimize possible equipment damage, occupant discomfort, or occupant injury in the event of a heat pump malfunction.

  8. Implications of global warming for the climate of African rainforests.

    PubMed

    James, Rachel; Washington, Richard; Rowell, David P

    2013-01-01

    African rainforests are likely to be vulnerable to changes in temperature and precipitation, yet there has been relatively little research to suggest how the regional climate might respond to global warming. This study presents projections of temperature and precipitation indices of relevance to African rainforests, using global climate model experiments to identify local change as a function of global temperature increase. A multi-model ensemble and two perturbed physics ensembles are used, one with over 100 members. In the east of the Congo Basin, most models (92%) show a wet signal, whereas in west equatorial Africa, the majority (73%) project an increase in dry season water deficits. This drying is amplified as global temperature increases, and in over half of coupled models by greater than 3% per °C of global warming. Analysis of atmospheric dynamics in a subset of models suggests that this could be partly because of a rearrangement of zonal circulation, with enhanced convection in the Indian Ocean and anomalous subsidence over west equatorial Africa, the Atlantic Ocean and, in some seasons, the Amazon Basin. Further research to assess the plausibility of this and other mechanisms is important, given the potential implications of drying in these rainforest regions.

  9. Implications of global warming for the climate of African rainforests.

    PubMed

    James, Rachel; Washington, Richard; Rowell, David P

    2013-01-01

    African rainforests are likely to be vulnerable to changes in temperature and precipitation, yet there has been relatively little research to suggest how the regional climate might respond to global warming. This study presents projections of temperature and precipitation indices of relevance to African rainforests, using global climate model experiments to identify local change as a function of global temperature increase. A multi-model ensemble and two perturbed physics ensembles are used, one with over 100 members. In the east of the Congo Basin, most models (92%) show a wet signal, whereas in west equatorial Africa, the majority (73%) project an increase in dry season water deficits. This drying is amplified as global temperature increases, and in over half of coupled models by greater than 3% per °C of global warming. Analysis of atmospheric dynamics in a subset of models suggests that this could be partly because of a rearrangement of zonal circulation, with enhanced convection in the Indian Ocean and anomalous subsidence over west equatorial Africa, the Atlantic Ocean and, in some seasons, the Amazon Basin. Further research to assess the plausibility of this and other mechanisms is important, given the potential implications of drying in these rainforest regions. PMID:23878329

  10. Climate variability and Port wine quality

    NASA Astrophysics Data System (ADS)

    Gouveia, Celia; Liberato, Margarida L. R.; Trigo, Ricardo M.; Dacamara, Carlos

    2010-05-01

    ), suggesting that this type of analysis may be used in developing a tool that may help anticipating a vintage year, based on already available seasonal climate outlooks. Célia Gouveia and Ricardo M. Trigo. "Influence of climate variability on wheat production in Portugal". GeoENV2006- 6th International Conference on Geostatistics for Environmental Applications, Rhodes, October, 25-27, 2006 Miranda, P.M.A., F. Coelho, A. R. Tomé, M. A Valente., A. Carvalho, C. Pires, H. O. Pires, V. C. Cabrinha and C. Ramalho (2002) "20th Century Portuguese Climate and Climate Scenarios", in Santos, F.D., K Forbes and R. Moita (eds) Climate Change in Portugal: Scenarios, Impacts and Adptation Measures", 27-83. Gradiva

  11. The Response of African Land Surface Phenology to Large Scale Climate Oscillations

    NASA Technical Reports Server (NTRS)

    Brown, Molly E.; de Beurs, Kirsten; Vrieling, Anton

    2010-01-01

    Variations in agricultural production due to rainfall and temperature fluctuations are a primary cause of food insecurity on the African continent. Analysis of changes in phenology can provide quantitative information on the effect of climate variability on growing seasons in agricultural regions. Using a robust statistical methodology, we describe the relationship between phenology metrics derived from the 26 year AVHRR NDVI record and the North Atlantic Oscillation index (NAO), the Indian Ocean Dipole (IOD), the Pacific Decadal Oscillation (PDO), and the Multivariate ENSO Index (MEI). We map the most significant positive and negative correlation for the four climate indices in Eastern, Western and Southern Africa between two phenological metrics and the climate indices. Our objective is to provide evidence of whether climate variability captured in the four indices has had a significant impact on the vegetative productivity of Africa during the past quarter century. We found that the start of season and cumulative NDVI were significantly affected by large scale variations in climate. The particular climate index and the timing showing highest correlation depended heavily on the region examined. In Western Africa the cumulative NDVI correlates with PDO in September-November. In Eastern Africa the start of the June-October season strongly correlates with PDO in March-May, while the PDO in December-February correlates with the start of the February-June season. The cumulative NDVI over this last season relates to the MEI of March-May. For Southern Africa, high correlations exist between SOS and NAO of September-November, and cumulative NDVI and MEI of March-May. The research shows that climate indices can be used to anticipate late start and variable vigor in the growing season of sensitive agricultural regions in Africa.

  12. Methods for assessing the vulnerability of African fisheries resources to climate change.

    SciTech Connect

    Hlohowskyj, I.; Brody, M. S.; Lackey, R. T.; Environmental Assessment; EPA

    1996-02-01

    Because of the dietary and financial importance of fisheries resources in many African countries, concerns have been expressed regarding the potential for adverse impacts to fisheries resources from climate change, and a need has been identified for assessment tools that can evaluate the potential for impacts in a timely and cost-effective manner. This paper presents a framework and set of methods for assessing the potential effects of climate change on fisheries resources in Africa. The framework identifies the need to first link predicted climate changes to changes in the aquatic environment, and only then can potential impacts to aquatic resources be evaluated. The approach developed for Africa was constrained by several factors, including availability of existing data and assessment technologies, and the need for a rapid evaluation of potential climate impacts. The assessment approach employs a variety of methods including empirical models which predict changes in mortality, maximum sustainable yield, and yearly catch, a bioenergetics model, and a habitat suitability model. Previously developed or newly derived site-specific empirical models can be used to compare mortality, yield, and annual catch estimates among historic, current, and predicted climate conditions. Similarly, bioenergetics modeling can be used to compare growth rates and biomass production among different climate conditions. Habitat suitability models can be developed for current climate conditions, and the effects of changes in climate-driven habitat variables such as water depth, temperature, and current velocity on habitat suitability can be evaluated for different climate conditions. Use of these approaches is recommended because they can utilize existing ecological data and do not require extensive new data collection activities, they are not technologically complex, and they can provide evaluations of potential climate change impacts in a timely and cost-effective manner.

  13. Latitudinal Hydrologic Variability Along the East African Rift, Over the Past 200 Kyr

    NASA Astrophysics Data System (ADS)

    Scholz, C. A.

    2014-12-01

    Within the deep sediments of the large lakes of Africa's Great Rift Valley are continuous environmental records of remarkable antiquity and fidelity. Not only do stratigraphic sections from these basins extend back millions of years, many of the intervals represented contain high-resolution material of decadal resolution or better. East African lake basins remain sparsely sampled however, with only a few long and continuous records available. Our ability to image the lakes using seismic reflection methods greatly exceeds our opportunities for coring and drilling however; assessing stratal relationships observed in the geophysical data permits powerful inferences about past hydrologic changes. With intensive hydrocarbon exploration work underway in East Africa, industry well data can also help constrain and ground truth basin histories. Substantial spatio-temporal hydrologic variability is observed in East African basins over the past 200 kyr. Paleohydrological changes in the late Pleistocene and early Holocene are now well constrained in the northern hemisphere East African topics, with widespread aridity and in some cases lake desiccation observed during Heinrich Event 1. A climate recovery followed in the northern hemisphere East African tropics, with the early Holocene African Humid Period a time of positive water balance across most of the rift valley. The paleohydrology of southern hemisphere tropical East Africa is more equivocal, for instance with negligible draw-down of Lake Malawi at HE1. Whereas these late Pleistocene events represent substantial climate reorganizations, severe droughts during the middle-late Pleistocene (150-65 kyr BP) were far more intense, and produced much more severe drawdowns of Lakes Malawi and Tanganyika. Scientific drill cores, kullenberg cores, and extensive seismic reflection data sets from Lakes Malawi and Tanganyika provide indisputable evidence for lowstands of -500m and -600 m respectively. Climate changes that lowered the

  14. Reconstruction of Holocene southern African continental climate using biomarkers from salt pan sediments

    NASA Astrophysics Data System (ADS)

    Belz, Lukas; Schüller, Irka; Wehrmann, Achim; Wilkes, Heinz

    2015-04-01

    The climate system of southern Africa is strongly influenced by large scale atmospheric and marine circulation processes and, therefore, very sensitive to global climate change. Recent publications provided evidence for strong spatial and temporal climate variability in southern Africa over the Holocene. It is of major importance to understand the mechanisms driving the southern African climate system in order to estimate regional implications of current global change. However, proxy datasets from continental geoarchives especially of the semi-arid western Kalahari region are still scarce. A main problem is the absence of conventional continental climatic archives, due to the lack of lacustrine systems. In this study we are exploring the utility of sediments from western Kalahari salt pans, i.e. local depressions which are flooded temporarily during rainfall events. Besides the analyses of basic geochemical bulk parameters including TOC, δ13Corg, TIC, δ13Ccarb, δ18Ocarb, TN, δ15N, the paleo-climatic approach focuses on reconstruction of local vegetation assemblages to identify changes in the ecosystem. This is pursued using plant biomarkers, particularly leaf wax n-alkanes and n-alcohols and their stable carbon and hydrogen isotopic signatures. Preliminary results show prominent shifts in n-alkane distribution and δ13C values of the C33 homologue during late Pleistocene and early Holocene. These shifts correlate to changes of the TOC content. Our data indicate changes in carbon sources which possibly reflect major environmental changes.

  15. Exploring Connections between Global Climate Indices and African Vegetation Phenology

    NASA Technical Reports Server (NTRS)

    Brown, Molly E.; deBeurs, Kirsten; Vrieling, Anton

    2009-01-01

    Variations in agricultural production due to rainfall and temperature fluctuations are a primary cause of food insecurity on the continent in Africa. Agriculturally destructive droughts and floods are monitored from space using satellite remote sensing by organizations seeking to provide quantitative and predictive information about food security crises. Better knowledge on the relation between climate indices and food production may increase the use of these indices in famine early warning systems and climate outlook forums on the continent. Here we explore the relationship between phenology metrics derived from the 26 year AVHRR NDVI record and the North Atlantic Oscillation index (NAO), the Indian Ocean Dipole (IOD), the Pacific Decadal Oscillation (PDO), the Multivariate ENSO Index (MEI) and the Southern Oscillation Index (SOI). We explore spatial relationships between growing conditions as measured by the NDVI and the five climate indices in Eastern, Western and Southern Africa to determine the regions and periods when they have a significant impact. The focus is to provide a clear indication as to which climate index has the most impact on the three regions during the past quarter century. We found that the start of season and cumulative NDVI were significantly affected by variations in the climate indices. The particular climate index and the timing showing highest correlation depended heavily on the region examined. The research shows that climate indices can contribute to understanding growing season variability in Eastern, Western and Southern Africa.

  16. Tectonics, orbital forcing, global climate change, and human evolution in Africa: introduction to the African paleoclimate special volume.

    PubMed

    Maslin, Mark A; Christensen, Beth

    2007-11-01

    The late Cenozoic climate of Africa is a critical component for understanding human evolution. African climate is controlled by major tectonic changes, global climate transitions, and local variations in orbital forcing. We introduce the special African Paleoclimate Issue of the Journal of Human Evolution by providing a background for and synthesis of the latest work relating to the environmental context for human evolution. Records presented in this special issue suggest that the regional tectonics, appearance of C(4) plants in East Africa, and late Cenozoic global cooling combined to produce a long-term drying trend in East Africa. Of particular importance is the uplift associated with the East African Rift Valley formation, which altered wind flow patterns from a more zonal to more meridinal direction. Results in this volume suggest a marked difference in the climate history of southern and eastern Africa, though both are clearly influenced by the major global climate thresholds crossed in the last 3 million years. Papers in this volume present lake, speleothem, and marine paleoclimate records showing that the East African long-term drying trend is punctuated by episodes of short, alternating periods of extreme wetness and aridity. These periods of extreme climate variability are characterized by the precession-forced appearance and disappearance of large, deep lakes in the East African Rift Valley and paralleled by low and high wind-driven dust loads reaching the adjacent ocean basins. Dating of these records show that over the last 3 million years such periods only occur at the times of major global climatic transitions, such as the intensification of Northern Hemisphere Glaciation (2.7-2.5 Ma), intensification of the Walker Circulation (1.9-1.7 Ma), and the Mid-Pleistocene Revolution (1-0.7 Ma). Authors in this volume suggest this onset occurs as high latitude forcing in both Hemispheres compresses the Intertropical Convergence Zone so that East Africa

  17. Food Price Volatility and Decadal Climate Variability

    NASA Astrophysics Data System (ADS)

    Brown, M. E.

    2013-12-01

    The agriculture system is under pressure to increase production every year as global population expands and more people move from a diet mostly made up of grains, to one with more meat, dairy and processed foods. Weather shocks and large changes in international commodity prices in the last decade have increased pressure on local food prices. This paper will review several studies that link climate variability as measured with satellite remote sensing to food price dynamics in 36 developing countries where local monthly food price data is available. The focus of the research is to understand how weather and climate, as measured by variations in the growing season using satellite remote sensing, has affected agricultural production, food prices and access to food in agricultural societies. Economies are vulnerable to extreme weather at multiple levels. Subsistence small holders who hold livestock and consume much of the food they produce are vulnerable to food production variability. The broader society, however, is also vulnerable to extreme weather because of the secondary effects on market functioning, resource availability, and large-scale impacts on employment in trading, trucking and wage labor that are caused by weather-related shocks. Food price variability captures many of these broad impacts and can be used to diagnose weather-related vulnerability across multiple sectors. The paper will trace these connections using market-level data and analysis. The context of the analysis is the humanitarian aid community, using the guidance of the USAID Famine Early Warning Systems Network and the United Nation's World Food Program in their response to food security crises. These organizations have worked over the past three decades to provide baseline information on food production through satellite remote sensing data and agricultural yield models, as well as assessments of food access through a food price database. Econometric models and spatial analysis are used

  18. Climate Change Affects the East African Rift Valley Lakes

    NASA Astrophysics Data System (ADS)

    O'Reilly, C. M.; Plisnier, P.; Cohen, A. S.

    2004-12-01

    Over the last 100 years, air temperatures in eastern African have been warming consistent with the global average temperature increase. This has led to warmer water temperatures in the East African Rift Valley lakes, increasing the stability of the water column. Subsequently, there has been a reduction in the upwelling of deep nutrient-rich waters that are the primary source of nutrients for most of these lakes. There were decreases in surface water N and P and increases in the Si:P ratio over the past 70 years for Lakes Malawi, Tanganyika, Edward, and Albert. The lower nutrient concentrations in the surface waters were associated with reduced algal biomass and increased water clarity. The consistent, regional-scale changes among these lakes provide strong evidence that climate warming may be having a large negative affect on these unique tropical lakes. A decrease in primary productivity of 20% has been indicated for Lake Tanganyika, which would be associated with a 30% decrease in fisheries yields. The human implications of such subtle, but progressive, environmental changes are potentially dire in this densely populated region of the world, where these large lakes are an important nutritional and economic resource.

  19. Impact of climate variability on tropospheric ozone.

    PubMed

    Grewe, Volker

    2007-03-01

    A simulation with the climate-chemistry model (CCM) E39/C is presented, which covers both the troposphere and stratosphere dynamics and chemistry during the period 1960 to 1999. Although the CCM, by its nature, is not exactly representing observed day-by-day meteorology, there is an overall model's tendency to correctly reproduce the variability pattern due to an inclusion of realistic external forcings, like observed sea surface temperatures (e.g. El Niño), major volcanic eruption, solar cycle, concentrations of greenhouse gases, and Quasi-Biennial Oscillation. Additionally, climate-chemistry interactions are included, like the impact of ozone, methane, and other species on radiation and dynamics, and the impact of dynamics on emissions (lightning). However, a number of important feedbacks are not yet included (e.g. feedbacks related to biogenic emissions and emissions due to biomass burning). The results show a good representation of the evolution of the stratospheric ozone layer, including the ozone hole, which plays an important role for the simulation of natural variability of tropospheric ozone. Anthropogenic NO(x) emissions are included with a step-wise linear trend for each sector, but no interannual variability is included. The application of a number of diagnostics (e.g. marked ozone tracers) allows the separation of the impact of various processes/emissions on tropospheric ozone and shows that the simulated Northern Hemisphere tropospheric ozone budget is not only dominated by nitrogen oxide emissions and other ozone pre-cursors, but also by changes of the stratospheric ozone budget and its flux into the troposphere, which tends to reduce the simulated positive trend in tropospheric ozone due to emissions from industry and traffic during the late 80s and early 90s. For tropical regions the variability in ozone is dominated by variability in lightning (related to ENSO) and stratosphere-troposphere exchange (related to Northern Hemisphere Stratospheric

  20. Impact of climate variability on tropospheric ozone.

    PubMed

    Grewe, Volker

    2007-03-01

    A simulation with the climate-chemistry model (CCM) E39/C is presented, which covers both the troposphere and stratosphere dynamics and chemistry during the period 1960 to 1999. Although the CCM, by its nature, is not exactly representing observed day-by-day meteorology, there is an overall model's tendency to correctly reproduce the variability pattern due to an inclusion of realistic external forcings, like observed sea surface temperatures (e.g. El Niño), major volcanic eruption, solar cycle, concentrations of greenhouse gases, and Quasi-Biennial Oscillation. Additionally, climate-chemistry interactions are included, like the impact of ozone, methane, and other species on radiation and dynamics, and the impact of dynamics on emissions (lightning). However, a number of important feedbacks are not yet included (e.g. feedbacks related to biogenic emissions and emissions due to biomass burning). The results show a good representation of the evolution of the stratospheric ozone layer, including the ozone hole, which plays an important role for the simulation of natural variability of tropospheric ozone. Anthropogenic NO(x) emissions are included with a step-wise linear trend for each sector, but no interannual variability is included. The application of a number of diagnostics (e.g. marked ozone tracers) allows the separation of the impact of various processes/emissions on tropospheric ozone and shows that the simulated Northern Hemisphere tropospheric ozone budget is not only dominated by nitrogen oxide emissions and other ozone pre-cursors, but also by changes of the stratospheric ozone budget and its flux into the troposphere, which tends to reduce the simulated positive trend in tropospheric ozone due to emissions from industry and traffic during the late 80s and early 90s. For tropical regions the variability in ozone is dominated by variability in lightning (related to ENSO) and stratosphere-troposphere exchange (related to Northern Hemisphere Stratospheric

  1. Regional Climate Modeling of West African Summer Monsoon Climate: Impact of Historical Boundary Forcing

    NASA Astrophysics Data System (ADS)

    Kebe, I.

    2015-12-01

    In this paper, we analyze and intercompare the performance of an ensemble of three Regional Climate Models (RCMs) driven by three set of Global Climate Models (GCMs), in reproducing seasonal mean climatologies with their annual cycle and the key features of West African summer monsoon over 20 years period (1985-2004) during the present day. The results show that errors in lateral boundary conditions from the GCM members, have an unexpected way on the skill of the RCMs in reproducing regional climate features such as the West African Monsoon features and the annual cycle of precipitation and temperature in terms of outperforming the GCM simulation. It also shows the occurrence of the West African Monsoon jump, the intensification and northward shift of the Saharan Heat Low (SHL) as expressed in some RCMs than the GCMs. Most RCMs also capture the mean annual cycle of precipitation and temperature, including, single and double-peaked during the summer months, in terms of events and amplitude. In a series of RCMs and GCMs experiments between the Sahara region and equatorial Africa, the presence of strong positive meridional temperature gradients at the surface and a strong meridional gradients in the potential temperatures near the surface are obvious, indicating the region of strong vertical shear development enough to establish easterly flow such as the African easterly jet. In addition, the isentropic potential vorticity (IPV) gradient decreases northward in the lower troposphere across northern Africa, with the maximum reversal on the 315-K surface. The region with negative IPV gradient favors the potential instability which has been associated with the growth of easterly waves.

  2. Using Remote Sensing to Understand Climate Variability

    NASA Astrophysics Data System (ADS)

    Green, J.; Gentine, P.

    2014-12-01

    While a major source of uncertainty in global climate model predictions is due to the coarseness of their resolution, a significant amount of error is also generated due to the lack of information regarding the interactions between atmospheric and land parameters over time. When the behavior of a certain parameter is not clearly understood it is frequently estimated as one specific value while in reality it may vary with time and space. Remote sensing is allowing researchers to better estimate each of these parameters so one can see how they change with time. This study is an effort to improve our knowledge of the inter-annual and seasonal variability in radiation, water and the carbon cycle using remote sensing products on a global scale. By examining monthly data over a multi-year period (data parameter and source are listed in Table 1) for fluorescence, groundwater, net radiation, vegetation indices, precipitation, soil moisture and evapotranspiration, we should be able to determine the behavior and interactions between these parameters and better understand how they vary together seasonally, annually and year to year. With this information it is our hope that global climate models can be improved to better understand what is occurring climatologically in the present as well as more accurately make predictions about future conditions. Table 1. Parameters and Sources Parameter Source Fluorescence Greenhouse gases Observing SATellite (GOSAT)1 Groundwater Gravity Recovery and Climate Experiment (GRACE) Net Radiation Clouds and the Earth's Radiant Energy System (CERES) Vegetation Indices Moderate Resolution Imaging Spectroradiometer (MODIS)/ Multiangle Implementation of Atmospheric Correction (MAIAC) Precipitation Global Precipitation Climatology Project (GPCP) Soil Moisture Water Cycle Mutimission Observation Strategy (WACMOS) Evapotranspiration Global Land-surface Evaporation: the Amsterdam Methodology (GLEAM) 1In future work, we hope to use fluorescence data from

  3. Climatic variability, plant phenology, and northern ungulates

    SciTech Connect

    Post, E.; Stenseth, N.C.

    1999-06-01

    Models of climate change predict that global temperatures and precipitation will increase within the next century, with the most pronounced changes occurring in northern latitudes and during winter. A large-scale atmospheric phenomenon, the North Atlantic Oscillation (NAO), is a strong determinant of both interannual variation and decadal trends in temperatures and precipitation during winter in northern latitudes, and its recent persistence in one extreme phase may be a substantial component of increases in global temperatures. Hence, the authors investigated the influences of large-scale climatic variability on plant phenology and ungulate population ecology by incorporating the NAO in statistical analyses of previously published data on: (1) the timing of flowering by plants in Norway, and (2) phenotypic and demographic variation in populations of northern ungulates. The authors analyzed 137 time series on plant phenology for 13 species of plants in Norway spanning up to 50 yr and 39 time series on phenotypic and demographic traits of 7 species of northern ungulates from 16 populations in North America and northern Europe spanning up to 30 yr.

  4. Climate variability and the Icelandic marine ecosystem

    NASA Astrophysics Data System (ADS)

    Astthorsson, Olafur S.; Gislason, Astthor; Jonsson, Steingrimur

    2007-11-01

    This paper describes the main features of the Icelandic marine ecosystem and its response to climate variations during the 20th century. The physical oceanographic character and faunal composition in the southern and western parts of the Icelandic marine ecosystem are different from those in the northern and the eastern areas. The former areas are more or less continuously bathed by warm and saline Atlantic water while the latter are more variable and influenced by Atlantic, Arctic and even Polar water masses to different degrees. Mean annual primary production is higher in the Atlantic water than in the more variable waters north and east of Iceland, and higher closer to land than farther offshore. Similarly, zooplankton production is generally higher in the Atlantic water than in the waters north and east of Iceland. The main spawning grounds of most of the exploited fish stocks are in the Atlantic water south of the country while nursery grounds are off the north coast. In the recent years the total catch of fish and invertebrates has been in the range of 1.6-2.4 million ton. Capelin ( Mallotus villosus) is the most important pelagic stock and cod ( Gadus morhua) is by far the most important demersal fish stock. Whales are an important component of the Icelandic marine ecosystem, and Icelandic waters are an important habitat for some of the largest seabird populations in the Northeast Atlantic. In the waters to the north and east of Iceland, available information suggests the existence of a simple bottom-up controlled food chain from phytoplankton through Calanus, capelin and to cod. Less is known about the structure of the more complex southern part of the ecosystem. The Icelandic marine ecosystem is highly sensitive to climate variations as demonstrated by abundance and distribution changes of many species during the warm period in the 1930s, the cold period in the late 1960s and warming observed during the recent years. Some of these are highlighted in the

  5. Evaluation of Dynamics of the West African Monsoon Jump Simulated by the MIT Regional Climate Model

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    The seasonal advance and retreat of the West African monsoon behaves abrupt northward jump of maximum rainfall from the Guinean coast to the Sahel region. Both global and regional climate models have difficulties in accurately reproducing such a behavior due to its complexity combined the dynamical and physical processes. In this study, we evaluate the performance of the MIT Regional Climate Model (MRCM) in simulating the West African monsoon. For this, 20-year long-term simulation (1989-2008) is performed using the ERAInterim reanalysis as the initial and boundary condition, and the analysis primarily focuses on the dynamics associated with abrupt phase transitions of the monsoon rainfall. We first examine detailed characteristics in terms of the onset, maximum, and retreat of the monsoon rainfall using daily precipitation. We then present the dynamical explanation behind rainfall variability from the analysis of the absolute vorticity near the tropopause and the meridional gradient of boundary-layer entropy within the dynamical theory proposed by Eltahir and Gong (1996). Acknowledgements : This research was supported by the National Research Foundation Singapore through the Singapore MIT Alliance for Research and Technology's Center for Environmental Sensing and Modeling interdisciplinary research program.

  6. Evaluation of the capability of RegCM4.0 in simulating East African climate

    NASA Astrophysics Data System (ADS)

    Ogwang, Bob Alex; Chen, Haishan; Li, Xing; Gao, Chujie

    2016-04-01

    The International Centre for Theoretical Physics (ICTP) regional climate model RegCM4.0 is used in this study to examine its ability to reproduce the climate of East Africa (EA) in regard to the annual cycle and June-to-August (JJA) seasonal climatology. Two domain sizes [large domain (LD) and small domain (SD)] and two cumulus convection schemes [Grell convection scheme with Fritsch-Chappell closure assumption (GRE scheme) and MIT scheme (EMA scheme)] are used. Simulations were done for the period 1989-2008 at a resolution of 50 km. The experiments were performed with the initial and lateral boundary conditions obtained from ERA-Interim-gridded reanalysis data at a 1.5° resolution. The variables investigated are precipitation, temperature, humidity, diurnal temperature range, and 850-hPa winds. Results show that the model realistically reproduces the East African climate, with a few discrepancies due to the different cumulus convection schemes and the domain sizes used. Grell with Fritsch-Chappell (Grell-FC) scheme captures well the observed climate in regard to the annual cycle and June-to-August seasonal climatology, with a tendency to underestimate rainfall over the JJA rainfall maximum region (RMR). This scheme performs better in LD than in SD. EMA scheme similarly captures well the observed climatology. It tends to overestimate rainfall over RMR. It however performs better in SD than in LD. The ensemble mean of simulations with GRE and EMA schemes (ENSM) tends to offer an improved representation of the observed climate, with a few discrepancies owing to the individual schemes used. In general, therefore, considering the performance of the model in both domains, the East African climate based on this study is better simulated by the Grell-FC scheme over LD. The observed biases in this study signify that the ability of the model in simulating climate over East Africa is still a significant challenge. Thus, future work must focus on improving the performance of

  7. How does spatial variability of climate affect catchment streamflow predictions?

    EPA Science Inventory

    Spatial variability of climate can negatively affect catchment streamflow predictions if it is not explicitly accounted for in hydrologic models. In this paper, we examine the changes in streamflow predictability when a hydrologic model is run with spatially variable (distribute...

  8. Influences of Social and Style Variables on Adult Usage of African American English Features

    ERIC Educational Resources Information Center

    Craig, Holly K.; Grogger, Jeffrey T.

    2012-01-01

    Purpose: In this study, the authors examined the influences of selected social (gender, employment status, educational achievement level) and style variables (race of examiner, interview topic) on the production of African American English (AAE) by adults. Method: Participants were 50 African American men and women, ages 20-30 years. The authors…

  9. The paleoclimate record of long-term climate variability

    SciTech Connect

    Webb, R.S.; Bartlein, P.J.; Overpeck, J.T. Univ. of Oregon, Eugene )

    1993-06-01

    Climate variability occurs on time scales ranging from decades or shorter to millions of years. An important step in determining the effects of trace-gas-induced warming on climate variability and ecosystems is characterizing past natural variability and change. Throughout the Quaternary long-term climate variability has been dominated by Milankovitch forcing of glacial/interglacial cycles. Superimposed on this millennia-scale orbitally forced variability have been more rapid climate events (e.g. Younger Dryas, Little Ice Age, Medieval Warm Period, Sahelian droughts). Although highly relevant to understanding possible responses of ecosystems to future climate change, most decade to century scale climate variability remains poorly understood. Insights into mechanisms and responses can be obtained from tree rings, ice cores, corals, marine, lake and fluvial sediments, pollen, and macrofossils. These paleoclimate records reveal that the range of natural climate variability is much larger than indicated by the instrumental record of the past 150 years. Global networks of well-dated, high-resolution paleocrunate records for key intervals of the past are currently being assembled. These networks should provide the baseline of natural variability required to understand climate-ecosystem dynamics and to identify anthropogenic-induced change.

  10. LAMPPOST: A Mnemonic Device for Teaching Climate Variables

    ERIC Educational Resources Information Center

    Fahrer, Chuck; Harris, Dan

    2004-01-01

    This article introduces the word "LAMPPOST" as a mnemonic device to aid in the instruction of climate variables. It provides instructors with a framework for discussing climate patterns that is based on eight variables: latitude, altitude, maritime influence and continentality, pressure systems, prevailing winds, ocean currents, storms, and…

  11. Present and Future Modes of Low Frequency Climate Variability

    SciTech Connect

    Cane, Mark A.

    2014-02-20

    This project addressed area (1) of the FOA, “Interaction of Climate Change and Low Frequency Modes of Natural Climate Variability”. Our overarching objective is to detect, describe and understand the changes in low frequency variability between model simulations of the preindustrial climate and simulations of a doubled CO2 climate. The deliverables are a set of papers providing a dynamical characterization of interannual, decadal, and multidecadal variability in coupled models with attention to the changes in this low frequency variability between pre-industrial concentrations of greenhouse gases and a doubling of atmospheric concentrations of CO2. The principle mode of analysis, singular vector decomposition, is designed to advance our physical, mechanistic understanding. This study will include external natural variability due to solar and volcanic aerosol variations as well as variability internal to the climate system. An important byproduct is a set of analysis tools for estimating global singular vector structures from the archived output of model simulations.

  12. Multi-decadal climate variability, New South Wales, Australia.

    PubMed

    Franks, S W

    2004-01-01

    Traditional hydrological risk estimation has treated the observations of hydro-climatological extremes as being independent and identically distributed, implying a static climate risk. However, recent research has highlighted the persistence of multi-decadal epochs of distinct climate states across New South Wales (NSW), Australia. Climatological studies have also revealed multi-decadal variability in the magnitude and frequency of El Niño/Southern Oscillation (ENSO) impacts. In this paper, examples of multi-decadal variability are presented with regard to flood and drought risk. The causal mechanisms for the observed variability are then explored. Finally, it is argued that the insights into climate variability provide (a) useful lead time for forecasting seasonal hydrological risk, (b) a strong rationale for a new framework for hydrological design and (c) a strong example of natural climate variability for use in the testing of General Circulation Models of climate change.

  13. Multi-decadal climate variability, New South Wales, Australia.

    PubMed

    Franks, S W

    2004-01-01

    Traditional hydrological risk estimation has treated the observations of hydro-climatological extremes as being independent and identically distributed, implying a static climate risk. However, recent research has highlighted the persistence of multi-decadal epochs of distinct climate states across New South Wales (NSW), Australia. Climatological studies have also revealed multi-decadal variability in the magnitude and frequency of El Niño/Southern Oscillation (ENSO) impacts. In this paper, examples of multi-decadal variability are presented with regard to flood and drought risk. The causal mechanisms for the observed variability are then explored. Finally, it is argued that the insights into climate variability provide (a) useful lead time for forecasting seasonal hydrological risk, (b) a strong rationale for a new framework for hydrological design and (c) a strong example of natural climate variability for use in the testing of General Circulation Models of climate change. PMID:15195429

  14. The Climate Shift and the Climate Variability in the Mediterranean region

    NASA Astrophysics Data System (ADS)

    Lopez Parages, Jorge; Rodriguez-Fonseca, Belen

    2010-05-01

    -based precipitation for the second half of the twenty century is used to investigate the precipitation variability over Europe and their links to the CS and the multidecadal variability. The seasonal modes are analyzed, using time series before and after the CS. To carry out this study, the NCEP-NCAR reanalysis field, the NCEP sea surface temperature (SST) and the ERA40 reanalysis data for the second half of the twenty century are used. To achieve a better understanding of the teleconnections linked to these changes, and its possible link to the SST variability, a long set of simulations with a General Circulation Model (AGCM), run with observed SSTs, has been analysed for the same time period. References: Hurrell, J.W., Kushnir Y., Ottersen G. and Visbeck M., (2003): An overview of the North Atlantic Oscillation. In: The North Atlantic Oscillation (Eds. Hurrell, J.W., Kushnir Y., Ottersen G. and Visbeck M.) AGU. Losada T, B Rodríguez-Fonseca, S Janicot, F Gervois, F Chauvin, P M Ruti (2009): A multi-model approach to the Atlantic equatorial mode. Impact on the West African monsoon and tropical teleconnections (submitted for a Spetial Issue at Climate Dynamics). Mantua, N.J. and S.R. Hare, Y. Zhang, J.M. Wallace, and R.C. Francis, (1997): A Pacific interdecadal climate oscillation with impacts on salmon production. Bulletin of the American Meteorological Society, 78, pp. 1069-1079. Mariotti, A., Zeng, N. and Lau, K.-M.,(2002): Euro-Mediterranean rainfall and ENSO- a seasonally varying relationship, Geophysical Research Letters, 29, 12. 10.1029/2001GL014248. Miller A J, D R Cayan, T P Barnett, N E Graham and J M Oberhuber (1994): The 1976-77 Climate Shift of the Pacific Ocean. Oceanogr. 7, 21-26. Polo I, B Rodríguez-Fonseca, T Losada and J García-Serrano (2008a): Tropical Atlantic Variability modes (1979-2002). Part I: time-evolving SST modes related to West African rainfall. J. Climate, 21, 6457-6475. Rodriguez-Fonseca B., I. Polo, J. Garcia-Serrano, T. Losada, E. Mohino, C. R

  15. Climate and hydrological variability: the catchment filtering role

    NASA Astrophysics Data System (ADS)

    Andrés-Doménech, I.; García-Bartual, R.; Montanari, A.; Marco, J. B.

    2015-01-01

    Measuring the impact of climate change on flood frequency is a complex and controversial task. Identifying hydrological changes is difficult given the factors, other than climate variability, which lead to significant variations in runoff series. The catchment filtering role is often overlooked and thus may hinder the correct identification of climate variability signatures on hydrological processes. Does climate variability necessarily imply hydrological variability? This research aims to analytically derive the flood frequency distribution based on realistic hypotheses about the rainfall process and the rainfall-runoff transformation. The annual maximum peak flow probability distribution is analytically derived to quantify the filtering effect of the rainfall-runoff process on climate change. A sensitivity analysis is performed according to typical semi-arid Mediterranean climatic and hydrological conditions, assuming a simple but common scheme for the rainfall-runoff transformation in small-size ungauged catchments, i.e. the CN-SCS model. Variability in annual maximum peak flows and its statistical significance are analysed when changes in the climatic input are introduced. Results show that depending on changes in the annual number of rainfall events, the catchment filtering role is particularly significant, especially when the event rainfall volume distribution is not strongly skewed. Results largely depend on the return period: for large return periods, peak flow variability is significantly affected by the climatic input, while for lower return periods, infiltration processes smooth out the impact of climate change.

  16. Climate and hydrological variability: the catchment filtering role

    NASA Astrophysics Data System (ADS)

    Andrés-Doménech, I.; García-Bartual, R.; Montanari, A.; Marco, J. B.

    2014-09-01

    Measuring the impact of climate change on flood frequency is a complex and controversial task. Identifying hydrological changes is difficult given the factors, other than climate variability, which lead to significant variations in runoff series. The catchment filtering role is often overlooked and in fact, this may hinder the correct identification of climate variability signatures on hydrological processes. Does climate variability necessarily imply hydrological variability? The research herein presented aims to analytically derive the flood frequency distribution basing on realistic hypotheses about the rainfall process and the rainfall-runoff transformation. The peak flow probability distribution is analytically derived to quantify the filtering effect operated by the rainfall-runoff process on climate change. A sensitivity analysis is performed according to typical semi-arid Mediterranean climatic and hydrological conditions, assuming a simple but common scheme for the rainfall-runoff transformation in small-size ungauged catchments, i.e. the CN-SCS model. Variability in peak flows and its statistical significance are analysed when changes in the climatic input are introduced. Results show that in regard to changes in the annual number of rainfall events, the catchment filtering role is particularly significant when the event rainfall volume distribution is not strongly skewed. Results largely depend on the return period: for large return periods, peak flow variability is significantly impacted by the climatic input, while for lower return periods, infiltration processes smooth out the effects of climate change.

  17. Disease in a more variable and unpredictable climate

    NASA Astrophysics Data System (ADS)

    McMahon, T. A.; Raffel, T.; Rohr, J. R.; Halstead, N.; Venesky, M.; Romansic, J.

    2014-12-01

    Global climate change is shifting the dynamics of infectious diseases of humans and wildlife with potential adverse consequences for disease control. Despite this, the role of global climate change in the decline of biodiversity and the emergence of infectious diseases remains controversial. Climate change is expected to increase climate variability in addition to increasing mean temperatures, making climate less predictable. However, few empirical or theoretical studies have considered the effects of climate variability or predictability on disease, despite it being likely that hosts and parasites will have differential responses to climatic shifts. Here we present a theoretical framework for how temperature variation and its predictability influence disease risk by affecting host and parasite acclimation responses. Laboratory experiments and field data on disease-associated frog declines in Latin America support this framework and provide evidence that unpredictable temperature fluctuations, on both monthly and diurnal timescales, decrease frog resistance to the pathogenic chytrid fungus Batrachochytrium dendrobatidis (Bd). Furthermore, the pattern of temperature-dependent growth of the fungus on frogs was inconsistent with the pattern of Bd growth in culture, emphasizing the importance of accounting for the host-parasite interaction when predicting climate-dependent disease dynamics. Consistent with our laboratory experiments, increased regional temperature variability associated with global El Niño climatic events was the best predictor of widespread amphibian losses in the genus Atelopus. Thus, incorporating the effects of small-scale temporal variability in climate can greatly improve our ability to predict the effects of climate change on disease.

  18. Sst and Ghg Impacts On The West African Monsoon Climate: A Superensemble Approach

    NASA Astrophysics Data System (ADS)

    Paeth, H.; Hense, A.

    West African rainfall has been subject to large interdecadal variations during the 20th century. The most prominent feature is a negative trend in annual precipitation after 1960, causing severe drought in the Sahel region and the southern part of West Africa, with some recoverage in recent years. We examine and quantify the influence of ob- served SST changes on low-frequency variability over the subcontinent and compare it with the additional impact of increasing GHG concentrations, as revealed by a su- perensemble of SST-driven experiments. SST is largely responsible for decadal and longer-term variability over the southern part of West Africa, accounting for almost 80 % of monsoonal rainfall variance. The additional impact of the enhanced green- house effect is weak but statistically significant by the year 1980, obviously associ- ated with a positive trend in annual precipitation. This positive trend is also found in GHG-induced coupled climate model projection into the future. The CO2 signal is again weak but statistically significant and consistent with different climate models, as revealed by a superensemble of coupled experiments.

  19. A Record of Early to Middle Holocene Hydroclimate Variability from the West African Sahel

    NASA Astrophysics Data System (ADS)

    McIntosh, R.; Douglas, P. M.; Warren, C.; Meyers, S. R.; Coutros, P.; Park, D. P.

    2011-12-01

    The African Humid Period (ca. 14.8 to 5.5 ka) is an interval of wet climates across northwest Africa, with evidence for widespread lake basins and savannah vegetation in areas that are now desert. There are few high-resolution continental records of hydrologic variability during the African humid period however. In particular, it remains uncertain how periods of north Atlantic climate variability were expressed in northwest Africa. We present results from a 5.4 meter sediment core from Lake Fati in northern Mali (16.29° N, 3.71° W), which represents the first lake sediment core from the western Sahel. The Lake Fati core contains a continuous record of lake mud from 10.43 to 4.66 kyr BP. Centimeter scale XRF scanning indicates strong covariation between iron, calcium, manganese and phosphorous abundance due to enrichment of these elements during periods of enhanced deposition of authigenic siderite. Preliminary oxygen isotope measurements indicate that authigenic siderite δ18O values are positively correlated with Fe counts, suggesting that siderite deposition increased during drier periods with greater evaporation of lake waters. These drying events occurred on decadal to centennial time scales, with higher-frequency variability during the early Holocene. Peaks in zirconium and titanium abundance coincide with some of the inferred dry periods, suggesting that deposition of aeolian silt coincided with periods of increased evaporation of lake water. A roughly 30 year interval of sand deposition at ~8.33 kyr BP suggests major drying and activation of aeolian sand deposition. This abrupt climate change could be related to the 8.2 ka event in the North Atlantic; further efforts to refine the sediment core age model will constrain the relationship of this rapid drying to abrupt climate change in the North Atlantic. Aluminum and silicon counts co-vary for much of the lake Fati record, and are related to input of terrigenous sediment, primarily during seasonal flooding

  20. ENSO variability in a changing climate

    NASA Astrophysics Data System (ADS)

    Feng, Jiaxin

    Since 1980, a new type of ENSO, i.e., central Pacific (CP) ENSO, where sea surface temperature anomalies (SSTAs) are mainly located in the equatorial central Pacific, has been frequently observed. Several studies have documented and predicted a higher occurrence ratio of CP ENSO to eastern Pacific (EP) ENSO, where SSTAs mainly occur in the equatorial eastern Pacific, in a warming climate. Most studies centered on the difference between CP and EP ENSO have used traditional analysis methods, such as PCA/EOF analysis and regression, to define or differentiate the aforementioned two types of ENSO. However, the results obtained using these methods can only reveal accumulated spatial information which contributed most to the variance of the data, which is the usually the spatial information during the mature (peak) stage of ENSO; this spatial information is a static pattern and is not able to reveal sequential development of ENSO, which should be crucial for physical interpretations. In addition, although this spatial information in generally true for the entire temporal span, it is not necessarily true for any subperiods and thus not able to reveal any potential characteristic change of ENSO over time. In this study, an alternative Nino 3.4 index is defined to reflect only the interannual variability of equatorial Pacific SSTAs. Using this alternative index, we identify 28 El Nino events and 31 La Nina events. Then, we employ a newly developed analysis method, i.e., fast multidimensional ensemble empirical mode decomposition (FMEEMD), to extract the interannual spatiotemporal evolution of SSTAs to examine the developments of the identified ENSO events. All events are classified into four types of ENSO based on the interannual evolutions of SSTAs early in the development stage: (1) EP ENSO, (2) eastern-central Pacific (ECP) ENSO, (3) western-central Pacific (WCP) ENSO, and (4) mixed (MIX) ENSO. We apply the same method to analyze surface horizontal wind and thermocline

  1. Millennial- to centennial-scale record of African climate variability and organic carbon accumulation in the Coniacian Santonian eastern tropical Atlantic (Ocean Drilling Program Site 959, off Ivory Coast and Ghana)

    NASA Astrophysics Data System (ADS)

    Hofmann, P.; Wagner, T.; Beckmann, B.

    2003-02-01

    Millennial- to centennial-scale geochemical records of Coniacian to Santonian deposits from the Deep Ivorian Basin are used to develop a model for the accumulation of black shales in equatorial regions during the final of the Cretaceous oceanic anoxic events (OAE). Proxy records from Ocean Drilling Program Site 959 document a strong precessional signal in the occurrence of black shales, the abundance of quartz, and clay mineralogy during OAE 3. We hypothesize that this signal reflects changes in atmospheric circulation patterns, which in turn caused latitudinal shifts of continental climate belts across western Africa. Furthermore we propose that the periodic deposition of black shales occurred in response to adjustments of oceanic circulation in the Deep Ivorian Basin resulting from climate-controlled fluctuations in continental runoff. A new high-resolution cyclostratigraphic framework allowed us to estimate a rapid change—within <1000 yr—from dysoxic (background) to anoxic or euxinic (black shale) environmental conditions, followed by black shale deposition for ˜10 k.y. and a gradual return to the initial dysoxic conditions. Our findings imply a highly dynamic Late Cretaceous atmosphere-ocean system.

  2. Future of West African Monsoon in A Warming Climate

    NASA Astrophysics Data System (ADS)

    Raj, Jerry; Kunhu Bangalath, Hamza; Stenchikov, Georgiy

    2016-04-01

    West Africa is the home of more than 300 million people whose agriculture based economy highly relies on West African Monsoon (WAM), which produces a mean annual rainfall of 150 - 2,500 mm and variability and change of which have devastating impact on the local population. The observed widespread drought in West Africa during the 1970s and 1980s was the most significant drought at regional scale during the twentieth century. In this study, a high resolution AGCM, High Resolution Atmospheric Model (HiRAM), is used to study the effects of anthropogenic greenhouse warming on WAM. HiRAM is developed at GFDL based on AM2 and employs a cubed-sphere finite volume dynamical core and uses shallow convective scheme (for moist convection and stratiform cloudiness) instead of deep convective parameterization. Future projections are done using two representative concentration pathways, RCP 4.5 and RCP 8.5 from 2007 to 2050 at C360 (~25 km) resolution. Both RCP 4.5 and RCP 8.5 scenarios predict warming over West Africa during boreal summer, especially over Western Sahara. Also, both scenarios predict southward shift in WAM rainfall pattern and drying over Southern Sahara, while RCP 8.5 predicts enhanced rainfall over Gulf of Guinea. The intensification of rainfall over tropical latitudes is caused by increased low level winds due to warm SST over Gulf of Guinea.

  3. Multi-Wheat-Model Ensemble Responses to Interannual Climate Variability

    NASA Technical Reports Server (NTRS)

    Ruane, Alex C.; Hudson, Nicholas I.; Asseng, Senthold; Camarrano, Davide; Ewert, Frank; Martre, Pierre; Boote, Kenneth J.; Thorburn, Peter J.; Aggarwal, Pramod K.; Angulo, Carlos

    2016-01-01

    We compare 27 wheat models' yield responses to interannual climate variability, analyzed at locations in Argentina, Australia, India, and The Netherlands as part of the Agricultural Model Intercomparison and Improvement Project (AgMIP) Wheat Pilot. Each model simulated 1981e2010 grain yield, and we evaluate results against the interannual variability of growing season temperature, precipitation, and solar radiation. The amount of information used for calibration has only a minor effect on most models' climate response, and even small multi-model ensembles prove beneficial. Wheat model clusters reveal common characteristics of yield response to climate; however models rarely share the same cluster at all four sites indicating substantial independence. Only a weak relationship (R2 0.24) was found between the models' sensitivities to interannual temperature variability and their response to long-termwarming, suggesting that additional processes differentiate climate change impacts from observed climate variability analogs and motivating continuing analysis and model development efforts.

  4. Climatic changes along the northwestern African Continental Margin over the last 30 kyrs

    NASA Astrophysics Data System (ADS)

    Ternois, Yann; Sicre, Marie-Alexandrine; Paterne, Martine

    2000-01-01

    Two sediment cores were investigated to study the regional climatic variability of the NW African upwelling over the late Quaternary. Biomarker data and Sea Surface Temperatures (SSTs) predicted from alkenones at 25°N and 21°N exhibited distinct features. The amplitude of the last deglaciation was estimated to 4.5°C at 25°N and 2-2.5°C at 21°N. At 25°N, terrestrial and marine glacial inputs were higher than Holocene ones as a result of a strengthening of the trade winds and intensification of oceanic production. In contrast, at 21°N, warmer SSTs and lower organic carbon and alkenone productions during the last glacial suggest a regression of the upwelling and therefore a change of wind regime. Low glacial n-alkanols are consistent with the migration of the vegetation belt during the maximum of African aridity, while their decrease towards the core-top may be indicative of anthropogenic disturbances.

  5. Observed decadal variability of southern African rainfall, their teleconnections, and uncertainties

    NASA Astrophysics Data System (ADS)

    Dieppois, Bastien; Pohl, Benjamin; Rouault, Mathieu; New, Mark; Lawler, Damian; Keenlyside, Noel

    2016-04-01

    This study examines for the first time the changing characteristics of summer and winter southern African rainfall, and their teleconnections with large-scale climate through the dominant timescales of variability. The summer and winter rainfall indices exhibit three significant timescales of variability over the 20th century: interdecadal (15-28 year), quasi-decadal (8-13 year) and interannual (2-8 year). Teleconnections with global sea-surface temperature and atmospheric circulation anomalies, which have been established here using different data sets, are different for each timescale. Uncertainty related to the choice of observed-based SST and reanalysis data sets appears stronger over the winter rainfall region and at the interdecadal timescale. However, only SST and atmospheric anomalies which show an agreement greater than 90% between data sets, or between the members of the reanalysis, have been described. Tropical/subtropical teleconnections emerge as the main driver of summer rainfall variability. Thus, shifts in the Walker circulation are linked to the El Niño Southern Oscillation (ENSO) and, at decadal timescales, to decadal ENSO-like patterns related to the Pacific Decadal Oscillation and the Interdecadal Pacific Oscillation. These global changes in the upper-zonal circulation interact with asymmetric ocean-atmospheric modifications between the South Atlantic and South Indian Oceans; together these lead to shift in the South Indian Convergence Zone, and a modulation of the development of convective rain bearing systems over southern Africa in summer. Such regional changes, embedded in quasi-annular geopotential patterns, consist of easterly moisture fluxes from the Mascarene High, which dominate southerly moisture fluxes from the St Helena High. Winter rainfall variability is more influenced by mid-latitude atmospheric variability, in particular the Southern Annular Mode, but interactions with ENSO remain, especially in the subtropics. Asymmetrical

  6. Interannual to interdecadal variability of winter and summer southern African rainfall, and their teleconnections

    NASA Astrophysics Data System (ADS)

    Dieppois, Bastien; Pohl, Benjamin; Rouault, Mathieu; New, Mark; Lawler, Damian; Keenlyside, Noel

    2016-06-01

    This study examines for the first time the changing characteristics of summer and winter southern African rainfall and their teleconnections with large-scale climate through the dominant time scales of variability. As determined by wavelet analysis, the austral summer and winter rainfall indices exhibit three significant time scales of variability over the twentieth century: interdecadal (15-28 years), quasi-decadal (8-13 years), and interannual (2-8 years). Teleconnections with global sea surface temperature and atmospheric circulation anomalies are established here but are different for each time scale. Tropical/subtropical teleconnections emerge as the main driver of austral summer rainfall variability. Thus, shifts in the Walker circulation are linked to the El Niño-Southern Oscillation (ENSO) and, at decadal time scales, to decadal ENSO-like patterns related to the Pacific Decadal Oscillation and the Interdecadal Pacific Oscillation. These global changes in the upper zonal circulation interact with asymmetric ocean-atmospheric conditions between the South Atlantic and South Indian Oceans; together, these lead to a shift in the South Indian Convergence Zone and a modulation of the development of convective rain-bearing systems over southern Africa in summer. Such regional changes, embedded in quasi-annular geopotential patterns, consist of easterly moisture fluxes from the South Indian High, which dominate southerly moisture fluxes from the South Atlantic High. Austral winter rainfall variability is more influenced by midlatitude atmospheric variability, in particular the Southern Annular Mode. The rainfall changes in the southwestern regions of southern Africa are determined by asymmetrical changes in the midlatitude westerlies between the Atlantic and Indian Oceans.

  7. A reassessment of lake and wetland feedbacks on the North African Holocene climate

    NASA Astrophysics Data System (ADS)

    Krinner, G.; Lézine, A.-M.; Braconnot, P.; Sepulchre, P.; Ramstein, G.; Grenier, C.; Gouttevin, I.

    2012-04-01

    Large parts of the Sahara were vegetated during the early to mid Holocene. Several positive feedbacks, most notably related to vegetation, have been shown to have favored the northward migration of the desert boundary. During this period, numerous lakes and wetlands existed in the Sahara region and might have acted as a local moisture source. However, earlier model studies of the effects of open water surfaces on the mid-Holocene North African climate suggested that these were weak and did not contribute significantly to this northward migration of the North African climate zones. Using a state-of-the-art climate model, we suggest that the effect of open-water surfaces on the mid-Holocene North African climate might have been much stronger than previously estimated, regionally more than doubling the simulated precipitation rates. It is thus possible that this effect, combined to other known positive feedbacks, favored the appearance of the “Green Sahara”.

  8. Climate and the landscape of fear in an African savanna.

    PubMed

    Riginos, Corinna

    2015-01-01

    Herbivores frequently have to make trade-offs between two basic needs: the need to acquire forage and the need to avoid predation. One manifestation of this trade-off is the 'landscape of fear' phenomenon - wherein herbivores avoid areas of high perceived predation risk even if forage is abundant or of high quality in those areas. Although this phenomenon is well established among invertebrates, its applicability to terrestrial large herbivores remains debated, in part because experimental evidence is scarce. This study was designed to (i) experimentally test the effects of tree density - a key landscape feature associated with predation risk for African ungulates - on herbivore habitat use and (ii) establish whether habitat use patterns could be explained by trade-offs between foraging opportunities and predation risk avoidance. In a Kenyan savanna system, replicate plots dominated by the tree Acacia drepanolobium were cleared, thinned or left intact. Ungulate responses were measured over four years, which included years of moderate rainfall as well as a severe drought. Under average rainfall conditions, most herbivores (primarily plains zebra, Grant's gazelle and hartebeest) favoured sites with fewer trees and higher visibility - regardless of grass production - while elephants (too large to be vulnerable to predation) favoured sites with many trees. During the drought, however, herbivores favoured sites that had high grass biomass, but not high visibility. Thus, during the drought, herbivores sought areas where food was more abundant, despite probable higher risk of predation. These results illustrate that the 'landscape of fear', and the associated interactions between top-down and bottom-up effects, is not static, but rather shifts markedly under different conditions. Climate thus has the potential to alter the strength and spatial dynamics of behaviourally mediated cascades in large herbivore systems.

  9. Climate and the landscape of fear in an African savanna.

    PubMed

    Riginos, Corinna

    2015-01-01

    Herbivores frequently have to make trade-offs between two basic needs: the need to acquire forage and the need to avoid predation. One manifestation of this trade-off is the 'landscape of fear' phenomenon - wherein herbivores avoid areas of high perceived predation risk even if forage is abundant or of high quality in those areas. Although this phenomenon is well established among invertebrates, its applicability to terrestrial large herbivores remains debated, in part because experimental evidence is scarce. This study was designed to (i) experimentally test the effects of tree density - a key landscape feature associated with predation risk for African ungulates - on herbivore habitat use and (ii) establish whether habitat use patterns could be explained by trade-offs between foraging opportunities and predation risk avoidance. In a Kenyan savanna system, replicate plots dominated by the tree Acacia drepanolobium were cleared, thinned or left intact. Ungulate responses were measured over four years, which included years of moderate rainfall as well as a severe drought. Under average rainfall conditions, most herbivores (primarily plains zebra, Grant's gazelle and hartebeest) favoured sites with fewer trees and higher visibility - regardless of grass production - while elephants (too large to be vulnerable to predation) favoured sites with many trees. During the drought, however, herbivores favoured sites that had high grass biomass, but not high visibility. Thus, during the drought, herbivores sought areas where food was more abundant, despite probable higher risk of predation. These results illustrate that the 'landscape of fear', and the associated interactions between top-down and bottom-up effects, is not static, but rather shifts markedly under different conditions. Climate thus has the potential to alter the strength and spatial dynamics of behaviourally mediated cascades in large herbivore systems. PMID:24942250

  10. Climate variability and climate change vulnerability and adaptation. Workshop summary

    SciTech Connect

    Bhatti, N.; Cirillo, R.R.; Dixon, R.K.

    1995-12-31

    Representatives from fifteen countries met in Prague, Czech Republic, on September 11-15, 1995, to share results from the analysis of vulnerability and adaptation to global climate change. The workshop focused on the issues of global climate change and its impacts on various sectors of a national economy. The U.N. Framework Convention on Climate Change (FCCC), which has been signed by more than 150 governments worldwide, calls on signatory parties to develop and communicate measures they are implementing to respond to global climate change. An analysis of a country`s vulnerability to changes in the climate helps it identify suitable adaptation measures. These analyses are designed to determine the extent of the impacts of global climate change on sensitive sectors such as agricultural crops, forests, grasslands and livestock, water resources, and coastal areas. Once it is determined how vulnerable a country may be to climate change, it is possible to identify adaptation measures for ameliorating some or all of the effects.The objectives of the vulnerability and adaptation workshop were to: The objectives of the vulnerability and adaptation workshop were to: Provide an opportunity for countries to describe their study results; Encourage countries to learn from the experience of the more complete assessments and adjust their studies accordingly; Identify issues and analyses that require further investigation; and Summarize results and experiences for governmental and intergovernmental organizations.

  11. Interactions of Mean Climate Change and Climate Variability on Food Security Extremes

    NASA Technical Reports Server (NTRS)

    Ruane, Alexander C.; McDermid, Sonali; Mavromatis, Theodoros; Hudson, Nicholas; Morales, Monica; Simmons, John; Prabodha, Agalawatte; Ahmad, Ashfaq; Ahmad, Shakeel; Ahuja, Laj R.

    2015-01-01

    Recognizing that climate change will affect agricultural systems both through mean changes and through shifts in climate variability and associated extreme events, we present preliminary analyses of climate impacts from a network of 1137 crop modeling sites contributed to the AgMIP Coordinated Climate-Crop Modeling Project (C3MP). At each site sensitivity tests were run according to a common protocol, which enables the fitting of crop model emulators across a range of carbon dioxide, temperature, and water (CTW) changes. C3MP can elucidate several aspects of these changes and quantify crop responses across a wide diversity of farming systems. Here we test the hypothesis that climate change and variability interact in three main ways. First, mean climate changes can affect yields across an entire time period. Second, extreme events (when they do occur) may be more sensitive to climate changes than a year with normal climate. Third, mean climate changes can alter the likelihood of climate extremes, leading to more frequent seasons with anomalies outside of the expected conditions for which management was designed. In this way, shifts in climate variability can result in an increase or reduction of mean yield, as extreme climate events tend to have lower yield than years with normal climate.C3MP maize simulations across 126 farms reveal a clear indication and quantification (as response functions) of mean climate impacts on mean yield and clearly show that mean climate changes will directly affect the variability of yield. Yield reductions from increased climate variability are not as clear as crop models tend to be less sensitive to dangers on the cool and wet extremes of climate variability, likely underestimating losses from water-logging, floods, and frosts.

  12. Projections of 21st Century African Climate: Implications for African Savanna Fire Dynamics, Human Health and Food Security

    NASA Astrophysics Data System (ADS)

    Adegoke, J. O.

    2015-12-01

    Fire is a key agent of change in the African savannas, which are shaped through the complex interactions between trees, C4 grasses, rainfall, temperature, CO2 and fire. These fires and their emitted smoke can have numerous direct and indirect effects on the environment, water resources, air quality, and climate. For instance, veld fires in southern Africa cause large financial losses to agriculture, livestock production and forestry on an annual basis. This study contributes to our understanding of the implications of projected surface temperature evolution in Africa for fire risk, human health and agriculture over the coming decades. We use an ensemble of high-resolution regional climate model simulations of African climate for the 21st century. Regional dowscalings and recent global circulation model projections obtained for Africa indicate that African temperatures are likely to rise at 1.5 times the global rate of temperature increase in the tropics, and at almost twice the global rate of increase in the subtropics. Warming is projected to occur during the 21st century, with increases of 4-6 °C over the subtropics and 3-5 °C over the tropics plausible by the end of the century relative to present-day climate under the A2 (low mitigation) scenario. We explore the significance of the projected warming by documenting increases in projected high fire danger days and heat-wave days. General drying is projected across the continent, even for areas (e.g. tropical Africa) where an increase in rainfall is plausible. This is due to the drastic increases in temperature that are projected, which leads to drier soils (through enhanced evaporation) despite the rainfall increases. This will likely impact negatively on crop yield, particularly on the maize crop that is of crucial importance in terms of African food security.

  13. Impact of Holocene climate variability on Arctic vegetation

    NASA Astrophysics Data System (ADS)

    Gajewski, K.

    2015-10-01

    This paper summarizes current knowledge about the postglacial history of the vegetation of the Canadian Arctic Archipelago (CAA) and Greenland. Available pollen data were used to understand the initial migration of taxa across the Arctic, how the plant biodiversity responded to Holocene climate variability, and how past climate variability affected primary production of the vegetation. Current evidence suggests that most of the flora arrived in the area during the Holocene from Europe or refugia south or west of the region immediately after local deglaciation, indicating rapid dispersal of propagules to the region from distant sources. There is some evidence of shrub species arriving later in Greenland, but it is not clear if this is dispersal limited or a response to past climates. Subsequent climate variability had little effect on biodiversity across the CAA, with some evidence of local extinctions in areas of Greenland in the late Holocene. The most significant impact of climate changes is on vegetation density and/or plant production.

  14. A Survey of African American Physicians on the Health Effects of Climate Change

    PubMed Central

    Sarfaty, Mona; Mitchell, Mark; Bloodhart, Brittany; Maibach, Edward W

    2014-01-01

    The U.S. National Climate Assessment concluded that climate change is harming the health of many Americans and identified people in some communities of color as particularly vulnerable to these effects. In Spring 2014, we surveyed members of the National Medical Association, a society of African American physicians who care for a disproportionate number of African American patients, to determine whether they were seeing the health effects of climate change in their practices; the response rate was 30% (n = 284). Over 86% of respondents indicated that climate change was relevant to direct patient care, and 61% that their own patients were already being harmed by climate change moderately or a great deal. The most commonly reported health effects were injuries from severe storms, floods, and wildfires (88%), increases in severity of chronic disease due to air pollution (88%), and allergic symptoms from prolonged exposure to plants or mold (80%). The majority of survey respondents support medical training, patient and public education regarding the impact of climate change on health, and advocacy by their professional society; nearly all respondents indicated that the US should invest in significant efforts to protect people from the health effects of climate change (88%), and to reduce the potential impacts of climate change (93%). These findings suggest that African American physicians are currently seeing the health impacts of climate change among their patients, and that they support a range of responses by the medical profession, and public policy makers, to prevent further harm. PMID:25464138

  15. A survey of African American physicians on the health effects of climate change.

    PubMed

    Sarfaty, Mona; Mitchell, Mark; Bloodhart, Brittany; Maibach, Edward W

    2014-12-01

    The U.S. National Climate Assessment concluded that climate change is harming the health of many Americans and identified people in some communities of color as particularly vulnerable to these effects. In Spring 2014, we surveyed members of the National Medical Association, a society of African American physicians who care for a disproportionate number of African American patients, to determine whether they were seeing the health effects of climate change in their practices; the response rate was 30% (n = 284). Over 86% of respondents indicated that climate change was relevant to direct patient care, and 61% that their own patients were already being harmed by climate change moderately or a great deal. The most commonly reported health effects were injuries from severe storms, floods, and wildfires (88%), increases in severity of chronic disease due to air pollution (88%), and allergic symptoms from prolonged exposure to plants or mold (80%). The majority of survey respondents support medical training, patient and public education regarding the impact of climate change on health, and advocacy by their professional society; nearly all respondents indicated that the US should invest in significant efforts to protect people from the health effects of climate change (88%), and to reduce the potential impacts of climate change (93%). These findings suggest that African American physicians are currently seeing the health impacts of climate change among their patients, and that they support a range of responses by the medical profession, and public policy makers, to prevent further harm. PMID:25464138

  16. A survey of African American physicians on the health effects of climate change.

    PubMed

    Sarfaty, Mona; Mitchell, Mark; Bloodhart, Brittany; Maibach, Edward W

    2014-11-28

    The U.S. National Climate Assessment concluded that climate change is harming the health of many Americans and identified people in some communities of color as particularly vulnerable to these effects. In Spring 2014, we surveyed members of the National Medical Association, a society of African American physicians who care for a disproportionate number of African American patients, to determine whether they were seeing the health effects of climate change in their practices; the response rate was 30% (n = 284). Over 86% of respondents indicated that climate change was relevant to direct patient care, and 61% that their own patients were already being harmed by climate change moderately or a great deal. The most commonly reported health effects were injuries from severe storms, floods, and wildfires (88%), increases in severity of chronic disease due to air pollution (88%), and allergic symptoms from prolonged exposure to plants or mold (80%). The majority of survey respondents support medical training, patient and public education regarding the impact of climate change on health, and advocacy by their professional society; nearly all respondents indicated that the US should invest in significant efforts to protect people from the health effects of climate change (88%), and to reduce the potential impacts of climate change (93%). These findings suggest that African American physicians are currently seeing the health impacts of climate change among their patients, and that they support a range of responses by the medical profession, and public policy makers, to prevent further harm.

  17. How EC-EARTH simulates the Earth's climate and it's variabilities

    NASA Astrophysics Data System (ADS)

    Wang, Xueli

    2010-05-01

    Recently an Earth system named EC-Earth has been developed at KNMI in collaboration with a number of EU country's meteorological institutes. It is a coupled model with IFS (Integrated Forecasting System) from ECMWF as the atmospheric model, NEMO as ocean model. H-Tessel land scheme is used as land model and LIM as thermodynamic ice model. It will be shown that the model produces the mean climate better or equal to the CMIP3 mean climate models and the major climate variabilities are reproduced by the model fairly well. In particular the ENSO and NAO are very well simulated. Just as most climate models have difficulties to simulate variabilities in the Atlantic, EC-Earth simulates well North Tropical Atlantic SST both for seasonal cycle and variability, it simulates less good equatorial SST variabilities. The SST seasonal cycle is correctly simulated but the equatorial cold tongue is too weak comparing to the observation, up to 3 degrees. Nevertheless the model simulates reasonably good west African monsoon distribution and seasonal cycle although it's a bit to week and not penetrating north enough compare to CMAP data. Experiment with future CO2 concentration shows that the rainfall at the coastal area of Guinea increased as result of increasing CO2 concentration while no or little change in the Sahel area.

  18. Land Use and Climate Variability Amplify Contaminant Pulses

    EPA Science Inventory

    Converting land to human-dominated uses has increased contaminant loads in streams and rivers and vastly transformed hydrological cycles (Vitousek et al. 1997). More recently, climate change has further altered hydrologic cycles and variability of precipitation (IPCC 2007). Toge...

  19. Use of Machine Learning Techniques for Identification of Robust Teleconnections to East African Rainfall Variability

    NASA Technical Reports Server (NTRS)

    Roberts, J. Brent; Robertson, F. R.; Funk, C.

    2014-01-01

    Hidden Markov models can be used to investigate structure of subseasonal variability. East African short rain variability has connections to large-scale tropical variability. MJO - Intraseasonal variations connected with appearance of "wet" and "dry" states. ENSO/IOZM SST and circulation anomalies are apparent during years of anomalous residence time in the subseasonal "wet" state. Similar results found in previous studies, but we can interpret this with respect to variations of subseasonal wet and dry modes. Reveal underlying connections between MJO/IOZM/ENSO with respect to East African rainfall.

  20. Impacts of Climate Change on the Global Invasion Potential of the African Clawed Frog Xenopus laevis

    PubMed Central

    Ihlow, Flora; Courant, Julien; Secondi, Jean; Herrel, Anthony; Rebelo, Rui; Measey, G. John; Lillo, Francesco; De Villiers, F. André; Vogt, Solveig; De Busschere, Charlotte; Backeljau, Thierry; Rödder, Dennis

    2016-01-01

    By altering or eliminating delicate ecological relationships, non-indigenous species are considered a major threat to biodiversity, as well as a driver of environmental change. Global climate change affects ecosystems and ecological communities, leading to changes in the phenology, geographic ranges, or population abundance of several species. Thus, predicting the impacts of global climate change on the current and future distribution of invasive species is an important subject in macroecological studies. The African clawed frog (Xenopus laevis), native to South Africa, possesses a strong invasion potential and populations have become established in numerous countries across four continents. The global invasion potential of X. laevis was assessed using correlative species distribution models (SDMs). SDMs were computed based on a comprehensive set of occurrence records covering South Africa, North America, South America and Europe and a set of nine environmental predictors. Models were built using both a maximum entropy model and an ensemble approach integrating eight algorithms. The future occurrence probabilities for X. laevis were subsequently computed using bioclimatic variables for 2070 following four different IPCC scenarios. Despite minor differences between the statistical approaches, both SDMs predict the future potential distribution of X. laevis, on a global scale, to decrease across all climate change scenarios. On a continental scale, both SDMs predict decreasing potential distributions in the species’ native range in South Africa, as well as in the invaded areas in North and South America, and in Australia where the species has not been introduced. In contrast, both SDMs predict the potential range size to expand in Europe. Our results suggest that all probability classes will be equally affected by climate change. New regional conditions may promote new invasions or the spread of established invasive populations, especially in France and Great

  1. Impacts of Climate Change on the Global Invasion Potential of the African Clawed Frog Xenopus laevis.

    PubMed

    Ihlow, Flora; Courant, Julien; Secondi, Jean; Herrel, Anthony; Rebelo, Rui; Measey, G John; Lillo, Francesco; De Villiers, F André; Vogt, Solveig; De Busschere, Charlotte; Backeljau, Thierry; Rödder, Dennis

    2016-01-01

    By altering or eliminating delicate ecological relationships, non-indigenous species are considered a major threat to biodiversity, as well as a driver of environmental change. Global climate change affects ecosystems and ecological communities, leading to changes in the phenology, geographic ranges, or population abundance of several species. Thus, predicting the impacts of global climate change on the current and future distribution of invasive species is an important subject in macroecological studies. The African clawed frog (Xenopus laevis), native to South Africa, possesses a strong invasion potential and populations have become established in numerous countries across four continents. The global invasion potential of X. laevis was assessed using correlative species distribution models (SDMs). SDMs were computed based on a comprehensive set of occurrence records covering South Africa, North America, South America and Europe and a set of nine environmental predictors. Models were built using both a maximum entropy model and an ensemble approach integrating eight algorithms. The future occurrence probabilities for X. laevis were subsequently computed using bioclimatic variables for 2070 following four different IPCC scenarios. Despite minor differences between the statistical approaches, both SDMs predict the future potential distribution of X. laevis, on a global scale, to decrease across all climate change scenarios. On a continental scale, both SDMs predict decreasing potential distributions in the species' native range in South Africa, as well as in the invaded areas in North and South America, and in Australia where the species has not been introduced. In contrast, both SDMs predict the potential range size to expand in Europe. Our results suggest that all probability classes will be equally affected by climate change. New regional conditions may promote new invasions or the spread of established invasive populations, especially in France and Great Britain

  2. Impacts of Climate Change on the Global Invasion Potential of the African Clawed Frog Xenopus laevis.

    PubMed

    Ihlow, Flora; Courant, Julien; Secondi, Jean; Herrel, Anthony; Rebelo, Rui; Measey, G John; Lillo, Francesco; De Villiers, F André; Vogt, Solveig; De Busschere, Charlotte; Backeljau, Thierry; Rödder, Dennis

    2016-01-01

    By altering or eliminating delicate ecological relationships, non-indigenous species are considered a major threat to biodiversity, as well as a driver of environmental change. Global climate change affects ecosystems and ecological communities, leading to changes in the phenology, geographic ranges, or population abundance of several species. Thus, predicting the impacts of global climate change on the current and future distribution of invasive species is an important subject in macroecological studies. The African clawed frog (Xenopus laevis), native to South Africa, possesses a strong invasion potential and populations have become established in numerous countries across four continents. The global invasion potential of X. laevis was assessed using correlative species distribution models (SDMs). SDMs were computed based on a comprehensive set of occurrence records covering South Africa, North America, South America and Europe and a set of nine environmental predictors. Models were built using both a maximum entropy model and an ensemble approach integrating eight algorithms. The future occurrence probabilities for X. laevis were subsequently computed using bioclimatic variables for 2070 following four different IPCC scenarios. Despite minor differences between the statistical approaches, both SDMs predict the future potential distribution of X. laevis, on a global scale, to decrease across all climate change scenarios. On a continental scale, both SDMs predict decreasing potential distributions in the species' native range in South Africa, as well as in the invaded areas in North and South America, and in Australia where the species has not been introduced. In contrast, both SDMs predict the potential range size to expand in Europe. Our results suggest that all probability classes will be equally affected by climate change. New regional conditions may promote new invasions or the spread of established invasive populations, especially in France and Great Britain.

  3. Climate variables as predictors of basal metabolic rate: new equations.

    PubMed

    Froehle, Andrew W

    2008-01-01

    Estimation of basal metabolic rate (BMR) and daily energy expenditure (DEE) in living humans and in fossil hominins can be used to understand the way populations adapt to different environmental and nutritional circumstances. One variable that should be considered in such estimates is climate, which may influence between-population variation in BMR. Overall, populations living in warmer climates tend to have lower BMR than those living in colder climates, even after controlling for body size and composition. Current methods of estimating BMR ignore climate, or deal with its effects in an insufficient manner. This may affect studies that use the factorial method to estimate DEE from BMR, when BMR is not measured but predicted using an equation. The present meta-analysis of published BMR uses stepwise regression to investigate whether the inclusion of climate variables can produce a generally applicable model for human BMR. Regression results show that mean annual temperature and high heat index temperature have a significant effect on BMR, along with body size, age and sex. Based on the regression analysis, equations predicting BMR from body size and climate variables were derived and compared with existing equations. The new equations are generally more accurate and more consistent across climates than the older ones. Estimates of DEE in living and fossil humans using the new equations are compared with estimates using previously published equations, illustrating the utility of including climate variables in estimates of BMR. The new equations derived here may prove useful for future studies of human energy expenditure.

  4. Aerosols implicated as a prime driver of twentieth-century North Atlantic climate variability.

    PubMed

    Booth, Ben B B; Dunstone, Nick J; Halloran, Paul R; Andrews, Timothy; Bellouin, Nicolas

    2012-04-04

    Systematic climate shifts have been linked to multidecadal variability in observed sea surface temperatures in the North Atlantic Ocean. These links are extensive, influencing a range of climate processes such as hurricane activity and African Sahel and Amazonian droughts. The variability is distinct from historical global-mean temperature changes and is commonly attributed to natural ocean oscillations. A number of studies have provided evidence that aerosols can influence long-term changes in sea surface temperatures, but climate models have so far failed to reproduce these interactions and the role of aerosols in decadal variability remains unclear. Here we use a state-of-the-art Earth system climate model to show that aerosol emissions and periods of volcanic activity explain 76 per cent of the simulated multidecadal variance in detrended 1860-2005 North Atlantic sea surface temperatures. After 1950, simulated variability is within observational estimates; our estimates for 1910-1940 capture twice the warming of previous generation models but do not explain the entire observed trend. Other processes, such as ocean circulation, may also have contributed to variability in the early twentieth century. Mechanistically, we find that inclusion of aerosol-cloud microphysical effects, which were included in few previous multimodel ensembles, dominates the magnitude (80 per cent) and the spatial pattern of the total surface aerosol forcing in the North Atlantic. Our findings suggest that anthropogenic aerosol emissions influenced a range of societally important historical climate events such as peaks in hurricane activity and Sahel drought. Decadal-scale model predictions of regional Atlantic climate will probably be improved by incorporating aerosol-cloud microphysical interactions and estimates of future concentrations of aerosols, emissions of which are directly addressable by policy actions.

  5. CLIMATE VARIABILITY, CHANGE, AND CONSEQUENCES IN ESTUARIES

    EPA Science Inventory

    Climate change operates at global, hemispheric, and regional scales, sometimes involving rapid shifts in ocean and atmospheric circulation. Changes of global scope occurred in the transition into the Little Ice Age (1350-1880) and subsequent warming during the 20th century. In th...

  6. Hydrologic Response to Climate Variability, Climate Change, and Climate Extreme in the U.S.: Climate Model Evaluation and Projections

    SciTech Connect

    Leung, Lai R.; Qian, Yun

    2005-08-01

    Water resources are sensitive to climate variability and change; predictions of seasonal to interannual climate variations and projections of long-term climate trends can provide significant values in managing water resources. This study examines the control (1975–1995) and future (1995–2100) climate simulated by a global climate model (GCM) and a regional climate simulation driven by the GCM control simulation for the U.S. Comparison of the regional climate simulation with observations across 13 subregions showed that the simulation captured the seasonality and the distributions of precipitation rate quite well. The GCM control and climate change simulations showed that, as a result of a 1% increase in greenhouse gas concentrations per year, there will be a warming of 2–3°C across the U.S. from 2000 to 2100. Although precipitation is not projected to change during this century, the warming trend will increase evapotranspiration to reduce annual basin mean runoff over five subregions along the coastal and south-central U.S.

  7. The Variable Climate Impact of Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    Graf, H.

    2011-12-01

    The main effect of big volcanic eruptions in the climate system is due to their efficient transport of condensable gases and their precursors into the stratosphere. There the formation of aerosols leads to effects on atmospheric radiation transfer inducing a reduction of incoming solar radiation by reflection (i.e. cooling of the Earth surface) and absorption of near infrared radiation (i.e. heating) in the aerosol laden layers. In the talk processes determining the climate effect of an eruption will be illustrated by examples, mainly from numerical modelling. The amount of gases released from a magma during an eruption and the efficiency of their transport into very high altitudes depends on the geological setting (magma type) and eruption style. While mid-sized eruption plumes of Plinian style quickly can develop buoyancy by entrainment of ambient air, very large eruptions with high magma flux rates often tend to collapsing plumes and co-ignimbrite style. These cover much bigger areas and are less efficient in entraining ambient air. Vertical transport in these plumes is chaotic and less efficient, leading to lower neutral buoyancy height and less gas and particles reaching high stratospheric altitudes. Explosive energy and amount of released condensable gases are not the only determinants for the climatic effect of an eruption. The effect on shortwave radiation is not linear with the amount of aerosols formed since according to the Lambert-Beer Law atmospheric optical depth reaches a saturation limit with increased absorber concentration. In addition, if more condensable gas is available for aerosol growth, particles become larger and this affects their optical properties to less reflection and more absorption. Larger particles settle out faster, thus reducing the life time of the aerosol disturbance. Especially for big tropical eruptions the strong heating of the stratosphere in low latitudes leads to changes in atmospheric wave propagation by strengthened

  8. Quality Assurance for Essential Climate Variables

    NASA Astrophysics Data System (ADS)

    Folkert Boersma, K.; Muller, Jan-Peter

    2015-04-01

    Satellite data are of central interest to the QA4ECV project. Satellites have revolutionized the Earth's observation system of climate change and air quality over the past three decades, providing continuous data for the entire Earth. However, many users of these data are lost in the fog as to the quality of these satellite data. Because of this, the European Union expressed in its 2013 FP7 Space Research Call a need for reliable, traceable, and understandable quality information on satellite data records that could serve as a blueprint contribution to a future Copernicus Climate Change Service. The potential of satellite data to benefit climate change and air quality services is too great to be ignored. QA4ECV therefore bridges the gap between end-users of satellite data and the satellite data products. We are developing an internationally acceptable Quality Assurance (QA) framework that provides understandable and traceable quality information for satellite data used in climate and air quality services. Such a framework should deliver the historically linked long-term data sets that users need, in a format that they can readily use. QA4ECV has approached more than 150 users and suppliers of satellite data to collect their needs and expectations. The project will use their response as a guideline for developing user-friendly tools to obtain information on the completeness, accuracy, and fitness-for-purpose of the satellite datasets. QA4ECV collaborates with 4 joint FP7 Space projects in reaching out to scientists, policy makers, and other end-users of satellite data to improve understanding of the special challenges -and also opportunities- of working with satellite data for climate and air quality purposes. As a demonstration of its capacity, QA4ECV will generate multi-decadal climate data records for 3 atmospheric ECV precursors (nitrogen dioxide, formaldehyde, and carbon monoxide) and 3 land ECVs (albedo, leaf area index and absorbed photosynthetically active

  9. Women's role in adapting to climate change and variability

    NASA Astrophysics Data System (ADS)

    Carvajal-Escobar, Y.; Quintero-Angel, M.; García-Vargas, M.

    2008-04-01

    Given that women are engaged in more climate-related change activities than what is recognized and valued in the community, this article highlights their important role in the adaptation and search for safer communities, which leads them to understand better the causes and consequences of changes in climatic conditions. It is concluded that women have important knowledge and skills for orienting the adaptation processes, a product of their roles in society (productive, reproductive and community); and the importance of gender equity in these processes is recognized. The relationship among climate change, climate variability and the accomplishment of the Millennium Development Goals is considered.

  10. Reservoirs performances under climate variability: a case study

    NASA Astrophysics Data System (ADS)

    Longobardi, A.; Mautone, M.; de Luca, C.

    2014-09-01

    A case study, the Piano della Rocca dam (southern Italy) is discussed here in order to quantify the system performances under climate variability conditions. Different climate scenarios have been stochastically generated according to the tendencies in precipitation and air temperature observed during recent decades for the studied area. Climate variables have then been filtered through an ARMA model to generate, at the monthly scale, time series of reservoir inflow volumes. Controlled release has been computed considering the reservoir is operated following the standard linear operating policy (SLOP) and reservoir performances have been assessed through the calculation of reliability, resilience and vulnerability indices (Hashimoto et al. 1982), comparing current and future scenarios of climate variability. The proposed approach can be suggested as a valuable tool to mitigate the effects of moderate to severe and persistent droughts periods, through the allocation of new water resources or the planning of appropriate operational rules.

  11. Future warming patterns linked to today’s climate variability

    DOE PAGES

    Dai, Aiguo

    2016-01-11

    The reliability of model projections of greenhouse gas (GHG)-induced future climate change is often assessed based on models’ ability to simulate the current climate, but there has been little evidence that connects the two. In fact, this practice has been questioned because the GHG-induced future climate change may involve additional physical processes that are not important for the current climate. Here I show that the spatial patterns of the GHG-induced future warming in the 21st century is highly correlated with the patterns of the year-to-year variations of surface air temperature for today’s climate, with areas of larger variations during 1950–1979more » having more GHG-induced warming in the 21st century in all climate models. Such a relationship also exists in other climate fields such as atmospheric water vapor, and it is evident in observed temperatures from 1950–2010. The results suggest that many physical processes may work similarly in producing the year-to-year climate variations in the current climate and the GHG-induced long-term changes in the 21st century in models and in the real world. Furthermore, they support the notion that models that simulate present-day climate variability better are likely to make more reliable predictions of future climate change.« less

  12. Future Warming Patterns Linked to Today's Climate Variability.

    PubMed

    Dai, Aiguo

    2016-01-01

    The reliability of model projections of greenhouse gas (GHG)-induced future climate change is often assessed based on models' ability to simulate the current climate, but there has been little evidence that connects the two. In fact, this practice has been questioned because the GHG-induced future climate change may involve additional physical processes that are not important for the current climate. Here I show that the spatial patterns of the GHG-induced future warming in the 21(st) century is highly correlated with the patterns of the year-to-year variations of surface air temperature for today's climate, with areas of larger variations during 1950-1979 having more GHG-induced warming in the 21(st) century in all climate models. Such a relationship also exists in other climate fields such as atmospheric water vapor, and it is evident in observed temperatures from 1950-2010. The results suggest that many physical processes may work similarly in producing the year-to-year climate variations in the current climate and the GHG-induced long-term changes in the 21(st) century in models and in the real world. They support the notion that models that simulate present-day climate variability better are likely to make more reliable predictions of future climate change.

  13. Pacific Decadal Climate Variability and Predictability

    NASA Astrophysics Data System (ADS)

    Kirtman, B.

    2006-12-01

    The current understanding of decadal variability in both the tropical and extra-tropical Pacific is presented. Modeling studies into causes of mid-latitude ocean variability often focus on to what extent the variability involves coupled ocean-atmosphere feedbacks versus the uncoupled response to atmospheric stochastic white noise forcing. The coupled feedbacks are either viewed as a generalization of the Hasselman (1976) theory to include local air-sea interactions, which could amplify the low frequency response without any preferred time scale or as involving a "delayed oscillator" due to ocean memory whereby the variability has some preferred time scale. Generally, the coupled air-sea feedbacks are stable requiring atmospheric stochastic forcing, and the inclusion of ocean dynamics is thought to enhance the variability. The uncoupled stochastic forcing of the ocean includes a number of proposed physical mechanisms for the preferred low frequency. These mechanisms include oceanic advection processes associated with the mid-latitude gyre, an atmospheric pattern of forcing with a preferred length scale or position, the dynamical adjustment of the extra-tropical ocean circulation via long baroclinic Rossby waves, and Ekman pumping. Another possibility is that tropical forcing via some atmospheric "bridge" acts as a source of North Pacific decadal variations, which may or may not be amplified by coupled feedbacks. The amplitude and frequency of ENSO exhibits variations on decadal timescales. Whether these variations are driven by low frequency variability in the tropical Pacific mean state or are just sampling issues associated with some sort of random walk process has been the subject of some debate. Accordingly, the current literature includes a number of studies proposing mechanisms for the decadal variability of the tropical Pacific, and, as a counter argument, studies examining the null hypothesis that the amplitude and frequency variations are simply related to

  14. Regional-scale climate-variability synchrony of cholera epidemics in West Africa

    PubMed Central

    Constantin de Magny, Guillaume; Guégan, Jean-François; Petit, Michel; Cazelles, Bernard

    2007-01-01

    Background The relationship between cholera and climate was explored in Africa, the continent with the most reported cases, by analyzing monthly 20-year cholera time series for five coastal adjoining West African countries: Côte d'Ivoire, Ghana, Togo, Benin and Nigeria. Methods We used wavelet analyses and derived methods because these are useful mathematical tools to provide information on the evolution of the periodic component over time and allow quantification of non-stationary associations between time series. Results The temporal variability of cholera incidence exhibits an interannual component, and a significant synchrony in cholera epidemics is highlighted at the end of the 1980's. This observed synchrony across countries, even if transient through time, is also coherent with both the local variability of rainfall and the global climate variability quantified by the Indian Oscillation Index. Conclusion Results of this study suggest that large and regional scale climate variability influence both the temporal dynamics and the spatial synchrony of cholera epidemics in human populations in the Gulf of Guinea, as has been described for two other tropical regions of the world, western South America and Bangladesh. PMID:17371602

  15. Do bioclimate variables improve performance of climate envelope models?

    USGS Publications Warehouse

    Watling, James I.; Romañach, Stephanie S.; Bucklin, David N.; Speroterra, Carolina; Brandt, Laura A.; Pearlstine, Leonard G.; Mazzotti, Frank J.

    2012-01-01

    Climate envelope models are widely used to forecast potential effects of climate change on species distributions. A key issue in climate envelope modeling is the selection of predictor variables that most directly influence species. To determine whether model performance and spatial predictions were related to the selection of predictor variables, we compared models using bioclimate variables with models constructed from monthly climate data for twelve terrestrial vertebrate species in the southeastern USA using two different algorithms (random forests or generalized linear models), and two model selection techniques (using uncorrelated predictors or a subset of user-defined biologically relevant predictor variables). There were no differences in performance between models created with bioclimate or monthly variables, but one metric of model performance was significantly greater using the random forest algorithm compared with generalized linear models. Spatial predictions between maps using bioclimate and monthly variables were very consistent using the random forest algorithm with uncorrelated predictors, whereas we observed greater variability in predictions using generalized linear models.

  16. WASCAL - West African Science Service Center on Climate Change and Adapted Land Use Regional Climate Simulations and Land-Atmosphere Simulations for West Africa at DKRZ and elsewhere

    NASA Astrophysics Data System (ADS)

    Hamann, Ilse; Arnault, Joel; Bliefernicht, Jan; Klein, Cornelia; Heinzeller, Dominikus; Kunstmann, Harald

    2014-05-01

    Changing climate and hydro-meteorological boundary conditions are among the most severe challenges to Africa in the 21st century. In particular West Africa faces an urgent need to develop effective adaptation and mitigation strategies to cope with negative impacts on humans and environment due to climate change, increased hydro-meteorological variability and land use changes. To help meet these challenges, the German Federal Ministry of Education and Research (BMBF) started an initiative with institutions in Germany and West African countries to establish together a West African Science Service Center on Climate Change and Adapted Land Use (WASCAL). This activity is accompanied by an establishment of trans-boundary observation networks, an interdisciplinary core research program and graduate research programs on climate change and related issues for strengthening the analytical capabilities of the Science Service Center. A key research activity of the WASCAL Competence Center is the provision of regional climate simulations in a fine spatio-temporal resolution for the core research sites of WASCAL for the present and the near future. The climate information is needed for subsequent local climate impact studies in agriculture, water resources and further socio-economic sectors. The simulation experiments are performed using regional climate models such as COSMO-CLM, RegCM and WRF and statistical techniques for a further refinement of the projections. The core research sites of WASCAL are located in the Sudanian Savannah belt in Northern Ghana, Southern Burkina Faso and Northern Benin. The climate in this region is semi-arid with six rainy months. Due to the strong population growth in West Africa, many areas of the Sudanian Savannah have been already converted to farmland since the majority of the people are living directly or indirectly from the income produced in agriculture. The simulation experiments of the Competence Center and the Core Research Program are

  17. Climate Change and Climate Variability in the Latin American Region

    NASA Astrophysics Data System (ADS)

    Magrin, G. O.; Gay Garcia, C.; Cruz Choque, D.; Gimenez-Sal, J. C.; Moreno, A. R.; Nagy, G. J.; Nobre, C.; Villamizar, A.

    2007-05-01

    Over the past three decades LA was subjected to several climate-related impacts due to increased El Niño occurrences. Two extremely intense episodes of El Niño and other increased climate extremes happened during this period contributing greatly to augment the vulnerability of human systems to natural disasters. In addition to weather and climate, the main drivers of the increased vulnerability are demographic pressure, unregulated urban growth, poverty and rural migration, low investment in infrastructure and services, and problems in inter-sector coordination. As well, increases in temperature and increases/decreases in precipitation observed during the last part of 20th century have yet led to intensification of glaciers melting, increases in floods/droughts and forest fires frequency, increases in morbidity and mortality, increases in plant diseases incidence; lost of biodiversity, reduction in dairy cattle production, and problems with hydropower generation, highly affecting LA human system. For the end of the 21st century, the projected mean warming for LA ranges from 1 to 7.5ºC and the frequency of weather and climate extremes could increase. Additionally, deforestation is projected to continue leading to a reduction of 25 percent in Amazonia forest in 2020 and 40 percent in 2050. Soybeans planted area in South America could increase by 55 percent by 2020 enhancing aridity/desertification in many of the already water- stressed regions. By 2050 LA population is likely to be 50 percent larger than in 2000, and migration from the country sides to the cities will continue. In the near future, these predicted changes are very likely to severely affect a number of ecosystems and sectors distribution; b) Disappearing most tropical glaciers; c) Reducing water availability and hydropower generation; d) Increasing desertification and aridity; e) Severely affecting people, resources and economic activities in coastal areas; f) Increasing crop's pests and diseases

  18. Deglacial climate variability in central Florida, USA

    USGS Publications Warehouse

    Willard, D.A.; Bernhardt, C.E.; Brooks, G.R.; Cronin, T. M.; Edgar, T.; Larson, R.

    2007-01-01

    Pollen and ostracode evidence from lacustrine sediments underlying modern Tampa Bay, Florida, document frequent and abrupt climatic and hydrological events superimposed on deglacial warming in the subtropics. Radiocarbon chronology on well-preserved mollusk shells and pollen residue from core MD02-2579 documents continuous sedimentation in a variety of non-marine habitats in a karst-controlled basin from 20 ka to 11.5 ka. During the last glacial maximum (LGM), much drier and cooler-than-modern conditions are indicated by pollen assemblages enriched in Chenopodiaceae and Carya, with rare Pinus (Pinus pollen increased to 20–40% during the warming of the initial deglaciation (∼ 17.2 ka), reaching near modern abundance (60–80%) during warmer, moister climates of the Bølling/Allerød interval (14.7–12.9 ka). Within the Bølling/Allerød, centennial-scale dry events corresponding to the Older Dryas and Intra-Allerød Cold Period indicate rapid vegetation response (

  19. Taking the pulse of mountains: Ecosystem responses to climatic variability

    USGS Publications Warehouse

    Fagre, D.B.; Peterson, D.L.; Hessl, A.E.

    2003-01-01

    An integrated program of ecosystem modeling and field studies in the mountains of the Pacific Northwest (U.S.A.) has quantified many of the ecological processes affected by climatic variability. Paleoecological and contemporary ecological data in forest ecosystems provided model parameterization and validation at broad spatial and temporal scales for tree growth, tree regeneration and treeline movement. For subalpine tree species, winter precipitation has a strong negative correlation with growth; this relationship is stronger at higher elevations and west-side sites (which have more precipitation). Temperature affects tree growth at some locations with respect to length of growing season (spring) and severity of drought at drier sites (summer). Furthermore, variable but predictable climate-growth relationships across elevation gradients suggest that tree species respond differently to climate at different locations, making a uniform response of these species to future climatic change unlikely. Multi-decadal variability in climate also affects ecosystem processes. Mountain hemlock growth at high-elevation sites is negatively correlated with winter snow depth and positively correlated with the winter Pacific Decadal Oscillation (PDO) index. At low elevations, the reverse is true. Glacier mass balance and fire severity are also linked to PDO. Rapid establishment of trees in subalpine ecosystems during this century is increasing forest cover and reducing meadow cover at many subalpine locations in the western U.S.A. and precipitation (snow depth) is a critical variable regulating conifer expansion. Lastly, modeling potential future ecosystem conditions suggests that increased climatic variability will result in increasing forest fire size and frequency, and reduced net primary productivity in drier, east-side forest ecosystems. As additional empirical data and modeling output become available, we will improve our ability to predict the effects of climatic change

  20. Intra-interglacial climate variability from Marine Isotope Stage 15 to the Holocene

    NASA Astrophysics Data System (ADS)

    Rachmayani, R.; Prange, M.; Schulz, M.

    2015-07-01

    Using the Community Climate System Model version 3 (CCSM3) including a dynamic global vegetation model a set of 13 interglacial time slice experiments was carried out to study global climate variability between and within the Quaternary interglaciations of Marine Isotope Stages (MIS) 1, 5, 11, 13, and 15. The different effects of obliquity, precession and greenhouse gas forcing on global surface temperature and precipitation fields are illuminated. Several similarities with previous idealized orbital-forcing experiments can be identified. In particular, a significant role of meridional insolation-gradient forcing by obliquity variations in forcing the West African monsoon is found. The sensitivity of the West African monsoon to this obliquity forcing, however, depends on the climatic precession. According to the CCSM3 results, the Indian monsoon is less sensitive to direct obliquity-induced insolation forcing, consistent with the interpretation of proxy records from the Arabian Sea. Moreover, the model results suggest that the two monsoon systems do not always vary in concert, challenging the concept of a global monsoon system at orbital timescales. High obliquity can also explain relatively warm Northern Hemisphere high-latitude summer temperatures despite maximum precession around 495 kyr BP (MIS 13) probably preventing a glacial inception at that time.

  1. North Atlantic Climate Variability. An Oceanographers's Perspective

    NASA Astrophysics Data System (ADS)

    Visbeck, M.

    Much of the interannual to decadal variability in the North Atlantic Ocean is strongly linked to changes in the atmospheric forcing. The dominant mode of Atmospheric Variability is associated with changes in the strength and location of the westerly winds, a mode which is known as the North Atlantic Oscillation. The oceans response can be divided into three related categories. First there are changes in the upper ocean transports (Ekman transport) which directly alter the oceans heat transport (fast re- sponse) and because of changes in the planetary vorticity balance generate Rossby and Kelvin waves which then establish a new balanced state (slow response). Sec- ondly changes in the air-sea fluxes by a combination of variable atmospheric advection (wind vector) and efficiency of exchange (wind speed) perturb the upper ocean heat content. Part of that signal is then advected in regions of large mean ocean currents. Finally changes of the surface ocean density can alter the amount and type of newly formed water masses. Thus the characteristics and types of deep water vary possibly altering the rate of the ocean overturning. Specifically I will review recent findings about the oceans response to NAO forcing and the associated propagation of upper ocean heat content anomalies. I will discuss observations of decadal salinity variations in the Labrador Sea. and finally touch upon how a simple ecosystem is effected by the above.

  2. Surface Ozone Variability and Trends over the South African Highveld from 1990 to 2007

    NASA Technical Reports Server (NTRS)

    Balashov, Nikolay V.; Thompson, Anne M.; Piketh, Stuart J.; Langerman, Kristy E.

    2014-01-01

    Surface ozone is a secondary air pollutant formed from reactions between nitrogen oxides (NOx = NO + NO2) and volatile organic compounds in the presence of sunlight. In this work we examine effects of the climate pattern known as the El Niño-Southern Oscillation (ENSO) and NOx variability on surface ozone from 1990 to 2007 over the South African Highveld, a heavily populated region in South Africa with numerous industrial facilities. Over summer and autumn (December-May) on the Highveld, El Niño, as signified by positive sea surface temperature (SST) anomalies over the central Pacific Ocean, is typically associated with drier and warmer than normal conditions favoring ozone formation. Conversely, La Niña, or negative SST anomalies over the central Pacific Ocean, is typically associated with cloudier and above normal rainfall conditions, hindering ozone production. We use a generalized regression model to identify any linear dependence that the Highveld ozone, measured at five air quality monitoring stations, may have on ENSO and NOx. Our results indicate that four out of the five stations exhibit a statistically significant sensitivity to ENSO at some point over the December-May period where El Niño amplifies ozone formation and La Niña reduces ozone formation. Three out of the five stations reveal statistically significant sensitivity to NOx variability, primarily in winter and spring. Accounting for ENSO and NOx effects throughout the study period of 18 years, two stations exhibit statistically significant negative ozone trends in spring, one station displays a statistically significant positive trend in August, and two stations show no statistically significant change in surface ozone.

  3. Impact of large-scale climate variability and change on crop yields in Africa: An observational assessment

    NASA Astrophysics Data System (ADS)

    Smoliak, B. V.; Po-Chedley, S.; Cullen, A. C.

    2011-12-01

    Assessments of the relationships between climate and agricultural production have progressed from opposite ends of the spatio-temporal spectrum. While studies of global-scale climate-yield relationships have provided estimates of the impact of multi-decadal trends in temperature and precipitation on recent production, studies of local weather impacts on yield have demonstrated the influence of temperature and precipitation variability on plant physiology, particularly with respect to the duration and timing of extremes. At intermediate spatial and temporal scales, somewhat of a gap in understanding exists. Our investigation contributes to better understanding climate-yield relationships at intermediate scales by assessing the impact of climate variability on crop yields at the country to continent scale on interannual to interdecadal timescales. Toward this end, we employ historical climatic data and reported cereal crop yields from the African continent, 1961 to 2009, in conjunction with principal component regression and partial least squares regression. Our results show that a discrete set of spatial patterns of climate variability account for up to half of the year-to-year variability in crop yields over portions of Africa. The impact of this climate variability is particularly strong in Sub-Saharan Africa, where large or prolonged deficits in yields can result in food shortages. The fundamental patterns of variability used to explain yield fluctuations are based on temperature and precipitation, chosen due to their influence on plant physiology; however, the time-varying behavior of the patterns may also be linked to coherent large-scale climate variability through regressions with sea surface temperature, sea level pressure and low-level wind fields. Results are distilled in terms of five UN designated geographic regions of Africa. Implications for short-term food security and future climate change are discussed.

  4. Terrestrial essential climate variables (ECVs) at a glance

    USGS Publications Warehouse

    Stitt, Susan; Dwyer, John; Dye, Dennis; Josberger, Edward

    2011-01-01

    The Global Terrestrial Observing System, Global Climate Observing System, World Meteorological Organization, and Committee on Earth Observation Satellites all support consistent global land observations and measurements. To accomplish this goal, the Global Terrestrial Observing System defined 'essential climate variables' as measurements of atmosphere, oceans, and land that are technically and economically feasible for systematic observation and that are needed to meet the United Nations Framework Convention on Climate Change and requirements of the Intergovernmental Panel on Climate Change. The following are the climate variables defined by the Global Terrestrial Observing System that relate to terrestrial measurements. Several of them are currently measured most appropriately by in-place observations, whereas others are suitable for measurement by remote sensing technologies. The U.S. Geological Survey is the steward of the Landsat archive, satellite imagery collected from 1972 to the present, that provides a potential basis for deriving long-term, global-scale, accurate, timely and consistent measurements of many of these essential climate variables.

  5. Earth System Science Education Centered on Natural Climate Variability

    NASA Astrophysics Data System (ADS)

    Ramirez, P. C.; Ladochy, S.; Patzert, W. C.; Willis, J. K.

    2009-12-01

    Several new courses and many educational activities related to climate change are available to teachers and students of all grade levels. However, not all new discoveries in climate research have reached the science education community. In particular, effective learning tools explaining natural climate change are scarce. For example, the Pacific Decadal Oscillation (PDO) is a main cause of natural climate variability spanning decades. While most educators are familiar with the shorter-temporal events impacting climate, El Niño and La Niña, very little has trickled into the climate change curriculum on the PDO. We have developed two online educational modules, using an Earth system science approach, on the PDO and its role in climate change and variability. The first concentrates on the discovery of the PDO through records of salmon catch in the Pacific Northwest and Alaska. We present the connection between salmon abundance in the North Pacific to changing sea surface temperature patterns associated with the PDO. The connection between sea surface temperatures and salmon abundance led to the discovery of the PDO. Our activity also lets students explore the role of salmon in the economy and culture of the Pacific Northwest and Alaska and the environmental requirements for salmon survival. The second module is based on the climate of southern California and how changes in the Pacific Ocean , such as the PDO and ENSO (El Niño-Southern Oscillation), influence regional climate variability. PDO and ENSO signals are evident in the long-term temperature and precipitation record of southern California. Students are guided in the module to discover the relationships between Pacific Ocean conditions and southern California climate variability. The module also provides information establishing the relationship between climate change and variability and the state's water, energy, agriculture, wildfires and forestry, air quality and health issues. Both modules will be

  6. The timing and magnitude of lake-level variability, in response to interannual climate variability

    NASA Astrophysics Data System (ADS)

    Huybers, K. M.; Rupper, S.; Roe, G.

    2013-12-01

    Some of the primary uncertainties and most critical consequences of both past and future climate change concern Earth's hydrological cycle. Lakes are key indicators of a region's hydrological cycle, directly reflecting the basin-wide balance between evaporation and precipitation. Lake-level records can therefore hold valuable information about the history of these climate variables. However, the interpretation of such records is not necessarily straightforward; because lakes integrate year-to-year climate fluctuations they will exhibit persistent fluctuations on timescales of decades or more. Any system with 'memory' (i.e., inertia, or a dynamic response time) will produce similar behavior. This inertia can make it difficult to distinguish lake-level fluctuations in response to stochastic climate forcing from a true shift in the climate -- a change in the mean or standard deviation of one or several climatic variables. The size and shape of a lake determines the response time to both stochastic forcing and climatic change, meaning that each individual lake will respond with a unique timescale and magnitude. We develop a general lake-level model to constrain a lake's response to interannual climate fluctuations. Because of its long historical lake-level and climatological records, we use the Great Salt Lake as a case-study for this work. We use mass-balance models to track the lake's response to synthetic, random time series of precipitation and evaporation, then compare the magnitude and frequency of our model's response to the historical record of the Great Salt Lake's rise and fall. We then compare simplified geometric representations of several lakes to illustrate how the timing and amplitude of a lake's response differs under unique climatic and geometric scenarios. We find that interannual climate variability alone can explain much of the decadal-centennial variations in the lake-level record. It is only after removing this background variability that a lake

  7. Vegetation Interaction Enhances Interdecadal Climate Variability in the Sahel

    NASA Technical Reports Server (NTRS)

    Zeng, Ning; Neelin, J. David; Lau, William K.-M.

    1999-01-01

    The role of naturally varying vegetation in influencing the climate variability in the Sahel is explored in a coupled atmosphere-land-vegetation model. The Sahel rainfall variability is influenced by sea surface temperature (SST) variations in the oceans. Land-surface feedback is found to increase this variability both on interannual and interdecadal time scales. Interactive vegetation enhances the interdecadal variation significantly, but can reduce year to year variability due to a phase lag introduced by the relatively slow vegetation adjustment time. Variations in vegetation accompany the changes in rainfall, in particular, the multi-decadal drying trend from the 1950s to the 80s.

  8. Northern high latitude climate variability of the last millennium

    NASA Astrophysics Data System (ADS)

    Andres, Heather J.

    This work explores the causes of northern high-latitude climate variations over the last millennium, and industrial and future periods. Attribution studies are performed on a suite of global climate simulations, and four historical reconstructions of Greenland surface temperatures and precipitation (two of which are new to this work). The simulations followed the protocols of the Palaeoclimate Modelling Intercomparison Project 3 and Coupled Model Intercomparison Project 5. At least half of the multi-decadal variability in simulated Greenland climate variations over the last millennium is reproduced by a linear, empirically-generated model including terms for volcanic emissions, solar insolation changes (including total solar irradiance and orbital components) and an index associated with latitudinal shifts in the North Atlantic jet. Empirical model parameters are obtained by regressing simulated Greenland temperatures and precipitation against time series for each of the response variables. Greenhouse gas radiative forcing changes are unimportant to simulated Greenland conditions over the last millennium, although they dominate after the mid-20th century. Most of the historical Greenland climate reconstructions are restricted to the industrial period, due to a lack of spatially-comprehensive climate records. They exhibit substantial differences in the timing, phasing and amplitudes of past climate variations, due to regional sensitivities in the source data and the reconstruction methodologies. Reconstructions indicate that Greenland temperatures did not begin to follow hemispheric greenhouse gas warming patterns until the mid-1990s. This discrepancy indicates either that the warming hiatus was associated with internal climate variability, or that the simulations are missing processes important to Greenland climate. For example, indirect effects of anthropogenic aerosols are not captured in the climate model employed here. All of the external climate forcings

  9. Experiences on climate variability education from an empirical perspective

    NASA Astrophysics Data System (ADS)

    Rodriguez-Puebla, Concepcion

    2015-04-01

    Education materials based on investigations are prepared for teaching climate matters using graphics representation, data analysis and GrADS software. An example of how climate teleconnection are included in the teaching activities would be presented. The goal is for students to learn about how climate variability and extreme events over a region are connected to large-scale atmospheric and oceanic circulation from an empirical perspective. Exercises and questions are prepared for collaborative and interactive learning considering the visualization and workshop activities included in the Moodle learning platform.

  10. Solar Variability and Climate Impact on Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    Bertaux, J.-L.

    2006-08-01

    Some possible factors of climate changes and of long term climate evolution are discussed with regard of the three terrestrial planets, Earth, Venus and Mars. Two positive feedback mechanisms involving liquid water, i.e., the albedo mechanism and the greenhouse effect of water vapour, are described. These feedback mechanisms respond to small external forcings, such as resulting from solar or astronomical constants variability, which might thus result in large influences on climatic changes on Earth. On Venus, reactions of the atmosphere with surface minerals play an important role in the climate system, but the involved time scales are much larger. On Mars, climate is changing through variations of the polar axis inclination over time scales of ˜105 106 years. Growing evidence also exists that a major climatic change happened on Mars some 3.5 to 3.8 Gigayears ago, leading to the disappearance of liquid water on the planet surface by eliminating most of the CO2 atmosphere greenhouse power. This change might be due to a large surge of the solar wind, or to atmospheric erosion by large bodies impacts. Indeed, except for their thermospheric temperature response, there is currently little evidence for an effect of long-term solar variability on the climate of Venus and Mars. This fact is possibly due to the absence of liquid water on these terrestrial planets.

  11. Effects of interannual climate variability on tropical tree cover

    NASA Astrophysics Data System (ADS)

    Holmgren, Milena; Hirota, Marina; van Nes, Egbert H.; Scheffer, Marten

    2013-08-01

    Climatic warming is substantially intensifying the global water cycle and is projected to increase rainfall variability. Using satellite data, we show that higher climatic variability is associated with reduced tree cover in the wet tropics globally. In contrast, interannual variability in rainfall can have neutral or even positive effects on tree cover in the dry tropics. In South America, tree cover in dry lands is higher in areas with high year-to-year variability in rainfall. This is consistent with evidence from case studies suggesting that in these areas rare wet episodes are essential for opening windows of opportunity where massive tree recruitment can overwhelm disturbance effects, allowing the establishment of extensive woodlands. In Australia, wet extremes have similar effects, but the net effect of rainfall variability is overwhelmed by negative effects of extreme dry years. In Africa, effects of rainfall variability are neutral for dry lands. It is most likely that differences in herbivore communities and fire regimes contribute to regulating tree expansion during wet extremes. Our results illustrate that increasing climatic variability may affect ecosystem services in contrasting, and sometimes surprising, ways. Expansion of dry tropical tree cover during extreme wet events may decrease grassland productivity but enhance carbon sequestration, soil nutrient retention and biodiversity.

  12. Rainfall variability over southern Africa: an overview of current research using satellite and climate model data

    NASA Astrophysics Data System (ADS)

    Williams, C.; Kniveton, D.; Layberry, R.

    2009-04-01

    It is increasingly accepted that any possible climate change will not only have an influence on mean climate but may also significantly alter climatic variability. A change in the distribution and magnitude of extreme rainfall events (associated with changing variability), such as droughts or flooding, may have a far greater impact on human and natural systems than a changing mean. This issue is of particular importance for environmentally vulnerable regions such as southern Africa. The subcontinent is considered especially vulnerable to and ill-equipped (in terms of adaptation) for extreme events, due to a number of factors including extensive poverty, famine, disease and political instability. Rainfall variability is a function of scale, so high spatial and temporal resolution data are preferred to identify extreme events and accurately predict future variability. In this research, satellite-derived rainfall data are used as a basis for undertaking model experiments using a state-of-the-art climate model, run at both high and low spatial resolution. Once the model's ability to reproduce extremes has been assessed, idealised regions of sea surface temperature (SST) anomalies are used to force the model, with the overall aim of investigating the ways in which SST anomalies influence rainfall extremes over southern Africa. In this paper, a brief overview is given of the authors' research to date, pertaining to southern African rainfall. This covers (i) a description of present-day rainfall variability over southern Africa; (ii) a comparison of model simulated daily rainfall with the satellite-derived dataset; (iii) results from sensitivity testing of the model's domain size; and (iv) results from the idealised SST experiments.

  13. Climate Variability and Phytoplankton in the Pacific Ocean

    NASA Technical Reports Server (NTRS)

    Rousseaux, Cecile

    2012-01-01

    The effect of climate variability on phytoplankton communities was assessed for the tropical and sub-tropical Pacific Ocean between 1998 and 2005 using an established biogeochemical assimilation model. The phytoplankton communities exhibited wide range of responses to climate variability, from radical shifts in the Equatorial Pacific, to changes of only a couple of phytoplankton groups in the North Central Pacific, to no significant changes in the South Pacific. In the Equatorial Pacific, climate variability dominated the variability of phytoplankton. Here, nitrate, chlorophyll and all but one of the 4 phytoplankton types (diatoms, cyanobacteria and coccolithophores) were strongly correlated (p<0.01) with the Multivariate El Nino Southern Oscillation Index (MEI). In the North Central Pacific, MEI and chlorophyll were significantly (p<0.01) correlated along with two of the phytoplankton groups (chlorophytes and coccolithophores). Ocean biology in the South Pacific was not significantly correlated with MEI. During La Nina events, diatoms increased and expanded westward along the cold tongue (correlation with MEI, r=-0.81), while cyanobacteria concentrations decreased significantly (r=0.78). El Nino produced the reverse pattern, with cyanobacteria populations increasing while diatoms plummeted. The diverse response of phytoplankton in the different major basins of the Pacific suggests the different roles climate variability can play in ocean biology.

  14. The West African monsoon: Contribution of the AMMA multidisciplinary programme to the study of a regional climate system.

    NASA Astrophysics Data System (ADS)

    Lebel, T.; Janicot, S.; Redelsperger, J. L.; Parker, D. J.; Thorncroft, C. D.

    2015-12-01

    The AMMA international project aims at improving our knowledge and understanding of the West African monsoon and its variability with an emphasis on daily-to-interannual timescales. AMMA is motivated by an interest in fundamental scientific issues and by the societal need for improved prediction of the WAM and its impacts on water resources, health and food security for West African nations. The West African monsoon (WAM) has a distinctive annual cycle in rainfall that remains a challenge to understand and predict. The location of peak rainfall, which resides in the Northern Hemisphere throughout the year, moves from the ocean to the land in boreal spring. Around the end of June there is a rapid shift in the location of peak rainfall between the coast and around 10°N where it remains until about the end of August. In September the peak rainfall returns equatorward at a relatively steady pace and is located over the ocean again by November. The fact that the peak rainfall migrates irregularly compared to the peak solar heating is due to the interactions that occur between the land, the atmosphere and the ocean. To gain a better understanding of this complex climate system, a large international research programme was launched in 2002, the biggest of its kind into environment and climate ever attempted in Africa. AMMA has involved a comprehensive field experiment bringing together ocean, land and atmospheric measurements, on timescales ranging from hourly and daily variability up to the changes in seasonal activity over a number of years. This presentation will focus on the description of the field programme and its accomplishments, and address some key questions that have been recently identified to form the core of AMMA-Phase 2.

  15. The West African monsoon: Contribution of the AMMA multidisciplinary programme to the study of a regional climate system.

    NASA Astrophysics Data System (ADS)

    Lebel, T.; Janicot, S.; Redelsperger, J. L.; Parker, D. J.; Thorncroft, C. D.

    2014-12-01

    The AMMA international project aims at improving our knowledge and understanding of the West African monsoon and its variability with an emphasis on daily-to-interannual timescales. AMMA is motivated by an interest in fundamental scientific issues and by the societal need for improved prediction of the WAM and its impacts on water resources, health and food security for West African nations. The West African monsoon (WAM) has a distinctive annual cycle in rainfall that remains a challenge to understand and predict. The location of peak rainfall, which resides in the Northern Hemisphere throughout the year, moves from the ocean to the land in boreal spring. Around the end of June there is a rapid shift in the location of peak rainfall between the coast and around 10°N where it remains until about the end of August. In September the peak rainfall returns equatorward at a relatively steady pace and is located over the ocean again by November. The fact that the peak rainfall migrates irregularly compared to the peak solar heating is due to the interactions that occur between the land, the atmosphere and the ocean. To gain a better understanding of this complex climate system, a large international research programme was launched in 2002, the biggest of its kind into environment and climate ever attempted in Africa. AMMA has involved a comprehensive field experiment bringing together ocean, land and atmospheric measurements, on timescales ranging from hourly and daily variability up to the changes in seasonal activity over a number of years. This presentation will focus on the description of the field programme and its accomplishments, and address some key questions that have been recently identified to form the core of AMMA-Phase 2.

  16. Sensitivity of global terrestrial ecosystems to climate variability.

    PubMed

    Seddon, Alistair W R; Macias-Fauria, Marc; Long, Peter R; Benz, David; Willis, Kathy J

    2016-03-10

    The identification of properties that contribute to the persistence and resilience of ecosystems despite climate change constitutes a research priority of global relevance. Here we present a novel, empirical approach to assess the relative sensitivity of ecosystems to climate variability, one property of resilience that builds on theoretical modelling work recognizing that systems closer to critical thresholds respond more sensitively to external perturbations. We develop a new metric, the vegetation sensitivity index, that identifies areas sensitive to climate variability over the past 14 years. The metric uses time series data derived from the moderate-resolution imaging spectroradiometer (MODIS) enhanced vegetation index, and three climatic variables that drive vegetation productivity (air temperature, water availability and cloud cover). Underlying the analysis is an autoregressive modelling approach used to identify climate drivers of vegetation productivity on monthly timescales, in addition to regions with memory effects and reduced response rates to external forcing. We find ecologically sensitive regions with amplified responses to climate variability in the Arctic tundra, parts of the boreal forest belt, the tropical rainforest, alpine regions worldwide, steppe and prairie regions of central Asia and North and South America, the Caatinga deciduous forest in eastern South America, and eastern areas of Australia. Our study provides a quantitative methodology for assessing the relative response rate of ecosystems--be they natural or with a strong anthropogenic signature--to environmental variability, which is the first step towards addressing why some regions appear to be more sensitive than others, and what impact this has on the resilience of ecosystem service provision and human well-being.

  17. Sensitivity of global terrestrial ecosystems to climate variability

    NASA Astrophysics Data System (ADS)

    Seddon, Alistair W. R.; Macias-Fauria, Marc; Long, Peter R.; Benz, David; Willis, Kathy J.

    2016-03-01

    The identification of properties that contribute to the persistence and resilience of ecosystems despite climate change constitutes a research priority of global relevance. Here we present a novel, empirical approach to assess the relative sensitivity of ecosystems to climate variability, one property of resilience that builds on theoretical modelling work recognizing that systems closer to critical thresholds respond more sensitively to external perturbations. We develop a new metric, the vegetation sensitivity index, that identifies areas sensitive to climate variability over the past 14 years. The metric uses time series data derived from the moderate-resolution imaging spectroradiometer (MODIS) enhanced vegetation index, and three climatic variables that drive vegetation productivity (air temperature, water availability and cloud cover). Underlying the analysis is an autoregressive modelling approach used to identify climate drivers of vegetation productivity on monthly timescales, in addition to regions with memory effects and reduced response rates to external forcing. We find ecologically sensitive regions with amplified responses to climate variability in the Arctic tundra, parts of the boreal forest belt, the tropical rainforest, alpine regions worldwide, steppe and prairie regions of central Asia and North and South America, the Caatinga deciduous forest in eastern South America, and eastern areas of Australia. Our study provides a quantitative methodology for assessing the relative response rate of ecosystems—be they natural or with a strong anthropogenic signature—to environmental variability, which is the first step towards addressing why some regions appear to be more sensitive than others, and what impact this has on the resilience of ecosystem service provision and human well-being.

  18. Sensitivity of global terrestrial ecosystems to climate variability.

    PubMed

    Seddon, Alistair W R; Macias-Fauria, Marc; Long, Peter R; Benz, David; Willis, Kathy J

    2016-03-10

    The identification of properties that contribute to the persistence and resilience of ecosystems despite climate change constitutes a research priority of global relevance. Here we present a novel, empirical approach to assess the relative sensitivity of ecosystems to climate variability, one property of resilience that builds on theoretical modelling work recognizing that systems closer to critical thresholds respond more sensitively to external perturbations. We develop a new metric, the vegetation sensitivity index, that identifies areas sensitive to climate variability over the past 14 years. The metric uses time series data derived from the moderate-resolution imaging spectroradiometer (MODIS) enhanced vegetation index, and three climatic variables that drive vegetation productivity (air temperature, water availability and cloud cover). Underlying the analysis is an autoregressive modelling approach used to identify climate drivers of vegetation productivity on monthly timescales, in addition to regions with memory effects and reduced response rates to external forcing. We find ecologically sensitive regions with amplified responses to climate variability in the Arctic tundra, parts of the boreal forest belt, the tropical rainforest, alpine regions worldwide, steppe and prairie regions of central Asia and North and South America, the Caatinga deciduous forest in eastern South America, and eastern areas of Australia. Our study provides a quantitative methodology for assessing the relative response rate of ecosystems--be they natural or with a strong anthropogenic signature--to environmental variability, which is the first step towards addressing why some regions appear to be more sensitive than others, and what impact this has on the resilience of ecosystem service provision and human well-being. PMID:26886790

  19. Climatic Variability Leads to Later Seasonal Flowering of Floridian Plants

    PubMed Central

    Von Holle, Betsy; Wei, Yun; Nickerson, David

    2010-01-01

    Understanding species responses to global change will help predict shifts in species distributions as well as aid in conservation. Changes in the timing of seasonal activities of organisms over time may be the most responsive and easily observable indicator of environmental changes associated with global climate change. It is unknown how global climate change will affect species distributions and developmental events in subtropical ecosystems or if climate change will differentially favor nonnative species. Contrary to previously observed trends for earlier flowering onset of plant species with increasing spring temperatures from mid and higher latitudes, we document a trend for delayed seasonal flowering among plants in Florida. Additionally, there were few differences in reproductive responses by native and nonnative species to climatic changes. We argue that plants in Florida have different reproductive cues than those from more northern climates. With global change, minimum temperatures have become more variable within the temperate-subtropical zone that occurs across the peninsula and this variation is strongly associated with delayed flowering among Florida plants. Our data suggest that climate change varies by region and season and is not a simple case of species responding to consistently increasing temperatures across the region. Research on climate change impacts need to be extended outside of the heavily studied higher latitudes to include subtropical and tropical systems in order to properly understand the complexity of regional and seasonal differences of climate change on species responses. PMID:20657765

  20. An examination of internally generated variability in long climate simulations

    SciTech Connect

    Schneider, E.K.; Kinter, J.L. III

    1994-09-01

    General circulation model experiments designed to estimate the magnitude and structure of internally generated variability and to help understand the mechanisms underlying this variability are described. The experiments consist of three multi-century integrations of a rhomboidal 15, 9 level, version of the Center for Ocean-Land-Atmosphere Studies atmospheric general circulation model: a run with fixed sea surface temperatures and equinox solar radiation, a run with seasonally varying climatological sea surface temperatures and seasonally varying solar forcing, and a run with seasonally varying solar forcing in which the state of the ocean is predicted by a 3{degree} by 3{degree}, 16 vertical level, nearly global domain version of the Geophysical Fluid Dynamics Laboratory Modular Ocean Model. No flux correction is used in the coupled model integration. Selected surface fields of the three runs are compared to each other as well as to the observed climate. Statistical properties of variability on interannual time scales are compared between the runs. Evidence is presented that climate time scale variability in the simulations is produced by random weather time scale forcing due to the integrating effect of elements of the system with long memories. The importance of ocean variability for land climate variability is demonstrated and attributed to both the memory effect and coupled atmosphere-ocean instability. 40 refs., 23 figs.

  1. 2500 Years of European Climate Variability and Human Susceptibility

    NASA Astrophysics Data System (ADS)

    Büntgen, Ulf; Tegel, Willy; Nicolussi, Kurt; McCormick, Michael; Frank, David; Trouet, Valerie; Kaplan, Jed O.; Herzig, Franz; Heussner, Karl-Uwe; Wanner, Heinz; Luterbacher, Jürg; Esper, Jan

    2011-02-01

    Climate variations influenced the agricultural productivity, health risk, and conflict level of preindustrial societies. Discrimination between environmental and anthropogenic impacts on past civilizations, however, remains difficult because of the paucity of high-resolution paleoclimatic evidence. We present tree ring-based reconstructions of central European summer precipitation and temperature variability over the past 2500 years. Recent warming is unprecedented, but modern hydroclimatic variations may have at times been exceeded in magnitude and duration. Wet and warm summers occurred during periods of Roman and medieval prosperity. Increased climate variability from ~250 to 600 C.E. coincided with the demise of the western Roman Empire and the turmoil of the Migration Period. Such historical data may provide a basis for counteracting the recent political and fiscal reluctance to mitigate projected climate change.

  2. Response of closed basin lakes to interannual climate variability

    NASA Astrophysics Data System (ADS)

    Huybers, Kathleen; Rupper, Summer; Roe, Gerard H.

    2016-06-01

    Lakes are key indicators of a region's hydrological cycle, directly reflecting the basin-wide balance between precipitation and evaporation. Lake-level records are therefore valuable repositories of climate history. However, the interpretation of such records is not necessarily straightforward. Lakes act as integrators of the year-to-year fluctuations in precipitation and evaporation that occur even in a constant climate. Therefore lake levels can exhibit natural, unforced fluctuations that persist on timescales of decades or more. This behavior is important to account for when distinguishing between true climate change and interannual variability as the cause of past lake-level fluctuations. We demonstrate the operation of this general principle for the particular case-study of the Great Salt Lake, which has long historical lake-level and climatological records. We employ both full water-balance and linear models. Both models capture the timing and size of the lake's historical variations. We then model the lake's response to much longer synthetic time series of precipitation and evaporation calibrated to the observations, and compare the magnitude and frequency of the modeled response to the Great Salt Lake's historical record. We find that interannual climate variability alone can explain much of the decadal-to-centennial variations in the lake-level record. Further, analytic solutions to the linear model capture much of the full model's behavior, but fail to predict the most extreme lake-level variations. We then apply the models to other lake geometries, and evaluate how the timing and amplitude of a lake-level response differs with climatic and geometric setting. A lake's response to a true climatic shift can only be understood in the context of these expected persistent lake-level variations. On the basis of these results, we speculate that lake response to interannual climate variability may play an important part in explaining much of Holocene lake

  3. Prediction and predictability of North American seasonal climate variability

    NASA Astrophysics Data System (ADS)

    Infanti, Johnna M.

    Climate prediction on short time-scales such as months to seasons is of broad and current interest in the scientific research community. Monthly and seasonal climate prediction of variables such as precipitation, temperature, and sea surface temperature (SST) has implications for users in the agricultural and water management domains, among others. It is thus important to further understand the complexities of prediction of these variables using the most recent practices in climate prediction. The overarching goal of this dissertation is to determine the important contributions to seasonal prediction skill, predictability, and variability over North America using current climate prediction models and approaches. This dissertation aims to study a variety of approaches to seasonal climate prediction of variables over North America, including both climate prediction systems and methods of analysis. We utilize the North American Multi-Model Ensemble (NMME) System for Intra-Seasonal to Inter-Annual Prediction (ISI) to study seasonal climate prediction skill of North American and in particular for southeast US precipitation. We find that NMME results are often equal to or better than individual model results in terms of skill, as expected, making it a reasonable choice for southeast US seasonal climate predictions. However, climate models, including those involved in NMME, typically overestimate eastern Pacific warming during central Pacific El Nino events, which can affect regions that are influenced by teleconnections, such as the southeast US. Community Climate System Model version 4.0 (CCSM4) hindacasts and forecasts are included in NMME, and we preform a series of experiments that examine contributions to skill from certain drivers of North American climate prediction. The drivers we focus on are sea surface temperatures (SSTs) and their accuracy, land and atmosphere initialization, and ocean-atmosphere coupling. We compare measures of prediction skill of

  4. Prediction and predictability of North American seasonal climate variability

    NASA Astrophysics Data System (ADS)

    Infanti, Johnna M.

    Climate prediction on short time-scales such as months to seasons is of broad and current interest in the scientific research community. Monthly and seasonal climate prediction of variables such as precipitation, temperature, and sea surface temperature (SST) has implications for users in the agricultural and water management domains, among others. It is thus important to further understand the complexities of prediction of these variables using the most recent practices in climate prediction. The overarching goal of this dissertation is to determine the important contributions to seasonal prediction skill, predictability, and variability over North America using current climate prediction models and approaches. This dissertation aims to study a variety of approaches to seasonal climate prediction of variables over North America, including both climate prediction systems and methods of analysis. We utilize the North American Multi-Model Ensemble (NMME) System for Intra-Seasonal to Inter-Annual Prediction (ISI) to study seasonal climate prediction skill of North American and in particular for southeast US precipitation. We find that NMME results are often equal to or better than individual model results in terms of skill, as expected, making it a reasonable choice for southeast US seasonal climate predictions. However, climate models, including those involved in NMME, typically overestimate eastern Pacific warming during central Pacific El Nino events, which can affect regions that are influenced by teleconnections, such as the southeast US. Community Climate System Model version 4.0 (CCSM4) hindacasts and forecasts are included in NMME, and we preform a series of experiments that examine contributions to skill from certain drivers of North American climate prediction. The drivers we focus on are sea surface temperatures (SSTs) and their accuracy, land and atmosphere initialization, and ocean-atmosphere coupling. We compare measures of prediction skill of

  5. Decadal Variability of Clouds and Comparison with Climate Model Simulations

    NASA Astrophysics Data System (ADS)

    Su, H.; Shen, T. J.; Jiang, J. H.; Yung, Y. L.

    2014-12-01

    An apparent climate regime shift occurred around 1998/1999, when the steady increase of global-mean surface temperature appeared to hit a hiatus. Coherent decadal variations are found in atmospheric circulation and hydrological cycles. Using 30-year cloud observations from the International Satellite Cloud Climatology Project, we examine the decadal variability of clouds and associated cloud radiative effects on surface warming. Empirical Orthogonal Function analysis is performed. After removing the seasonal cycle and ENSO signal in the 30-year data, we find that the leading EOF modes clearly represent a decadal variability in cloud fraction, well correlated with the indices of Pacific Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO). The cloud radiative effects associated with decadal variations of clouds suggest a positive cloud feedback, which would reinforce the global warming hiatus by a net cloud cooling after 1998/1999. Climate model simulations driven by observed sea surface temperature are compared with satellite observed cloud decadal variability. Copyright:

  6. Effects of climate variability on global scale flood risk

    NASA Astrophysics Data System (ADS)

    Ward, P.; Dettinger, M. D.; Kummu, M.; Jongman, B.; Sperna Weiland, F.; Winsemius, H.

    2013-12-01

    In this contribution we demonstrate the influence of climate variability on flood risk. Globally, flooding is one of the worst natural hazards in terms of economic damages; Munich Re estimates global losses in the last decade to be in excess of $240 billion. As a result, scientifically sound estimates of flood risk at the largest scales are increasingly needed by industry (including multinational companies and the insurance industry) and policy communities. Several assessments of global scale flood risk under current and conditions have recently become available, and this year has seen the first studies assessing how flood risk may change in the future due to global change. However, the influence of climate variability on flood risk has as yet hardly been studied, despite the fact that: (a) in other fields (drought, hurricane damage, food production) this variability is as important for policy and practice as long term change; and (b) climate variability has a strong influence in peak riverflows around the world. To address this issue, this contribution illustrates the influence of ENSO-driven climate variability on flood risk, at both the globally aggregated scale and the scale of countries and large river basins. Although it exerts significant and widespread influences on flood peak discharges in many parts of the world, we show that ENSO does not have a statistically significant influence on flood risk once aggregated to global totals. At the scale of individual countries, though, strong relationships exist over large parts of the Earth's surface. For example, we find particularly strong anomalies of flood risk in El Niño or La Niña years (compared to all years) in southern Africa, parts of western Africa, Australia, parts of Central Eurasia (especially for El Niño), the western USA (especially for La Niña), and parts of South America. These findings have large implications for both decadal climate-risk projections and long-term future climate change

  7. Determining the response of African biota to climate change: using the past to model the future.

    PubMed

    Willis, K J; Bennett, K D; Burrough, S L; Macias-Fauria, M; Tovar, C

    2013-01-01

    Prediction of biotic responses to future climate change in tropical Africa tends to be based on two modelling approaches: bioclimatic species envelope models and dynamic vegetation models. Another complementary but underused approach is to examine biotic responses to similar climatic changes in the past as evidenced in fossil and historical records. This paper reviews these records and highlights the information that they provide in terms of understanding the local- and regional-scale responses of African vegetation to future climate change. A key point that emerges is that a move to warmer and wetter conditions in the past resulted in a large increase in biomass and a range distribution of woody plants up to 400-500 km north of its present location, the so-called greening of the Sahara. By contrast, a transition to warmer and drier conditions resulted in a reduction in woody vegetation in many regions and an increase in grass/savanna-dominated landscapes. The rapid rate of climate warming coming into the current interglacial resulted in a dramatic increase in community turnover, but there is little evidence for widespread extinctions. However, huge variation in biotic response in both space and time is apparent with, in some cases, totally different responses to the same climatic driver. This highlights the importance of local features such as soils, topography and also internal biotic factors in determining responses and resilience of the African biota to climate change, information that is difficult to obtain from modelling but is abundant in palaeoecological records.

  8. Variability in Vertical Profiles of Water Vapor Associated with African Aerosol over the Tropical Atlantic

    NASA Astrophysics Data System (ADS)

    Huang, J.; Zhang, C.; Prospero, J. M.

    2007-12-01

    We used four years (2003-2006) of MODIS aerosol optical depth and concurrent AIRS profiled water vapor to explore how the vertical distribution of water vapor may systematically change with outbreaks of African aerosol over the tropical Atlantic Ocean. The first step was to look for a relationship in the Barbados region using in-situ Barbados dust record and the profiled relative humidity from meteorological soundings. We extended the study to the synoptic scale in the West Indies using the MODIS and AIRS products. In the tropical Atlantic, preliminary results indicate that water vapor at 850-1000 hPa is significantly less in July on dusty days than clean days over the northeastern tropical Atlantic [5-25N, 30-20W] where African dust is predominant. In contrast, over the southeastern tropical Atlantic [15S-0, 5W-10E], where African biomass burning smoke prevails, water vapor at 600-1000 hPa is significantly higher in August on smoky days than clean days. Additionally, in January when African mixed aerosol (dust and smoke) is anomalously high over the equatorial eastern tropical Atlantic [5S-5N, 15W-5E], less water vapor is observed at two levels: 925-1000 hPa and 500-600 hPa. It is hypothesized that these results are associated with the non-hygroscopic nature of African dust, the hygroscopic properties of African smoke, and their transport pathways over the tropical Atlantic. These results are useful in the design and diagnostics of model simulations of climate effects of aerosols such as aerosol related precipitation change.

  9. Persistence of African American Men in Science: Exploring the Influence of Scientist Identity, Mentoring, and Campus Climate

    ERIC Educational Resources Information Center

    Guy, Breonte Stephan

    2013-01-01

    The scant literature on persistence of African American males in science typically takes a deficits-based approach to encapsulate the myriad reasons this population is so often underrepresented. Scientist Identity, Mentoring, and Campus Climate have, individually, been found to be related to the persistence of African American students. However,…

  10. Revealing Relationships among Relevant Climate Variables with Information Theory

    NASA Technical Reports Server (NTRS)

    Knuth, Kevin H.; Golera, Anthony; Curry, Charles T.; Huyser, Karen A.; Kevin R. Wheeler; Rossow, William B.

    2005-01-01

    The primary objective of the NASA Earth-Sun Exploration Technology Office is to understand the observed Earth climate variability, thus enabling the determination and prediction of the climate's response to both natural and human-induced forcing. We are currently developing a suite of computational tools that will allow researchers to calculate, from data, a variety of information-theoretic quantities such as mutual information, which can be used to identify relationships among climate variables, and transfer entropy, which indicates the possibility of causal interactions. Our tools estimate these quantities along with their associated error bars, the latter of which is critical for describing the degree of uncertainty in the estimates. This work is based upon optimal binning techniques that we have developed for piecewise-constant, histogram-style models of the underlying density functions. Two useful side benefits have already been discovered. The first allows a researcher to determine whether there exist sufficient data to estimate the underlying probability density. The second permits one to determine an acceptable degree of round-off when compressing data for efficient transfer and storage. We also demonstrate how mutual information and transfer entropy can be applied so as to allow researchers not only to identify relations among climate variables, but also to characterize and quantify their possible causal interactions.

  11. The longitudinal variability of equatorial electrojet and vertical drift velocity in the African and American sectors

    NASA Astrophysics Data System (ADS)

    Yizengaw, E.; Moldwin, M. B.; Zesta, E.; Biouele, C. M.; Damtie, B.; Mebrahtu, A.; Rabiu, B.; Valladares, C. F.; Stoneback, R.

    2014-03-01

    While the formation of equatorial electrojet (EEJ) and its temporal variation is believed to be fairly well understood, the longitudinal variability at all local times is still unknown. This paper presents a case and statistical study of the longitudinal variability of dayside EEJ for all local times using ground-based observations. We found EEJ is stronger in the west American sector and decreases from west to east longitudinal sectors. We also confirm the presence of significant longitudinal difference in the dusk sector pre-reversal drift, using the ion velocity meter (IVM) instrument onboard the C/NOFS satellite, with stronger pre-reversal drift in the west American sector compared to the African sector. Previous satellite observations have shown that the African sector is home to stronger and year-round ionospheric bubbles/irregularities compared to the American and Asian sectors. This study's results raises the question if the vertical drift, which is believed to be the main cause for the enhancement of Rayleigh-Taylor (RT) instability growth rate, is stronger in the American sector and weaker in the African sector - why are the occurrence and amplitude of equatorial irregularities stronger in the African sector?

  12. Orbital- versus glacial-mode forcing of tropical African climate: Results of scientific drilling in Lake Malawi, East Africa

    NASA Astrophysics Data System (ADS)

    Scholz, C. A.; Cohen, A. S.; Johnson, T. C.; King, J. W.; Brown, E. T.; Lyons, R. P.; Stone, J. R.; Beuning, K. R.

    2007-12-01

    Lake Malawi extends from 9-14 degrees S within the East African Rift Valley, and at 700 m deep, contains more than 20 percent of the surface water on the African continent. In 2005 the Lake Malawi Scientific Drilling Project drilled 7 holes at two sites in the lake, recovering a continuous sediment record that samples much of the Quaternary. Detailed studies completed to date on sediments deposited during the past 145 ka indicate periods of severe aridity at precessional frequency between 135 and 75 ka, when the lake's water volume was periodically reduced by at least 95 percent. These dramatic drops in lake level (more than 550 m), signifying markedly arid conditions in the catchment, are documented in sediment lithology (decreased organic carbon content and increased authigenic carbonate content during severe lowstands), aquatic microfossils (appearance of a littoral ostracode fauna, and saline/alkaline lake diatom flora during extreme low lake stages), as well as in dramatic reductions in catchment pollen production. These intervals of pronounced tropical African aridity in the early late-Pleistocene were much more severe than the Last Glacial Maximum, and are consistent with sediment records from Lakes Tanganyika (East Africa) and Bosumtwi (West Africa). In all three lakes a major rise in water levels and a shift to more humid conditions is observed after ~70 ka. The transition to wetter, more stable conditions coincides with the relaxation of orbital eccentricity and a reduction in the amplitude of precession. The observed climate mode switch to decreased environmental variability is consistent with terrestrial and marine records from in and around tropical Africa, but these new drill cores provide evidence for dramatically drier conditions prior to 70 ka that have not as yet been detected in marine sediment records. Such climate change may have stimulated the expansion and migrations of early modern human populations.

  13. The influence of climate variables on dengue in Singapore.

    PubMed

    Pinto, Edna; Coelho, Micheline; Oliver, Leuda; Massad, Eduardo

    2011-12-01

    In this work we correlated dengue cases with climatic variables for the city of Singapore. This was done through a Poisson Regression Model (PRM) that considers dengue cases as the dependent variable and the climatic variables (rainfall, maximum and minimum temperature and relative humidity) as independent variables. We also used Principal Components Analysis (PCA) to choose the variables that influence in the increase of the number of dengue cases in Singapore, where PC₁ (Principal component 1) is represented by temperature and rainfall and PC₂ (Principal component 2) is represented by relative humidity. We calculated the probability of occurrence of new cases of dengue and the relative risk of occurrence of dengue cases influenced by climatic variable. The months from July to September showed the highest probabilities of the occurrence of new cases of the disease throughout the year. This was based on an analysis of time series of maximum and minimum temperature. An interesting result was that for every 2-10°C of variation of the maximum temperature, there was an average increase of 22.2-184.6% in the number of dengue cases. For the minimum temperature, we observed that for the same variation, there was an average increase of 26.1-230.3% in the number of the dengue cases from April to August. The precipitation and the relative humidity, after analysis of correlation, were discarded in the use of Poisson Regression Model because they did not present good correlation with the dengue cases. Additionally, the relative risk of the occurrence of the cases of the disease under the influence of the variation of temperature was from 1.2-2.8 for maximum temperature and increased from 1.3-3.3 for minimum temperature. Therefore, the variable temperature (maximum and minimum) was the best predictor for the increased number of dengue cases in Singapore.

  14. Variable climatic conditions dominate recent phytoplankton dynamics in Chesapeake Bay

    PubMed Central

    Harding, Jr., Lawrence W.; Mallonee, Michael E.; Perry, Elgin S.; Miller, W. David; Adolf, Jason E.; Gallegos, Charles L.; Paerl, Hans W.

    2016-01-01

    Variable climatic conditions strongly influence phytoplankton dynamics in estuaries globally. Our study area is Chesapeake Bay, a highly productive ecosystem providing natural resources, transportation, and recreation for nearly 16 million people inhabiting a 165,000-km2 watershed. Since World War II, nutrient over-enrichment has led to multiple ecosystem impairments caused by increased phytoplankton biomass as chlorophyll-a (chl-a). Doubled nitrogen (N) loadings from 1945–1980 led to increased chl-a, reduced water clarity, and low dissolved oxygen (DO), while decreased N loadings from 1981–2012 suggest modest improvement. The recent 30+ years are characterized by high inter-annual variability of chl-a, coinciding with irregular dry and wet periods, complicating the detection of long-term trends. Here, we synthesize time-series data for historical and recent N loadings (TN, NO2 + NO3), chl-a, floral composition, and net primary productivity (NPP) to distinguish secular changes caused by nutrient over-enrichment from spatio-temporal variability imposed by climatic conditions. Wet years showed higher chl-a, higher diatom abundance, and increased NPP, while dry years showed lower chl-a, lower diatom abundance, and decreased NPP. Our findings support a conceptual model wherein variable climatic conditions dominate recent phytoplankton dynamics against a backdrop of nutrient over-enrichment, emphasizing the need to separate these effects to gauge progress toward improving water quality in estuaries. PMID:27026279

  15. Solar forcing synchronizes decadal North Atlantic climate variability.

    PubMed

    Thiéblemont, Rémi; Matthes, Katja; Omrani, Nour-Eddine; Kodera, Kunihiko; Hansen, Felicitas

    2015-01-01

    Quasi-decadal variability in solar irradiance has been suggested to exert a substantial effect on Earth's regional climate. In the North Atlantic sector, the 11-year solar signal has been proposed to project onto a pattern resembling the North Atlantic Oscillation (NAO), with a lag of a few years due to ocean-atmosphere interactions. The solar/NAO relationship is, however, highly misrepresented in climate model simulations with realistic observed forcings. In addition, its detection is particularly complicated since NAO quasi-decadal fluctuations can be intrinsically generated by the coupled ocean-atmosphere system. Here we compare two multi-decadal ocean-atmosphere chemistry-climate simulations with and without solar forcing variability. While the experiment including solar variability simulates a 1-2-year lagged solar/NAO relationship, comparison of both experiments suggests that the 11-year solar cycle synchronizes quasi-decadal NAO variability intrinsic to the model. The synchronization is consistent with the downward propagation of the solar signal from the stratosphere to the surface. PMID:26369503

  16. Variable climatic conditions dominate recent phytoplankton dynamics in Chesapeake Bay

    NASA Astrophysics Data System (ADS)

    Harding, Lawrence W., Jr.; Mallonee, Michael E.; Perry, Elgin S.; Miller, W. David; Adolf, Jason E.; Gallegos, Charles L.; Paerl, Hans W.

    2016-03-01

    Variable climatic conditions strongly influence phytoplankton dynamics in estuaries globally. Our study area is Chesapeake Bay, a highly productive ecosystem providing natural resources, transportation, and recreation for nearly 16 million people inhabiting a 165,000-km2 watershed. Since World War II, nutrient over-enrichment has led to multiple ecosystem impairments caused by increased phytoplankton biomass as chlorophyll-a (chl-a). Doubled nitrogen (N) loadings from 1945–1980 led to increased chl-a, reduced water clarity, and low dissolved oxygen (DO), while decreased N loadings from 1981–2012 suggest modest improvement. The recent 30+ years are characterized by high inter-annual variability of chl-a, coinciding with irregular dry and wet periods, complicating the detection of long-term trends. Here, we synthesize time-series data for historical and recent N loadings (TN, NO2 + NO3), chl-a, floral composition, and net primary productivity (NPP) to distinguish secular changes caused by nutrient over-enrichment from spatio-temporal variability imposed by climatic conditions. Wet years showed higher chl-a, higher diatom abundance, and increased NPP, while dry years showed lower chl-a, lower diatom abundance, and decreased NPP. Our findings support a conceptual model wherein variable climatic conditions dominate recent phytoplankton dynamics against a backdrop of nutrient over-enrichment, emphasizing the need to separate these effects to gauge progress toward improving water quality in estuaries.

  17. Variable climatic conditions dominate recent phytoplankton dynamics in Chesapeake Bay.

    PubMed

    Harding, Lawrence W; Mallonee, Michael E; Perry, Elgin S; Miller, W David; Adolf, Jason E; Gallegos, Charles L; Paerl, Hans W

    2016-01-01

    Variable climatic conditions strongly influence phytoplankton dynamics in estuaries globally. Our study area is Chesapeake Bay, a highly productive ecosystem providing natural resources, transportation, and recreation for nearly 16 million people inhabiting a 165,000-km(2) watershed. Since World War II, nutrient over-enrichment has led to multiple ecosystem impairments caused by increased phytoplankton biomass as chlorophyll-a (chl-a). Doubled nitrogen (N) loadings from 1945-1980 led to increased chl-a, reduced water clarity, and low dissolved oxygen (DO), while decreased N loadings from 1981-2012 suggest modest improvement. The recent 30+ years are characterized by high inter-annual variability of chl-a, coinciding with irregular dry and wet periods, complicating the detection of long-term trends. Here, we synthesize time-series data for historical and recent N loadings (TN, NO2 + NO3), chl-a, floral composition, and net primary productivity (NPP) to distinguish secular changes caused by nutrient over-enrichment from spatio-temporal variability imposed by climatic conditions. Wet years showed higher chl-a, higher diatom abundance, and increased NPP, while dry years showed lower chl-a, lower diatom abundance, and decreased NPP. Our findings support a conceptual model wherein variable climatic conditions dominate recent phytoplankton dynamics against a backdrop of nutrient over-enrichment, emphasizing the need to separate these effects to gauge progress toward improving water quality in estuaries. PMID:27026279

  18. Variable climatic conditions dominate recent phytoplankton dynamics in Chesapeake Bay.

    PubMed

    Harding, Lawrence W; Mallonee, Michael E; Perry, Elgin S; Miller, W David; Adolf, Jason E; Gallegos, Charles L; Paerl, Hans W

    2016-03-30

    Variable climatic conditions strongly influence phytoplankton dynamics in estuaries globally. Our study area is Chesapeake Bay, a highly productive ecosystem providing natural resources, transportation, and recreation for nearly 16 million people inhabiting a 165,000-km(2) watershed. Since World War II, nutrient over-enrichment has led to multiple ecosystem impairments caused by increased phytoplankton biomass as chlorophyll-a (chl-a). Doubled nitrogen (N) loadings from 1945-1980 led to increased chl-a, reduced water clarity, and low dissolved oxygen (DO), while decreased N loadings from 1981-2012 suggest modest improvement. The recent 30+ years are characterized by high inter-annual variability of chl-a, coinciding with irregular dry and wet periods, complicating the detection of long-term trends. Here, we synthesize time-series data for historical and recent N loadings (TN, NO2 + NO3), chl-a, floral composition, and net primary productivity (NPP) to distinguish secular changes caused by nutrient over-enrichment from spatio-temporal variability imposed by climatic conditions. Wet years showed higher chl-a, higher diatom abundance, and increased NPP, while dry years showed lower chl-a, lower diatom abundance, and decreased NPP. Our findings support a conceptual model wherein variable climatic conditions dominate recent phytoplankton dynamics against a backdrop of nutrient over-enrichment, emphasizing the need to separate these effects to gauge progress toward improving water quality in estuaries.

  19. Solar forcing synchronizes decadal North Atlantic climate variability.

    PubMed

    Thiéblemont, Rémi; Matthes, Katja; Omrani, Nour-Eddine; Kodera, Kunihiko; Hansen, Felicitas

    2015-09-15

    Quasi-decadal variability in solar irradiance has been suggested to exert a substantial effect on Earth's regional climate. In the North Atlantic sector, the 11-year solar signal has been proposed to project onto a pattern resembling the North Atlantic Oscillation (NAO), with a lag of a few years due to ocean-atmosphere interactions. The solar/NAO relationship is, however, highly misrepresented in climate model simulations with realistic observed forcings. In addition, its detection is particularly complicated since NAO quasi-decadal fluctuations can be intrinsically generated by the coupled ocean-atmosphere system. Here we compare two multi-decadal ocean-atmosphere chemistry-climate simulations with and without solar forcing variability. While the experiment including solar variability simulates a 1-2-year lagged solar/NAO relationship, comparison of both experiments suggests that the 11-year solar cycle synchronizes quasi-decadal NAO variability intrinsic to the model. The synchronization is consistent with the downward propagation of the solar signal from the stratosphere to the surface.

  20. Assessing the impact of climate change on water resources in a tropical West African catchment using an ensemble of CORDEX climate simulations (Dano, Burkina Faso)

    NASA Astrophysics Data System (ADS)

    Yira, Yacouba; Diekkrüger, Bernd; Steup, Gero; Yaovi Bossa, Aymar

    2016-04-01

    This study assesses the potential impact of climate change on water resources in the Dano catchment (Burkina Faso, West Africa). There is now essential consensus on the importance of performing multi (climate)-model assessments in order to estimate the response of the West African climate to global change. Taking advantage of the results of the COordinated Regional climate Downscaling Experiment (CORDEX-Africa) project, this study evaluates climate change impacts on water resources using an ensemble of six Regional Climate Models (RCMs) in a catchment that is potentially vulnerable to climate change and presents a low adaptive capacity. The ensemble of RCMs was first evaluated to get an estimate of the historical simulated rainfall for the catchment by comparing RCM-based simulated historical rainfall to the observed rainfall data provided by the National Meteorological Service (DGM). In general, the simulated historical rainfall agrees within some degree of variability with the observed rainfall in regard to the mean annual cycle of precipitation. However, significant biases such as a double-peaked rainy season as well as the timing of the rainy season were exhibited by individual RCMs. A statistical bias correction (Quantile mapping) was then applied to the RCM-based simulated daily rainfall for the overlapping period of 1971-2000. The results confirm the effectiveness of the applied bias correction method for rainfall. Temperature and bias corrected rainfall data from the ensemble of RCMs was used as input for the Water flow and balance Simulation Model (WaSiM) to simulate river discharge, soil moisture, evapotranspiration and groundwater depth. To take into account the concern of the potential alteration of the climate change signal due to bias correction, uncorrected climate data for a single RCM was also applied to the hydrological model. The simulated hydrological variables show a similar behavior under observed and bias corrected climate data for the

  1. A distal 140 kyr sediment record of Nile discharge and East African monsoon variability

    NASA Astrophysics Data System (ADS)

    Ehrmann, Werner; Schmiedl, Gerhard; Seidel, Martin; Krüger, Stefan; Schulz, Hartmut

    2016-03-01

    Clay mineral assemblages in a sediment core from the distal Nile discharge plume off Israel have been used to reconstruct the late Quaternary Nile sediment discharge into the eastern Mediterranean Sea (EMS). The record spans the last ca. 140 kyr. Smectite abundances indicate the influence of the Blue Nile and the Atbara River that have their headwaters in the volcanic rocks of the Ethiopian Highlands. Kaolinite abundances indicate the influence of wadis, which contribute periodically to the suspension load of the Nile. Due to the geographical position, the climate and the sedimentary framework of the EMS is controlled by two climate systems. The long-term climate regime was governed by the African monsoon that caused major African humid periods (AHPs) with enhanced sediment discharge at 132 to < 126 (AHP 5), 116 to 99 (AHP4), and 89 to 77 ka (AHP3). They lasted much longer than the formation of the related sapropel layers S5 (> 2 kyr), S4 (3.5 kyr), and S3 (5 kyr). During the last glacial period (Marine Isotope Stages (MISs) 4-2), the long-term changes in the monsoonal system were superimposed by millennial-scale changes in an intensified midlatitude glacial system. This climate regime caused short but pronounced drought periods in the Nile catchment, which are linked to Heinrich events and alternate with more humid interstadials. The clay mineral record further implies that feedback mechanisms between vegetation cover and sediment discharge of the Nile are detectable but of minor importance for the sedimentary record in the southeastern Mediterranean Sea during the investigated African humid periods.

  2. The projected timing of climate departure from recent variability.

    PubMed

    Mora, Camilo; Frazier, Abby G; Longman, Ryan J; Dacks, Rachel S; Walton, Maya M; Tong, Eric J; Sanchez, Joseph J; Kaiser, Lauren R; Stender, Yuko O; Anderson, James M; Ambrosino, Christine M; Fernandez-Silva, Iria; Giuseffi, Louise M; Giambelluca, Thomas W

    2013-10-10

    Ecological and societal disruptions by modern climate change are critically determined by the time frame over which climates shift beyond historical analogues. Here we present a new index of the year when the projected mean climate of a given location moves to a state continuously outside the bounds of historical variability under alternative greenhouse gas emissions scenarios. Using 1860 to 2005 as the historical period, this index has a global mean of 2069 (±18 years s.d.) for near-surface air temperature under an emissions stabilization scenario and 2047 (±14 years s.d.) under a 'business-as-usual' scenario. Unprecedented climates will occur earliest in the tropics and among low-income countries, highlighting the vulnerability of global biodiversity and the limited governmental capacity to respond to the impacts of climate change. Our findings shed light on the urgency of mitigating greenhouse gas emissions if climates potentially harmful to biodiversity and society are to be prevented.

  3. Assessment of human health vulnerability to climate variability and change in Cuba.

    PubMed

    Bultó, Paulo Lázaro Ortíz; Rodríguez, Antonio Pérez; Valencia, Alina Rivero; Vega, Nicolás León; Gonzalez, Manuel Díaz; Carrera, Alina Pérez

    2006-12-01

    In this study we assessed the potential effects of climate variability and change on population health in Cuba. We describe the climate of Cuba as well as the patterns of climate-sensitive diseases of primary concern, particularly dengue fever. Analyses of the associations between climatic anomalies and disease patterns highlight current vulnerability to climate variability. We describe current adaptations, including the application of climate predictions to prevent disease outbreaks. Finally, we present the potential economic costs associated with future impacts due to climate change. The tools used in this study can be useful in the development of appropriate and effective adaptation options to address the increased climate variability associated with climate change.

  4. Late Holocene interdecadal climate variability in the Sahel: inferences from a marine dust record offshore Senegal

    NASA Astrophysics Data System (ADS)

    Meyer, I.; Stuut, J.-B.; Mollenhauer, G.; Mulitza, S.; Zabel, M.

    2009-04-01

    Present-day climate in northwestern Africa strongly depends on the avaiability of water. At least since the Pliocene the Saharan Desert and the semiarid Sahel belt (tropical North Afrika) have been frequently affected by sudden shifts to more arid climate. The rate of change from arid to humid conditions is presently under heavy debate (e.g., deMenocal et al., 2001, Kröpelin et al., 2008). A recent example of abrupt droughts occurred in the early 70's and 80's of the last century. In this study we compare different high-resolution marine sediment records of Sahel climate variability from the Senegal mud belt, northwest Africa. Marine sediment cores show the variations of terrigenous input (both aeolian dust and fluvial matter) from the African continent. Due to their different distinctive grain-size distributions, aeolian dust and fluvial mud can be recognised and quantified in marine sediments (e.g., Stuut et al., 2002). Based on these variations in the grain-size distributions of the terrigenous sediment fraction, deconvolved with an end-member modelling algorithm (Weltje, 1997), are used to reconstruct rainfall variability and dust production on land for the last 4,000 years. References P. B. deMenocal, et al. (2001). Late Holocene Cultural Responses to Climate Change During the Holocene. Science 292, 667 S. Kröpelin, et al. (2008) Response to Comment on "Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years" Science 322, 1326c G. J. Weltje (1997) End-member modeling of compositional data: Numerical-statistical algorithms for solving the explicit mixing problem. Mathematical Geology 9, 4

  5. Climatic variability, plasticity, and dispersal: A case study from Lake Tana, Ethiopia.

    PubMed

    Grove, Matt; Lamb, Henry; Roberts, Helen; Davies, Sarah; Marshall, Mike; Bates, Richard; Huws, Dei

    2015-10-01

    The numerous dispersal events that have occurred during the prehistory of hominin lineages are the subject of longstanding and increasingly active debate in evolutionary anthropology. As well as research into the dating and geographic extent of such dispersals, there is an increasing focus on the factors that may have been responsible for dispersal. The growing body of detailed regional palaeoclimatic data is invaluable in demonstrating the often close relationship between changes in prehistoric environments and the movements of hominin populations. The scenarios constructed from such data are often overly simplistic, however, concentrating on the dynamics of cyclical contraction and expansion during severe and ameliorated conditions respectively. This contribution proposes a two-stage hypothesis of hominin dispersal in which populations (1) accumulate high levels of climatic tolerance during highly variable climatic phases, and (2) express such heightened tolerance via dispersal in subsequent low-variability phases. Likely dispersal phases are thus proposed to occur during stable climatic phases that immediately follow phases of high climatic variability. Employing high resolution palaeoclimatic data from Lake Tana, Ethiopia, the hypothesis is examined in relation to the early dispersal of Homo sapiens out of East Africa and into the Levant. A dispersal phase is identified in the Lake Tana record between c. 112,550 and c. 96,975 years ago, a date bracket that accords well with the dating evidence for H. sapiens occupation at the sites of Qafzeh and Skhul. Results are discussed in relation to the complex pattern of H. sapiens dispersal out of East Africa, with particular attention paid to the implications of recent genetic chronologies for the origin of non-African modern humans. PMID:26472274

  6. Evidence of multidecadal climate variability in the Gulf of Mexico

    USGS Publications Warehouse

    Poore, Richard Z.; Brock, John C.

    2011-01-01

    The northern Gulf of Mexico coastal region is vulnerable to a variety of natural hazards, many of which are linked to climate and climate variability. Hurricanes, which are one such climate-related hazard, are a major recurring problem, and the active hurricane seasons of 2004 and 2005 raised interest in better understanding the controls and risks of hurricanes. Examination of historical records reveals intervals of alternating low and high hurricane activity that appear to be related to changes in average sea-surface temperature in the North Atlantic Ocean. Analyses of instrumental temperature records from the North Atlantic show decadal-scale oscillations of slightly higher versus slightly lower average temperature extending back in time for over 100 years. This oscillation is known as the Atlantic Multidecadal Oscillation (AMO).

  7. Impacts of climate change and internal climate variability on french rivers streamflows

    NASA Astrophysics Data System (ADS)

    Dayon, Gildas; Boé, Julien; Martin, Eric

    2016-04-01

    The assessment of the impacts of climate change often requires to set up long chains of modeling, from the model to estimate the future concentration of greenhouse gases to the impact model. Throughout the modeling chain, sources of uncertainty accumulate making the exploitation of results for the development of adaptation strategies difficult. It is proposed here to assess the impacts of climate change on the hydrological cycle over France and the associated uncertainties. The contribution of the uncertainties from greenhouse gases emission scenario, climate models and internal variability are addressed in this work. To have a large ensemble of climate simulations, the study is based on Global Climate Models (GCM) simulations from the Coupled Model Intercomparison Phase 5 (CMIP5), including several simulations from the same GCM to properly assess uncertainties from internal climate variability. Simulations from the four Radiative Concentration Pathway (RCP) are downscaled with a statistical method developed in a previous study (Dayon et al. 2015). The hydrological system Isba-Modcou is then driven by the downscaling results on a 8 km grid over France. Isba is a land surface model that calculates the energy and water balance and Modcou a hydrogeological model that routes the surface runoff given by Isba. Based on that framework, uncertainties uncertainties from greenhouse gases emission scenario, climate models and climate internal variability are evaluated. Their relative importance is described for the next decades and the end of this century. In a last part, uncertainties due to internal climate variability on streamflows simulated with downscaled GCM and Isba-Modcou are evaluated against observations and hydrological reconstructions on the whole 20th century. Hydrological reconstructions are based on the downscaling of recent atmospheric reanalyses of the 20th century and observations of temperature and precipitation. We show that the multi-decadal variability

  8. Tropical cloud feedbacks and natural variability of climate

    SciTech Connect

    Miller, R.L.; Del Genio, A.D. )

    1994-09-01

    Simulations of natural variability by two GCMs are examined. One GCM is a sector model, allowing relatively rapid integration without simplification of the model physics, which would potentially exclude mechanisms of variability. Two mechanisms are found in which tropical surface temperature and SST vary on interannual and longer timescales. Both are related to changes in cloud cover that modulate SST through the surface radiative flux. Over the equatorial ocean, SST and surface temperature vary on an interannual timescale, which is determined by the magnitude of the associated cloud cover anomalies. Over the subtropical ocean, variations in low cloud cover drive SST variations. In the sector model, the variability has no preferred timescale, but instead is characterized by a [open quotes]red[close quotes] spectrum with increasing power at longer periods. In the terrestrial GCM, SST variability associated with low cloud anomalies has a decadal timescale and is the dominant form of global temperature variability. Both GCMs are coupled to a mixed layer ocean model, where dynamical heat transports are prescribed, thus filtering out ENSO and thermohaline circulation variability. The occurrence of variability in the absence of dynamical ocean feedbacks suggests that climatic variability on long timescales can arise from atmospheric processes alone. 28 refs., 13 figs., 2 tabs.

  9. Tropical cloud feedbacks and natural variability of climate

    NASA Technical Reports Server (NTRS)

    Miller, R. L.; Del Genio, A. D.

    1994-01-01

    Simulations of natural variability by two general circulation models (GCMs) are examined. One GCM is a sector model, allowing relatively rapid integration without simplification of the model physics, which would potentially exclude mechanisms of variability. Two mechanisms are found in which tropical surface temperature and sea surface temperature (SST) vary on interannual and longer timescales. Both are related to changes in cloud cover that modulate SST through the surface radiative flux. Over the equatorial ocean, SST and surface temperature vary on an interannual timescale, which is determined by the magnitude of the associated cloud cover anomalies. Over the subtropical ocean, variations in low cloud cover drive SST variations. In the sector model, the variability has no preferred timescale, but instead is characterized by a 'red' spectrum with increasing power at longer periods. In the terrestrial GCM, SST variability associated with low cloud anomalies has a decadal timescale and is the dominant form of global temperature variability. Both GCMs are coupled to a mixed layer ocean model, where dynamical heat transports are prescribed, thus filtering out El Nino-Southern Oscillation (ENSO) and thermohaline circulation variability. The occurrence of variability in the absence of dynamical ocean feedbacks suggests that climatic variability on long timescales can arise from atmospheric processes alone.

  10. Climate dynamics and fluid mechanics: Natural variability and related uncertainties

    NASA Astrophysics Data System (ADS)

    Ghil, Michael; Chekroun, Mickaël D.; Simonnet, Eric

    2008-08-01

    The purpose of this review-and-research paper is twofold: (i) to review the role played in climate dynamics by fluid-dynamical models; and (ii) to contribute to the understanding and reduction of the uncertainties in future climate-change projections. To illustrate the first point, we review recent theoretical advances in studying the wind-driven circulation of the oceans. In doing so, we concentrate on the large-scale, wind-driven flow of the mid-latitude oceans, which is dominated by the presence of a larger, anticyclonic and a smaller, cyclonic gyre. The two gyres share the eastward extension of western boundary currents, such as the Gulf Stream or Kuroshio, and are induced by the shear in the winds that cross the respective ocean basins. The boundary currents and eastward jets carry substantial amounts of heat and momentum, and thus contribute in a crucial way to Earth’s climate, and to changes therein. Changes in this double-gyre circulation occur from year to year and decade to decade. We study this low-frequency variability of the wind-driven, double-gyre circulation in mid-latitude ocean basins, via the bifurcation sequence that leads from steady states through periodic solutions and on to the chaotic, irregular flows documented in the observations. This sequence involves local, pitchfork and Hopf bifurcations, as well as global, homoclinic ones. The natural climate variability induced by the low-frequency variability of the ocean circulation is but one of the causes of uncertainties in climate projections. The range of these uncertainties has barely decreased, or even increased, over the last three decades. Another major cause of such uncertainties could reside in the structural instability-in the classical, topological sense-of the equations governing climate dynamics, including but not restricted to those of atmospheric and ocean dynamics. We propose a novel approach to understand, and possibly reduce, these uncertainties, based on the concepts and

  11. Remote sensing of climate changes effects on forest biophysical variables

    NASA Astrophysics Data System (ADS)

    Zoran, Maria A.; Dida, Adrian I.; Zoran, Liviu Florin V.

    2014-10-01

    Climate variability represents the ensemble of net radiation, precipitation, wind and temperature characteristic for a region in a certain time scale (e.g.monthly, seasonal annual). The temporal and/or spatial sensitivity of forest vegetation dynamics to climate variability is used to characterize the quantitative relationship between these two quantities in temporal and/or spatial scales. So, climate variability has a great impact on the forest vegetation dynamics. Forest vegetation phenology constitutes an efficient bio-indicator of climate and anthropogenic changes impacts and a key parameter for understanding and modeling vegetation-climate interactions. Satellite remote sensing is a very useful tool to assess the main phenological events based on tracking significant changes on temporal trajectories of forest biophysical parameters like as Normalized Difference Vegetation Index (NDVIs) and Leaf Aria Index (LAI), which requires time-series data with good time resolution, over homogeneous area, cloud-free and not affected by atmospheric and geometric effects and variations in sensor characteristics (calibration, spectral responses). This paper will quantify this impact over a forest ecosystem Cernica- Branesti placed in the North-Eastern part of Bucharest town, Romania, with NDVI and LAI parameters extracted from MODIS Terra and NOAA AVHRR satellite images in synergy with meteorological data over 2000-2013 periods. For investigated test area, considerable NDVI and LAI decline have been observed during heat wave and drought events of 2003, 2007 and 2012 years. Under water stress conditions, it is evident that environmental factors such as soil type, parent material, and topography are not correlated with NDVI dynamics.

  12. Does Irrigation Buffer Agriculture from Climatic Variability? - Evidence from India

    NASA Astrophysics Data System (ADS)

    Fishman, R.

    2010-12-01

    One of the key potential benefits of water storage and irrigation is the buffering of agricultural production from natural fluctuations in rainfall, be they intra-seasonal, inter-annual or decadal, by storing excess rainfall for times when it is deficient. Economically, the ability to protect food production and income from climatic and weather variability has always been important, especially in developing countries. This ability can be a key asset in adaptation to the uncertainties and enhanced variability in precipitation that is predicted to accompany climate change. It is therefore important to investigate empirically how well irrigation of different kinds has performed in this regard. We use agricultural production statistics in India, a country whose fortune has always been at the mercy of the stochastic monsoon rains, to investigate this question statistically, and study the performance of both surface and groundwater irrigation in different hydro-geologies.

  13. Monthly means of selected climate variables for 1985 - 1989

    NASA Technical Reports Server (NTRS)

    Schubert, S.; Wu, C.-Y.; Zero, J.; Schemm, J.-K.; Park, C.-K.; Suarez, M.

    1992-01-01

    Meteorologists are accustomed to viewing instantaneous weather maps, since these contain the most relevant information for the task of producing short-range weather forecasts. Climatologists, on the other hand, tend to deal with long-term means, which portray the average climate. The recent emphasis on dynamical extended-range forecasting and, in particular measuring and predicting short term climate change makes it important that we become accustomed to looking at variations on monthly and longer time scales. A convenient toll for researchers to familiarize themselves with the variability which occurs in selected parameters on these time scales is provided. The format of the document was chosen to help facilitate the intercomparison of various parameters and highlight the year-to-year variability in monthly means.

  14. Using short-term climate variability to infer equilibrium climate sensitivity

    NASA Astrophysics Data System (ADS)

    Dessler, A. E.; Zhou, C.

    2015-12-01

    We provide a constraint on the magnitude of the Earth's equilibrium climate sensitivity (ECS) using observations short-term climate variability between 2000 and 2014 along with short- and long-term climate model simulations. Our best estimate of the ECS from this analysis 2.5°C, with a likely range of 1.5-3.4°C, which falls in the bottom half of the canonical IPCC ECS range of 1.5-4.5°C.

  15. The role of African easterly waves on Atlantic tropical cyclone variability

    NASA Astrophysics Data System (ADS)

    Hopsch, Susanna B.

    Coherent vorticity structures were identified at 850hPa over West Africa and the tropical Atlantic in the ERA40 reanalysis. The presence of two dominant source regions for stormtracks over the Atlantic was found. Results show that the southern stormtrack provides most storms that reach the MDR where most tropical cyclones develop. Marked seasonal variability in location and intensity of storms leaving the West African coast exists, which may influence the likelihood of downstream intensification and longevity. There exists considerable year-to-year variability in number of West African storms, both over land and continuing out over the tropical Atlantic Ocean. While the low-frequency variability is well correlated with Atlantic tropical cyclone activity, West African rainfall and SSTs, the interannual variability is found to be uncorrelated. In contrast, variance of 2-6-day-filtered meridional wind, which provides a synoptic-scale measure of AEW activity, shows a significant, positive correlation with TC activity at interannual timescales. The extent to which the nature of AEWs leaving the West African coast is important for influencing the probability of becoming named storms downstream was also explored. The ERA40 dataset has been analyzed for July through September from 1979-2001 to generate a climatology of AEWs leaving the West African coast. A composite view of the structure of the AEWs and their large-scale environment was obtained by identifying all AEWs that were associated with named storms over the MDR. This was compared to the composite of all disturbances that ultimately failed to develop. It is shown that substantial differences in structure and characteristics exist of AEWs that become associated with tropical cyclones and the ones that don't. The most important differences between developing and non-developing AEWs include: (1) Developing AEWs have a distinctive cold-core structure before reaching the West coast. (2) They transform towards more warm

  16. Disproportionate Climate-Induced Range Loss Forecast for the Most Threatened African Antelopes.

    PubMed

    Payne, Benjamin Luke; Bro-Jørgensen, Jakob

    2016-05-01

    Despite increasing evidence that climatic changes are having a widespread effect on the global distribution and abundance of wildlife [1, 2], the key question of whether the ranges of species that are already threat-listed are likely to be disproportionately affected lacks quantitative assessment. According to the "small-range climate-hypersensitivity hypothesis," we predict small range size to be directly linked to large climate-induced range reduction. Antelopes, an exemplary macroecological model due to their striking ecological diversity and species richness, present an ideal opportunity to test this. Here we provide the first empirical evidence that climate change will cause a disproportionate decline in African antelopes with small geographic ranges, which places the most threatened taxa in double jeopardy. This substantiates our theoretical expectation that the link between small range size and large climate-induced range reduction is a general phenomenon. Our empirically based models also allow specific recommendations for mitigating climate-induced species declines. Gap analysis shows high priorities for antelope conservation to include creation of new protected areas in the horn of Africa and Liberia, as well as improved connectivity between existing protected areas. Predicted extinction of four species unable to reach areas with suitable climatic conditions by 2080 moreover highlights a potentially important role for ex situ conservation. The study emphasizes the urgent need to incorporate climate change into the IUCN threat assessment by extending the timeframe over which population trends are assessed [3].

  17. Disproportionate Climate-Induced Range Loss Forecast for the Most Threatened African Antelopes.

    PubMed

    Payne, Benjamin Luke; Bro-Jørgensen, Jakob

    2016-05-01

    Despite increasing evidence that climatic changes are having a widespread effect on the global distribution and abundance of wildlife [1, 2], the key question of whether the ranges of species that are already threat-listed are likely to be disproportionately affected lacks quantitative assessment. According to the "small-range climate-hypersensitivity hypothesis," we predict small range size to be directly linked to large climate-induced range reduction. Antelopes, an exemplary macroecological model due to their striking ecological diversity and species richness, present an ideal opportunity to test this. Here we provide the first empirical evidence that climate change will cause a disproportionate decline in African antelopes with small geographic ranges, which places the most threatened taxa in double jeopardy. This substantiates our theoretical expectation that the link between small range size and large climate-induced range reduction is a general phenomenon. Our empirically based models also allow specific recommendations for mitigating climate-induced species declines. Gap analysis shows high priorities for antelope conservation to include creation of new protected areas in the horn of Africa and Liberia, as well as improved connectivity between existing protected areas. Predicted extinction of four species unable to reach areas with suitable climatic conditions by 2080 moreover highlights a potentially important role for ex situ conservation. The study emphasizes the urgent need to incorporate climate change into the IUCN threat assessment by extending the timeframe over which population trends are assessed [3]. PMID:27133868

  18. Impacts of tectonic and orbital forcing on East African climate: A comparison based on global climate model simulations.

    NASA Astrophysics Data System (ADS)

    Kaspar, F.; Prömmel, K.; Cubasch, U.

    2009-04-01

    Tectonic uplift and erosional denudation can have drastic effects on global and regional climate patterns, which in turn have a significant impact on ecosystems and the distribution of biogeographic zones. The interdisciplinary Research Unit RiftLink (www.riftlink.de) addresses the causes of rift-flank uplift in the East African Rift, its impact on climate changes in equatorial Africa, and the possible connection to the evolution of hominids. Understanding the mechanisms and origin of atmospheric moisture transport is essential for the interpretation of paleoclimatic proxies. Here, we present results from the climate modelling component of RiftLink. The global atmosphere-ocean model ECHO-G has been forced with topographic and orbital scenarios in order to evaluate the relative role of both factors for the past climate of East Africa. The model consists of the ECHAM4 atmosphere model at approx. 3.75° resolution coupled to the HOPE-G ocean model at approx. 2.8°. Forcing the model with a significantly reduced topography in Eastern and Southern Africa leads to a distinct increase in moisture transport from the Indian ocean into the eastern part of the continent and increased precipitation in Eastern Africa. Simulations with step-wise reduced height show that this climate change occurs continuously with the change in topography, i.e. an abrupt change of local climatic features with a critical height is not found. If these results are used for the interpretation of proxy data, it has do be considered that other forcing factors can lead to comparable changes in moisture availability. As an example, we tested the impact of changes in the Earth's orbit around the Sun. For these simulations, we forced the same climate model with the orbital configuration of the last interglacial (at 125,000 years before present, i.e. the Eemian interglacial) and the last glacial inception (at 115,000 years before present). The induced changes in the seasonal and spatial structure of

  19. Holocene Climatic Variability in the Indian Monsoon Domain

    NASA Astrophysics Data System (ADS)

    Mishra, Praveen Kumar; Anoop, Ambili; Menzel, Philip; Gaye, Birgit; Basavaiah, Nathani; Jehangir, Arshid; Prasad, Sushma

    2013-04-01

    The available data on Holocene climate variability from Asia indicates spatio-temporal changes in the precipitation over this vast region. Detailed information on the timing, duration, regionality, and causes of these fluctuations is not well understood, especially over the Indian subcontinent. My work focuses on long core sediments from lake Tso Moriri (78°14'-78°25'N and 32°40'-33°02'E; altitude: 4500 m) situated in climatically sensitive zone of NW Himalayas affected by both mid-latitude westerlies and Indian summer monsoon. Two cores ca.7 m were retrieved from the lake at different water depths (ca. 40m and 105m) in July 2011. Investigations reveal marked changes in grain size, lamination quality, mineralogy, organic and carbonate content suggesting changes in lake level, direction of inflow, and biological productivity that in turn are influenced by regional climate. As the lake lies in a tectonically active region, I have also undertaken detailed geomorphometric (knick-point, Hack index), and drainage pattern analysis of the major inflowing streams to decipher the active tectonics in the region. Sharp changes in river course and slope gradient indicates the presence of an active N-S trending fault in western flank of the lake. The data from lake Tso Moriri will be compared with other high-resolution records from lake Lonar and stalagmites in NE India to reconstruct the forcing mechanism of Holocene climatic variability.

  20. West African monsoon decadal variability and surface-related forcings: second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II)

    NASA Astrophysics Data System (ADS)

    Xue, Yongkang; De Sales, Fernando; Lau, William K.-M.; Boone, Aaron; Kim, Kyu-Myong; Mechoso, Carlos R.; Wang, Guiling; Kucharski, Fred; Schiro, Kathleen; Hosaka, Masahiro; Li, Suosuo; Druyan, Leonard M.; Sanda, Ibrah Seidou; Thiaw, Wassila; Zeng, Ning; Comer, Ruth E.; Lim, Young-Kwon; Mahanama, Sarith; Song, Guoqiong; Gu, Yu; Hagos, Samson M.; Chin, Mian; Schubert, Siegfried; Dirmeyer, Paul; Ruby Leung, L.; Kalnay, Eugenia; Kitoh, Akio; Lu, Cheng-Hsuan; Mahowald, Natalie M.; Zhang, Zhengqiu

    2016-06-01

    The second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II) is designed to improve understanding of the possible roles and feedbacks of sea surface temperature (SST), land use land cover change (LULCC), and aerosols forcings in the Sahel climate system at seasonal to decadal scales. The project's strategy is to apply prescribed observationally based anomaly forcing, i.e., "idealized but realistic" forcing, in simulations by climate models. The goal is to assess these forcings' effects in producing/amplifying seasonal and decadal climate variability in the Sahel between the 1950s and the 1980s, which is selected to characterize the great drought period of the last century. This is the first multi-model experiment specifically designed to simultaneously evaluate such relative contributions. The WAMME II models have consistently demonstrated that SST forcing is a major contributor to the twentieth century Sahel drought. Under the influence of the maximum possible SST forcing, the ensemble mean of WAMME II models can produce up to 60 % of the precipitation difference during the period. The present paper also addresses the role of SSTs in triggering and maintaining the Sahel drought. In this regard, the consensus of WAMME II models is that both Indian and Pacific Ocean SSTs greatly contributed to the drought, with the former producing an anomalous displacement of the Intertropical Convergence Zone before the WAM onset, and the latter mainly contributes to the summer WAM drought. The WAMME II models also show that the impact of LULCC forcing on the Sahel climate system is weaker than that of SST forcing, but still of first order magnitude. According to the results, under LULCC forcing the ensemble mean of WAMME II models can produces about 40 % of the precipitation difference between the 1980s and the 1950s. The role of land surface processes in responding to and amplifying the drought is also identified. The results suggest that catastrophic

  1. Towards multi-resolution global climate modeling with ECHAM6-FESOM. Part II: climate variability

    NASA Astrophysics Data System (ADS)

    Rackow, T.; Goessling, H. F.; Jung, T.; Sidorenko, D.; Semmler, T.; Barbi, D.; Handorf, D.

    2016-06-01

    This study forms part II of two papers describing ECHAM6-FESOM, a newly established global climate model with a unique multi-resolution sea ice-ocean component. While part I deals with the model description and the mean climate state, here we examine the internal climate variability of the model under constant present-day (1990) conditions. We (1) assess the internal variations in the model in terms of objective variability performance indices, (2) analyze variations in global mean surface temperature and put them in context to variations in the observed record, with particular emphasis on the recent warming slowdown, (3) analyze and validate the most common atmospheric and oceanic variability patterns, (4) diagnose the potential predictability of various climate indices, and (5) put the multi-resolution approach to the test by comparing two setups that differ only in oceanic resolution in the equatorial belt, where one ocean mesh keeps the coarse ~1° resolution applied in the adjacent open-ocean regions and the other mesh is gradually refined to ~0.25°. Objective variability performance indices show that, in the considered setups, ECHAM6-FESOM performs overall favourably compared to five well-established climate models. Internal variations of the global mean surface temperature in the model are consistent with observed fluctuations and suggest that the recent warming slowdown can be explained as a once-in-one-hundred-years event caused by internal climate variability; periods of strong cooling in the model (`hiatus' analogs) are mainly associated with ENSO-related variability and to a lesser degree also to PDO shifts, with the AMO playing a minor role. Common atmospheric and oceanic variability patterns are simulated largely consistent with their real counterparts. Typical deficits also found in other models at similar resolutions remain, in particular too weak non-seasonal variability of SSTs over large parts of the ocean and episodic periods of almost absent

  2. Can climate variability contribute to the ``missing'' CO2 sink?

    NASA Astrophysics Data System (ADS)

    Dai, Aiguo; Fung, Inez Y.

    1993-09-01

    The contemporary carbon budget for the atmosphere requires a large "missing" carbon sink to balance anthropogenic carbon inputs. We investigated climatic effects on carbon exchanges between the atmosphere and the undisturbed biosphere and assessed the possible contribution of climate variability to the carbon sink. Empirical models and global temperature and precipitation data sets were used in the study. It was found that climate perturbations during 1940-1988 caused considerable variations in plant productivity and soil respiration. The different sensitivities of the fluxes to climate perturbations led to a significant carbon accumulation in the biosphere. The cumulative carbon sink for the period 1950-1984 (˜20±5 GtC or 1012 kg C) was predominantly located in mid-latitudes in the northern hemisphere (30°-60°N) and could amount to half of the missing CO2 sink as derived from deconvolution analyses. Our results indicate that climate variations have unequal impacts on biospheric carbon fluxes from different ecosystems and imply that caution must be exercised in generalizing in situ observations to the globe.

  3. Smallholder agriculture in India and adaptation to current and future climate variability and climate change

    NASA Astrophysics Data System (ADS)

    Murari, K. K.; Jayaraman, T.

    2014-12-01

    Modeling studies have indicated that global warming, in many regions, will increase the exposure of major crops to rainfall and temperature stress, leading to lower crop yields. Climate variability alone has a potential to decrease yield to an extent comparable to or greater than yield reductions expected due to rising temperature. For India, where agriculture is important, both in terms of food security as well as a source of livelihoods to a majority of its population, climate variability and climate change are subjects of serious concern. There is however a need to distinguish the impact of current climate variability and climate change on Indian agriculture, especially in relation to their socioeconomic impact. This differentiation is difficult to determine due to the secular trend of increasing production and yield of the past several decades. The current research in this aspect is in an initial stage and requires a multi-disciplinary effort. In this study, we assess the potential differential impacts of environmental stress and shock across different socioeconomic strata of the rural population, using village level survey data. The survey data from eight selected villages, based on the Project on Agrarian Relations in India conducted by the Foundation for Agrarian Studies, indicated that income from crop production of the top 20 households (based on the extent of operational land holding, employment of hired labour and asset holdings) is a multiple of the mean income of the village. In sharp contrast, the income of the bottom 20 households is a fraction of the mean and sometimes negative, indicating a net loss from crop production. The considerable differentials in output and incomes suggest that small and marginal farmers are far more susceptible to climate variability and climate change than the other sections. Climate change is effectively an immediate threat to small and marginal farmers, which is driven essentially by socioeconomic conditions. The impact

  4. Climate variability slows evolutionary responses of Colias butterflies to recent climate change.

    PubMed

    Kingsolver, Joel G; Buckley, Lauren B

    2015-03-01

    How does recent climate warming and climate variability alter fitness, phenotypic selection and evolution in natural populations? We combine biophysical, demographic and evolutionary models with recent climate data to address this question for the subalpine and alpine butterfly, Colias meadii, in the southern Rocky Mountains. We focus on predicting patterns of selection and evolution for a key thermoregulatory trait, melanin (solar absorptivity) on the posterior ventral hindwings, which affects patterns of body temperature, flight activity, adult and egg survival, and reproductive success in Colias. Both mean annual summer temperatures and thermal variability within summers have increased during the past 60 years at subalpine and alpine sites. At the subalpine site, predicted directional selection on wing absorptivity has shifted from generally positive (favouring increased wing melanin) to generally negative during the past 60 years, but there is substantial variation among years in the predicted magnitude and direction of selection and the optimal absorptivity. The predicted magnitude of directional selection at the alpine site declined during the past 60 years and varies substantially among years, but selection has generally been positive at this site. Predicted evolutionary responses to mean climate warming at the subalpine site since 1980 is small, because of the variability in selection and asymmetry of the fitness function. At both sites, the predicted effects of adaptive evolution on mean population fitness are much smaller than the fluctuations in mean fitness due to climate variability among years. Our analyses suggest that variation in climate within and among years may strongly limit evolutionary responses of ectotherms to mean climate warming in these habitats.

  5. Climate variability slows evolutionary responses of Colias butterflies to recent climate change.

    PubMed

    Kingsolver, Joel G; Buckley, Lauren B

    2015-03-01

    How does recent climate warming and climate variability alter fitness, phenotypic selection and evolution in natural populations? We combine biophysical, demographic and evolutionary models with recent climate data to address this question for the subalpine and alpine butterfly, Colias meadii, in the southern Rocky Mountains. We focus on predicting patterns of selection and evolution for a key thermoregulatory trait, melanin (solar absorptivity) on the posterior ventral hindwings, which affects patterns of body temperature, flight activity, adult and egg survival, and reproductive success in Colias. Both mean annual summer temperatures and thermal variability within summers have increased during the past 60 years at subalpine and alpine sites. At the subalpine site, predicted directional selection on wing absorptivity has shifted from generally positive (favouring increased wing melanin) to generally negative during the past 60 years, but there is substantial variation among years in the predicted magnitude and direction of selection and the optimal absorptivity. The predicted magnitude of directional selection at the alpine site declined during the past 60 years and varies substantially among years, but selection has generally been positive at this site. Predicted evolutionary responses to mean climate warming at the subalpine site since 1980 is small, because of the variability in selection and asymmetry of the fitness function. At both sites, the predicted effects of adaptive evolution on mean population fitness are much smaller than the fluctuations in mean fitness due to climate variability among years. Our analyses suggest that variation in climate within and among years may strongly limit evolutionary responses of ectotherms to mean climate warming in these habitats. PMID:25631995

  6. The Climate-Population Nexus in the East African Horn: Emerging Degradation Trends in Rangeland and Pastoral Livelihood Zones

    NASA Astrophysics Data System (ADS)

    Pricope, N. G.; Husak, G. J.; Funk, C. C.; Lopez-Carr, D.

    2014-12-01

    Increasing climate variability and extreme weather conditions along with declining trends in both rainfall and temperature represent major risk factors affecting agricultural production and food security in many regions of the world. We identify regions where significant rainfall decrease from 1979-2011 over the entire continent of Africa couples with significant human population density increase. The rangelands of Ethiopia, Kenya, and Somalia in the East African Horn remain one of the world's most food insecure regions, yet have significantly increasing human populations predominantly dependent on pastoralist and agro-pastoralist livelihoods. Vegetation in this region is characterized by a variable mosaic of land covers, generally dominated by grasslands necessary for agro-pastoralism, interspersed by woody vegetation. Recent assessments indicate that widespread degradation is occurring, adversely impacting fragile ecosystems and human livelihoods. Using two underutilized MODIS products, we observe significant changes in vegetation patterns and productivity over the last decade all across the East African Horn. We observe significant vegetation browning trends in areas experiencing drying precipitation trends in addition to increasing population pressures. We also found that the drying precipitation trends only partially statistically explain the vegetation browning trends, further indicating that other factors such as population pressures and land use changes are responsible for the observed declining vegetation health. Furthermore, we show that the general vegetation browning trends persist even during years with normal rainfall conditions such as 2012, indicating potential long-term degradation of rangelands on which approximately 10 million people depend. These findings have serious implications for current and future regional food security monitoring and forecasting as well as for mitigation and adaptation strategies in a region where population is expected

  7. Colorado River Water Availability Assessment Under Climate Variability

    NASA Astrophysics Data System (ADS)

    Yarberry, A. J.; Rajagopalan, B.; Prairie, J. R.

    2010-12-01

    The Colorado River is ruled by a complex system of agreements and regulations that fully allocate its resources. During the drought from 2000 to 2008, decision makers and stakeholders began to question the abilities of existing operating procedures to handle such events; and whether dry events were historically common. A recent study found that a scenario of 20% reduction in the mean annual Colorado River flow due to climate change by 2057 resulted in a nearly 10-fold increase in the probability of annual reservoir depletion by 2057. That study also suggested that flexibility in current management practices could mitigate some of the increased risk from climate change-induced reductions in flows. The general approach of past studies has been to model and generate streamflow scenarios under climate change that are then driven through decision and management models of water resources systems to quantify the risk and reliability of various aspects of the system. Management alternatives are considered to improve the reliability to a desired level under streamflow variability. The methodology used by previous studies assumed that the projected demand growth is a given and that it has to be met in the future. We are of the opinion that this need not be the case, which motivates the present study. To this end an assessment of water availability in the basin was performed using a simple heuristic model under different climate scenarios for the available storage capacity and minimum storage requirements. From the simulations, using the predicted future levels of demand of 13.5 and 14.4 MAF as per current agreements in the basin and the current consumptive use of 12.7 MAF, the key findings are that (i) The reliability of meeting a demand of 13.5 MAF, decreases from 99% to 94% for natural climate variability and a 20% reduction in mean streamflow due to climate change, respectively; and, (ii) For a demand of 14.4 MAF, the reliability decreases from 97% to 70%. However, for

  8. Alternating high and low climate variability: The context of natural selection and speciation in Plio-Pleistocene hominin evolution.

    PubMed

    Potts, Richard; Faith, J Tyler

    2015-10-01

    Interaction of orbital insolation cycles defines a predictive model of alternating phases of high- and low-climate variability for tropical East Africa over the past 5 million years. This model, which is described in terms of climate variability stages, implies repeated increases in landscape/resource instability and intervening periods of stability in East Africa. It predicts eight prolonged (>192 kyr) eras of intensified habitat instability (high variability stages) in which hominin evolutionary innovations are likely to have occurred, potentially by variability selection. The prediction that repeated shifts toward high climate variability affected paleoenvironments and evolution is tested in three ways. In the first test, deep-sea records of northeast African terrigenous dust flux (Sites 721/722) and eastern Mediterranean sapropels (Site 967A) show increased and decreased variability in concert with predicted shifts in climate variability. These regional measurements of climate dynamics are complemented by stratigraphic observations in five basins with lengthy stratigraphic and paleoenvironmental records: the mid-Pleistocene Olorgesailie Basin, the Plio-Pleistocene Turkana and Olduvai Basins, and the Pliocene Tugen Hills sequence and Hadar Basin--all of which show that highly variable landscapes inhabited by hominin populations were indeed concentrated in predicted stages of prolonged high climate variability. Second, stringent null-model tests demonstrate a significant association of currently known first and last appearance datums (FADs and LADs) of the major hominin lineages, suites of technological behaviors, and dispersal events with the predicted intervals of prolonged high climate variability. Palynological study in the Nihewan Basin, China, provides a third test, which shows the occupation of highly diverse habitats in eastern Asia, consistent with the predicted increase in adaptability in dispersing Oldowan hominins. Integration of fossil, archeological

  9. Predicting the effect of climate change on African trypanosomiasis: integrating epidemiology with parasite and vector biology.

    PubMed

    Moore, Sean; Shrestha, Sourya; Tomlinson, Kyle W; Vuong, Holly

    2012-05-01

    Climate warming over the next century is expected to have a large impact on the interactions between pathogens and their animal and human hosts. Vector-borne diseases are particularly sensitive to warming because temperature changes can alter vector development rates, shift their geographical distribution and alter transmission dynamics. For this reason, African trypanosomiasis (sleeping sickness), a vector-borne disease of humans and animals, was recently identified as one of the 12 infectious diseases likely to spread owing to climate change. We combine a variety of direct effects of temperature on vector ecology, vector biology and vector-parasite interactions via a disease transmission model and extrapolate the potential compounding effects of projected warming on the epidemiology of African trypanosomiasis. The model predicts that epidemics can occur when mean temperatures are between 20.7°C and 26.1°C. Our model does not predict a large-range expansion, but rather a large shift of up to 60 per cent in the geographical extent of the range. The model also predicts that 46-77 million additional people may be at risk of exposure by 2090. Future research could expand our analysis to include other environmental factors that influence tsetse populations and disease transmission such as humidity, as well as changes to human, livestock and wildlife distributions. The modelling approach presented here provides a framework for using the climate-sensitive aspects of vector and pathogen biology to predict changes in disease prevalence and risk owing to climate change.

  10. Impacts of Austrian Climate Variability on Honey Bee Mortality

    NASA Astrophysics Data System (ADS)

    Switanek, Matt; Brodschneider, Robert; Crailsheim, Karl; Truhetz, Heimo

    2015-04-01

    Global food production, as it is today, is not possible without pollinators such as the honey bee. It is therefore alarming that honey bee populations across the world have seen increased mortality rates in the last few decades. The challenges facing the honey bee calls into question the future of our food supply. Beside various infectious diseases, Varroa destructor is one of the main culprits leading to increased rates of honey bee mortality. Varroa destructor is a parasitic mite which strongly depends on honey bee brood for reproduction and can wipe out entire colonies. However, climate variability may also importantly influence honey bee breeding cycles and bee mortality rates. Persistent weather events affects vegetation and hence foraging possibilities for honey bees. This study first defines critical statistical relationships between key climate indicators (e.g., precipitation and temperature) and bee mortality rates across Austria, using 6 consecutive years of data. Next, these leading indicators, as they vary in space and time, are used to build a statistical model to predict bee mortality rates and the respective number of colonies affected. Using leave-one-out cross validation, the model reduces the Root Mean Square Error (RMSE) by 21% with respect to predictions made with the mean mortality rate and the number of colonies. Furthermore, a Monte Carlo test is used to establish that the model's predictions are statistically significant at the 99.9% confidence level. These results highlight the influence of climate variables on honey bee populations, although variability in climate, by itself, cannot fully explain colony losses. This study was funded by the Austrian project 'Zukunft Biene'.

  11. Recurrence network-based time series analysis for identifying tipping points in Plio-Pleistocene African climate

    NASA Astrophysics Data System (ADS)

    Donges, J. F.; Donner, R. V.; Trauth, M. H.; Marwan, N.; Schellnhuber, H. J.; Kurths, J.

    2012-04-01

    The analysis of paleoclimate time series is usually affected by severe methodological problems, resulting primarily from non-equidistant sampling and uncertain age models. As an alternative to existing methods of time series analysis, the statistical properties of recurrence networks are promising candidates for characterizing a system's nonlinear dynamics and quantifying structural changes in its reconstructed phase space as time evolves. The results of recurrence network analysis are robust under changes in the age model and are not directly affected by non-equidistant sampling of the data. Specifically, we investigate three marine records of African climate variability during the Plio-Pleistocene. We detect several statistically significant dynamical transitions or tipping points and show that the obtained results are qualitatively robust under changes of the relevant parameters of our method, including detrending, size of the running window used for analysis, and embedding delay. Finally, relating the identified tipping points in paleoclimate-variability to speciation and extinction events in the available fossil record of human ancestors contributes to the understanding of climatic mechanisms driving human evolution in Africa during the past 5 million years.

  12. Surprising differences in the variability of Y chromosomes in African and cosmopolitan populations of Drosophila melanogaster.

    PubMed

    Larracuente, Amanda M; Clark, Andrew G

    2013-01-01

    The nonrecombining Drosophila melanogaster Y chromosome is heterochromatic and has few genes. Despite these limitations, there remains ample opportunity for natural selection to act on the genes that are vital for male fertility and on Y factors that modulate gene expression elsewhere in the genome. Y chromosomes of many organisms have low levels of nucleotide variability, but a formal survey of D. melanogaster Y chromosome variation had yet to be performed. Here we surveyed Y-linked variation in six populations of D. melanogaster spread across the globe. We find surprisingly low levels of variability in African relative to Cosmopolitan (i.e., non-African) populations. While the low levels of Cosmopolitan Y chromosome polymorphism can be explained by the demographic histories of these populations, the staggeringly low polymorphism of African Y chromosomes cannot be explained by demographic history. An explanation that is entirely consistent with the data is that the Y chromosomes of Zimbabwe and Uganda populations have experienced recent selective sweeps. Interestingly, the Zimbabwe and Uganda Y chromosomes differ: in Zimbabwe, a European Y chromosome appears to have swept through the population.

  13. Climatic controls on central African hydrology during the past 20,000 years.

    PubMed

    Schefuss, Enno; Schouten, Stefan; Schneider, Ralph R

    2005-10-13

    Past hydrological changes in Africa have been linked to various climatic processes, depending on region and timescale. Long-term precipitation changes in the regions of northern and southern Africa influenced by the monsoons are thought to have been governed by precessional variations in summer insolation. Conversely, short-term precipitation changes in the northern African tropics have been linked to North Atlantic sea surface temperature anomalies, affecting the northward extension of the Intertropical Convergence Zone and its associated rainbelt. Our knowledge of large-scale hydrological changes in equatorial Africa and their forcing factors is, however, limited. Here we analyse the isotopic composition of terrigenous plant lipids, extracted from a marine sediment core close to the Congo River mouth, in order to reconstruct past central African rainfall variations and compare this record to sea surface temperature changes in the South Atlantic Ocean. We find that central African precipitation during the past 20,000 years was mainly controlled by the difference in sea surface temperatures between the tropics and subtropics of the South Atlantic Ocean, whereas we find no evidence that changes in the position of the Intertropical Convergence Zone had a significant influence on the overall moisture availability in central Africa. We conclude that changes in ocean circulation, and hence sea surface temperature patterns, were important in modulating atmospheric moisture transport onto the central African continent.

  14. Reconstruction of principal dynamical modes from climatic variability: nonlinear approach

    NASA Astrophysics Data System (ADS)

    Mukhin, Dmitry; Gavrilov, Andrey; Loskutov, Evgeny; Feigin, Alexander; Kurths, Juergen

    2015-04-01

    Analysis of multivariate time-series produced by complex systems requires efficient tools for reduction of data dimension. We consider this problem in relation to empirical modeling of climate, which implies an analysis of spatial-distributed time-series. The main goal is to establish the number of principal modes which have key contribution to data and actually governs the observed variability. Currently, the number of widely used linear methods based on PCA and factor analysis exists, which yield different data decompositions taking into consideration simultanious/time-lag correlations between spatial grid points. However, the question about possibility of improving the decomposition by taking into account nonlinear couplings between variables often remains untouched. In the report the method for constructing principal dynamic modes on the basis of low-dimensional nonlinear parametric representation of observed multivariate time-series is suggested. It is aimed to extracting the set of latent modes that both explains an essential part of variability, and obeys the simplest evolution law. Thus, this approach can be used for optimal reconstruction of the phase space for empirical prognostic modeling of observed dynamics. The evidence of nonlinear couplings in SST space-distributed data covering the Globe is investigated by the proposed approach. It is demonstrated that the obtained principal modes capture more part of SST variability than principal components (PCs) constructed by either EOF decomposition or its spatio-temporal extension. Relation of these modes to various climate phenomena is shown and discussed in the report. The application of the approach to data-driven forecast of climate bahavior is also discussed.

  15. The Hydroclimate of East Africa: Seasonal cycle, Decadal Variability, and Human-induced Climate Change

    NASA Astrophysics Data System (ADS)

    Yang, Wenchang

    The hydroclimate of East Africa shows distinctive variabilities on seasonal to decadal time scales and poses a great challenge to climatologists attempting to project its response to anthropogenic emissions of greenhouse gases (GHGs). Increased frequency and intensity of droughts over East Africa in recent decades raise the question of whether the drying trend will continue into the future. To address this question, we first examine the decadal variability of the East African rainfall during March--May (MAM, the major rainy season in East Africa) and assess how well a series of models simulate the observed features. Observational results show that the drying trend during MAM is associated with decadal natural variability of sea surface temperature (SST) variations over the Pacific Ocean. The multimodel mean of the SST-forced, Coupled Model Intercomparison Project Phase 5 (CMIP5) AMIP experiment models reproduces both the climatological annual cycle and the drying trend in recent decades. The fully coupled models from the CMIP5 historical experiment, however, have systematic errors in simulating the East African rainfall annual cycle by underestimating the MAM rainfall while overestimating the October--December (OND, the second rainy season in East Africa) rainfall. The multimodel mean of the historical coupled runs of the MAM rainfall anomalies, which is the best estimate of the radiatively-forced change, shows a weak wetting trend associated with anthropogenic forcing. However, the SST anomaly pattern associated with the MAM rainfall has large discrepancies with the observations. The errors in simulating the East African hydroclimate with coupled models raise questions about how reliable model projections of future East African climate are. This motivates a fundamental study of why East African climate is the way it is and why coupled models get it wrong. East African hydroclimate is characterized by a dry annual mean climatology compared to other deep tropical

  16. Early human speciation, brain expansion and dispersal influenced by African climate pulses.

    PubMed

    Shultz, Susanne; Maslin, Mark

    2013-01-01

    Early human evolution is characterised by pulsed speciation and dispersal events that cannot be explained fully by global or continental paleoclimate records. We propose that the collated record of ephemeral East African Rift System (EARS) lakes could be a proxy for the regional paleoclimate conditions experienced by early hominins. Here we show that the presence of these lakes is associated with low levels of dust deposition in both West African and Mediterranean records, but is not associated with long-term global cooling and aridification of East Africa. Hominin expansion and diversification seem to be associated with climate pulses characterized by the precession-forced appearance and disappearance of deep EARS lakes. The most profound period for hominin evolution occurs at about 1.9 Ma; with the highest recorded diversity of hominin species, the appearance of Homo (sensu stricto) and major dispersal events out of East Africa into Eurasia. During this period, ephemeral deep-freshwater lakes appeared along the whole length of the EARS, fundamentally changing the local environment. The relationship between the local environment and hominin brain expansion is less clear. The major step-wise expansion in brain size around 1.9 Ma when Homo appeared was coeval with the occurrence of ephemeral deep lakes. Subsequent incremental increases in brain size are associated with dry periods with few if any lakes. Plio-Pleistocene East African climate pulses as evinced by the paleo-lake records seem, therefore, fundamental to hominin speciation, encephalisation and migration.

  17. Early Human Speciation, Brain Expansion and Dispersal Influenced by African Climate Pulses

    PubMed Central

    Shultz, Susanne; Maslin, Mark

    2013-01-01

    Early human evolution is characterised by pulsed speciation and dispersal events that cannot be explained fully by global or continental paleoclimate records. We propose that the collated record of ephemeral East African Rift System (EARS) lakes could be a proxy for the regional paleoclimate conditions experienced by early hominins. Here we show that the presence of these lakes is associated with low levels of dust deposition in both West African and Mediterranean records, but is not associated with long-term global cooling and aridification of East Africa. Hominin expansion and diversification seem to be associated with climate pulses characterized by the precession-forced appearance and disappearance of deep EARS lakes. The most profound period for hominin evolution occurs at about 1.9 Ma; with the highest recorded diversity of hominin species, the appearance of Homo (sensu stricto) and major dispersal events out of East Africa into Eurasia. During this period, ephemeral deep-freshwater lakes appeared along the whole length of the EARS, fundamentally changing the local environment. The relationship between the local environment and hominin brain expansion is less clear. The major step-wise expansion in brain size around 1.9 Ma when Homo appeared was coeval with the occurrence of ephemeral deep lakes. Subsequent incremental increases in brain size are associated with dry periods with few if any lakes. Plio-Pleistocene East African climate pulses as evinced by the paleo-lake records seem, therefore, fundamental to hominin speciation, encephalisation and migration. PMID:24146922

  18. Aerosol-climate interactions over southern Africa: the ENSO signal and interannual variability

    NASA Astrophysics Data System (ADS)

    Tummon, Fiona

    2010-05-01

    Southern Africa is a region that experiences high interannual climatic variability. It is also a region that, in general is poorly developed, has a high population growth rate and is at times politically unstable. As a whole, the region is extremely vulnerable to climatic changes, with a large proportion of the population depending on rain-fed agriculture as a source of income and subsistence. It is well known that the El-Nino/La-Nina oscillation contributes significantly to the climate variability over much of southern Africa; with El-Nino years generally being dry and warm in the southeastern parts and unusually wet in the eastern equatorial regions, whilst La-Nina years are generally wet and cool in the southeast, but dry in the eastern tropics. This in turn effects vegetation growth, and as a result the extent of biomass burning in the following dry season; with above-average wet seasons leading to increased burning, and drier than average seasons being followed by less extensive burning. The savannas of Africa experience some of the most extensive burning in the world, and contribute a very significant portion of the aerosol loading over southern Africa during the dry austral winter season, from June through October. At present, however, the climatic impact of aerosols over southern Africa is poorly understood, particularly in terms of the interannual variability of these impacts. The regional climate model RegCM3 is used to investigate the climatic impacts of the aerosol burden over southern African further, with particular focus on interannual variability and the role of ENSO. Preliminary results indicate that the impacts of the direct and semi-direct aerosol-effects on regional temperature, precipitation and circulation patterns vary between dry (El-Nino) and wet (La-Nina) years. There is a strong seasonality to these effects, with significant impacts occurring only during the austral winter, when biomass burning peaks throughout the southern Africa

  19. Societal Adaptation to Decadal Climate Variability in the United States

    NASA Astrophysics Data System (ADS)

    Rosenberg, Norman J.; Mehta, Vikram M.; Olsen, J. Rolf; von Storch, Hans; Varady, Robert G.; Hayes, Michael J.; Wilhite, Donald

    2007-10-01

    CRCES Workshop on Societal Impacts of Decadal Climate Variability in the United States, 26-28 April 2007, Waikoloa, Hawaii The search for evidence of decadal climatic variability (DCV) has a very long history. In the past decade, a research community has coalesced around a series of roughly biennial workshops that have emphasized description of past DCV events; their causes and their ``teleconnections'' responsible for droughts, floods, and warm and cold spells around the world; and recently, the predictability of DCV events. Researchers studying climate change put great emphasis on prospective impacts, but the DCV community has yet to do so. To begin rectifying this deficiency, a short but ambitious workshop was convened in Waikoloa, near Kona, Hawaii, from 26-28 April 2007. This workshop, sponsored by the Center for Research on the Changing Earth System (CRCES), NOAA, the U.S. Geological Survey, and the U.S. Army Corps of Engineers, brought together climatologists and sectoral specialists representing agriculture, water resources, economics, the insurance industry, and developing country interests.

  20. Southern African continental climate since the late Pleistocene: Insights from biomarker analyses of Kalahari salt pan sediments

    NASA Astrophysics Data System (ADS)

    Belz, Lukas; Schüller, Irka; Wehrmann, Achim; Wilkes, Heinz

    2016-04-01

    The climate system of sub-tropical southern Africa is mainly controlled by large scale atmospheric and marine circulation processes and, therefore, very sensitive to global climate change. This underlines the importance of paleoenvironmental reconstructions in order to estimate regional implications of current global changes. However, the majority of studies on southern African paleoclimate are based on the investigation of marine sedimentary archives and past climate development especially in continental areas is still poorly understood. This emphasizes the necessity of continental proxy-data from this area. Proxy datasets from local geoarchives especially of the southwestern Kalahari region are still scarce. A main problem is the absence of conventional continental climatic archives, due to the lack of lacustrine systems. In this study we are exploring the utility of sediments from western Kalahari salt pans, i.e. local depressions which are flooded temporarily during rainfall events. An age model based on 14C dating of total organic carbon (TOC) shows evidence that sedimentation predominates over erosional processes with respect to pan formation. Besides the analyses of basic geochemical bulk parameters including TOC, δ13CTOC, total inorganic carbon, δ13CTIC, δ18OTIC, total nitrogen and δ15N, our paleo-climatic approach focuses on reconstruction of local vegetation assemblages to identify changes in the ecosystem. This is pursued using plant biomarkers, particularly leaf wax n-alkanes and n-alcohols and their stable carbon and hydrogen isotopic signatures. Results show prominent shifts in n-alkane and n-alkanol distributions and compound specific carbon isotope values, pointing to changes to a more grass dominated environment during Heinrich Stadial 1 (18.5-14.6 ka BP), while hydrogen isotope values suggest wetter phases during Holocene and LGM. This high variability indicates the local vulnerability to global change.

  1. Seasonal variability and trends in coastal upwelling across the Northwest African coastline, 1981-2012

    NASA Astrophysics Data System (ADS)

    Cropper, T. E.; Hanna, E.; Bigg, G. R.

    2013-12-01

    real by using additional resources such as ocean colour data (SEAWIFS), scatterometer wind speeds (QuickSCAT), bias-adjusted wind measurements (WASWIND) and homogenised wind speeds from near-coastal weather stations. Fisheries landing data suggests a strong upwelling increase but isn't necessarily a pure climate signal. Internal modes of variability (NAO, EA, ENSO, AMO) are shown to weakly correlate with upwelling indices, but cannot explain much of the (summer) variation. We surmise that further warming is necessary for upwelling intensification to be fully realised, although the effects of coastal upwelling (i.e. negative coastal SST trends across certain areas) are already strongly recognized.

  2. Variable use of African American English across two language sampling context.

    PubMed

    Washington, J A; Craig, H K; Kushmaul, A J

    1998-10-01

    This investigation compares the impact of two language sampling elicitation contexts, free play and picture description, on variability in the use of African American English (AAE). Subjects were 65 normally-developing African American 4;4- to 6;3-year-old boys and girls from lower socioeconomic status homes. Comparisons of AAE production in the first 50 C units revealed significant differences by context. Picture descriptions elicited more AAE usage overall, a larger set of AAE types, and took less time. Gender differences in the use of AAE tokens were also apparent, with the boys using significantly more tokens than girls in the free play context. The use of AAE types and tokens was comparable for boys and girls in the picture description context. The advantages of language sampling with pictures to determine dialect usage is discussed.

  3. A distal 145 ka sediment record of Nile discharge and East African monsoon variability

    NASA Astrophysics Data System (ADS)

    Ehrmann, W.; Schmiedl, G.; Seidel, M.; Krüger, S.; Schulz, H.

    2015-09-01

    Clay mineral assemblages in a sediment core from the distal Nile discharge plume off Israel have been used to reconstruct the late Quaternary Nile sediment discharge into the Eastern Mediterranean Sea (EMS). The record spans the last ca. 145 ka. Smectite abundances indicate the influence of the Blue Nile and Atbara that have their headwaters in the volcanic rocks of the Ethiopian highlands. Kaolinite abundances indicate the influence of wadis, which contribute periodically to the suspension load of the Nile. Due to the geographical position, the climate and the sedimentary framework of the EMS is controlled by two climate systems. The long-term climate regime was governed by the African monsoon that caused major humid periods with enhanced sediment discharge at 132 to < 122 ka (AHP 5), 113 to 104 ka (AHP 4), and 86 to 74 ka (AHP 3). They lasted much longer than the formation of the related sapropel layers S5, S4 and S3. During the last glacial period (MIS 4-2) the long-term changes of the monsoonal system were superimposed by millennial-scale changes of an intensified mid-latitude glacial system. This climate regime caused short but pronounced drought periods in the Nile catchment, which are linked to Heinrich Events and alternate with more humid interstadials. The clay mineral record further implies that feedback mechanisms between vegetation cover and sediment discharge of the Nile are detectable but of minor importance for the sedimentary record in the southeastern Mediterranean Sea during the investigated African Humid Periods.

  4. Climate change and climate variability: personal motivation for adaptation and mitigation

    PubMed Central

    2011-01-01

    Background Global climate change impacts on human and natural systems are predicted to be severe, far reaching, and to affect the most physically and economically vulnerable disproportionately. Society can respond to these threats through two strategies: mitigation and adaptation. Industry, commerce, and government play indispensable roles in these actions but so do individuals, if they are receptive to behavior change. We explored whether the health frame can be used as a context to motivate behavioral reductions of greenhouse gas emissions and adaptation measures. Methods In 2008, we conducted a cross-sectional survey in the United States using random digit dialing. Personal relevance of climate change from health threats was explored with the Health Belief Model (HBM) as a conceptual frame and analyzed through logistic regressions and path analysis. Results Of 771 individuals surveyed, 81% (n = 622) acknowledged that climate change was occurring, and were aware of the associated ecologic and human health risks. Respondents reported reduced energy consumption if they believed climate change could affect their way of life (perceived susceptibility), Odds Ratio (OR) = 2.4 (95% Confidence Interval (CI): 1.4 - 4.0), endanger their life (perceived severity), OR = 1.9 (95% CI: 1.1 - 3.1), or saw serious barriers to protecting themselves from climate change, OR = 2.1 (95% CI: 1.2 - 3.5). Perceived susceptibility had the strongest effect on reduced energy consumption, either directly or indirectly via perceived severity. Those that reported having the necessary information to prepare for climate change impacts were more likely to have an emergency kit OR = 2.1 (95% CI: 1.4 - 3.1) or plan, OR = 2.2 (95% CI: 1.5 -3.2) for their household, but also saw serious barriers to protecting themselves from climate change or climate variability, either by having an emergency kit OR = 1.6 (95% CI: 1.1 - 2.4) or an emergency plan OR = 1.5 (95%CI: 1.0 - 2.2). Conclusions Motivation for

  5. Intraseasonal and Interannual Variability of Mars Present Climate

    NASA Astrophysics Data System (ADS)

    Hollingsworth, Jeffery L.; Bridger, Alison F. C.; Haberle, Robert M.

    1996-01-01

    This is a Final Report for a Joint Research Interchange (JRI) between NASA Ames Research Center and San Jose State University, Department of Meteorology. The focus of this JRI has been to investigate the nature of intraseasonal and interannual variability of Mars'present climate. We have applied a three-dimensional climate model based on the full hydrostatic primitive equations to determine the spatial, but primarily, the temporal structures of the planet's large-scale circulation as it evolves during a given seasonal advance, and, over multi-annual cycles. The particular climate model applies simplified physical parameterizations and is computationally efficient. It could thus easily be integrated in a perpetual season or advancing season configuration, as well as over many Mars years. We have assessed both high and low-frequency components of the circulation (i.e., motions having periods of Omicron(2-10 days) or greater than Omicron(10 days), respectively). Results from this investigation have explored the basic issue whether Mars' climate system is naturally 'chaotic' associated with nonlinear interactions of the large-scale circulation-regardless of any allowance for year-to-year variations in external forcing mechanisms. Titles of papers presented at scientific conferences and a manuscript to be submitted to the scientific literature are provided. An overview of a areas for further investigation is also presented.

  6. A toy model of climatic variability with scaling behaviour

    NASA Astrophysics Data System (ADS)

    Koutsoyiannis, Demetris

    2006-05-01

    It is demonstrated that a simple deterministic model in discrete time can reproduce the scaling behaviour of hydroclimatic processes at timescales coarser than annual, a behaviour more widely known in hydrology as the Hurst phenomenon. This toy model is based on a generalised 'chaotic tent map', which may be considered as the compound result of a positive and a negative feedback mechanism, and involves two degrees of freedom. The model is not a realistic representation of a climatic system, but rather a radical simplification of real climatic dynamics. However, its simplicity helps understand the physical mechanisms that cause the scaling behaviour and simultaneously enables easy implementation and convenient experimentation. Application of the toy model gives traces that can resemble historical time series of hydroclimatic variables, such as temperature and river flow. In particular, such traces exhibit scaling behaviour with a Hurst coefficient greater than 0.5 and their statistical properties are similar to that of observed time series. Moreover, application demonstrates that large-scale synthetic 'climatic' fluctuations (like upward or downward trends) can emerge without any specific reason and their evolution is unpredictable, even when they are generated by this simple fully deterministic model with only two degrees of freedom. Thus, the model emphasises the large uncertainty associated with the scaling behaviour, rather than enhances the prediction capability, despite the simple deterministic dynamics it uses, which obviously, are only a caricature of the much more complex dynamics of the real climatic system.

  7. Evaluating environmental flows under climate variability and change

    NASA Astrophysics Data System (ADS)

    Wilby, R.

    2012-04-01

    How much river flow is needed to ensure healthy freshwater ecosystems? This is a question that has exercised environmental managers for decades and one that is being made even harder by the prospect of anthropogenic climate change. The response requires balancing the long-term water demands of society with the needs of the environment in a sustainable and least cost way. Meeting these challenges will require more flexible water management systems and processes that recognise changing environmental limits, incentivise more environmentally-sensitive behaviours by water users and abstractors during times of water scarcity, and a move away from capital intensive, supply-side solutions. This talk evaluates the sensitivity of river flows to decadal variations in rainfall, abstraction amounts, licensing regime, and climate change. The overall objective is to determine how achievable abstraction volumes vary with different e-flow standards and water licensing regimes, under climate variability and change. The River Itchen in southern England has historically experienced unsustainable levels of water abstraction and is used as a test basin. The talk will consider the extent to which a 'smarter' approach to abstraction licensing could ensure that e-flow standards are met despite large uncertainty in the future climate, whilst having a minimal impact on security of water supplies.

  8. European climate variability and human susceptibility over the past 2500 years

    NASA Astrophysics Data System (ADS)

    Buentgen, U.

    2010-09-01

    Climate variations including droughts in the western US and African Sahel, landfalls of Atlantic hurricanes, and shifts in the Asian monsoon have affected human societies throughout history mainly by modulating water supply and agricultural productivity, health risk and civil conflict. Yet, discriminations of environmental impacts from political, economical and technological drivers of societal shifts are may be hampered by the indirect effects of climate on society, but certainly by the paucity of high-resolution palaeoclimatic evidence. Here we present a tree-ring network of 7284 precipitation sensitive oak series from lower elevations in France and Germany, and a compilation of 1546 temperature responsive conifers from higher elevations in the Austrian Alps, both covering the past 2500 years. Temporal distribution of historical felling dates of construction timber refers to changes in settlement activity that mirror different stages of economic wealth. Variations in Central European summer precipitation and temperature are contrasted with societal benchmarks. Prolonged periods of generally wet and warm summers, favourable for cultural prosperity, appeared during the Roman epoch between ~200 BC and 200 AD and from ~700-1000 AD, with the latter facilitating the rapid economic, cultural and political growth of medieval Europe. Unprecedented climate variability from ~200-500 AD coincides with the demise of the Western Roman Empire and the subsequent Barbarian Migrations. This period was characterized by continental-scale political turmoil, cultural stagnation and socio-economic instability including settlement abandonment, population migration, and societal collapse. Driest and coldest summers of the Late Holocene concurred in the 6th century, during which regional consolidation began. The recent political, cultural and fiscal reluctance to adapt to and mitigate projected climate change reflects the common belief of societal insusceptibility to environmental

  9. Impacts of forced and unforced climate variability on extreme floods using a large climate ensemble

    NASA Astrophysics Data System (ADS)

    Martel, Jean-Luc; Brissette, François; Chen, Jie

    2016-04-01

    Frequency analysis has been widely used for the inference of flood magnitude and rainfall intensity required in engineering design. However, this inference is based on the concept of stationarity. How accurate is it when taking into account climate variability (i.e. both internal- and externally-forced variabilities)? Even in the absence of human-induced climate change, the short temporal horizon of the historical records renders this task extremely difficult to accomplish. To overcome this situation, large ensembles of simulations from a single climate model can be used to assess the impact of climate variability on precipitation and streamflow extremes. Thus, the objective of this project is to determine the reliability of return period estimates using the CanESM2 large ensemble. The spring flood annual maxima metric over snowmelt-dominated watersheds was selected to take into account the limits of global circulation models to properly simulate convective precipitation. The GR4J hydrological model coupled with the CemaNeige snow model was selected and calibrated using gridded observation datasets on snowmelt-dominated watersheds in Quebec, Canada. Using the hydrological model, streamflows were simulated using bias corrected precipitation and temperature data from the 50 members of CanESM2. Flood frequency analyses on the spring flood annual maxima were then computed using the Gumbel distribution with a 90% confidence interval. The 20-year return period estimates were then compared to assess the impact of natural climate variability over the 1971-2000 return period. To assess the impact of global warming, this methodology was then repeated for three time slices: reference period (1971-2000), near future (2036-2065) and far future (2071-2100). Over the reference period results indicate that the relative error between the return period estimates of two members can be up to 25%. Regarding the near future and far future periods, natural climate variability of extreme

  10. Mapping the climate: guidance on appropriate techniques to map climate variables and their uncertainty

    NASA Astrophysics Data System (ADS)

    Kaye, N. R.; Hartley, A.; Hemming, D.

    2012-02-01

    Maps are a crucial asset in communicating climate science to a diverse audience, and there is a wealth of software available to analyse and visualise climate information. However, this availability makes it easy to create poor maps as users often lack an underlying cartographic knowledge. Unlike traditional cartography, where many known standards allow maps to be interpreted easily, there is no standard mapping approach used to represent uncertainty (in climate or other information). Consequently, a wide range of techniques have been applied for this purpose, and users may spend unnecessary time trying to understand the mapping approach rather than interpreting the information presented. Furthermore, communicating and visualising uncertainties in climate data and climate change projections, using for example ensemble based approaches, presents additional challenges for mapping that require careful consideration. The aim of this paper is to provide background information and guidance on suitable techniques for mapping climate variables, including uncertainty. We assess a range of existing and novel techniques for mapping variables and uncertainties, comparing "intrinsic" approaches that use colour in much the same way as conventional thematic maps with "extrinsic" approaches that incorporate additional geometry such as points or features. Using cartographic knowledge and lessons learned from mapping in different disciplines we propose the following 6 general mapping guidelines to develop a suitable mapping technique that represents both magnitude and uncertainty in climate data:

    - use a sensible sequential or diverging colour scheme;

    - use appropriate colour symbolism if it is applicable;

    - ensure the map is usable by colour blind people;

    - use a data classification scheme that does not misrepresent the data;

    - use a map

  11. Attributing Sources of Variability in Regional Climate Model Experiments

    NASA Astrophysics Data System (ADS)

    Kaufman, C. G.; Sain, S. R.

    2008-12-01

    Variability in regional climate model (RCM) projections may be due to a number of factors, including the choice of RCM itself, the boundary conditions provided by a driving general circulation model (GCM), and the choice of emission scenario. We describe a new statistical methodology, Gaussian Process ANOVA, which allows us to decompose these sources of variability while also taking account of correlations in the output across space. Our hierarchical Bayesian framework easily allows joint inference about high probability envelopes for the functions, as well as decompositions of total variance that vary over the domain of the functions. These may be used to create maps illustrating the magnitude of each source of variability across the domain of the regional model. We use this method to analyze temperature and precipitation data from the Prudence Project, an RCM intercomparison project in which RCMs were crossed with GCM forcings and scenarios in a designed experiment. This work was funded by the North American Regional Climate Change Assessment Program (NARCCAP).

  12. Plasticity of oxidative metabolism in variable climates: molecular mechanisms.

    PubMed

    Seebacher, Frank; Brand, Martin D; Else, Paul L; Guderley, Helga; Hulbert, Anthony J; Moyes, Christopher D

    2010-01-01

    Converting food to chemical energy (ATP) that is usable by cells is a principal requirement to sustain life. The rate of ATP production has to be sufficient for housekeeping functions, such as protein synthesis and maintaining membrane potentials, as well as for growth and locomotion. Energy metabolism is temperature sensitive, and animals respond to environmental variability at different temporal levels, from within-individual to evolutionary timescales. Here we review principal molecular mechanisms that underlie control of oxidative ATP production in response to climate variability. Nuclear transcription factors and coactivators control expression of mitochondrial proteins and abundance of mitochondria. Fatty acid and phospholipid concentrations of membranes influence the activity of membrane-bound proteins as well as the passive leak of protons across the mitochondrial membrane. Passive proton leak as well as protein-mediated proton leak across the inner mitochondrial membrane determine the efficacy of ATP production but are also instrumental in endothermic heat production and as a defense against reactive oxygen species. Both transcriptional mechanisms and membrane composition interact with environmental temperature and diet, and this interaction between diet and temperature in determining mitochondrial function links the two major environmental variables that are affected by changing climates. The limits to metabolic plasticity could be set by the production of reactive oxygen species leading to cellular damage, limits to substrate availability in mitochondria, and a disproportionally large increase in proton leak over ATP production. PMID:20586603

  13. Understanding Potential Climate Variability Impacts on the Offshore Energy Industry

    NASA Astrophysics Data System (ADS)

    Stear, J.

    2014-12-01

    Climate variability may have important implications for the offshore energy industry. Scenarios of increased storm activity and changes in sea level could require the retrofit of existing offshore platforms and coastal infrastructure, the decommissioning of facilities for which upgrade or relocation is not economically viable, and the development of new methods and equipment which are removed from or less sensitive to environmental loads. Over the past years the energy industry has been actively involved in collaborative research efforts with government and academia to identify the potential changes in the offshore operating environment, and corresponding risk implications. This presentation will review several of these efforts, and for several of the hypothetical climate variation scenarios, review the potential impacts on and possible mitigations for offshore and coastal energy infrastructure and operations.

  14. Functional cereals for production in new and variable climates.

    PubMed

    Henry, Robert J; Rangan, Parimalan; Furtado, Agnelo

    2016-04-01

    Adaptation of cereal crops to variable or changing climates requires that essential quality attributes are maintained to deliver food that will be acceptable to human consumers. Advances in cereal genomics are delivering insights into the molecular basis of nutritional and functional quality traits in cereals and defining new genetic resources. Understanding the influence of the environment on expression of these traits will support the retention of these essential functional properties during climate adaptation. New cereals for use as whole grain or ground to flour for other food products may be based upon the traditional species such as rice and wheat currently used in these food applications but may also include new options exploiting genomics tools to allow accelerated domestication of new species. PMID:26828379

  15. Linking lake variability, climate, and human activity in Basotu, Tanzania.

    NASA Astrophysics Data System (ADS)

    Higgins, Lindsey; Westerberg, Lars-Ove; Risberg, Jan

    2016-04-01

    Lake Basotu (4.3697°S, 35.0728°E) is a crater lake in north-central Tanzania. This lake is an important source of freshwater for local people as no perennial rivers are present. Due to intensive agricultural methods and climatic factors, lake level has fluctuated greatly over time. A history of environmental variability of the past 1800 years was established using the diatom record, magnetic parameters, and carbon content from a three meter long sediment core. Fluctuations in modern lake extent (1973 - 2015) were calculated using archived Landsat images and compared to meteorological records and documents of activity around the lake to determine the greatest impacts and their consequences on this essential water resource. Variations in the paleo-record indicate that fluctuations in lake level are not abnormal, however human influence has likely increased the sensitivity of Lake Basotu to climatic fluctuations.

  16. From precipitation to runoff: Climatic controls on discharge variability

    NASA Astrophysics Data System (ADS)

    Rossi, M. W.; Whipple, K. X.; Vivoni, E. R.

    2012-12-01

    exponential distribution), discharge is often described as a heavy-tailed process (i.e. a power law distribution). Choosing among these two different climate forcings has significant implications for fluvial incision models where only events exceeding a threshold do geomorphic work. While many precipitation records do exhibit approximately exponential distributions, many are better described by more variable stretched exponential distributions with best fit exponents ranging from ~0.5 (heavy-tailed) to ~1.0 (exponential). Moreover, while many discharge records plausibly exhibit power-law behavior, many do not (~70%). By identifying correlations between the stretched exponential and power law exponents, we map the spatial distribution of climate variability in a way that better isolates regional patterns in the precipitation-runoff relationship. To this end, we present two detailed climate transects that exemplify relationships between mean annual runoff and discharge variability, and their relation to rainfall, aridity, and other climate variables. We also present new strategies that make fuller use of hydro-meteorological observations when testing other explanations for the non-linear transformation from precipitation to runoff including the role of the soil water balance (2) and the spatial organization of channel networks (3).

  17. Some results applying flicker-noise spectroscopy on climate variables

    NASA Astrophysics Data System (ADS)

    Casanovas, Alexandre; Gomez, Vicent

    2000-02-01

    Several quality data sets of different climate variables have been analyzed by Timashev's flicker-noise spectroscopy (FNS) methods. The data include Mauna Loa and Barrow ozone concentration, GISP2 and GRIP ice core temperature proxies, Great Salt Lake volume, down-welling longwave irradiation and atmospheric clearness index. The data cover very different time scales ranging from few years to ice-ages. All of them show a coloured spectrum with a negative power f-n dependence on frequency, characteristic of correlations that die out in time and are therefore suitable for applying FNS methods. Results indicate that FNS methods are promising for analysing climate data and that these methods can give more insight into the implied phenomena, if the time series fulfill certain requisites of length and quality. Since the parameters obtained are phenomenological in nature, additional work should be done to connect the phenomenological parameters with model physical parameters.

  18. Information transfer across the scales of climate data variability

    NASA Astrophysics Data System (ADS)

    Palus, Milan; Jajcay, Nikola; Hartman, David; Hlinka, Jaroslav

    2015-04-01

    Multitude of scales characteristic of the climate system variability requires innovative approaches in analysis of instrumental time series. We present a methodology which starts with a wavelet decomposition of a multi-scale signal into quasi-oscillatory modes of a limited band-with, described using their instantaneous phases and amplitudes. Then their statistical associations are tested in order to search for interactions across time scales. In particular, an information-theoretic formulation of the generalized, nonlinear Granger causality is applied together with surrogate data testing methods [1]. The method [2] uncovers causal influence (in the Granger sense) and information transfer from large-scale modes of climate variability with characteristic time scales from years to almost a decade to regional temperature variability on short time scales. In analyses of daily mean surface air temperature from various European locations an information transfer from larger to smaller scales has been observed as the influence of the phase of slow oscillatory phenomena with periods around 7-8 years on amplitudes of the variability characterized by smaller temporal scales from a few months to annual and quasi-biennial scales [3]. In sea surface temperature data from the tropical Pacific area an influence of quasi-oscillatory phenomena with periods around 4-6 years on the variability on and near the annual scale has been observed. This study is supported by the Ministry of Education, Youth and Sports of the Czech Republic within the Program KONTAKT II, Project No. LH14001. [1] M. Palus, M. Vejmelka, Phys. Rev. E 75, 056211 (2007) [2] M. Palus, Entropy 16(10), 5263-5289 (2014) [3] M. Palus, Phys. Rev. Lett. 112, 078702 (2014)

  19. Estimating maritime snow density from seasonal climate variables

    NASA Astrophysics Data System (ADS)

    Bormann, K. J.; Evans, J. P.; Westra, S.; McCabe, M. F.; Painter, T. H.

    2013-12-01

    Snow density is a complex parameter that influences thermal, optical and mechanical snow properties and processes. Depth-integrated properties of snowpacks, including snow density, remain very difficult to obtain remotely. Observations of snow density are therefore limited to in-situ point locations. In maritime snowfields such as those in Australia and in parts of the western US, snow densification rates are enhanced and inter-annual variability is high compared to continental snow regions. In-situ snow observation networks in maritime climates often cannot characterise the variability in snowpack properties at spatial and temporal resolutions required for many modelling and observations-based applications. Regionalised density-time curves are commonly used to approximate snow densities over broad areas. However, these relationships have limited spatial applicability and do not allow for interannual variability in densification rates, which are important in maritime environments. Physically-based density models are relatively complex and rely on empirical algorithms derived from limited observations, which may not represent the variability observed in maritime snow. In this study, seasonal climate factors were used to estimate late season snow densities using multiple linear regressions. Daily snow density estimates were then obtained by projecting linearly to fresh snow densities at the start of the season. When applied spatially, the daily snow density fields compare well to in-situ observations across multiple sites in Australia, and provide a new method for extrapolating existing snow density datasets in maritime snow environments. While the relatively simple algorithm for estimating snow densities has been used in this study to constrain snowmelt rates in a temperature-index model, the estimates may also be used to incorporate variability in snow depth to snow water equivalent conversion.

  20. Land - Ocean Climate Linkages and the Human Evolution - New ICDP and IODP Drilling Initiatives in the East African Rift Valley and SW Indian Ocean

    NASA Astrophysics Data System (ADS)

    Zahn, R.; Feibel, C.; Co-Pis, Icdp/Iodp

    2009-04-01

    The past 5 Ma were marked by systematic shifts towards colder climates and concomitant reorganizations in ocean circulation and marine heat transports. Some of the changes involved plate-tectonic shifts such as the closure of the Panamanian Isthmus and restructuring of the Indonesian archipelago that affected inter-ocean communications and altered the world ocean circulation. These changes induced ocean-atmosphere feedbacks with consequences for climates globally and locally. Two new ICDP and IODP drilling initiatives target these developments from the perspectives of marine and terrestrial palaeoclimatology and the human evolution. The ICDP drilling initiative HSPDP ("Hominid Sites and Paleolakes Drilling Project"; ICDP ref. no. 10/07) targets lacustrine depocentres in Ethiopia (Hadar) and Kenya (West Turkana, Olorgesailie, Magadi) to retrieve sedimentary sequences close to the places and times where various species of hominins lived over currently available outcrop records. The records will provide a spatially resolved record of the East African environmental history in conjunction with climate variability at orbital (Milankovitch) and sub-orbital (ENSO decadal) time scales. HSPDP specifically aims at (1) compiling master chronologies for outcrops around each of the depocentres; (2) assessing which aspects of the paleoenvironmental records are a function of local origin (hydrology, hydrogeology) and which are linked with regional or larger-scale signals; (3) correlating broad-scale patterns of hominin phylogeny with the global beat of climate variability and (4) correlating regional shifts in the hominin fossil and archaeological record with more local patterns of paleoenvironmental change. Ultimately the aim is to test hypotheses that link physical and cultural adaptations in the course of the hominin evolution to local environmental change and variability. The IODP initiative SAFARI ("Southern African Climates, Agulhas Warm Water Transports and Retroflection

  1. Identifying climatic drivers of glacier mass balance variability of Lewis glacier, Mt. Kenya

    NASA Astrophysics Data System (ADS)

    Nicholson, Lindsey; Prinz, Rainer; Kaser, Georg

    2013-04-01

    Lewis Glacier (Kenya, 0°09' S; 37°18' E) has a 20 year historical annual mass balance record, spanning 1979-1996 and 2010-2012. This offers an opportunity to investigate the glacier-climate interactions at ~4800m a.s.l. in the equatorial zone, which in turn allows investigation of the possible tropical mid-tropospheric conditions that must have prevailed in order to permit formerly larger glacier extents on the mountain. Here we use field data of glacier annual mass balance, seasonal glacier surface height changes and monthly precipitation records to test the impact of potential drivers on the glacier variability. We examine relationships between these glaciological data and ERA-interim atmospheric fields, satellite measurements of outgoing long wave radiation and sea surface temperatures. In all years except the mass balance year of 1989 Lewis glacier experiences a negative mass balance. Strongly negative annual mass balances occur only if one or both of the wet seasons fail to bring snowfall to the summit and both annual mass balance and rainy season surface change is well correlated with measured precipitation and enhanced convection within the equatorial rain belt in East Africa and the western Indian Ocean. Seasonal glacier surface height change is correlated with air temperature throughout the whole tropical African zone during the dry months of January and February, but the only positive mass balance year experienced seasonal cold temperature anomalies over equatorial Africa in all seasons. No single season emerges as the dominant driver of the inter-annual mass balance variability, and the climate sensitivity of the glacier surface change differs between seasons. However Lewis Glacier mass balance over the study period can be explained by moisture variability as the primary driver and temperature variability as an additional driver of glacier mass change.

  2. Predicting and attributing recent East African Spring droughts with dynamical-statistical climate model ensembles

    NASA Astrophysics Data System (ADS)

    Funk, C. C.; Shukla, S.; Hoerling, M. P.; Robertson, F. R.; Hoell, A.; Liebmann, B.

    2013-12-01

    During boreal spring, eastern portions of Kenya and Somalia have experienced more frequent droughts since 1999. Given the region's high levels of food insecurity, better predictions of these droughts could provide substantial humanitarian benefits. We show that dynamical-statistical seasonal climate forecasts, based on the latest generation of coupled atmosphere-ocean and uncoupled atmospheric models, effectively predict boreal spring rainfall in this area. Skill sources are assessed by comparing ensembles driven with full-ocean forcing with ensembles driven with ENSO-only sea surface temperatures (SSTs). Our analysis suggests that both ENSO and non-ENSO Indo-Pacific SST forcing have played an important role in the increase in drought frequencies. Over the past 30 years, La Niña drought teleconnections have strengthened, while non-ENSO Indo-Pacific convection patterns have also supported increased (decreased) Western Pacific (East African) rainfall. To further examine the relative contribution of ENSO, low frequency warming and the Pacific Decadal Oscillation, we present decompositions of ECHAM5, GFS, CAM4 and GMAO AMIP simulations. These decompositions suggest that rapid warming in the western Pacific and steeper western-to-central Pacific SST gradients have likely played an important role in the recent intensification of the Walker circulation, and the associated increase in East African aridity. A linear combination of time series describing the Pacific Decadal Oscillation and the strength of Indo-Pacific warming are shown to track East African rainfall reasonably well. The talk concludes with a few thoughts linking the potentially important interplay of attribution and prediction. At least for recent East African droughts, it appears that a characteristic Indo-Pacific SST and precipitation anomaly pattern can be linked statistically to support forecasts and attribution analyses. The combination of traditional AGCM attribution analyses with simple yet

  3. Adaptation strategies to climate change and climate variability: a comparative study between seven contrasting river basins.

    NASA Astrophysics Data System (ADS)

    Droogers, P.

    2003-04-01

    Climate change and climate variability is and will have a tremendous impact on hydrology and consequently on food security and environmental protection. From the four major components in climate change and climate variability studies, projection, mitigation, impact and adaptation, has the latter so far received less attention than the other three. An international collaboration of ten institutions is comparing adaptation strategies between contrasting basins ranging from wet to dry and from poor to rich. Basins included are: Mekong, Walawe (Sri Lanka), Rhine, Sacramento, Syr Darya, Volta, and Zayandeh (Iran). Simulation models at basin and field scale have been set up and possible adaptation strategies are explored by these models. Preliminary results indicate that appropriate adaptation strategies are different between these seven contrasting basins. It is also clear that these adaptation strategies should focus on increased variability rather than on the overall change of the mean. The focus was hereby not only on an increase in variation but especially on the number of successive dry and wet years. Results show that the studies on these adaptation strategies could not be performed only at one scale, but that a combination of field scale as well as basin scale analysis is essential.

  4. Satellite Intercalibration and Evaluation of Climate Trends and Variability

    NASA Astrophysics Data System (ADS)

    Wentz, Frank; Meissner, Thomas; Hilburn, Kyle

    2013-04-01

    A realistic and reliable assessment of climate trends and variability requires long-term, accurate, and homogeneous time series of climate data. Microwave radiometers provide the most accurate remote sensing measurements over the ocean of several essential climate variables crucial for the water cycle, including surface wind speed, vertically integrated water vapor, cloud water, and rain rate. We are approaching the point of having a 30-year long record of Earth observations by microwave radiometers. This long-term record requires the combination of time series measured by several different radiometer designs orbiting on a dozen different satellites, including 6 SSM/I, 3 SSMIS, TMI, AMSR-E, and WindSat. To obtain an accurate and homogeneous data record, the systematic differences due to radiometer design must be taken into account, otherwise biases specific to one satellite or another will introduce artificial shifts in the time series. These shifts can have a huge impact on the results of climate analysis, especially those of climate trend analysis. Satellite intercalibration provides the needed bias-correction and homogenization to ensure accurate time series. We will present our physically-based satellite intercalibration technique and evaluate the long-term trends and variability of the intercalibrated time series. Our technique has been designed to ensure a consistent and traceable calibration starting from raw sensor counts. There are many potential sources of error in sensor calibration, but we have found four primary sources dominate the error budget. First is error in pre-launch determination of the antenna spillover. The spillover is part of the familiar antenna pattern correction, which is the crucial conversion from antenna temperature to brightness temperature. Second is error due to specifying the effective hot load temperature on orbit. The design of the hot load for F16 SSMIS, for example, allows sunlight to enter, either via directly or via a

  5. Testing for Links Between Geomagnetic Field Variability and Climate Change

    NASA Astrophysics Data System (ADS)

    Wetter, L.; Acton, G.; Hill, T.

    2006-12-01

    Although orbital forcing controls much of long-term climate change and increases in greenhouse gases are thought to be driving recent global warming, other factors may also play a significant role. Recent studies have hypothesized various forms of links between climate change and solar irradiance, solar activity, and cosmic ray flux. Because changes in geomagnetic field strength affect the cosmic ray flux, it is possible that changes in the geomagnetic field contribute to long- and short-term climate change. Alternatively, it has been hypothesized that geomagnetic field variability is influenced by climate change or solar activity. We test such claims through a paleomagnetic and stable isotope study of Ocean Drilling Program (ODP) sediment cores from the Blake Outer Ridge (BOR), western North Atlantic Ocean. The goal of the study is to create a continuous, high-resolution record of geomagnetic field variability with an accurate, astronomically tuned chronology. Sediment cored on the BOR in four holes at Site 1061 during ODP Leg 172 is being used for this investigation. The high sedimentation rate, averaging 22 cm/k.y. over the Brunhes, and the exceptional paleomagnetic properties of the area make Site 1061 an excellent candidate to test for links between short- term geomagnetic events and climate. The paleomagnetic record, originally constructed mainly from continuous split-core measurements, is being refined and rock magnetic analyses are being conducted on U- channel samples that span the Brunhes. We have also refined the between-hole correlation and constructed a more detailed composite stratigraphic section for Site 1061 in order to improve the continuity and relative chronology of the record and to confirm the existence of distinct geomagnetic excursions and other short-term events in multiple drill holes. Additionally, planktonic forams are being measured for δ18 O variations across, and extending to one meter beyond each observed excursion, allowing for

  6. Assessment of climate change impacts on climate variables using probabilistic ensemble modeling and trend analysis

    NASA Astrophysics Data System (ADS)

    Safavi, Hamid R.; Sajjadi, Sayed Mahdi; Raghibi, Vahid

    2016-08-01

    Water resources in snow-dependent regions have undergone significant changes due to climate change. Snow measurements in these regions have revealed alarming declines in snowfall over the past few years. The Zayandeh-Rud River in central Iran chiefly depends on winter falls as snow for supplying water from wet regions in high Zagrous Mountains to the downstream, (semi-)arid, low-lying lands. In this study, the historical records (baseline: 1971-2000) of climate variables (temperature and precipitation) in the wet region were chosen to construct a probabilistic ensemble model using 15 GCMs in order to forecast future trends and changes while the Long Ashton Research Station Weather Generator (LARS-WG) was utilized to project climate variables under two A2 and B1 scenarios to a future period (2015-2044). Since future snow water equivalent (SWE) forecasts by GCMs were not available for the study area, an artificial neural network (ANN) was implemented to build a relationship between climate variables and snow water equivalent for the baseline period to estimate future snowfall amounts. As a last step, homogeneity and trend tests were performed to evaluate the robustness of the data series and changes were examined to detect past and future variations. Results indicate different characteristics of the climate variables at upstream stations. A shift is observed in the type of precipitation from snow to rain as well as in its quantities across the subregions. The key role in these shifts and the subsequent side effects such as water losses is played by temperature.

  7. High-Frequency Climate Variability Associated with Stochastic Weather-Climate Interaction

    NASA Astrophysics Data System (ADS)

    Cavanaugh, Nicholas Robert

    The statistics of high-frequency climate variability in observations and reanalyses are markedly non-Gaussian and show coherence across spatiotemporal scales. Dynamically, this complexity comes about as a manifestation of nonlinear terms in the equations of state and motion which dictate the time evolution of geophysical fluids in the oceans and atmosphere. A different perspective is to consider the climate system as consisting of dynamically resolved low-frequency components augmented by unresolved high-frequency components parameterized as stochastic noise. A stochastic formulation such as this is naturally suited toward studying climate variability and uncertainty since all spatiotemporal scales are explicitly or implicitly resolved in its dynamics. The purpose of this dissertation is to examine weather predictability, variability, and uncertainty in the atmosphere as a function of spatiotemporal scale. A particular emphasis is placed on the quantification of the non-Gaussianity observed in surface air temperature (SAT) and precipitation time series at daily resolution and how these distributions scale in space and time. The linear stochastic predictability of the tropical atmosphere is first examined through the use of linear inverse modeling (LIM) techniques. LIM extended-range weather predictions are nearly as skillful as fully nonlinear numerical climate models, suggesting that the tropics at daily timescales behave as a primarily linear dynamical system. Next, the variability and trends of daily SAT are studied using the first four statistical moments. It is shown that daily SAT behaves as an approximately locally homogeneous quasi-Gaussian random field whose statistics are consistent with correlated additive and multiplicative stochastic noise. The probability distributions of SAT at scale are shown to be related to regionally varying correlation length scales in the atmosphere. It is also shown that SAT distributions have undergone significant systematic

  8. Interglacial Climate Variability in the Mid-Latitude North Atlantic

    NASA Astrophysics Data System (ADS)

    Chapman, M. R.; Farmer, E. J.

    2009-04-01

    It is widely believed that the last interglacial period had significantly elevated temperatures relative to the Holocene, and sea levels were around 6m above the modern level due to the partial melting of the Greenland Ice Sheet and the West Antarctic Ice Sheet. A pattern of enhanced peak interglacial warmth is particularly evident in the Arctic region, but these differences are thought to be significant at a wider scale as global mean surface temperatures were raised by around +2°C (Otto-Bliesner et al., 2006). Elevated last interglacial temperatures are likewise evident in the deep ocean. The positive temperature anomalies and changes in ocean circulation patterns have largely been ascribed to differences in the distribution of insolation. In this study we use high resolution records of last interglacial climate to examine the extent of variability in the subpolar North Atlantic, corresponding to the Marine Isotope Stage (MIS) 5e interval. Sea surface temperature (SST) estimates are calculated using a variety of planktonic foraminiferal transfer functions, based on faunal assemblage counts, which together with stable isotope and ice rafted debris (IRD) data are used to reconstruct surface hydrography. Benthic stable isotope data provide stratigraphic control and allow us to assess the relative dominance of northern waters of the North Atlantic Deep Water (NADW) in comparison to southern source waters such as the Antarctic Bottom Water. These records provide a detailed picture of climate variability for the period from 65 to 140 ka (approximately from the end of MIS 6 to early MIS 4). Last Interglacial temperature estimates also are compared to the previous and subsequent periods of interglacial warmth to assess the scale and extent of regional variability within the surface ocean environment. Our results highlight two features of particular interest: the internal variability of the MIS 5e period and the pronounced climate fluctuations during the MIS 5

  9. Farmers' Perceptions of Climate Variability and Factors Influencing Adaptation: Evidence from Anhui and Jiangsu, China

    NASA Astrophysics Data System (ADS)

    Kibue, Grace Wanjiru; Liu, Xiaoyu; Zheng, Jufeng; zhang, Xuhui; Pan, Genxing; Li, Lianqing; Han, Xiaojun

    2016-05-01

    Impacts of climate variability and climate change are on the rise in China posing great threat to agriculture and rural livelihoods. Consequently, China is undertaking research to find solutions of confronting climate change and variability. However, most studies of climate change and variability in China largely fail to address farmers' perceptions of climate variability and adaptation. Yet, without an understanding of farmers' perceptions, strategies are unlikely to be effective. We conducted questionnaire surveys of farmers in two farming regions, Yifeng, Jiangsu and Qinxi, Anhui achieving 280 and 293 responses, respectively. Additionally, we used climatological data to corroborate the farmers' perceptions of climate variability. We found that farmers' were aware of climate variability such that were consistent with climate records. However, perceived impacts of climate variability differed between the two regions and were influenced by farmers' characteristics. In addition, the vast majorities of farmers were yet to make adjustments in their farming practices as a result of numerous challenges. These challenges included socioeconomic and socio-cultural barriers. Results of logit modeling showed that farmers are more likely to adapt to climate variability if contact with extension services, frequency of seeking information, household heads' education, and climate variability perceptions are improved. These results suggest the need for policy makers to understand farmers' perceptions of climate variability and change in order to formulate policies that foster adaptation, and ultimately protect China's agricultural assets.

  10. Farmers' Perceptions of Climate Variability and Factors Influencing Adaptation: Evidence from Anhui and Jiangsu, China.

    PubMed

    Kibue, Grace Wanjiru; Liu, Xiaoyu; Zheng, Jufeng; Zhang, Xuhui; Pan, Genxing; Li, Lianqing; Han, Xiaojun

    2016-05-01

    Impacts of climate variability and climate change are on the rise in China posing great threat to agriculture and rural livelihoods. Consequently, China is undertaking research to find solutions of confronting climate change and variability. However, most studies of climate change and variability in China largely fail to address farmers' perceptions of climate variability and adaptation. Yet, without an understanding of farmers' perceptions, strategies are unlikely to be effective. We conducted questionnaire surveys of farmers in two farming regions, Yifeng, Jiangsu and Qinxi, Anhui achieving 280 and 293 responses, respectively. Additionally, we used climatological data to corroborate the farmers' perceptions of climate variability. We found that farmers' were aware of climate variability such that were consistent with climate records. However, perceived impacts of climate variability differed between the two regions and were influenced by farmers' characteristics. In addition, the vast majorities of farmers were yet to make adjustments in their farming practices as a result of numerous challenges. These challenges included socioeconomic and socio-cultural barriers. Results of logit modeling showed that farmers are more likely to adapt to climate variability if contact with extension services, frequency of seeking information, household heads' education, and climate variability perceptions are improved. These results suggest the need for policy makers to understand farmers' perceptions of climate variability and change in order to formulate policies that foster adaptation, and ultimately protect China's agricultural assets.

  11. Farmers' Perceptions of Climate Variability and Factors Influencing Adaptation: Evidence from Anhui and Jiangsu, China.

    PubMed

    Kibue, Grace Wanjiru; Liu, Xiaoyu; Zheng, Jufeng; Zhang, Xuhui; Pan, Genxing; Li, Lianqing; Han, Xiaojun

    2016-05-01

    Impacts of climate variability and climate change are on the rise in China posing great threat to agriculture and rural livelihoods. Consequently, China is undertaking research to find solutions of confronting climate change and variability. However, most studies of climate change and variability in China largely fail to address farmers' perceptions of climate variability and adaptation. Yet, without an understanding of farmers' perceptions, strategies are unlikely to be effective. We conducted questionnaire surveys of farmers in two farming regions, Yifeng, Jiangsu and Qinxi, Anhui achieving 280 and 293 responses, respectively. Additionally, we used climatological data to corroborate the farmers' perceptions of climate variability. We found that farmers' were aware of climate variability such that were consistent with climate records. However, perceived impacts of climate variability differed between the two regions and were influenced by farmers' characteristics. In addition, the vast majorities of farmers were yet to make adjustments in their farming practices as a result of numerous challenges. These challenges included socioeconomic and socio-cultural barriers. Results of logit modeling showed that farmers are more likely to adapt to climate variability if contact with extension services, frequency of seeking information, household heads' education, and climate variability perceptions are improved. These results suggest the need for policy makers to understand farmers' perceptions of climate variability and change in order to formulate policies that foster adaptation, and ultimately protect China's agricultural assets. PMID:26796698

  12. Bias reduction in decadal predictions of West African monsoon rainfall using regional climate models

    NASA Astrophysics Data System (ADS)

    Paxian, A.; Sein, D.; Panitz, H.-J.; Warscher, M.; Breil, M.; Engel, T.; Tödter, J.; Krause, A.; Cabos Narvaez, W. D.; Fink, A. H.; Ahrens, B.; Kunstmann, H.; Jacob, D.; Paeth, H.

    2016-02-01

    The West African monsoon rainfall is essential for regional food production, and decadal predictions are necessary for policy makers and farmers. However, predictions with global climate models reveal precipitation biases. This study addresses the hypotheses that global prediction biases can be reduced by dynamical downscaling with a multimodel ensemble of three regional climate models (RCMs), a RCM coupled to a global ocean model and a RCM applying more realistic soil initialization and boundary conditions, i.e., aerosols, sea surface temperatures (SSTs), vegetation, and land cover. Numerous RCM predictions have been performed with REMO, COSMO-CLM (CCLM), and Weather Research and Forecasting (WRF) in various versions and for different decades. Global predictions reveal typical positive and negative biases over the Guinea Coast and the Sahel, respectively, related to a southward shifted Intertropical Convergence Zone (ITCZ) and a positive tropical Atlantic SST bias. These rainfall biases are reduced by some regional predictions in the Sahel but aggravated by all RCMs over the Guinea Coast, resulting from the inherited SST bias, increased westerlies and evaporation over the tropical Atlantic and shifted African easterly waves. The coupled regional predictions simulate high-resolution atmosphere-ocean interactions strongly improving the SST bias, the ITCZ shift and the Guinea Coast and Central Sahel precipitation biases. Some added values in rainfall bias are found for more realistic SST and land cover boundary conditions over the Guinea Coast and improved vegetation in the Central Sahel. Thus, the ability of RCMs and improved boundary conditions to reduce rainfall biases for climate impact research depends on the considered West African region.

  13. KZai 02 pollen record, an insight into West African monsoon fluctuations during the Last Climatic Cycle

    NASA Astrophysics Data System (ADS)

    Dalibard, M.; Popescu, S.; Maley, J.; Suc, J.

    2012-12-01

    Climate of the circum-Atlantic intertropical zone is driven by the ocean/atmosphere dynamics in response to variations of yearly insolation. These latitudes correspond to the convergence of the Hadley cells expressed on earth surface by intense trade winds and in lower troposphere by the African easterly jet making the edges of the intertropical zone relatively dry, while humidity is concentrated near the Equator. This phenomenon generates a precipitation front, known as the InterTropical Convergence Zone (ITCZ), the oscillations of which regulate the latitudinal vegetation distribution. Pollen record of core KZai 02 (Guinea Gulf) allows high resolution reconstruction of variations of past ecosystems over Central Africa during the Last Climatic Cycle. Plant taxa recorded in pollen analyses have been clustered according to their ecological requirements and African phytogeography. Fluctuations of these groups inform on precipitation intensity and their distribution during the last 130 ka. During Glacials, an open vegetation made of Cyperaceae marshes developed in the central Zaire/Congo Basin, surrounded by savannah on borders and afromontane forests on reliefs. Composition and distribution of vegetation indicate a decrease in monsoon activity and the strengthening of the precipitation front in the center of the basin. Interglacial phases are characterized by rain forest expansion over Central Africa in response to a precipitation enhancement associated with a northward shift of the rainfall front. Replacement of afromontane forest and marsh ecosystems by savannah then lowland pioneering, warm-temperate and rain forests characterized glacial/interglacial transitions. This succession suggests the increasing influence of at least two climatic parameters: the water availability and temperature and/or CO2 fluctuation. Spectral analysis applied to vegetation groups evidences the forcing of insolation, mainly driven by precession, on the West African monsoon system. Sub

  14. Decadal climatic variability and regional weather simulation: stochastic nature of forest fuel moisture and climatic forcing

    NASA Astrophysics Data System (ADS)

    Tsinko, Y.; Johnson, E. A.; Martin, Y. E.

    2014-12-01

    Natural range of variability of forest fire frequency is of great interest due to the current changing climate and seeming increase in the number of fires. The variability of the annual area burned in Canada has not been stable in the 20th century. Recently, these changes have been linked to large scale climate cycles, such as Pacific Decadal Oscillation (PDO) phases and El Nino Southern Oscillation (ENSO). The positive phase of the PDO was associated with the increased probability of hot dry spells leading to drier fuels and increased area burned. However, so far only one historical timeline was used to assess correlations between the natural climate oscillations and forest fire frequency. To counteract similar problems, weather generators are extensively used in hydrological and agricultural modeling to extend short instrumental record and to synthesize long sequences of daily weather parameters that are different from but statistically similar to historical weather. In the current study synthetic weather models were used to assess effects of alternative weather timelines on fuel moisture in Canada by using Canadian Forest Fire Weather Index moisture codes and potential fire frequency. The variability of fuel moisture codes was found to increase with the increased length of simulated series, thus indicating that the natural range of variability of forest fire frequency may be larger than that calculated from available short records. It may be viewed as a manifestation of a Hurst effect. Since PDO phases are thought to be caused by diverse mechanisms including overturning oceanic circulation, some of the lower frequency signals may be attributed to the long term memory of the oceanic system. Thus, care must be taken when assessing natural variability of climate dependent processes without accounting for potential long-term mechanisms.

  15. Impacts of climate variability and future climate change on harmful algal blooms and human health.

    PubMed

    Moore, Stephanie K; Trainer, Vera L; Mantua, Nathan J; Parker, Micaela S; Laws, Edward A; Backer, Lorraine C; Fleming, Lora E

    2008-11-07

    Anthropogenically-derived increases in atmospheric greenhouse gas concentrations have been implicated in recent climate change, and are projected to substantially impact the climate on a global scale in the future. For marine and freshwater systems, increasing concentrations of greenhouse gases are expected to increase surface temperatures, lower pH, and cause changes to vertical mixing, upwelling, precipitation, and evaporation patterns. The potential consequences of these changes for harmful algal blooms (HABs) have received relatively little attention and are not well understood. Given the apparent increase in HABs around the world and the potential for greater problems as a result of climate change and ocean acidification, substantial research is needed to evaluate the direct and indirect associations between HABs, climate change, ocean acidification, and human health. This research will require a multidisciplinary approach utilizing expertise in climatology, oceanography, biology, epidemiology, and other disciplines. We review the interactions between selected patterns of large-scale climate variability and climate change, oceanic conditions, and harmful algae.

  16. Impacts of climate variability and future climate change on harmful algal blooms and human health

    PubMed Central

    Moore, Stephanie K; Trainer, Vera L; Mantua, Nathan J; Parker, Micaela S; Laws, Edward A; Backer, Lorraine C; Fleming, Lora E

    2008-01-01

    Anthropogenically-derived increases in atmospheric greenhouse gas concentrations have been implicated in recent climate change, and are projected to substantially impact the climate on a global scale in the future. For marine and freshwater systems, increasing concentrations of greenhouse gases are expected to increase surface temperatures, lower pH, and cause changes to vertical mixing, upwelling, precipitation, and evaporation patterns. The potential consequences of these changes for harmful algal blooms (HABs) have received relatively little attention and are not well understood. Given the apparent increase in HABs around the world and the potential for greater problems as a result of climate change and ocean acidification, substantial research is needed to evaluate the direct and indirect associations between HABs, climate change, ocean acidification, and human health. This research will require a multidisciplinary approach utilizing expertise in climatology, oceanography, biology, epidemiology, and other disciplines. We review the interactions between selected patterns of large-scale climate variability and climate change, oceanic conditions, and harmful algae. PMID:19025675

  17. On the role of climate variability on tropospheric ozone

    NASA Astrophysics Data System (ADS)

    Lin, M.

    2014-12-01

    The response of tropospheric ozone to changing atmospheric circulation is poorly understood owing to a lack of reliable long-term observations. There is great current interest in quantifying the extent to which observed ozone trends over recent decades at northern mid-latitude sites are driven by changes in precursor emissions versus shifts in atmospheric circulation patterns. In this talk, I present a detailed analysis of the impact of interannual to decadal climate variability on tropospheric ozone, based on observations and a suite of chemistry-climate model hindcast simulations. Decadal shifts in circulation regimes modulate long-range transport of Asian pollution, leading to very different seasonal ozone trends at Mauna Loa Observatory in the subtropical Pacific Ocean. During autumn, the flow of ozone-rich air from Eurasia towards Hawaii strengthened in the mid-1990s onwards, as a result of the positive phase of the Pacific North American pattern, increasing ozone at Mauna Loa. During spring, weakening airflow from Asia in the 2000s, tied to La-Niña-like decadal cooling in the equatorial Pacific Ocean, offsets ozone increases at Mauna Loa that otherwise would have occurred due to rising Asian emissions. The circulation-driven variability in Asian pollution over the subtropical North Pacific regions manifests mainly as changes in the mean as opposed to in transport events. At high-elevation Western U.S. sites, intrusions of stratospheric ozone deep into the troposphere during spring exert a greater influence than Asian pollution, particularly on the high tail of observed surface ozone distribution. We show that year-to-year variability in springtime high-ozone episodes measured in Western U.S. surface air is tied to known modes of climate variability, which modulate meanders in the polar frontal jet conducive to deep stratospheric ozone intrusions. Specifically, the La Niña-related increase in the frequency of deep stratospheric intrusion events plays a

  18. Multidecadal climate variability of global lands and oceans

    USGS Publications Warehouse

    McCabe, G.J.; Palecki, M.A.

    2006-01-01

    Principal components analysis (PCA) and singular value decomposition (SVD) are used to identify the primary modes of decadal and multidecadal variability in annual global Palmer Drought Severity Index (PDSI) values and sea-surface temperature (SSTs). The PDSI and SST data for 1925-2003 were detrended and smoothed (with a 10-year moving average) to isolate the decadal and multidecadal variability. The first two principal components (PCs) of the PDSI PCA explained almost 38% of the decadal and multidecadal variance in the detrended and smoothed global annual PDSI data. The first two PCs of detrended and smoothed global annual SSTs explained nearly 56% of the decadal variability in global SSTs. The PDSI PCs and the SST PCs are directly correlated in a pairwise fashion. The first PDSI and SST PCs reflect variability of the detrended and smoothed annual Pacific Decadal Oscillation (PDO), as well as detrended and smoothed annual Indian Ocean SSTs. The second set of PCs is strongly associated with the Atlantic Multidecadal Oscillation (AMO). The SVD analysis of the cross-covariance of the PDSI and SST data confirmed the close link between the PDSI and SST modes of decadal and multidecadal variation and provided a verification of the PCA results. These findings indicate that the major modes of multidecadal variations in SSTs and land-surface climate conditions are highly interrelated through a small number of spatially complex but slowly varying teleconnections. Therefore, these relations may be adaptable to providing improved baseline conditions for seasonal climate forecasting. Published in 2006 by John Wiley & Sons, Ltd.

  19. Climate and species richness predict the phylogenetic structure of African mammal communities.

    PubMed

    Kamilar, Jason M; Beaudrot, Lydia; Reed, Kaye E

    2015-01-01

    We have little knowledge of how climatic variation (and by proxy, habitat variation) influences the phylogenetic structure of tropical communities. Here, we quantified the phylogenetic structure of mammal communities in Africa to investigate how community structure varies with respect to climate and species richness variation across the continent. In addition, we investigated how phylogenetic patterns vary across carnivores, primates, and ungulates. We predicted that climate would differentially affect the structure of communities from different clades due to between-clade biological variation. We examined 203 communities using two metrics, the net relatedness (NRI) and nearest taxon (NTI) indices. We used simultaneous autoregressive models to predict community phylogenetic structure from climate variables and species richness. We found that most individual communities exhibited a phylogenetic structure consistent with a null model, but both climate and species richness significantly predicted variation in community phylogenetic metrics. Using NTI, species rich communities were composed of more distantly related taxa for all mammal communities, as well as for communities of carnivorans or ungulates. Temperature seasonality predicted the phylogenetic structure of mammal, carnivoran, and ungulate communities, and annual rainfall predicted primate community structure. Additional climate variables related to temperature and rainfall also predicted the phylogenetic structure of ungulate communities. We suggest that both past interspecific competition and habitat filtering have shaped variation in tropical mammal communities. The significant effect of climatic factors on community structure has important implications for the diversity of mammal communities given current models of future climate change.

  20. Climate and Species Richness Predict the Phylogenetic Structure of African Mammal Communities

    PubMed Central

    Kamilar, Jason M.; Beaudrot, Lydia; Reed, Kaye E.

    2015-01-01

    We have little knowledge of how climatic variation (and by proxy, habitat variation) influences the phylogenetic structure of tropical communities. Here, we quantified the phylogenetic structure of mammal communities in Africa to investigate how community structure varies with respect to climate and species richness variation across the continent. In addition, we investigated how phylogenetic patterns vary across carnivores, primates, and ungulates. We predicted that climate would differentially affect the structure of communities from different clades due to between-clade biological variation. We examined 203 communities using two metrics, the net relatedness (NRI) and nearest taxon (NTI) indices. We used simultaneous autoregressive models to predict community phylogenetic structure from climate variables and species richness. We found that most individual communities exhibited a phylogenetic structure consistent with a null model, but both climate and species richness significantly predicted variation in community phylogenetic metrics. Using NTI, species rich communities were composed of more distantly related taxa for all mammal communities, as well as for communities of carnivorans or ungulates. Temperature seasonality predicted the phylogenetic structure of mammal, carnivoran, and ungulate communities, and annual rainfall predicted primate community structure. Additional climate variables related to temperature and rainfall also predicted the phylogenetic structure of ungulate communities. We suggest that both past interspecific competition and habitat filtering have shaped variation in tropical mammal communities. The significant effect of climatic factors on community structure has important implications for the diversity of mammal communities given current models of future climate change. PMID:25875361

  1. Changes in the variability of extreme climate events in Latvia

    NASA Astrophysics Data System (ADS)

    Avotniece, Zanita; Lizuma, Lita; Briede, Agrita; Klavins, Maris

    2015-04-01

    Recent changes in the mean values of surface air temperature and precipitation have led to significant local changes in hazardous and extreme events in many parts of the world, including the Northern Europe and Latvia. The observed trends in the changes of such extreme climate events indicate that extremes associated with high temperatures and precipitation are becoming more frequent in Latvia, however not much is known about the changes in variability of these extreme events. This study investigated the long-term trends and variability of extreme temperature and precipitation events as defined by the ECA&D in 10 meteorological observation stations in Latvia over the period 1925-2012. In order to detect and study the changes in variability and anomalies of extreme events, a comparison of three different time scales was performed: 1931-1960, 1961-1990,1981-2010. The results of the analysis revealed steady changes in some extremes while others have experienced a significant change in variability in the most recent 30-year period. Due to the specifics in the spatial distribution of extreme events, the results show differences in the behaviour of extreme events over the country.

  2. Decadal-Interdecadal SST Variability and Regional Climate Teleconnections

    NASA Technical Reports Server (NTRS)

    Lau, William K. M.; Weng, H.; Einaudi, Franco (Technical Monitor)

    2001-01-01

    Dominant modes of decadal and interdecadal SST variability and their impacts on summertime rainfall variability over East Asia and the North America are studied. Two dominant modes of interdecadal SST variability, one associated with El Nino-like warming in the global oceans and one with an east-west seesaw variation in the equatorial Pacific have been identified. The first mode is associated in part with a long-term warming trend in the topical oceans and cooling over the northern Pacific. The second mode suggests an westward shift and strengthening of the Walker circulation from 1960s to the 1980s. Over East Asian, the first SST mode is correlated with reduced rainfall in northern China and excessive rainfall in central China. This SST mode is also associated with the tendency for increased rainfall over the midwest region, and reduced rainfall over the east Coast of the US. The results suggest a teleconnection pattern which links the occurrences of drought and floods over the Asian monsoon and the US summertime time climate. This teleconnection is likely to be associated with decadal variability of the East Asian jetstream, which are affected by strong land surface heating over the Siberian region, as well as El Nino-like SST forcings. The occurrences of major droughts and floods in the East Asian and US continent in recent decades are discussed in light of the above teleconnection patterns.

  3. Climate variability and wildfire risk and occurrence in northern Spain

    NASA Astrophysics Data System (ADS)

    Garcia Codron, J. C.; Rasilla, D.; Diego, C.; Carracedo, V.

    2009-04-01

    In spite of their reputation of wetness, wildfires are a frequent event in Cantabria (Northern Spain), but their seasonality does not match the typical warm season maximum generalized in most of the Iberian Peninsula. They occur at the end of the winter and the beginning of the spring (January to March), being mostly anthropogenically triggered due to the necessity of preparing pastures in the uplands. However, catastrophic episodes of generalized burning are controlled by different atmospheric mechanisms, namely the occurrence of "Suradas", a downslope windstorms which combines high winds speeds and low humidities, and long periods of drought in late fall and winter. This contribution analyzes long term trends (1961 onwards) of several climatic variables during the highest wildfire risk period in order to assess to what extent the occurrence of wildfires may be linked to the recent climatic variability. Raw meteorological values of temperature, humidity, wind speed and precipitation are transformed into a well-known meteorological fire weather index, the Canadian Forest Fire Index (FWI). Besides, monthly values of the Palmer Drought Severity Index we used to assess the spatial and temporal magnitude and intensity of droughts. Our results show that the regional climate has become warmer and drier, due to the combined effects of increases in temperatures, sunshine duration, and the decrease in relative humidity and precipitation, variables that are likely to play an important role in drought. Unknown in the 60s, 70s and most of the 80s, drought has become a relatively frequent phenomenon during the last two decades, and, in fact, the two most extreme episodes of drought at century scale, during 1989-1990 and 1993, occur in the 90. However, both the frequency and the intensity of "Suradas" have reduced, and consequently, the high fire risk episodes are now less frequent, but their absolute maximum values remain unchanged. Those regional climate trends are strongly

  4. Arctic climate response to the termination of the African Humid Period

    NASA Astrophysics Data System (ADS)

    Muschitiello, Francesco; Zhang, Qiong; Sundqvist, Hanna S.; Davies, Frazer J.; Renssen, Hans

    2015-10-01

    The Earth's climate response to the rapid vegetation collapse at the termination of the African Humid Period (AHP) (5.5-5.0 kyr BP) is still lacking a comprehensive investigation. Here we discuss the sensitivity of mid-Holocene Arctic climate to changes in albedo brought by a rapid desertification of the Sahara. By comparing a network of surface temperature reconstructions with output from a coupled global climate model, we find that, through a system of land-atmosphere feedbacks, the end of the AHP reduced the atmospheric and oceanic poleward heat transport from tropical to high northern latitudes. This entails a general weakening of the mid-latitude Westerlies, which results in a shift towards cooling over the Arctic and North Atlantic regions, and a change from positive to negative Arctic Oscillation-like conditions. This mechanism would explain the sign of rapid hydro-climatic perturbations recorded in several reconstructions from high northern latitudes at 5.5-5.0 kyr BP, suggesting that these regions are sensitive to changes in Saharan land cover during the present interglacial. This is central in the debate surrounding Arctic climate amplification and future projections for subtropical precipitation changes.

  5. Saharan dust, climate variability, and asthma in Grenada, the Caribbean.

    PubMed

    Akpinar-Elci, Muge; Martin, Francis E; Behr, Joshua G; Diaz, Rafael

    2015-11-01

    Saharan dust is transported across the Atlantic and interacts with the Caribbean seasonal climatic conditions, becoming respirable and contributing to asthma presentments at the emergency department. This study investigated the relationships among dust, climatic variables, and asthma-related visits to the emergency room in Grenada. All asthma visits to the emergency room (n = 4411) over 5 years (2001-2005) were compared to the dust cover and climatic variables for the corresponding period. Variation in asthma was associated with change in dust concentration (R(2) = 0.036, p < 0.001), asthma was positively correlated with rainfall (R(2) = 0.055, p < 0.001), and rainfall was correlated with dust (R(2) = 0.070, p = 0.003). Despite the similarities and the short distance between Trinidad, Barbados, and Grenada, they have markedly different geographies, cultures, population sizes, industrialization level, and economies. Therefore, different than from the studies in Trinidad and Barbados, Grenada is a non-industrialized low-income small island without major industrialized air pollution addition; asthma visits were inversely related to mean sea level pressure (R(2) = 0.123, p = 0.006) and positively correlated with relative humidity (R(2) = 0.593, p = 0.85). Saharan dust in conjunction with seasonal humidity allows for inhalable particulate matter that exacerbates asthma among residents in the Caribbean island of Grenada. These findings contribute evidence suggesting a broader public health impact from Saharan dust. Thus, this research may inform strategic planning of resource allocation among the Caribbean public health agencies.

  6. Precipitation variability and the sugarcane climate demand in Brazil

    NASA Astrophysics Data System (ADS)

    Pereira, V. R.; de Avila, A. M. H.; Blain, G.; Zullo, J., Jr.

    2014-12-01

    This study presents the precipitation variability in São Paulo state/Brazil considering the climate demand for high sugarcane productivity. The Brazilian sugarcane and the bioethanol chain are facing an increase demand in response of the biofuel industry expansion. The productivity improvement is the key point to face the challenges about the land expansion in the Brazilian agriculture. The sugarcane phenology is climate dependent even being efficient in the decarboxylation process. The sprouting, growing, yield and the sugar content are determined by the climate. The accumulated rainy days during the pre harvest or more than 180 days of dry period can reduce the sugar content during the maturation process. Daily rainfall time series for the period 1960-2003 from 210 rain gauges at São Paulo state - the major Brazilian producer - are used. We subset the time series in the annual, seasonal, ten-day totals and dry and wet spells analysis. We used the mann- kendall non-parametric test to calculate the trends. The annual, the seasonal totals and the dry and wet spells did not showed a significant change in time. However, the ten-day total analysis in the beginning of the rainy season - i.e. in October - showed an interesting changing pattern - 24% of gauges showed a significant negative trend (p_value<0.1). These gauges are located in specific regions with the highest sugarcane production. Also, the October totals showed significant and negative trends (p_value<0.1) for more than 95% of precipitation gauges. These results are strongly indicating a longer dry season in the last twenty years. These changes in the precipitation variability can be related with the instability of the sugarcane market in Brazil in the last years.

  7. Saharan dust, climate variability, and asthma in Grenada, the Caribbean

    NASA Astrophysics Data System (ADS)

    Akpinar-Elci, Muge; Martin, Francis E.; Behr, Joshua G.; Diaz, Rafael

    2015-11-01

    Saharan dust is transported across the Atlantic and interacts with the Caribbean seasonal climatic conditions, becoming respirable and contributing to asthma presentments at the emergency department. This study investigated the relationships among dust, climatic variables, and asthma-related visits to the emergency room in Grenada. All asthma visits to the emergency room ( n = 4411) over 5 years (2001-2005) were compared to the dust cover and climatic variables for the corresponding period. Variation in asthma was associated with change in dust concentration ( R 2 = 0.036, p < 0.001), asthma was positively correlated with rainfall ( R 2 = 0.055, p < 0.001), and rainfall was correlated with dust ( R 2 = 0.070, p = 0.003). Despite the similarities and the short distance between Trinidad, Barbados, and Grenada, they have markedly different geographies, cultures, population sizes, industrialization level, and economies. Therefore, different than from the studies in Trinidad and Barbados, Grenada is a non-industrialized low-income small island without major industrialized air pollution addition; asthma visits were inversely related to mean sea level pressure ( R 2 = 0.123, p = 0.006) and positively correlated with relative humidity ( R 2 = 0.593, p = 0.85). Saharan dust in conjunction with seasonal humidity allows for inhalable particulate matter that exacerbates asthma among residents in the Caribbean island of Grenada. These findings contribute evidence suggesting a broader public health impact from Saharan dust. Thus, this research may inform strategic planning of resource allocation among the Caribbean public health agencies.

  8. Saharan dust, climate variability, and asthma in Grenada, the Caribbean.

    PubMed

    Akpinar-Elci, Muge; Martin, Francis E; Behr, Joshua G; Diaz, Rafael

    2015-11-01

    Saharan dust is transported across the Atlantic and interacts with the Caribbean seasonal climatic conditions, becoming respirable and contributing to asthma presentments at the emergency department. This study investigated the relationships among dust, climatic variables, and asthma-related visits to the emergency room in Grenada. All asthma visits to the emergency room (n = 4411) over 5 years (2001-2005) were compared to the dust cover and climatic variables for the corresponding period. Variation in asthma was associated with change in dust concentration (R(2) = 0.036, p < 0.001), asthma was positively correlated with rainfall (R(2) = 0.055, p < 0.001), and rainfall was correlated with dust (R(2) = 0.070, p = 0.003). Despite the similarities and the short distance between Trinidad, Barbados, and Grenada, they have markedly different geographies, cultures, population sizes, industrialization level, and economies. Therefore, different than from the studies in Trinidad and Barbados, Grenada is a non-industrialized low-income small island without major industrialized air pollution addition; asthma visits were inversely related to mean sea level pressure (R(2) = 0.123, p = 0.006) and positively correlated with relative humidity (R(2) = 0.593, p = 0.85). Saharan dust in conjunction with seasonal humidity allows for inhalable particulate matter that exacerbates asthma among residents in the Caribbean island of Grenada. These findings contribute evidence suggesting a broader public health impact from Saharan dust. Thus, this research may inform strategic planning of resource allocation among the Caribbean public health agencies. PMID:25707919

  9. Influence of climate model variability on projected Arctic shipping futures

    NASA Astrophysics Data System (ADS)

    Stephenson, Scott R.; Smith, Laurence C.

    2015-11-01

    Though climate models exhibit broadly similar agreement on key long-term trends, they have significant temporal and spatial differences due to intermodel variability. Such variability should be considered when using climate models to project the future marine Arctic. Here we present multiple scenarios of 21st-century Arctic marine access as driven by sea ice output from 10 CMIP5 models known to represent well the historical trend and climatology of Arctic sea ice. Optimal vessel transits from North America and Europe to the Bering Strait are estimated for two periods representing early-century (2011-2035) and mid-century (2036-2060) conditions under two forcing scenarios (RCP 4.5/8.5), assuming Polar Class 6 and open-water vessels with medium and no ice-breaking capability, respectively. Results illustrate that projected shipping viability of the Northern Sea Route (NSR) and Northwest Passage (NWP) depends critically on model choice. The eastern Arctic will remain the most reliably accessible marine space for trans-Arctic shipping by mid-century, while outcomes for the NWP are particularly model-dependent. Omitting three models (GFDL-CM3, MIROC-ESM-CHEM, and MPI-ESM-MR), our results would indicate minimal NWP potential even for routes from North America. Furthermore, the relative importance of the NSR will diminish over time as the number of viable central Arctic routes increases gradually toward mid-century. Compared to vessel class, climate forcing plays a minor role. These findings reveal the importance of model choice in devising projections for strategic planning by governments, environmental agencies, and the global maritime industry.

  10. Enhanced blood pressure variability in a high cardiovascular risk group of African Americans: FIT4Life Study.

    PubMed

    Veerabhadrappa, Praveen; Diaz, Keith M; Feairheller, Deborah L; Sturgeon, Kathleen M; Williamson, Sheara; Crabbe, Deborah L; Kashem, Abul; Ahrensfield, Debra; Brown, Michael D

    2010-01-01

    High blood pressure (BP) levels in African Americans elicit vascular inflammation resulting in vascular remodeling. BP variability (BPV) correlates with target organ damage. We aimed to investigate the relationship between inflammatory markers and BPV in African Americans. Thirty-six African Americans underwent 24-hour ambulatory BP monitoring (ABPM). BPV was calculated using the average real variability index. Fasting blood samples were assayed for high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-alpha (TNF-alpha), and white blood cell (WBC) count. Significant associations between hs-CRP and 24-hour systolic variability (r=0.50; P=.012) and awake systolic variability (r=0.45; P=.02) were identified after adjusting for age, body mass index, and 24-hour mean BP. ABPM variables were compared between the hs-CRP tertile groups. In post-hoc analysis, there was a significant difference in 24-hour and awake periods for both systolic and diastolic variability among the groups. TNF-alpha and WBC count showed no associations with ABPM variables. hs-CRP was associated with systolic variability, and higher levels of hs-CRP were related with greater BPV. Higher inflammatory status influences wider fluctuations in systolic BP, which in turn could facilitate early progression to target organ damage independent of absolute BP levels in African Americans.

  11. On how climate variability influences regional sea level change

    NASA Astrophysics Data System (ADS)

    Brunnabend, Sandra-Esther; Kusche, Jürgen; Rietbroek, Roelof; Forootan, Ehsan

    2016-04-01

    Regional trends in sea level change are strongly influenced by climate variations, such as ENSO (El-Nino Southern Oscillation), the IOD (Indian Ocean Dipole), or the PDO (Pacific Decadal Oscillation). Hence, before computing long term regional sea level change, these sea level variations need to be taken into account as they lead to strong dependencies of computed regional sea level trends on the time period of the investigation. In this study, sea level change during the years 1993 to 2013 is analysed to identify the dominant modes of sea level change caused by climate variations. Here, two different gridded altimetry products are analysed, namely ESA's combined CCI SeaLevel v1.1 ECV product (doi: 10.5270/esa-sea_level_cci-1993_2013-v_1.1-201412), and absolute dynamic topography produced by Ssalto/Duacs and distributed by Aviso, with support from Cnes (http://www.aviso.altimetry.fr/duacs/). Reconstructions using the different decomposition techniques including the standard principle component analysis (PCA), rotated empirical orthogonal functions (REOF) and independent component analysis (ICA) method are analysed. They are compared with sea level change modelled with the global finite-element sea-ice ocean model (FESOM). The results indicate that from the applied methods, ICA is most suitable to separate the individual climate variability signals in independent modes of sea level change. This especially holds for extracting the ENSO contribution in sea level changes, which was better separated by applying ICA, from both altimetry and modelled sea level products. In addition, it is presented how modelled sea level change reflects climate variations compared to that identified in the altimetry products.

  12. Stratospheric variability of wave activity and parameters in equatorial coastal and tropical sites during the West African monsoon

    NASA Astrophysics Data System (ADS)

    Kafando, P.; Chane-Ming, F.; Petitdidier, M.

    2015-08-01

    Recent numerical studies in stratospheric dynamics and its variability as well as climate, have highlighted the need of more observational analyses to improve simulation of the West African monsoon (WAM). In this paper, activity and spectral characteristics of short-scale vertical waves (wavelengths <4 km) are analysed in equatorial coastal and tropical lower stratosphere during the WAM. A first detailed description of such waves over West Africa is derived from high-resolution vertical profiles of temperature and horizontal wind obtained during Intensive Observation Period of the African Monsoon Multidisciplinary Analyses (AMMA) Campaign 2006. Monthly variation of wave energy density is revealed to trace the progression of the inter-tropical convergence zone (ITCZ) over West Africa. Mesoscale inertia gravity-waves structures with vertical and horizontal wavelengths of 1.5-2.5 and 400-1100 km respectively and intrinsic frequencies of 1.1-2.2 f or periods <2 days are observed in the tropical LS with intense activity during July and August when the WAM is installed over the tropical West Africa. Over equatorial region, gravity waves with intrinsic frequencies of 1.4-4 f or periods <5.2 days, vertical wavelength of 2.1 km and long horizontal wavelengths of 1300 km are intense during the WAM coastal phase. From July to October, gravity waves with intrinsic frequencies of 1.2-3.8 f or periods <6 days, vertical wavelength of 2.1 km and horizontal wavelengths of 1650 km are less intense during the WAM Sahelian phase of the WAM, March-June. Unlike potential energy density, kinetic energy density is observed to be a good proxy for the activity of short-scale vertical waves during the WAM because quasi-inertial waves are dominant. Long-term wave activity variation from January 2001 to December 2009, highlights strong year-to-year variation superimposed on convective activity and quasi-biennial oscillation-like variations especially above tropical stations.

  13. Climate change sensitivity of the African ivory nut palm, Hyphaene petersiana Klotzsch ex Mart. (Arecaceae) - a keystone species in SE Africa

    NASA Astrophysics Data System (ADS)

    Blach-Overgaard, A.; Svenning, J.-C.; Balslev, H.

    2009-11-01

    Africa is the most vulnerable continent to future climate change. Profound changes are projected for southwestern Africa with increased drying, notably with delayed onset of the rainy season in September-November, and temperature increases in all seasons. The projected climate changes combined with land-use changes are thought to constitute the main threats to biodiversity in the 21st century. To be able to predict the potential impact on biodiversity, it is crucial to achieve a better insight into the controls of contemporary species ranges. Using species distribution modeling, we assessed the climate sensitivity of the key-stone palm species Hyphaene petersiana (African ivory nut palm) in southern Africa. We tested the relative roles of climate vs. non-climatic range-controls and found that climate had a clear effect on the range of H. petersiana and that especially water-related variables (annual precipitation and precipitation driest quarter) were of high importance. Nevertheless, latitude was the overall most dominant variable, reflecting spatial constraints on the continental-scale distribution. Of the remaining non-climatic factors, soil type and human influence were as important as the climatic factors. A future decrease in annual precipitation below 400 mm and hydrological changes towards drier conditions could cause a dramatic decline in H. petersiana populations, while the influence of temperature changes is less clear. The ongoing, unsustainable utilization pressures on this palm species by humans and livestock are likely to exacerbate the negative effect of future climate changes on its populations, especially, given the expected human population increase in Africa.

  14. Influences of Social and Style Variables on Adult Usage of African American English Features

    PubMed Central

    Craig, Holly K.; Grogger, Jeffrey T.

    2013-01-01

    Purpose In this study, the authors examined the influences of selected social (gender, employment status, educational achievement level) and style variables (race of examiner, interview topic) on the production of African American English (AAE) by adults. Method Participants were 50 African American men and women, ages 20–30 years. The authors used Rapid and Anonymous Survey (RAS) methods to collect responses to questions on informal situational and formal message-oriented topics in a short interview with an unacquainted interlocutor. Results Results revealed strong systematic effects for academic achievement, but not gender or employment status. Most features were used less frequently by participants with higher educational levels, but sharp declines in the usage of 5 specific features distinguished the participants differing in educational achievement. Strong systematic style effects were found for the 2 types of questions, but not race of addressee. The features that were most commonly used across participants—copula absence, variable subject–verb agreement, and appositive pronouns—were also the features that showed the greatest style shifting. Conclusions The findings lay a foundation with mature speakers for rate-based and feature inventory methods recently shown to be informative for the study of child AAE and demonstrate the benefits of the RAS. PMID:22361105

  15. Streamflow projections for a Southwestern river: Climate change and climate variability

    NASA Astrophysics Data System (ADS)

    Gutzler, D. S.

    2013-12-01

    Climate projections for flows in the upper Gila River in southwestern New Mexico are assessed. The State of New Mexico is currently considering proposals for new consumptive uses of water extracted from the Gila, pursuant to a recent interstate stream settlement. Among the factors being considered is the prospect of decreasing flow in this snow-fed river associated with projected 21st Century climate change. Southwestern North America already exhibits a sustained and pronounced trend toward warmer temperature. Policymakers requested a projection for the next several decades as input to their ongoing deliberations over new extractions from the river. For lead times of several decades the predictability derived from current climatic conditions, the source of most prediction skill for seasonal forecasts, is minimal. On the other hand, the magnitude of the signal of greenhouse-gas forced long-term climate change in streamflow, driven largely by temperature change, is modest compared to the large natural decadal variability of flow. The upper Gila is known to exhibit tremendous decadal variability, driven largely by precipitation, as seen in a century of instrumental gage data and from a much longer dendrochronological reconstruction of flow. We have compared dynamical projections of flow in the upper Gila generated by the Bureau of Reclamation's West-Wide Climate Risk Assessment, with a statistical projection derived from a regression of observed precipitation and temperature onto historical flows. The latter approach assumes statistical stationarity. We show that the stationarity assumption will be violated by mid-century but is defensible on the time scale of interest set by policymakers. These two approaches yield consistent projections of 5-10% average decline in flow on the upper Gila for the period 2021-2050, if -- and only if -- a long historical period is chosen to represent baseline "average" flow. An averaging period much longer than the 30 year "climate

  16. Comparing impacts of climate change on streamflow in four large African river basins

    NASA Astrophysics Data System (ADS)

    Aich, V.; Liersch, S.; Vetter, T.; Huang, S.; Tecklenburg, J.; Hoffmann, P.; Koch, H.; Fournet, S.; Krysanova, V.; Müller, E. N.; Hattermann, F. F.

    2013-11-01

    This study aims to compare impacts of climate change on streamflow in four large representative African river basins: the Niger, the Upper Blue Nile, the Ubangi and the Limpopo. We set up the eco-hydrological model SWIM (Soil and Water Integrated Model) for all four basins individually. The validation of the models for four basins shows results from adequate to very good, depending on the quality and availability of input (observed climate, soils, land use, water management) and calibration (discharge) data. For the climate impact assessment we drive the model with outputs of five bias-corrected Earth System Models of Coupled Model Intercomparison Project Phase 5 (CMIP5) for the Representative Concentration Pathways (RCPs) 2.6 and 8.5. This climate input is put into the context of climate trends of the whole African continent and compared to a CMIP5 ensemble of 19 models in order to test their representativeness. Subsequently, we compare the trends in mean discharges, seasonality and hydrological extremes in the 21st century. The uncertainty of results for all basins is high, mainly due to the climate input. Still, climate change impact is clearly visible for mean discharges but also for extremes in high and low flows. The uncertainty of the projections is the lowest in the Upper Blue Nile, where an increase in streamflow is most likely. In the Niger and the Limpopo Basins, the magnitude of trends in both directions is high and has a wide range of uncertainty. In the Ubangi, impacts are the least significant. Our results confirm partly the findings of previous continental impact analyses for Africa. However, contradictory to these studies we find a tendency for increased streamflows in three of the four basins (not for the Ubangi). Guided by these results, we argue for attention to the possible risks of increasing high flows in the face of the dominant water scarcity in Africa. In conclusion, the study shows that impact intercomparisons have added value to the

  17. Recent intensification of tropical climate variability in the Indian Ocean

    NASA Astrophysics Data System (ADS)

    Abram, Nerilie J.; Gagan, Michael K.; Cole, Julia E.; Hantoro, Wahyoe S.; Mudelsee, Manfred

    2008-12-01

    The interplay of the El Niño Southern Oscillation, Asian monsoon and Indian Ocean Dipole (IOD) drives climatic extremes in and around the Indian Ocean. Historical and proxy records reveal changes in the behaviour of the El Niño Southern Oscillation and the Asian monsoon over recent decades. However, reliable instrumental records of the IOD cover only the past 50years, and there is no consensus on long-term variability of the IOD or its possible response to greenhouse gas forcing. Here we use a suite of coral oxygen-isotope records to reconstruct a basin-wide index of IOD behaviour since AD1846. Our record reveals an increase in the frequency and strength of IOD events during the twentieth century, which is associated with enhanced seasonal upwelling in the eastern Indian Ocean. Although the El Niño Southern Oscillation has historically influenced the variability of both the IOD and the Asian monsoon, we find that the recent intensification of the IOD coincides with the development of direct, positive IOD-monsoon feedbacks. We suggest that projected greenhouse warming may lead to a redistribution of rainfall across the Indian Ocean and a growing interdependence between the IOD and Asian monsoon precipitation variability.

  18. Bringing Together Simulated ~20 Year Variability in Coupled Climate Models

    NASA Astrophysics Data System (ADS)

    Menary, M.; Hodson, D.; Robson, J.; Sutton, R.; Wood, R. A.

    2014-12-01

    Many climate models simulate significant spectral power in large scale, North Atlantic subpolar gyre indices at timescales of around 20 years. Despite similar periodicities, the underlying mechanisms reported in individual models can vary greatly. For example, the timescale can be set by any combination of geostrophic self advection, Rossby wave propagation, or advection by the mean circulation. The role of the overturning circulation can either be active or passive, and the ultimate driver of density changes in the deep water formation regions is split roughly evenly in the literature between salinity and temperature - with implications for any feedback mechanisms. These simulations typically span many centuries with constant external forcings to capture internal climate variability. The extent to which either this periodicity carries over to the real world under increasingly strong external forcing, or which, if any, of the modelled feedbacks are applicable, is unclear. We present new results from a state-of-the-art high resolution coupled climate model (HadGEM3) in which the mechanism of internal decadal variability in the North Atlantic is diagnosed and discuss the causes of differences from previous work. Due to the non-linear equation of state, biases in the simulated mean state can explain some of the inter-model differences via the relative importance of temperature or salinity in density changes. These biases can then propagate throughout the mechanistic chain resulting in fundamentally different simulated mechanisms. For example, whether temperature or salinity control densities in the Labrador Sea influences whether a strengthening overturning circulation acts as a negative or positive feedback. Although analysis of the model proceeds via lagged regressions, this is generally not possible with observational data. We use a combination of palaeo reconstructions and targeted process-based analysis to investigate whether there is any signal of bidecadal

  19. 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.

  20. A plant’s perspective of extremes: Terrestrial plant responses to changing climatic variability

    PubMed Central

    Reyer, C.; Leuzinger, S.; Rammig, A.; Wolf, A.; Bartholomeus, R. P.; Bonfante, A.; de Lorenzi, F.; Dury, M.; Gloning, P.; Abou Jaoudé, R.; Klein, T.; Kuster, T. M.; Martins, M.; Niedrist, G.; Riccardi, M.; Wohlfahrt, G.; de Angelis, P.; de Dato, G.; François, L.; Menzel, A.; Pereira, M.

    2013-01-01

    We review observational, experimental and model results on how plants respond to extreme climatic conditions induced by changing climatic variability. Distinguishing between impacts of changing mean climatic conditions and changing climatic variability on terrestrial ecosystems is generally underrated in current studies. The goals of our review are thus (1) to identify plant processes that are vulnerable to changes in the variability of climatic variables rather than to changes in their mean, and (2) to depict/evaluate available study designs to quantify responses of plants to changing climatic variability. We find that phenology is largely affected by changing mean climate but also that impacts of climatic variability are much less studied but potentially damaging. We note that plant water relations seem to be very vulnerable to extremes driven by changes in temperature and precipitation and that heatwaves and flooding have stronger impacts on physiological processes than changing mean climate. Moreover, interacting phenological and physiological processes are likely to further complicate plant responses to changing climatic variability. Phenological and physiological processes and their interactions culminate in even more sophisticated responses to changing mean climate and climatic variability at the species and community level. Generally, observational studies are well suited to study plant responses to changing mean climate, but less suitable to gain a mechanistic understanding of plant responses to climatic variability. Experiments seem best suited to simulate extreme events. In models, temporal resolution and model structure are crucial to capture plant responses to changing climatic variability. We highlight that a combination of experimental, observational and /or modeling studies have the potential to overcome important caveats of the respective individual approaches. PMID:23504722

  1. Seasonal Evolution and Variability Associated with the West African Monsoon System

    NASA Technical Reports Server (NTRS)

    Gu, Guojun; Adler, Robert F.

    2003-01-01

    In this study, we investigate the seasonal variations in surface rainfall and associated large-scale processes in the tropical eastern Atlantic and West African region. The 5-yr (1998-2002) high-quality TRMM rainfall, sea surface temperature (SST), water vapor and cloud liquid water observations are applied along with the NCEP/NCAR reanalysis wind components and a 3-yr (2000-2002) Quickscat satellite-observed surface wind product. Major mean rainfall over West Africa tends to be concentrated in two regions and is observed in two different seasons, manifesting an abrupt shift of the mean rainfall zone during June-July. (i) Near the Gulf of Guinea (about 5 degN), intense convection and rainfall are seen during April-June and roughly follow the seasonality of SST in the tropical eastern Atlantic. (ii) Along the latitudes of about 10 deg. N over the interior West African continent, a second intense rain belt begins to develop from July and remains there during the later summer season. This belt co-exists with a northwardmoved African Easterly Jet (AEJ) and its accompanying horizonal and vertical shear zones, the appearance and intensification of an upper tropospheric Tropical Easterly Jet (TEJ), and a strong low-level westerly flow. Westward-propagating wave signals [ i e . , African easterly waves (AEWs)] dominate the synoptic-scale variability during July-September, in contrast to the evident eastward-propagating wave signals during May- June. The abrupt shift of mean rainfall zone thus turns out to be a combination of two different physical processes: (i) Evident seasonal cycles in the tropical eastern Atlantic ocean which modulate convection and rainfall in the Gulf of Guinea by means of SST thermal forcing and SST-related meridional gradient; (ii) The interaction among the AEJ, TEJ, low-level westerly flow, moist convection and AEWs during July-September which modulates rainfall variability in the interior West Africa, primarily within the ITCZ rain band. Evident

  2. Stochastic investigation of temperature process for climatic variability identification

    NASA Astrophysics Data System (ADS)

    Lerias, Eleutherios; Kalamioti, Anna; Dimitriadis, Panayiotis; Markonis, Yannis; Iliopoulou, Theano; Koutsoyiannis, Demetris

    2016-04-01

    The temperature process is considered as the most characteristic hydrometeorological process and has been thoroughly examined in the climate-change framework. We use a dataset comprising hourly temperature and dew point records to identify statistical variability with emphasis on the last period. Specifically, we investigate the occurrence of mean, maximum and minimum values and we estimate statistical properties such as marginal probability distribution function and the type of decay of the climacogram (i.e., mean process variance vs. scale) for various time periods. Acknowledgement: This research is conducted within the frame of the undergraduate course "Stochastic Methods in Water Resources" of the National Technical University of Athens (NTUA). The School of Civil Engineering of NTUA provided moral support for the participation of the students in the Assembly.

  3. Stochastic investigation of wind process for climatic variability identification

    NASA Astrophysics Data System (ADS)

    Deligiannis, Ilias; Tyrogiannis, Vassilis; Daskalou, Olympia; Dimitriadis, Panayiotis; Markonis, Yannis; Iliopoulou, Theano; Koutsoyiannis, Demetris

    2016-04-01

    The wind process is considered one of the hydrometeorological processes that generates and drives the climate dynamics. We use a dataset comprising hourly wind records to identify statistical variability with emphasis on the last period. Specifically, we investigate the occurrence of mean, maximum and minimum values and we estimate statistical properties such as marginal probability distribution function and the type of decay of the climacogram (i.e., mean process variance vs. scale) for various time periods. Acknowledgement: This research is conducted within the frame of the undergraduate course "Stochastic Methods in Water Resources" of the National Technical University of Athens (NTUA). The School of Civil Engineering of NTUA provided moral support for the participation of the students in the Assembly.

  4. Climate variability and dengue fever in warm and humid Mexico.

    PubMed

    Colón-González, Felipe J; Lake, Iain R; Bentham, Graham

    2011-05-01

    Multiple linear regression models were fitted to look for associations between changes in the incidence rate of dengue fever and climate variability in the warm and humid region of Mexico. Data were collected for 12 Mexican provinces over a 23-year period (January 1985 to December 2007). Our results show that the incidence rate or risk of infection is higher during El Niño events and in the warm and wet season. We provide evidence to show that dengue fever incidence was positively associated with the strength of El Niño and the minimum temperature, especially during the cool and dry season. Our study complements the understanding of dengue fever dynamics in the region and may be useful for the development of early warning systems.

  5. Impacts of Interannual Climate Variability on Agricultural and Marine Ecosystems

    NASA Technical Reports Server (NTRS)

    Cane, M. A.; Zebiak, S.; Kaplan, A.; Chen, D.

    2001-01-01

    The El Nino - Southern Oscillation (ENSO) is the dominant mode of global interannual climate variability, and seems to be the only mode for which current prediction methods are more skillful than climatology or persistence. The Zebiak and Cane intermediate coupled ocean-atmosphere model has been in use for ENSO prediction for more than a decade, with notable success. However, the sole dependence of its original initialization scheme and the improved initialization on wind fields derived from merchant ship observations proved to be a liability during 1997/1998 El Nino event: the deficiencies of wind observations prevented the oceanic component of the model from reaching the realistic state during the year prior to the event, and the forecast failed. Our work on the project was concentrated on the use of satellite data for improving various stages of ENSO prediction technology: model initialization, bias correction, and data assimilation. Close collaboration with other teams of the IDS project was maintained throughout.

  6. Nevada Monitoring System to Assess Climate Variability and Change

    NASA Astrophysics Data System (ADS)

    Devitt, D. A.; Arnone, J.; Biondi, F.; Fenstermaker, L. F.; Saito, L.; Young, M.; Riddle, B.; Strachan, S. D.; Bird, B.; McCurdy, G.; Lyles, B. F.

    2010-12-01

    The Nevada System of Higher Education (University of Nevada Las Vegas, University of Nevada Reno and the Desert Research Institute) was awarded a multiyear NSF EPSCoR grant to support infrastructure associated with regional climate change research. The overall project is comprised of 5 components: education, cyberinfrastructure, policy, climate modeling and water/ecology. The water and ecology components are using their infrastructure funding for the assessment of climate variability and change on ecosystem function and hydrologic services. A series of 10 m tall towers are under construction and are being equipped with a wide array of sensors to monitor atmospheric, soil and plant parameters over time. The towers are located within the Mojave and Great Basin Deserts in two transects; the Mojave Desert transect is located in the southern Nevada Sheep Mountain Range and the Great Basin transect is located in the east central Nevada Snake Mountain Range. The towers are centrally positioned in well-defined vegetation zones. In southern Nevada these zones are represented by the following plant species: Creosote/Bursage (Creosotebush scrub zone); Blackbrush/Joshua Tree (Blackbrush zone); Pinyon/ Juniper (pygmy conifer zone), Ponderosa Pine (montane zone) and Bristlecone Pine (subalpine zone). The Snake Mountain transect incorporates the eastern and western valleys on both sides of the mountain range. The vegetation zones are represented by: Greasewood and mixed shrub (salt desert zone); Big Sage (sagebrush zone); Pinyon/Juniper (pygmy conifer zone); White/Douglas Fir, Ponderosa Pine and Aspen (montane zone); and Bristlecone/Limber Pine and Engelmann Spruce (subalpine zone). We are currently in the third year of funding with a goal of having the majority of towers fully operational by winter 2010. In close collaboration with our cyberinfrastructure component team, all data acquired from the transect monitoring stations will be made available to other researchers and the

  7. Diagnostic statistics of daily rainfall variability in an evolving climate

    NASA Astrophysics Data System (ADS)

    Panagoulia, D.; Bárdossy, A.; Lourmas, G.

    2006-06-01

    To investigate the character of daily rainfall variability under present and future climate described via global warming a suite of diagnostic statistics was used. The rainfall was modeled as a stochastic process coupled with atmospheric circulation. In this study we used an automated objective classification of daily patterns based on optimized fuzzy rules. This kind of classification method provided circulation patterns suitable for downscaling of General Circulation Model (GCM)-generated precipitation. The precipitation diagnostics included first and second order moments, wet and dry-day renewal process probabilities and spell lengths as well as low-frequency variability via the standard deviation of monthly totals. These descriptors were applied to nine elevation zones and entire area of the Mesochora mountainous catchment in Central Greece for observed, 1×CO2 and 2×CO2 downscaled precipitation. The statistics' comparison revealed significant differences in the most of the daily diagnostics (e.g. mean wet-day amount, 95th percentile of wet-day amount, dry to wet probability), spell statistics (e.g. mean wet/dry spell length), and low-frequency diagnostic (standard deviation of monthly precipitation total) between warm (2×CO2) and observed scenario in a progressive rate from lower to upper zone. The differences were very greater for the catchment area. In the light of these results, an increase in rainfall occurrence with diminished rainfall amount and a sequence of less consecutive dry days could describe the behaviour of a possible future climate on the examined catchment.

  8. Analysis of the Relationship Between Climate and NDVI Variability at Global Scales

    NASA Technical Reports Server (NTRS)

    Zeng, Fan-Wei; Collatz, G. James; Pinzon, Jorge; Ivanoff, Alvaro

    2011-01-01

    interannual variability in modeled (CASA) C flux is in part caused by interannual variability in Normalized Difference Vegetation Index (NDVI) Fraction of Photosynthetically Active Radiation (FPAR). This study confirms a mechanism producing variability in modeled NPP: -- NDVI (FPAR) interannual variability is strongly driven by climate; -- The climate driven variability in NDVI (FPAR) can lead to much larger fluctuation in NPP vs. the NPP computed from FPAR climatology

  9. Assessment of Human Health Vulnerability to Climate Variability and Change in Cuba

    PubMed Central

    Bultó, Paulo Lázaro Ortíz; Rodríguez, Antonio Pérez; Valencia, Alina Rivero; Vega, Nicolás León; Gonzalez, Manuel Díaz; Carrera, Alina Pérez

    2006-01-01

    In this study we assessed the potential effects of climate variability and change on population health in Cuba. We describe the climate of Cuba as well as the patterns of climate-sensitive diseases of primary concern, particularly dengue fever. Analyses of the associations between climatic anomalies and disease patterns highlight current vulnerability to climate variability. We describe current adaptations, including the application of climate predictions to prevent disease outbreaks. Finally, we present the potential economic costs associated with future impacts due to climate change. The tools used in this study can be useful in the development of appropriate and effective adaptation options to address the increased climate variability associated with climate change. PMID:17185289

  10. Response of Seasonal Atlantic Tropical Cyclone Activity to Suppression of African Easterly Waves in a Regional Climate Model

    NASA Astrophysics Data System (ADS)

    Patricola, C. M.; Saravanan, R.; Chang, P.

    2014-12-01

    Atlantic tropical cyclones and African easterly waves (AEWs) are strongly linked on the synoptic timescale, with about 85% of observed major Atlantic hurricanes originating from AEWs (e.g., Landsea et al. 1993). However, the influence of variability in AEWs on seasonal Atlantic tropical cyclone activity is not fully understood; a positive correlation between AEW activity and Atlantic tropical cyclone activity exists on the interannual timescale during just some periods of the observational record (e.g., Thorncroft and Hodges, 2001; Hopsch et al. 2007). This study investigates the impact of AEWs on seasonal Atlantic tropical cyclone activity using regional climate model simulations in which AEWs were either prescribed or removed through the lateral boundary condition (LBC). The control simulation (10-member ensemble) was run at 27 km resolution and used 6-hourly LBCs from the NCEP CFS Reanalysis and daily NOAA Optimum Interpolation (OI) V2 sea surface temperature (SST) from the year 2005. In the experiment AEWs were suppressed by filtering 2-10 day variability over tropical latitudes from the eastern LBC, located along the west coast of the Sahel. The difference in Atlantic tropical cyclone frequency was insignificant between the simulations in which AEWs were prescribed versus suppressed, indicating that AEWs are not necessary to maintain climatological tropical cyclone frequency even though tropical cyclones readily originate from these features. This further implies that seasonal Atlantic tropical cyclone frequency is uninfluenced by variability in AEWs, and that the value of AEW variability as a predictor of Atlantic tropical cyclones is limited to the weekly timescale. However in response to filtering AEWs, accumulated cyclone energy significantly increased by about 15% of the control simulation mean and the spatial pattern of track density shifted in association with changes in steering winds. This suggests the importance of AEWs in impacting tropical cyclone

  11. Developing climate data records and essential climate variables from landsat data

    USGS Publications Warehouse

    Dwyer, John; Dinardo, Thomas P.; Muchoney, Douglas M.

    2011-01-01

    The series of Landsat missions has compiled the longest record of satellite observation of the Earth’s land surface, extending for more than 38 years for most areas of the globe. Landsat data are particularly important as long term climate data records because the scale of observation is sufficient to differentiate between natural and human drivers of land cover change. The USGS has established consistent radiometric calibration across the Landsat TM and ETM+ sensors, and have extended the calibration back to the earlier MSS sensors. The USGS is developing capabilities to create fundamental climate data records (FCDRs), thematic climate data records (TCDRs), and essential climate variables (ECVs) from the Landsat data archive. Two high priority TCDRs were identified: surface reflectance and land surface temperature because they have direct application or are required as input to the generation of ECVs. We will focus development on a few of the terrestrial ECVs that have a high potential for being derived from Landsat data, that include land cover, albedo, fire disturbance, surface water, snow and ice, and leaf area index (LAI). We are collaborating with scientists who have demonstrated successful algorithm development and application of these science products to develop a framework of processing capabilities to support research projects and land management applications, along with an independent strategy for product validation. Our goal is to scale the creation and validation of these products from specific sites in the conterminous U.S. and Alaska, for extension to continental and global scales.

  12. Bipolar modulation of millennial-scale West African monsoon variability during the last glacial (75,000-25,000 years ago)

    NASA Astrophysics Data System (ADS)

    Weldeab, Syee

    2012-04-01

    Time series of planktonic foraminiferal δ18O and Ba/Ca-based sea surface salinity (SSS) estimates from the eastern Gulf of Guinea (eastern equatorial Atlantic) indicate changes in runoff that reflect variability of spatially integrated precipitation over the equatorial West African monsoon area. Millennial-scale and recurring runoff-induced SSS rises and declines in the range of 1.5 and 2 psu (practical salinity unit) reveal rapid oscillation between dry and wet phases. The timing of decreased runoff coincides with oscillation of Dansgaard-Oeschger stadials and Heinrich events, the most severe monsoon weakening correlating with the latter. δ18Oresidual time series, derived by removing temperature, ice volume, and salinity components from the foraminiferal δ18O record, suggest that weak monsoon precipitation during stadials and Heinrich events was accompanied by significant shifts in δ18Oprecipitation toward higher values. Furthermore, δ18O analysis of individual tests of Globigerinoides ruber pink (δ18Oindiv) during dry episodes show a total range and variance of 2.3‰ and 0.25 (n = 121), indicating that seasonal contrast of sea surface freshening was significantly reduced during Heinrich events relative to that of interstadials which show a total range and variance of 3.35‰ and 0.42 (n = 140). On the basis of the timing and magnitude of changes in the monsoon record, it is evident that northern high latitude climate was the most dominant control on the West African monsoon variability. However, a southern high latitude imprint is also apparent during some episodes. This centennially resolved climate record demonstrates that the equatorial West African monsoon experienced profound changes in the amount, seasonal contrast, and moisture source of summer monsoon precipitation during the last glacial. The most plausible mechanism is a large-scale southward displacement of the monsoon trough, most likely initiated by large-scale reorganization of atmospheric

  13. Insights on Antarctic climate variability from paleo-temperature proxies

    NASA Astrophysics Data System (ADS)

    Orsi, A. J.; Landais, A.; Stenni, B.; Severinghaus, J. P.

    2015-12-01

    Few direct meteorological observations exist in Antarctica, which limits our understanding of the modes of climate variability in this region. In particular, atmospheric reanalyses do not produce a coherent picture of the known warming trend since 1979. Here we analyze a suite of paleo-temperature proxies to gain insight into both the recent temperature trend and the multi-decadal climate variability in Antarctica over the last 1000 years. We present temperature records from two sites in Antarctica: WAIS Divide (79°S, 112°W, 1766 m a.s.l), and Talos Dome (72°S, 159°E, 2315 m a.s.l), reconstructed from the combination of inert gas isotopes from the ice core and borehole temperature measurements. Borehole temperature provides an absolute estimate of long-term trends, while noble gases track decadal to centennial scale changes. In addition, we use water isotopes to infer information about circulation changes. We find a strong warming trend in West Antarctica over the last 50 years (+0.23°C/decade), which is accelerating (+0.8°C/decade since 1980). The longer temperature record shows that such a trend has analogs happening about every 200 years. However, the study of other climate proxies suggests that the recent trend is due to a different mechanism than the previous events. We also find a long term cooling trend over the last 1000 years, which is stronger in East Antarctica (Talos Dome) than in West Antarctica (WAIS-Divide). At WAIS Divide, we find that "Little Ice Age" cold period of 1400-1800 was 0.52°C colder than the last century. Overall, both records are consistent with the idea that the solar minima and persistent volcanic activity of the Little Ice Age (1400-1850 A.D.) had a significant impact on the surface temperature in Antarctica. The feedbacks amplifying the forcing were likely stronger on the East Antarctic plateau than on the more marine-influenced West Antarctica.

  14. Future agricultural water demand under climate change: regional variability and uncertainties arising from CMIP5 climate projections

    NASA Astrophysics Data System (ADS)

    Schewe, J.; Wada, Y.; Wisser, D.

    2012-12-01

    The agricultural sector (irrigation and livestock) uses by far the largest amount of water among all sectors and is responsible for 70% of the global water withdrawal. At a country scale, irrigation water withdrawal often exceeds 90% of the total water used in many of emerging and developing countries such as India, Pakistan, Iran and Mexico, sustaining much of food production and the livelihood of millions of people. The livestock sector generally accounts less than 1-2% of total water withdrawal, yet exceeds 10-30% of the total water used in many of the African countries. Future agricultural water demand is, however, subject to large uncertainties due to anticipated climate change, i.e. warming temperature and changing precipitation variability, in various regions of the world. Here, we use a global hydrological and water resources model to quantify the impact of climate change on regional irrigation and livestock water demand, and the resulting uncertainties arsing from newly available CMIP5 climate projections obtained through Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP; http://www.isi-mip.org/). Irrigation water requirement per unit crop area is estimated by simulating daily soil water balance with crop-related data. Livestock water demand is calculated by combining livestock densities with their drinking water requirements that is a function of air temperature. The results of the ensemble mean show that global irrigation and livestock water demand increased by ~6% and ~12% by 2050 respectively primarily due to higher evaporative demand as a result of increased temperature. At a regional scale, agricultural water demand decreased over some parts of Europe (e.g., Italy, Germany) and Southeast Asia (e.g., the Philippines, Malaysia), but increased over South Asia, the U.S., the Middle East and Africa. However, the projections are highly uncertain over many parts of the world. The results of the ensemble projections in agricultural water demand

  15. Climate Variability and Oceanographic Settings Associated with Interannual Variability in the Initiation of Dinophysis acuminata Blooms

    PubMed Central

    Díaz, Patricio A.; Reguera, Beatriz; Ruiz-Villarreal, Manuel; Pazos, Yolanda; Velo-Suárez, Lourdes; Berger, Henrick; Sourisseau, Marc

    2013-01-01

    In 2012, there were exceptional blooms of D. acuminata in early spring in what appeared to be a mesoscale event affecting Western Iberia and the Bay of Biscay. The objective of this work was to identify common climatic patterns to explain the observed anomalies in two important aquaculture sites, the Galician Rías Baixas (NW Spain) and Arcachon Bay (SW France). Here, we examine climate variability through physical-biological couplings, Sea Surface Temperature (SST) anomalies and time of initiation of the upwelling season and its intensity over several decades. In 2012, the mesoscale features common to the two sites were positive anomalies in SST and unusual wind patterns. These led to an atypical predominance of upwelling in winter in the Galician Rías, and increased haline stratification associated with a southward advection of the Gironde plume in Arcachon Bay. Both scenarios promoted an early phytoplankton growth season and increased stability that enhanced D. acuminata growth. Therefore, a common climate anomaly caused exceptional blooms of D. acuminata in two distant regions through different triggering mechanisms. These results increase our capability to predict intense diarrhetic shellfish poisoning outbreaks in the early spring from observations in the preceding winter. PMID:23959151

  16. Educating At-Risk Urban African American Children: The Effects of School Climate on Motivation and Academic Achievement

    ERIC Educational Resources Information Center

    Fenzel, L. Mickey; O'Brennan, Lindsey M.

    2007-01-01

    The present study examines the mediating effects of student intrinsic motivation and teacher ratings of student academic engagement on the relation between school climate perceptions and student academic performance among 282 urban African American middle school students. Results provided support for the hypothesized model and suggest the…

  17. Application of Infrared Hyperspectral Sounder Data to Climate Research: Interannual Variability and climate trend evaluation.

    NASA Astrophysics Data System (ADS)

    Aumann, H. H.; Gregorich, D. T.

    2007-12-01

    Satellite measurements of the spectrally resolved upwelling infrared radiances have a unique role in the observation of climate and climate change: They give direct insight into the way the Earth Climate System responds to periodic and long term changes in forcing with changes in surface and atmospheric temperatures and changes in large scale atmospheric circulation patterns. The Atmospheric Infrared Sounder (AIRS), the first in a series of hyper-spectral polar orbiting sounders, was launch on the EOS Aqua into a 1:30 pm polar orbit at 705 km altitude in May 2002, with an anticipated lifetime of 12 years. The Infrared Atmospheric Sounding Interferometer (IASI) was launched in October 2006 into a 9:30 AM orbit, to be followed by the Crosstrack InfraRed Sounder (CRIS) in a 2 PM orbit in 2010. The AIRS radiometric stability since 2002 has been verified at the better than 0.01 K/year level. We report on observations of the oceans between 30S and 30N. The 0.05 K/year trend in co2 sensitive channels due to the 2 ppmv/year increase in the co2 column abundance is readily detectable and statistically reliable. The AIRS data show very consistent seasonal modulations of key surface, cloud, water vapor and atmospheric temperatures. After removing the seasonal variation, the anomaly shows interannual rms variability in the monthly means larger than 0.1 K. The rms variability in the monthly means in the mid- tropospheric temperature with peak excursions as large as 0.6 K are observed by the AIRS 2388 cm-1 channel and AMSU channel 5 at 57 GHz. The interannual variability is not obviously correlated with the Multivariate Enso Index (MEI). This variability places limits on the length of time required to measure global warming trends at the 0.1 K/decade level. These limits exceed the expected 12 year lifetime of AIRS and need to be taken into account in the design of space missions and instruments to measure climate change.

  18. Exploring the climate response to the 1815 Tambora eruption with respect to natural climate variability

    NASA Astrophysics Data System (ADS)

    Lorenz, Stephan J.; Timmreck, Claudia; Jungclaus, Johann H.

    2010-05-01

    The largest historic volcanic eruption with known origin was the explosion of Mount Tambora in Indonesia in April 1815. In the aftermath of this devastating eruption, the following year 1816 came to be known as the "year without a summer", in particular in USA, Canada, and Europe, where the worst famine over a century as well as typhus epidemics accompanied by enhanced emigration from Europe were recorded. The stratospheric aerosol mass load was estimated to be about three times that of the Pinatubo eruption in 1991, leading to strong impact on the Earth's climate system. In a series of ensemble simulations of the last Millennium we applied our Earth system model, based on the ECHAM5/MPIOM model family, to investigate the climate signal of the Tambora eruption with respect to natural and forced variability. This event contributed to one of the strongest cooling periods during the last Millennium in the ensemble of simulations. However, this period is associated with a large ensemble spread in simulated air temperature on a hemispheric and global as well as on a regional scale, with limited to very strong atmospheric response. The unique path of the climate evolution through the Earth's history yielding the extreme summer in 1816 in North America and Europe is compared with the simulations. A special focus of our analysis is Tambora's impact on climate and its relationship with the status of the climate system, e.g. the ENSO state, at the time of the eruption. Additionally, the contribution of the large volcanic eruption with tropical but unknown location about six years prior to the Tambora in 1809 will be discussed.

  19. Climate, herbivory, and fire controls on tropical African forest for the last 60ka

    NASA Astrophysics Data System (ADS)

    Ivory, Sarah J.; Russell, James

    2016-09-01

    The Last Glacial Maximum (LGM) in Africa was drier than today and was followed by rapid step-wise climate changes during the last deglacial period. In much of Africa, these changes led to a drastic reduction of lowland forest area during the LGM, followed by recolonization of the lowlands by forest and woodland in concert with regional warming and wetting. However, the history of southeastern African vegetation contrasts with that observed further north. In particular, forest expansion appears to have occurred in southeastern Africa during episodes of high-latitude northern hemisphere cooling. Although vegetation history in Africa is generally assumed to relate purely to climate, previous studies have not addressed potential feedbacks between climate, vegetation, and disturbance regimes (fire, herbivory) that may create tipping points in ecosystems. This climate-vegetation history has profound implications for our understanding of the modern architecture of lowland and highland forests, both thought to be at risk from future climate change. Here we present analyses of fossil pollen, charcoal, and Sporormiella (dung fungus) on a continuous 60 kyr record from central Lake Tanganyika, Southeast Africa, that illustrates the interplay of climate and disturbance regimes in shaping vegetation composition and structure. We observe that extensive forests dominated the region during the last glacial period despite evidence of decreased rainfall. At the end of the LGM, forest opening at ∼17.5 ka followed warming temperatures but preceded rising precipitation, suggesting that temperature-induced water stress and disturbance from fire and herbivory affected initial landscape transformation. Our Sporormiella record indicates that mega-herbivore populations increased at the early Holocene. This higher animal density increased plant species richness and encouraged landscape heterogeneity until the mid-Holocene. At this time, regional drying followed by the onset of the Iron Age

  20. Incorporating Climate Variability into Precipitation Isoscapes for Interpreting Animal Migration

    NASA Astrophysics Data System (ADS)

    Vander Zanden, H.; Hobson, K. A.; Wassenaar, L. I.; Wunder, M. B.; Welker, J. M.; Bowen, G. J.

    2013-12-01

    Large-scale continental gradients in δ2H and δ18O values of precipitation lead to predictable isotopic patterns across the landscape. These light isotopes are thus useful endogenous markers in tracing long-distance movements of animals. Hydrogen in water is assimilated into tissues that are inert after synthesis, such as chitin or keratin, that are not altered when the animal moves so that the tissue reflects the environment or region from which it originated at the time when the tissue was synthesized. Models to predict the patters of δ2H in precipitation with the Global Network of Isotopes in Precipitation (GNIP) use long-term averages because models allowing estimation of isotopic values in more specific time periods have often not been available. Yet, inter-annual variation in precipitation and other climate variables may lead to large deviations from the mean values modeled over four decades, and particular regions may be more susceptible to higher departures from long-term average δ2H values. We examine whether incorporating such variation offers an improvement over static isoscapes to understand patterns of animal movement and geographic origin. Here we investigate the accuracy of Bayesian geographic assignments to predict the origin of two migratory species (monarch butterflies in the eastern United States and reed warblers in western Europe) using time-specific isoscapes. We use known-origin data from these organisms to provide calibration and validation datasets to compare the sensitivity of predictions from both year-specific and long-term isoscapes developed in IsoMAP, a freely available online workspace for modeling and predicting isotope ratio variation in precipitation. Determining how to incorporate climate and inter-annual variation into models that predict isotopic values of animal tissues can aid in improving geospatial assignments across a wide range of taxa.

  1. Simulation of Snow Dynamics in Response to Climate Variability

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Wang, S.; Trishchenko, A.

    2004-05-01

    to climate variability were investigated through model simulations.

  2. Impacts of climate variability on functional diversity and species distribution in dryland ecosystems

    NASA Astrophysics Data System (ADS)

    Caylor, K. K.; Franz, T.

    2008-12-01

    The role rainfall heterogeneity is an important but poorly understood aspect of ecosystem function in dryland communities. While general relationships between annual rainfall and tree cover have been revealed through meta-analysis and inter-site comparisons, the impact of rainfall variability on both functional and species-level biodiversity has received less attention. However, it is likely that shifts in the seasonality, and distribution of rainfall (i.e. changes in daily storm frequency and/or storm intensity) could substantially alter waterbalance of dryland ecosystems. In particular, the distribution of plant water use and plant water stress (proxies for growth and survival, respectively) are highly dependent on the temporal signatures of rainfall events within and between growing seasons. Therefore, ecosystem resilience is likely to be dependent on the functional - and species-level - responses of ecosystems to shifts in rainfall timing and intensity. This presentation will explore the potential and observed impacts of both seasonal and inter-annual variability in rainfall distribution in two classic dryland ecosystems. The first is the Kalahari region of southern Africa, where seasonal variability in rainfall patterns leads to functional organization of trees and grasses across a large climate gradient that optimize water use and minimize water stress. The second example is drawn from an east African savanna in Kenya, where observed shifts in rainfall seasonality are used to infer changes in the spatial distributions in the dominant woody species. Finally, I will address the critical need for new observational frameworks capable of directly measuring plant and ecosystem-scale responses to rainfall heterogeneity and propose a sampling design capable of resolving the functional response of vegetation to rainfall heterogeneity in water-limited landscapes.

  3. Decadal-scale Holocene climate variability in the Nordic seas

    NASA Astrophysics Data System (ADS)

    Koc, N.; Andersen, C.; Andrews, J.; Jennings, A.

    2003-04-01

    Sea-surface temperatures (SST) at decadal resolution have been reconstructed from core MD 95-2011, core MD 99-2269 and core BS88-6-5A based on diatom transfer functions. Core MD 95-2011 is located on the Vöring Plateau (66^o58.18N; 07^o38.36E, 1050 m water depth) along the main axis of the northward flowing warm Atlantic water. It is, therefore, in an ideal position to monitor changes in the northward heat flux to northwestern Europe. Core MD 99-2269 is located in the deep Hunafloi trough, off N Iceland (66^o37.53N; 20^o51.16W, 365 m water depth). Today the core lies under the influence of the Irminger current, but it also may be influenced by the cold East Greenland current (EGC) as the Polar front migrates eastward. Core BS88-6-5A is located on the East Greenland shelf (67^o07.54N; 30^o54.26W, 707 m water depth) and is influenced by the EGC. The cores has been dated by AMS C-14 and Pb 210 isotope profiles. SST variations are estimated by means of 3 different diatom transfer function methods. Results indicate a division of the Holocene into three periods and a climate development in step with the decreasing Northern Hemisphere insolation. However, regional differences between the surface currents occur regarding both timing and magnitude of changes. Superimposed on the general Holocene cooling trend there is a high frequency SST variability, which is in the order of 1--1.5 degrees C for the Vöring Plateau and the East Greenland shelf, and 2.5--3 degrees C for the North Iceland shelf. There is clear evidence for late Holocene climatic events such as the "Little Ice Age" and the "Medieval Warm Period". Timing of late Holocene climatic events at the eastern versus western Nordic Seas will be discussed.

  4. Climate Variability Impacts on Watershed Nutrient Delivery and Reservoir Production

    NASA Astrophysics Data System (ADS)

    White, J. D.; Prochnow, S. J.; Zygo, L. M.; Byars, B. W.

    2005-05-01

    Reservoirs in agricultural dominated watersheds tend to exhibit pulse-system behavior especially if located in climates dominated by summer convective precipitation inputs. Concentration and bulk mass of nutrient and sediment inputs into reservoir systems vary in terms of timing and magnitude of delivery from watershed sources to reservoirs under these climate conditions. Reservoir management often focuses on long-term average inputs without considering short and long-term impacts of variation in loading. In this study we modeled a watershed-reservoir system to assess how climate variability affects reservoir primary production through shifts in external loading and internal recycling of limiting nutrients. The Bosque watershed encompasses 423,824 ha in central Texas which delivers water to Lake Waco, a 2900 ha reservoir that is the primary water source for the city of Waco and surrounding areas. Utilizing the Soil Water Assessment Tool for the watershed and river simulations and the CE-Qual-2e model for the reservoir, hydrologic and nutrient dynamics were simulated for a 10 year period encompassing two ENSO cycles. The models were calibrated based on point measurement of water quality attributes for a two year time period. Results indicated that watershed delivery of nutrients was affected by the presence and density of small flood-control structure in the watershed. However, considerable nitrogen and phosphorus loadings were derived from soils in the upper watershed which have had long-term waste-application from concentrated animal feeding operations. During El Niño years, nutrient and sediment loads increased by 3 times above non-El Niño years. The simulated response within the reservoir to these nutrient and sediment loads had both direct and indirect. Productivity evaluated from chlorophyll a and algal biomass increased under El Niño conditions, however species composition shifts were found with an increase in cyanobacteria dominance. In non-El Niño years

  5. Holocene climate variability in south-western France

    NASA Astrophysics Data System (ADS)

    Oliveira, D.; Naughton, F.; Trigo, R.; Rodrigues, T.; Jouanneau, J.-M.; Weber, O.

    2012-04-01

    Vegetation and climate changes in western France/northern Spain are documented for the last c. 9000 cal. yr BP in a well dated shelf core, KS05-10, retrieved in the southwestern margin of the Bay of Biscay (Basque country) (43°22'765N, 2°16'744W). The continuous high resolution pollen record shows orbital and suborbital climate fluctuations similar to those noticed for the North Atlantic region and Greenland. A long-term Pinus, Quercus and Corylus forest reduction follows the cooling trend in Greenland and the general decrease of mid-latitude summer insolation until approximately 350 yr cal. BP. Within the millennial scale variability, the southwestern Bay of Biscay pollen record shows 6 main phases: The first phase, c. 9000 and 6600 cal. yr BP, is marked by a Pinus and deciduous Quercus forest with Corylus, indicating a humid and temperate climate. During the phase, c. 6600 - 4500 cal. yr BP, the pollen record shows a stable period of rich, mixed Quercus forest. During this interval occurred the establishment of Alnus, Ulmus, Tilia, Fraxinus excelsior-type and Fagus trees and the reduction of Pinus forest. This vegetation assemblage probably indicates an increase in moisture in relatively mild conditions. Fagus became continuously present in the region after c. 4500 c. cal. yr BP in agreement with what have been noticed by continental pollen sequences. An important contraction of Pinus, deciduous Quercus and Corylus forest occur after c. 3600 cal. yr BP. This evolution is contemporaneous to the maximum expansion of Fagus and the increase of heaths, which may be linked to a weakening of seasonality and more humid summer conditions. A strong forest reduction, involving all trees except pine, and a marked spread of herbaceous plants took place after c. 1400 cal. years BP. The presence of Juglans, Cerealia type and Castanea after c. 550 cal. yr BP and the re-expansion of Pinus after c. 350 cal. yr BP testify the increasing role played by the human activity in the

  6. Interannual climate variability and snowpack in the western United States

    USGS Publications Warehouse

    Cayan, Daniel R.

    1996-01-01

    An important part of the water supply in the western United States is derived from runoff fed by mountain snowmelt Snow accumulation responds to both precipitation and temperature variations, and forms an interesting climatic index, since it integrates these influences over the entire late fall-spring period. Here, effects of cool season climate variability upon snow water equivalent (SWE) over the western part of the conterminous United States are examined. The focus is on measurements on/and 1 April, when snow accumulation is typically greatest. The primary data, from a network of mountainous snow courses, provides a good description of interannual fluctuations in snow accumulations, since many snow courses have records of five decades or more. For any given year, the spring SWE anomaly at a particular snow course is likely to be 25%–60% of its long-term average. Five separate regions of anomalous SWE variability are distinguished, using a rotated principal components analysis. Although effects vary with region and with elevation, in general, the anomalous winter precipitation has the strongest influence on spring SWE fluctuations. Anomalous temperature has a weaker effect overall, but it has great influence in lower elevations such as in the coastal Northwest, and during spring in higher elevations. The regional snow anomaly patterns are associated with precipitation and temperature anomalies in winter and early spring. Patterns of the precipitation, temperature, and snow anomalies extend over broad regional areas, much larger than individual watersheds. These surface anomalies are organized by the atmospheric circulation, with primary anomaly centers over the North Pacific Ocean as well as over western North America. For most of the regions, anomalously low SWE is associated with a winter circulation resembling the PNA pattern. With a strong low in the central North Pacific and high pressure over the Pacific Northwest, this pattern diverts North Pacific

  7. Can the 2011 East African drought be attributed to human-induced climate change?

    NASA Astrophysics Data System (ADS)

    Lott, Fraser; Christidis, Nikolaos; Stott, Peter

    2013-04-01

    Can the 2011 East African drought be attributed to human-induced climate change? Fraser C Lott, Nikolaos Christidis, Peter A Stott Met Office Hadley Centre, Fitzroy Road, Exeter EX1 3BP, UK In early 2011, the Greater Horn of Africa was impacted by a particularly severe drought. It consisted of the failure of two successive rainy seasons, known in Kenya as the "short rains" (typically October to December) and the "long rains" (March to June). This study applies the technique of event attribution to the two rainy seasons preceding the drought of 2011, aiming to quantify how the probability of this event has changed due to anthropogenic climate change. Using observed sea surface temperatures (SSTs) with the state-of-the-art atmosphere model HadGEM3-A, the precipitation totals during late 2010 (the "short rains") and early 2011 (the "long rains") were simulated in a 100-member ensemble to produce possible distributions of precipitation consistent with observed SSTs, sea ice conditions and atmospheric concentrations of greenhouse gases. Several 100-member alternative "natural" distributions of precipitation (consistent with a world in which there was no human influence on climate) were also simulated by removing anthropogenic emissions in the atmosphere and by subtracting the difference in SSTs and sea ice that are due to anthropogenic forcings, as produced in a range of coupled atmosphere-ocean simulations (HadCM3, HadGEM1, HadGEM2-ES). Comparing these simulated precipitation distributions to the observed TAMSAT African rainfall dataset, no evidence was found for a human influence on the 2010 short rains, with their failure being more clearly affected by La Niña. However, human influence was found to significantly increase the probability of long rains as dry as, or drier than, those in 2011. The magnitude of this increase in probability depends on the pattern by which human influence is estimated to have changed observed SSTs, and in turn on the coupled model chosen

  8. The value of seasonal forecasting and crop mix adaptation to climate variability for agriculture under climate change

    NASA Astrophysics Data System (ADS)

    Choi, H. S.; Schneider, U.; Schmid, E.; Held, H.

    2012-04-01

    Changes to climate variability and frequency of extreme weather events are expected to impose damages to the agricultural sector. Seasonal forecasting and long range prediction skills have received attention as an option to adapt to climate change because seasonal climate and yield predictions could improve farmers' management decisions. The value of seasonal forecasting skill is assessed with a crop mix adaptation option in Spain where drought conditions are prevalent. Yield impacts of climate are simulated for six crops (wheat, barely, cotton, potato, corn and rice) with the EPIC (Environmental Policy Integrated Climate) model. Daily weather data over the period 1961 to 1990 are used and are generated by the regional climate model REMO as reference period for climate projection. Climate information and its consequent yield variability information are given to the stochastic agricultural sector model to calculate the value of climate information in the agricultural market. Expected consumers' market surplus and producers' revenue is compared with and without employing climate forecast information. We find that seasonal forecasting benefits not only consumers but also producers if the latter adopt a strategic crop mix. This mix differs from historical crop mixes by having higher shares of crops which fare relatively well under climate change. The corresponding value of information is highly sensitive to farmers' crop mix choices.

  9. Earth science: An extended yardstick for climate variability

    NASA Astrophysics Data System (ADS)

    Meckler, Nele

    2016-06-01

    Decoded and precisely dated information encrypted in stalagmites from a cave in China reveal past climatic changes and provide insight into the complex interactions in today's climate system. See Letter p.640

  10. Impact of climate change on vegetation dynamics in a West African river basin

    NASA Astrophysics Data System (ADS)

    Sawada, Y.; Koike, T.

    2012-12-01

    Future changes in terrestrial biomass distribution under climate change will have a tremendous impact on water availability and land productivity in arid and semi-arid regions. Assessment of future change of biomass distribution in the regional or the river basin scale is strongly needed. An eco-hydrological model that fully couples a dynamic vegetation model (DVM) with a distributed biosphere hydrological model is applied to multi-model assessment of climate change impact on vegetation dynamics in a West African river basin. In addition, a distributed and auto optimization system of parameters in DVM is developed to make it possible to model a diversity of phonologies of plants by using different parameters in the different model grids. The simple carbon cycle modeling in a distributed hydrological model shows reliable accuracy in simulating the seasonal cycle of vegetation on the river basin scale. Model outputs indicate that generally, an extension of dry season duration and surface air temperature rising caused by climate change may cause a dieback of vegetation in West Africa. However, we get different seasonal and spatial changes of leaf area index and different mechanisms of the degradation when we used different general circulation models' outputs as meteorological forcing of the eco-hydrological model. Therefore, multi-model analysis like this study is important to deliver meaningful information to the society because we can discuss the uncertainties of our prediction by this methodology. This study makes it possible to discuss the impact of future change of terrestrial biomass on climate and water resources in the regional or the river basin scale although we need further sophistications of the system. Performance of the eco-hydrological model (WEB-DHM+DVM) in Volta River Basin, with basin-averaged leaf area index from model (blue solid line) and AVHRR satellite-derived product (red rectangles).

  11. Assessing risks of climate variability and climate change for Indonesian rice agriculture.

    PubMed

    Naylor, Rosamond L; Battisti, David S; Vimont, Daniel J; Falcon, Walter P; Burke, Marshall B

    2007-05-01

    El Niño events typically lead to delayed rainfall and decreased rice planting in Indonesia's main rice-growing regions, thus prolonging the hungry season and increasing the risk of annual rice deficits. Here we use a risk assessment framework to examine the potential impact of El Niño events and natural variability on rice agriculture in 2050 under conditions of climate change, with a focus on two main rice-producing areas: Java and Bali. We select a 30-day delay in monsoon onset as a threshold beyond which significant impact on the country's rice economy is likely to occur. To project the future probability of monsoon delay and changes in the annual cycle of rainfall, we use output from the Intergovernmental Panel on Climate Change AR4 suite of climate models, forced by increasing greenhouse gases, and scale it to the regional level by using empirical downscaling models. Our results reveal a marked increase in the probability of a 30-day delay in monsoon onset in 2050, as a result of changes in the mean climate, from 9-18% today (depending on the region) to 30-40% at the upper tail of the distribution. Predictions of the annual cycle of precipitation suggest an increase in precipitation later in the crop year (April-June) of approximately 10% but a substantial decrease (up to 75% at the tail) in precipitation later in the dry season (July-September). These results indicate a need for adaptation strategies in Indonesian rice agriculture, including increased investments in water storage, drought-tolerant crops, crop diversification, and early warning systems. PMID:17483453

  12. Assessing risks of climate variability and climate change for Indonesian rice agriculture.

    PubMed

    Naylor, Rosamond L; Battisti, David S; Vimont, Daniel J; Falcon, Walter P; Burke, Marshall B

    2007-05-01

    El Niño events typically lead to delayed rainfall and decreased rice planting in Indonesia's main rice-growing regions, thus prolonging the hungry season and increasing the risk of annual rice deficits. Here we use a risk assessment framework to examine the potential impact of El Niño events and natural variability on rice agriculture in 2050 under conditions of climate change, with a focus on two main rice-producing areas: Java and Bali. We select a 30-day delay in monsoon onset as a threshold beyond which significant impact on the country's rice economy is likely to occur. To project the future probability of monsoon delay and changes in the annual cycle of rainfall, we use output from the Intergovernmental Panel on Climate Change AR4 suite of climate models, forced by increasing greenhouse gases, and scale it to the regional level by using empirical downscaling models. Our results reveal a marked increase in the probability of a 30-day delay in monsoon onset in 2050, as a result of changes in the mean climate, from 9-18% today (depending on the region) to 30-40% at the upper tail of the distribution. Predictions of the annual cycle of precipitation suggest an increase in precipitation later in the crop year (April-June) of approximately 10% but a substantial decrease (up to 75% at the tail) in precipitation later in the dry season (July-September). These results indicate a need for adaptation strategies in Indonesian rice agriculture, including increased investments in water storage, drought-tolerant crops, crop diversification, and early warning systems.

  13. How does complex terrain influence responses of carbon and water cycle processes to climate variability and climate change?

    EPA Science Inventory

    We are pursuing the ambitious goal of understanding how complex terrain influences the responses of carbon and water cycle processes to climate variability and climate change. Our studies take place in H.J. Andrews Experimental Forest, an LTER (Long Term Ecological Research) site...

  14. Climate variability and wine quality over Portuguese regions

    NASA Astrophysics Data System (ADS)

    Gouveia, Célia M.; Gani, Érico A.; Liberato, Margarida L. R.

    2015-04-01

    characterized in each region by high/low quality wines. Finally, we also investigated how climate variability is related to DOC wine quality for different regions using North Atlantic Oscillation (NAO) index. Results reveal a strong dependence of wine quality for all regions on maximum temperature and precipitation during spring and summer (the growing season) as expected. However the role of temperature on wine quality seems to be distinct among the diverse regions probably due to their different climate zoning. Moreover, it is shown that the differences associated with high/low quality wine are in agreement with different synoptic fields patterns. Our results suggest that this type of analysis may be used in developing a tool that may help anticipating a vintage/high quality year, based on already available seasonal climate outlooks. Santo F.E., de Lima M.I.P., Ramos A.M., Trigo R.M., Trends in seasonal surface air temperature in mainland Portugal, since 1941, International Journal Climatolology, 34: 1814-1837, doi: 10.1002/joc.3803 (2014) de Lima M.I.P., Santo F.E., Ramos A.M. , Trigo, R.M., Trends and correlations in annual extreme precipitation indices for mainland Portugal, 1941-2007, Theoretical and Applied Climatology, DOI:10.1007/s00704-013-1079-6 (2014) Acknowledgements: This work was partially supported by national funds through FCT (Fundação para a Ciência e a Tecnologia, Portugal) under project QSECA (PTDC/AAGGLO/4155/2012).

  15. Long-term ERP time series as indicators for global climate variability and climate change

    NASA Astrophysics Data System (ADS)

    Lehmann, E.; Grötzsch, A.; Ulbrich, U.; Leckebusch, G. C.; Nevir, P.; Thomas, M.

    2009-04-01

    This study assesses whether variations in observed Earth orientation parameters (EOPs, IERS) such as length-of day (LOD EOP C04) and polar motion (PM EOP C04) can be applied as climate indicators. Data analyses suggest that observed EOPs are differently affected by parameters associated with the atmosphere and ocean. On interannual time scales the varying ocean-atmosphere effects on EOPs are in particular pronounced during episodes of the coupled ocean-atmosphere phenomenon El Niño-Southern Oscillation (ENSO). Observed ENSO anomalies of spatial patterns of parameters affected by atmosphere and ocean (climate indices and sea surface temperatures) are related to LOD and PM variability and associated with possible physical background processes. Present time analyses (1962 - 2000) indicate that the main source of the varying ENSO signal on observed LOD can be associated with anomalies of the relative angular momentum (AAM) related to variations in location and strength of jet streams of the upper troposphere. While on interannual time scales observed LOD and AAM are highly correlated (r=0.75), results suggest that strong El Niño events affect the observed LOD - AAM relation differently strong (explained variance 71%- 98%). Accordingly, the relation between AAM and ocean sea surface temperatures (SST) in the NIÑO 3.4 region differs (explained variances 15%-73%). Corresponding analysis is conducted on modelled EOPs (ERA40 reanalysis, ECHAM5-OM1) to obtain Earth rotation parameters undisturbed by core-mantle activities, and to study rotational variations under climate variability and change. A total of 91 strong El Niño events are analysed in coupled ocean-atmosphere ECHAM5-OM1 scenarios concerning the 20th century (20C), climate warming (A1B) and pre-industrial climate variability. Analyses on a total of 61 strong El Niño events covering a time period of 505 simulation years under pre-industrial climate conditions indicate a range of El Niño events with a strong or

  16. The West African Monsoon: variability and teleconnection with ENSO during the years 1948-57

    NASA Astrophysics Data System (ADS)

    Stickler, Alexander; Brönnimann, Stefan

    2010-05-01

    The intensity of the West African Monsoon (WAM) has been shown to be influenced by different factors. Most important for the existence of the monsoon system is the land-sea thermal contrast between the North African landmass and the Gulf of Guinea. ENSO plays an important role for its interannual variability via an atmospheric teleconnection bridging the Pacific and Atlantic oceanic basins and favouring either descent/weak low-level monsoon flow or ascent/strong low-level monsoon flow over tropical West Africa. Most published studies on the WAM variability are based on reanalysis datasets. However, while reproducing quite well the interannual variability, reanalysis products have been found to contain major biases in certain tropical regions before 1968. These lead to an unrealistic low frequency behaviour and might be explained by the lack of observations assimilated into the reanalyses, as is the case e.g. for tropical Africa where only the much sparser radiosonde data have been assimilated into the NCEP/NCAR Reanalysis (NNR). Here we present an analysis of the interannual WAM variability and its teleconnection with ENSO for the years 1948-57 which is not based on a reanalysis, but on early pilot balloon observational wind data from the Comprehensive Historical Upper Air Network (CHUAN). We have examined wind data from all 36 stations located in the domain (10°S-30°N, 20°W-20°E) on 5 levels up to the mid troposphere (corresponding roughly to the 925, 850, 700, 600 and 500 hPa pressure levels). This analysis shows that 7 subregions can be defined which are characterised by similar vertical wind profiles as well as seasonality: the NW (Mauritania, northern Senegal), the SW (southern Senegal to coastal Guinea), central sub-Saharan West Africa (SSWA, from interior Guinea in the W to coastal Cameroon and southern Niger in the E), central and eastern Niger, western Chad, the western Central African Republic, and the southern coastal regions east of the Gulf of

  17. Impact of Mascarene High variability on the East African `short rains'

    NASA Astrophysics Data System (ADS)

    Manatsa, Desmond; Morioka, Yushi; Behera, Swadhin K.; Matarira, Caxston H.; Yamagata, Toshio

    2014-03-01

    The interannual variability of East African `short rains' (EASR) and its link with the Mascarene High (MH) variation are explored, using observations and reanalysis data. Correlation and composite analyses for flood and drought events reveal that the EASR variability is strongly linked to the MH zonal displacement, in particular, the zonal movement of the MH eastern ridge. When the MH eastern ridge is anomalously displaced to the west (east) of its normal position, the south east (SE) trade winds over the South Indian Ocean (SIO) anomalously strengthen (weaken). This enhances (reduces) the relatively cool and dry SE trade winds and induces cold (warm) sea surface temperature anomaly in the SIO. As a result, convection over the western equatorial SIO is suppressed (enhanced) and leads to rainfall deficits (excess) over East Africa. Droughts in East Africa are associated with a westward migration of the MH eastern ridge, while the relationship is less clear for flood events and their link to an eastward migration of the MH. Therefore, the zonal migration of the MH eastern ridge provides a novel indicator for the EASR extremes especially droughts. This revelation has immense social application for rainfall forecast over East Africa where rainfall deficits have become more prevalent against the background of deteriorating conventional forecasts for EASR droughts.

  18. Some Examples Of Water Resources Variability In The Context Of Climatic Fluctuations

    NASA Astrophysics Data System (ADS)

    Laignel, B.; Massei, N.; Rossi, A.; Mesquita, J.; Slimani, S.

    2008-12-01

    The determination of the impact of climate change on hydrological systems and their water resource constitutes a major stake of the 21st century to which the scientists must answer. First of all, it is necessary to understand how climate are expressed in the hydrosystems. For several years, the M2C laboratory of the University of Rouen has tried to answer this question by working within the framework of many regional, national and international programs as well as PhD works. Those studies involve analyses of hydrological systems located: (1) in various climatic and geomorphological contexts on both sides of the Atlantic Ocean, (2) in various hydrological compartments (surface and ground water), (3) at various spatial scales (watersheds smaller than 1000 km2 and large rivers). The approach consists in studying the long-term changes, oscillations and fluctuations of hydrologic variables by the analysis of time series (precipitation, discharge, piezometry), in particular by means of signal analysis and processing methods. The studied hydrosystems are small watersheds and aquifer in Haute- Normandie, the Seine river (NW France), north-african watersheds (W Morocco and N Algeria), small watersheds and aquifer in Texas, the Colorado river (Texas) and the Mississippi river. Although the identification of structured variations might be uneasy - sometimes just impossible - in raw data, wavelet analysis, for instance, makes it possible to detect localized energetic structures and possible periodicities in all the studied hydrosystems and to quantify them. In many surface hydrosystems we note an intensification of the annual energy band which corresponds to the hydrological cycle. In the NW of France and North Africa, we observe 2-3-year and 5-7-year modes which could be linearly related to fluctuations in the NAO using wavelet coherence. In the USA, we notice similar 2- 3-year and 5-7-year modes that might be possibly related to the characteristic 2-4-year and 4-8-year of

  19. Western equatorial African forest-savanna mosaics: a legacy of late Holocene climatic change?

    NASA Astrophysics Data System (ADS)

    Ngomanda, A.; Chepstow-Lusty, A.; Makaya, M.; Favier, C.; Schevin, P.; Maley, J.; Fontugne, M.; Oslisly, R.; Jolly, D.

    2009-10-01

    Past vegetation and climate changes reconstructed using two pollen records from Lakes Maridor and Nguène, located in the coastal savannas and inland rainforest of Gabon, respectively, provide new insights into the environmental history of western equatorial African rainforests during the last 4500 cal yr BP. These pollen records indicate that the coastal savannas of western equatorial Africa did not exist during the mid-Holocene and instead the region was covered by evergreen rainforests. From ca. 4000 cal yr BP a progressive decline of inland evergreen rainforest, accompanied by the expansion of semi-deciduous rainforest, occurred synchronously with grassland colonisation in the coastal region of Gabon. The contraction of moist evergreen rainforest and the establishment of coastal savannas in Gabon suggest decreasing humidity from ca. 4000 cal yr BP. The marked reduction in evergreen rainforest and subsequent savanna expansion was followed from 2700 cal yr BP by the colonization of secondary forests dominated by the palm, Elaeis guineensis, and the shrub, Alchornea cordifolia (Euphorbiaceae). A return to wetter climatic conditions from about 1400 cal yr BP led to the renewed spread of evergreen rainforest inland, whereas a forest-savanna mosaic still persists in the coastal region. There is no evidence to suggest that the major environmental changes observed were driven by human impact.

  20. Western equatorial African forest-savanna mosaics: a legacy of late Holocene climatic change?

    NASA Astrophysics Data System (ADS)

    Ngomanda, A.; Chepstow-Lusty, A.; Makaya, M.; Favier, C.; Schevin, P.; Maley, J.; Fontugne, M.; Oslisly, R.; Jolly, D.

    2009-02-01

    Past vegetation and climate changes reconstructed using two pollen records from Lakes Maridor and Nguène, Gabon, provide new insights into the environmental history of western equatorial African rainforests during the last 4500 cal yr BP. The Lake Maridor pollen record indicates that the coastal savannas of western equatorial Africa did not exist during the mid-Holocene and instead the region was covered by evergreen rainforests. In the Lake Nguène pollen record, a rapid decline of hygrophilous evergreen rainforest occurred around 4000 cal yr BP, synchronously with grassland expansion around Lake Maridor. The establishment of coastal savannas in Gabon suggests decreasing humidity at the onset of the late Holocene. The marked reduction in evergreen rainforest and subsequent savanna expansion was associated with the colonization of secondary forests dominated by the palm, Elaeis guineensis, in the coastal region and the shrub, Alchornea cordifolia, further inland. A return to wetter climatic conditions from about 1400 cal yr BP led to the renewed spread of evergreen rainforest inland, whereas a forest-savanna mosaic still persists in the coastal region. There is no evidence to suggest that the major environmental changes observed are driven by human impact.

  1. Water resources transfers through southern African food trade: water efficiency and climate signals

    NASA Astrophysics Data System (ADS)

    Dalin, Carole; Conway, Declan

    2016-01-01

    Temporal and spatial variability of precipitation in southern Africa is particularly high. The associated drought and flood risks, combined with a largely rain-fed agriculture, pose a challenge for water and food security in the region. As regional collaboration strengthens through the Southern Africa Development Community and trade with other regions increases, it is thus important to understand both how climate variability affects agricultural productivity and how food trade (regional and extra-regional) can contribute to the region's capacity to deal with climate-related shocks. We combine global hydrological model simulations with international food trade data to quantify the water resources embedded in international food trade in southern Africa and with the rest of the world, from 1986-2011. We analyze the impacts of socio-economic changes and climatic variability on agricultural trade and embedded water resources during this period. We find that regional food trade is efficient in terms of water use but may be unsustainable because water-productive exporters, like South Africa, rely on increasingly stressed water resources. The role of imports from the rest of the world in the region's food supply is important, in particular during severe droughts. This reflects how trade can efficiently redistribute water resources across continents in response to a sudden gap in food production. In a context of regional and global integration, our results highlight opportunities for improved water-efficiency and sustainability of the region's food supply via trade.

  2. Precessional(?) Variability in East African Aridity During the Past Few Hundred Thousand Years

    NASA Astrophysics Data System (ADS)

    Shi, J.; Brown, E. T.; Johnson, T. C.; Scholz, C. A.; Cohen, A. S.; King, J.

    2007-12-01

    We used scanning X-ray fluorescence to investigate fluctuations in calcium abundance in the upper 200 m of cores MAL05-1B and 1C recovered by the Lake Malawi Drilling Project from a central lake site. Conspicuous variations in calcium concentrations reflect the abundance of endogenic calcite, which accumulates during periods of relatively dry conditions in the Malawi basin. Major calcium peaks occur at fairly regular intervals down core. The power spectrum of calcium on a depth scale reveals a large concentration of variance in the 20-meter- band. More detailed analyses were undertaken on MAL05-1C which has a well-constrained age-depth model built on radiocarbon, paleointensity, inclination, 10Be, and OSL dating [Scholz et al., in press]. We attribute the cycles of calcium fluctuation in MAL05-1C to monsoonal climate driven by variations in local insolation dominated by eccentricity-modulated precession. Scholz, C.A., T.C. Johnson, A.S. Cohen, J.W. King, J.A. Peck, J.T. Overpeck, M.K. Talbot, E.T. Brown, L. Kalindekafe, P.Y.O. Amoako, R.P. Lyons, T.M. Shanahan, I.S. Castaneda, C.W. Heil, S.L. Forman, L.R. McHargue, K. Beuning, J. Gomez, and J. Pierson, East African megadroughts between 135-75 kyr ago and implications for early human history, Proceedings of the National Academy of Sciences, in press.

  3. Changing Seasonality of Tundra Vegetation and Associated Climatic Variables

    NASA Astrophysics Data System (ADS)

    Bhatt, U. S.; Walker, D. A.; Raynolds, M. K.; Bieniek, P.; Epstein, H. E.; Comiso, J. C.; Pinzon, J.; Tucker, C. J.; Steele, M.; Ermold, W. S.; Zhang, J.

    2014-12-01

    This study documents changes in the seasonality of tundra vegetation productivity and its associated climate variables using long-term data sets. An overall increase of Pan-Arctic tundra greenness potential corresponds to increased land surface temperatures and declining sea ice concentrations. While sea ice has continued to decline, summer land surface temperature and vegetation productivity increases have stalled during the last decade in parts of the Arctic. To understand the processes behind these features we investigate additional climate parameters. This study employs remotely sensed weekly 25-km sea ice concentration, weekly surface temperature, and bi-weekly NDVI from 1982 to 2013. Maximum NDVI (MaxNDVI, Maximum Normalized Difference Vegetation Index), Time Integrated NDVI (TI-NDVI), Summer Warmth Index (SWI, sum of degree months above freezing during May-August), ocean heat content (PIOMAS, model incorporating ocean data assimilation), and snow water equivalent (GlobSnow, assimilated snow data set) are explored. We analyzed the data for the full period (1982-2013) and for two sub-periods (1982-1998 and 1999-2013), which were chosen based on the declining Pan-Arctic SWI since 1998. MaxNDVI has increased from 1982-2013 over most of the Arctic but has declined from 1999 to 2013 over western Eurasia, northern Canada, and southwest Alaska. TI-NDVI has trends that are similar to those for MaxNDVI for the full period but displays widespread declines over the 1999-2013 period. Therefore, as the MaxNDVI has continued to increase overall for the Arctic, TI-NDVI has been declining since 1999. SWI has large relative increases over the 1982-2013 period in eastern Canada and Greenland and strong declines in western Eurasia and southern Canadian tundra. Weekly Pan-Arctic tundra land surface temperatures warmed throughout the summer during the 1982-1998 period but display midsummer declines from 1999-2013. Weekly snow water equivalent over Arctic tundra has declined over

  4. Analysis of climate variability in mainland Portugal using a combined Climate Extremes Index

    NASA Astrophysics Data System (ADS)

    Espírito Santo, Fátima; de Lima, Isabel P.

    2014-05-01

    summer and winter there is an increase (not statistically significant) towards more widespread events in both the dry and wet extremes. Overall, this study shows the usefulness of the CEI in regional applications, by allowing the increased understanding of the spatial and temporal development of extreme events while combining the air temperature and precipitation extremes. These climate variables are usually inspected separately whereas their combined analysis provides additional important information.

  5. A study of mathematics and science achievement scores among African American students and the impact of teacher-oriented variables on them through the Educational Longitudinal Study, 2002 (ELS: 2002) data

    NASA Astrophysics Data System (ADS)

    Walker, Valentine

    The purpose of this dissertation was to utilize the ELS: 2002 longitudinal data to highlight the achievement of African American students relative to other racial sub-groups in mathematics and science and to highlight teacher oriented variables that might influence their achievement. Various statistical tools, including descriptive statistics, ANOVA, Multiple Regression were used to analyze data that was derived from the students', teachers' and administrations' questionnaires compiled in the base year of the study (2002) as well as the first follow-up transcript study (2006). The major findings are as follows: African American students performed lower than all other major racial subgroups in mathematics and science; Parental variables including SES and parental education were strong correlates of achievement in mathematics and science: The amount and type of mathematics and science courses students took were strong predictors of achievement in mathematics and science; Teachers' race, experience, certification status, graduate courses completed and professional development influenced African American students' achievement in mathematics and science; Aspects of classroom climate including teacher-pupil relationship, classroom management, students' perception of quality instructions, praise and rewards system might influence African American students' achievement in mathematics and science; Teachers' beliefs pertaining to students' background and intellectual ability might influence their educational expectation of African American students and subsequently student achievement in mathematics and science; Teaching strategies such as reviewing, lecturing and using graphing calculators had a positive influence on mathematics achievement while using computers, discussion and using other books than mathematics textbooks had negative influences on mathematics achievement; Computer use in science had positive influence on science achievement while homework had a positive

  6. Detection of trends in surface ozone in the presence of climate variability

    NASA Astrophysics Data System (ADS)

    Barnes, Elizabeth A.; Fiore, Arlene M.; Horowitz, Larry W.

    2016-05-01

    Trends in trace atmospheric constituents can be driven not also by trends in their (precursor) emissions but also by trends in meteorology. Here we use ground-level ozone as an example to highlight the extent to which unforced, low-frequency climate variability can drive multidecadal trends. Using output from six experiments of the Geophysical Fluid Dynamics Laboratory chemistry-climate model (CM3), we demonstrate that 20 year trends in surface ozone driven by climate variability alone can be as large as those forced by changes in ozone precursor emissions or by anthropogenic climate change. We highlight regions and seasons where surface ozone is strongly influenced by climate variability and thus where a given forced trend may be more difficult to detect. A corollary is that this approach identifies regions and seasons of low variability, where measurement sites may be most effectively deployed to detect a particular trend driven by changing precursor emissions. We find that the representative concentration pathways 4.5 (RCP4.5) and RCP8.5 forced surface ozone trends in most locations emerge over background variability during the first half of the 21st century. Ozone trends are found to respond mostly to changes in emissions of ozone precursors and unforced climate variability, with a comparatively small impact from anthropogenic climate change. Thus, attempts to attribute observed trends to regional emissions changes require consideration of internal climate variability, particularly for short record lengths and small forced trends.

  7. Australia: Climate-Ecosystem Variability and Impacts on Disease

    NASA Astrophysics Data System (ADS)

    Gustafson, K. C.; Diabate, M.; Anyamba, A.

    2012-12-01

    Climate variability in Australia is largely driven by an atmospheric phenomenon called the Southern Oscillation (SO), which involves a see-saw like behavior between low and high pressure systems within the equatorial Pacific regions. The interaction of SO with abnormally high sea surface temperatures (SSTs) - El Niño - or abnormally low SSTs - La Niña ("anti-El Niño") - creates extreme drought or extreme flooding respectively throughout the Australian continent. These El Niño-Southern Oscillation (ENSO) events have significant impacts on Australia's landscape, ecosystems, agriculture production, and, as this report show, human health. The teleconnection between ENSO and human health is straight forward but not obvious. During La Niña years, when ENSO events are characterized by increased rainfall and consequential flooding, Australia's tropical, warm climate in addition to an associated increase in vegetation growth from the increased rainfall creates an ideal habitat for mosquito population increase. Certain species of Australian mosquitoes [Culux annulirostris] are carriers of Murray Valley Encephalitis (MVE) virus which is a rare but potentially fatal infection that attacks neurological and muscular functioning. It is hypothesized that a widespread increase in vegetation indicates an expansion of ideal mosquito production habitats and will translate to an increased risk of MVE contraction. The objective of this research is to show if a correlation exists between the ENSO-driven climate- and consequential ecosystem- changes and MVE outbreaks throughout Australia. To do so, this study makes use of the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor operating on NASA's Terra satellite to obtain monthly Normalized Difference Vegetation Index (NDVI) data. It is assumed in this research that an anomalous increase in NDVI values - indicative of vegetation growth - occurs as a result of increased rainfall. Due to Australia's tropical positioning and

  8. Experimental climate warming decreases photosynthetic efficiency of lichens in an arid South African ecosystem.

    PubMed

    Maphangwa, Khumbudzo Walter; Musil, Charles F; Raitt, Lincoln; Zedda, Luciana

    2012-05-01

    Elevated temperatures and diminished precipitation amounts accompanying climate warming in arid ecosystems are expected to have adverse effects on the photosynthesis of lichen species sensitive to elevated temperature and/or water limitation. This premise was tested by artificially elevating temperatures (increase 2.1-3.8°C) and reducing the amounts of fog and dew precipitation (decrease 30.1-31.9%), in an approximation of future climate warming scenarios, using transparent hexagonal open-top warming chambers placed around natural populations of four lichen species (Xanthoparmelia austroafricana, X. hyporhytida , Xanthoparmelia. sp., Xanthomaculina hottentotta) at a dry inland site and two lichen species (Teloschistes capensis and Ramalina sp.) at a humid coastal site in the arid South African Succulent Karoo Biome. Effective photosynthetic quantum yields ([Formula: see text]) were measured hourly throughout the day at monthly intervals in pre-hydrated lichens present in the open-top warming chambers and in controls which comprised demarcated plots of equivalent open-top warming chamber dimensions constructed from 5-cm-diameter mesh steel fencing. The cumulative effects of the elevated temperatures and diminished precipitation amounts in the open-top warming chambers resulted in significant decreases in lichen [Formula: see text]. The decreases were more pronounced in lichens from the dry inland site (decline 34.1-46.1%) than in those from the humid coastal site (decline 11.3-13.7%), most frequent and prominent in lichens at both sites during the dry summer season, and generally of greatest magnitude at or after the solar noon in all seasons. Based on these results, we conclude that climate warming interacting with reduced precipitation will negatively affect carbon balances in endemic lichens by increasing desiccation damage and reducing photosynthetic activity time, leading to increased incidences of mortality.

  9. Delayed detection of climate mitigation benefits due to climate inertia and variability.

    PubMed

    Tebaldi, Claudia; Friedlingstein, Pierre

    2013-10-22

    Climate change mitigation acts by reducing greenhouse gas emissions, and thus curbing, or even reversing, the increase in their atmospheric concentration. This reduces the associated anthropogenic radiative forcing, and hence the size of the warming. Because of the inertia and internal variability affecting the climate system and the global carbon cycle, it is unlikely that a reduction in warming would be immediately discernible. Here we use 21st century simulations from the latest ensemble of Earth System Model experiments to investigate and quantify when mitigation becomes clearly discernible. We use one of the scenarios as a reference for a strong mitigation strategy, Representative Concentration Pathway (RCP) 2.6 and compare its outcome with either RCP4.5 or RCP8.5, both of which are less severe mitigation pathways. We analyze global mean atmospheric CO2, and changes in annually and seasonally averaged surface temperature at global and regional scales. For global mean surface temperature, the median detection time of mitigation is about 25-30 y after RCP2.6 emissions depart from the higher emission trajectories. This translates into detection of a mitigation signal by 2035 or 2045, depending on whether the comparison is with RCP8.5 or RCP4.5, respectively. The detection of climate benefits of emission mitigation occurs later at regional scales, with a median detection time between 30 and 45 y after emission paths separate. Requiring a 95% confidence level induces a delay of several decades, bringing detection time toward the end of the 21st century.

  10. Delayed detection of climate mitigation benefits due to climate inertia and variability.

    PubMed

    Tebaldi, Claudia; Friedlingstein, Pierre

    2013-10-22

    Climate change mitigation acts by reducing greenhouse gas emissions, and thus curbing, or even reversing, the increase in their atmospheric concentration. This reduces the associated anthropogenic radiative forcing, and hence the size of the warming. Because of the inertia and internal variability affecting the climate system and the global carbon cycle, it is unlikely that a reduction in warming would be immediately discernible. Here we use 21st century simulations from the latest ensemble of Earth System Model experiments to investigate and quantify when mitigation becomes clearly discernible. We use one of the scenarios as a reference for a strong mitigation strategy, Representative Concentration Pathway (RCP) 2.6 and compare its outcome with either RCP4.5 or RCP8.5, both of which are less severe mitigation pathways. We analyze global mean atmospheric CO2, and changes in annually and seasonally averaged surface temperature at global and regional scales. For global mean surface temperature, the median detection time of mitigation is about 25-30 y after RCP2.6 emissions depart from the higher emission trajectories. This translates into detection of a mitigation signal by 2035 or 2045, depending on whether the comparison is with RCP8.5 or RCP4.5, respectively. The detection of climate benefits of emission mitigation occurs later at regional scales, with a median detection time between 30 and 45 y after emission paths separate. Requiring a 95% confidence level induces a delay of several decades, bringing detection time toward the end of the 21st century. PMID:24101485

  11. Population variability complicates the accurate detection of climate change responses.

    PubMed

    McCain, Christy; Szewczyk, Tim; Bracy Knight, Kevin

    2016-06-01

    The rush to assess species' responses to anthropogenic climate change (CC) has underestimated the importance of interannual population variability (PV). Researchers assume sampling rigor alone will lead to an accurate detection of response regardless of the underlying population fluctuations of the species under consideration. Using population simulations across a realistic, empirically based gradient in PV, we show that moderate to high PV can lead to opposite and biased conclusions about CC responses. Between pre- and post-CC sampling bouts of modeled populations as in resurvey studies, there is: (i) A 50% probability of erroneously detecting the opposite trend in population abundance change and nearly zero probability of detecting no change. (ii) Across multiple years of sampling, it is nearly impossible to accurately detect any directional shift in population sizes with even moderate PV. (iii) There is up to 50% probability of detecting a population extirpation when the species is present, but in very low natural abundances. (iv) Under scenarios of moderate to high PV across a species' range or at the range edges, there is a bias toward erroneous detection of range shifts or contractions. Essentially, the frequency and magnitude of population peaks and troughs greatly impact the accuracy of our CC response measurements. Species with moderate to high PV (many small vertebrates, invertebrates, and annual plants) may be inaccurate 'canaries in the coal mine' for CC without pertinent demographic analyses and additional repeat sampling. Variation in PV may explain some idiosyncrasies in CC responses detected so far and urgently needs more careful consideration in design and analysis of CC responses.

  12. Spatio-temporal Trends of Climate Variability in North Carolina

    NASA Astrophysics Data System (ADS)

    Sayemuzzaman, Mohammad

    Climatic trends in spatial and temporal variability of maximum temperature (Tmax), minimum temperature (Tmin), mean temperature (Tmean) and precipitation were evaluated for 249 ground-based stations in North Carolina for 1950-2009. The Mann-Kendall (MK), the Theil-Sen Approach (TSA) and the Sequential Mann-Kendall (SQMK) tests were applied to quantify the significance of trend, magnitude of trend and the trend shift, respectively. The lag-1 serial correlation and double mass curve techniques were used to address the data independency and homogeneity. The pre-whitening technique was used to eliminate the effect of auto correlation of the data series. The difference between minimum and maximum temperatures, and so the diurnal temperature range (DTR), at some stations was found to be decreasing on both an annual and a seasonal basis, with an overall increasing trend in the mean temperature. For precipitation, a statewide increasing trend in fall (highest in November) and decreasing trend in winter (highest in February) were detected. No pronounced increasing/decreasing trends were detected in annual, spring, and summer precipitation time series. Trend analysis on a spatial scale (for three physiographic regions: mountain, piedmont and coastal) revealed mixed results. Coastal zone exhibited increasing mean temperature (warming) trend as compared to other locations whereas mountain zone showed decreasing trend (cooling). Three main moisture components (precipitation, total cloud cover, and soil moisture) and the two major atmospheric circulation modes (North Atlantic Oscillation and Southern Oscillation) were used for correlative analysis purposes with the temperature (specifically with DTR) and precipitation trends. It appears that the moisture components are associated with DTR more than the circulation modes in North Carolina.

  13. West African Climate and Linkages with the Atlantic Ocean, the Mediterranean Basin and Eurasia

    NASA Astrophysics Data System (ADS)

    Paz, S.; Tourre, Y. M.

    2010-09-01

    Large-scale Atlantic, Mediterranean and European climate conditions are not independent from anomalous rainfall patterns over the Sahel. Sahelian droughts are indeed linked to low-frequency climate variability in the North Atlantic i.e., multi-decadal (MDO) and quasi-decadal (QDO). As such, linkages (significant correlations) were investigated for the 1926-2006 period between the Sahelian rainfall and the following Atlantic climate indices: 1. Atlantic Multi-decadal Oscillation (AMO) 2. Atlantic Meridional Mode (AMM, SST and Wind) 3. North Africa-West Asia index (NAWA, and NA & WA poles) 4. Multi-Decadal Oscillation (MDO) 5. Quasi-Decadal Oscillation (QDO) 6. Tropical North Atlantic (TNA, SST), 7. Tropical South Atlantic (TSA, SST) The main results are: Significant relationships (0.05 level, Z-test) were detected between the spring NA pole of the NAWA index and summer Sahelian rainfall of the same year. Correlations (r = 0.54/0.43) were found between the winter AMO and summer Sahelian rainfall indices for the 1950-2006 and 1926-2006 periods, respectively. During the 20th century, the north Atlantic SST anomalies have changed phases three times. The last cooling phase (between 1968 and 1995) resulted in the long-lasting drought in the Sahel. This is also the period when the Azores anticyclone was displaced anomalously south-eastward and the ITCZ further south. It is also found that the cooling over the northern latitudes of Eurasia is associated with a warming tendency over the Sahel. Correlations between fall AMO and summer NA (r = 0.57/0.63) were found for the 1950-2006 period. Significant correlation were detected between summer AMM (wind and SST) and the Sahelian rainfall (r = 0.65 and 0.42 respectively). Linkages were also found with TNA-TSA (summer and fall). MDO/AMO and QDO SST/SLP displayed coherent patterns during the spatio-temporal evolution of the low-frequency climate signals. These findings add more insight on the variability of northern atmospheric

  14. Incorporating climate change trends to near future variability of crop yields in Iberia Peninsula

    NASA Astrophysics Data System (ADS)

    Capa-Morocho, Mirian; Baethgen, Walter E.; Fernandes, Kátia; Rodríguez-Fonseca, Belén; Ruiz-Ramos, Margarita

    2016-04-01

    In this study, we analyze the effects of near future climate variability on cropping systems in Iberian Peninsula (IP). For this purpose, we generated climate sequences that simulate realistic variability on annual to decadal time scales. The sequences incorporate nonlinear climate change trends, using statistical methods and and an ensemble of global climate models from the Coupled Model Intercomparison Project (CMIP5). Then, the climate sequences are temporal downscaled into daily weather data and used as inputs to crop models. As case study, we evaluate the impacts of plausible future climate scenarios on rain-fed wheat yield two agricultural locations in IP. We adapted the method by Greene et al., (2012 and 2015) for informing climate projections for the coming decades with a combination of seasonal to interannual and anthropogenically forced climate change information for accounting the Near-term Climate Change. Long-term data containing solar radiation, maximum and minimum temperature and rainfall are needed to apply this method. The climate variability observed was decomposed into long-range trend, decadal and interannual variability to understand the relative importance of each time scale. The interannual variability was modeled based on the observational records. The results of this study may have important implications on public and private sectors to analyze the probabilistic projections of impacts and agronomic adaptations of near future climate variability in Iberian Peninsula. This study has been funded by MACSUR project from FACCE-JPI. References Greene, A.M., Goddard, L., Gonzalez, P.L., Ines, A.V. and Chryssanthacopoulos, J., 2015.A climate generator for agricultural planning in southeastern South America.Agricultural and Forest Meteorology, 203: 217-228. Greene, A.M., Hellmuth, M. and Lumsden, T., 2012. Stochastic decadal climate simulations for the Berg and Breede water management areas, western Cape province, South Africa. Water Resources

  15. Beyond a climate-centric view of plant distribution: edaphic variables add value to distribution models.

    PubMed

    Beauregard, Frieda; de Blois, Sylvie

    2014-01-01

    Both climatic and edaphic conditions determine plant distribution, however many species distribution models do not include edaphic variables especially over large geographical extent. Using an exceptional database of vegetation plots (n = 4839) covering an extent of ∼55,000 km2, we tested whether the inclusion of fine scale edaphic variables would improve model predictions of plant distribution compared to models using only climate predictors. We also tested how well these edaphic variables could predict distribution on their own, to evaluate the assumption that at large extents, distribution is governed largely by climate. We also hypothesized that the relative contribution of edaphic and climatic data would vary among species depending on their growth forms and biogeographical attributes within the study area. We modelled 128 native plant species from diverse taxa using four statistical model types and three sets of abiotic predictors: climate, edaphic, and edaphic-climate. Model predictive accuracy and variable importance were compared among these models and for species' characteristics describing growth form, range boundaries within the study area, and prevalence. For many species both the climate-only and edaphic-only models performed well, however the edaphic-climate models generally performed best. The three sets of predictors differed in the spatial information provided about habitat suitability, with climate models able to distinguish range edges, but edaphic models able to better distinguish within-range variation. Model predictive accuracy was generally lower for species without a range boundary within the study area and for common species, but these effects were buffered by including both edaphic and climatic predictors. The relative importance of edaphic and climatic variables varied with growth forms, with trees being more related to climate whereas lower growth forms were more related to edaphic conditions. Our study identifies the potential

  16. Beyond a Climate-Centric View of Plant Distribution: Edaphic Variables Add Value to Distribution Models

    PubMed Central

    Beauregard, Frieda; de Blois, Sylvie

    2014-01-01

    Both climatic and edaphic conditions determine plant distribution, however many species distribution models do not include edaphic variables especially over large geographical extent. Using an exceptional database of vegetation plots (n = 4839) covering an extent of ∼55000 km2, we tested whether the inclusion of fine scale edaphic variables would improve model predictions of plant distribution compared to models using only climate predictors. We also tested how well these edaphic variables could predict distribution on their own, to evaluate the assumption that at large extents, distribution is governed largely by climate. We also hypothesized that the relative contribution of edaphic and climatic data would vary among species depending on their growth forms and biogeographical attributes within the study area. We modelled 128 native plant species from diverse taxa using four statistical model types and three sets of abiotic predictors: climate, edaphic, and edaphic-climate. Model predictive accuracy and variable importance were compared among these models and for species' characteristics describing growth form, range boundaries within the study area, and prevalence. For many species both the climate-only and edaphic-only models performed well, however the edaphic-climate models generally performed best. The three sets of predictors differed in the spatial information provided about habitat suitability, with climate models able to distinguish range edges, but edaphic models able to better distinguish within-range variation. Model predictive accuracy was generally lower for species without a range boundary within the study area and for common species, but these effects were buffered by including both edaphic and climatic predictors. The relative importance of edaphic and climatic variables varied with growth forms, with trees being more related to climate whereas lower growth forms were more related to edaphic conditions. Our study identifies the potential for

  17. Water resources transfers through southern African food trade: water efficiency and climate signals

    NASA Astrophysics Data System (ADS)

    Dalin, C.; Conway, D.

    2015-12-01

    Temporal and spatial variability of precipitation in Southern Africa is particularly high. The associated drought and flood risks, combined with a largely rainfed agriculture, pose a challenge for water and food security in this region. It is thus important to understand both how climate variability affects agricultural productivity and how intra- and extra-regional trade can contribute to the region's capacity to deal with climate-related shocks. We combine international food trade data and a global hydrological model to quantify the water resources embedded in international food trade in southern Africa and with the rest of the world, from 1986-2011. We analyze the impacts of socio-economic, political and climatic changes on agricultural trade and embedded water resources during that period. We find that regional food trade is efficient in terms of water resources but may be unsustainable because water-productive exporters, like South Africa, rely on increasingly scarce water resources. The role of imports from the rest of the world in the region's food supply is important, in particular during severe droughts. This reflects how trade can efficiently redistribute water resources across continents in response to a sudden gap in food production and water productivity. As regional collaboration strengthens through the Southern Africa Development Community (SADC) and trade with other regions increases, our results point out opportunities for improved water-efficiency and sustainability of the region's food production via trade.

  18. Long-term Variability of NorthWest African coastal upwelling

    NASA Astrophysics Data System (ADS)

    Wade, Malick; Rodríguez-Fonseca, Belen; Lazar, Alban

    2014-05-01

    The NorthWest African sea surface temperature variability can be due to changes in the coastal upwelling system, which in turn can be due to alterations in local winds, global winds induced by teleconnections and propagation of waves from wind burst in remote regions. The two last processes could be due in turn to changes in the sea surface temperature in extended regions remote from the upwelling region, as changes in Pacific SSTs associated with ENSO, or in the Equatorial Atlantic SSTs. This work demonstrates that the whole signal cannot be explained by local wind/Ekman pumping and large scale winds induced by teleconnections play an important role. Using observational data of SSTs and winds from atmospheric reanalysis, and applying different statistical technics, as correlation analysis, filtering and discriminant analysis, the different influences and its stationarity along the observational period are tested pointing to the non stationarity of El Niño influence in FMA and to other possible predictors influencing in the region.

  19. Effects of Climate Variability and Change on Groundwater Resources of the United States

    USGS Publications Warehouse

    Gurdak, Jason S.; Hanson, Randall T.; Green, Timothy R.

    2009-01-01

    Groundwater is an important part of the global fresh water supply and is affected by climate. U.S. Geological Survey (USGS) scientists are working with local, State, Federal, and international partners to understand how the availability and sustainability of groundwater resources in the United States will be affected by climate variability and change. This fact sheet describes climate variability and change, important groundwater resources of the Nation, and how USGS research is helping to answer critical questions about the effects of climate on groundwater.

  20. Natural variability of the climate as predicted by a simple ocean model with parameterized thermohaline circulation

    SciTech Connect

    Watts, R.G.; Li, S.

    1995-12-31

    Variability of the Earth`s climate can take place on many time scales as a result of internal features. This natural variability is important to humans since it affects such important human enterprises as agriculture, floods, droughts, etc. The authors investigate natural variability within a simple ocean model.

  1. Revisiting the role of global SST anomalies and their effects on West African monsoon variability

    NASA Astrophysics Data System (ADS)

    Pomposi, Catherine; Kushnir, Yochanan; Giannini, Alessandra

    2016-04-01

    The West African Monsoon is a significant component of the global monsoon system, delivering the majority of annual precipitation for the Sahel and varying on timescales from seasons to decades and beyond. Much of the internal variability of this system is driven by sea surface temperature (SST) anomalies and their resulting atmospheric teleconnections linking oceanic changes to land-based precipitation. Previous idealized studies have identified the role of particular ocean basins in driving monsoon variations on a number of key timescales, including the Atlantic basin as the main driver behind decadal-scale changes and the Pacific basin for interannual variability. However, understanding of how the monsoon responds to global SSTs remains incomplete because the system can be affected by moisture availability locally as well as tropical atmospheric stability, both of which are influenced by ocean temperatures. Furthermore, the complexity of how the global ocean basins change in relation to one another (what we refer to as superposition of anomalies) can result in Sahel precipitation anomalies that are contrary to what one might posit when considering the state of a single basin alone (e.g. the 2015 El Niño event and a relatively wet Sahel). The aim of this work is to revisit the role of global SSTs in driving Sahel rainfall variability over the recent past using a blending of observations and new model output. We seek to disentangle the state of various basins in combination with each other in driving normal or anomalously dry or wet years, resolving the ways that remote and local ocean forcings affect the movement of convection from the Guinea coast inland and northward into the Sahel, and include the study of circulation and stability components of the atmosphere. Preliminary diagnostic work suggests that varying SST conditions across ocean basins could imprint distinctly different precipitation responses in the Sahel. For example, precipitation anomalies are

  2. Assessing the importance of climate variables for the spatial distribution of modern pollen data in China

    NASA Astrophysics Data System (ADS)

    Li, Jianyong; Xu, Qinghai; Zheng, Zhuo; Lu, Houyuan; Luo, Yunli; Li, Yuecong; Li, Chunhai; Seppä, Heikki

    2015-03-01

    To assess the importance of climate variables for the distribution of modern pollen data in China, we present a continental-scale dataset consisting of 1374 samples. Boosted regression trees and constrained ordination techniques are employed to quantify the importance of six climate variables (annual precipitation, PANN; actual/potential evapotranspiration ratio, Alpha; mean annual temperature, TANN; mean temperature of the warmest month, MTWA; mean temperature of the coldest month, MTCO; annual sum of the growing degree days above 5°C, GDD5) for the distribution of individual pollen taxa and modern pollen assemblages. The results show that taxon-specific responses to the climate variables display a wide regional diversity and that the climate variables with low collinearity that best account for the spatial variability of modern pollen assemblages differ regionally. PANN is the most important variable in northwestern and northeastern China and the Tibetan Plateau, while MTWA and MTCO are the dominant variables in east-central and southern China. This suggests that the climate variables that can be optimally reconstructed from fossil pollen data vary in different bioclimatic regions of China. This feature is typical to many continental-scale modern pollen datasets and needs to be considered in pollen-based climate reconstructions.

  3. Slowing down of North Pacific climate variability and its implications for abrupt ecosystem change.

    PubMed

    Boulton, Chris A; Lenton, Timothy M

    2015-09-15

    Marine ecosystems are sensitive to stochastic environmental variability, with higher-amplitude, lower-frequency--i.e., "redder"--variability posing a greater threat of triggering large ecosystem changes. Here we show that fluctuations in the Pacific Decadal Oscillation (PDO) index have slowed down markedly over the observational record (1900-present), as indicated by a robust increase in autocorrelation. This "reddening" of the spectrum of climate variability is also found in regionally averaged North Pacific sea surface temperatures (SSTs), and can be at least partly explained by observed deepening of the ocean mixed layer. The progressive reddening of North Pacific climate variability has important implications for marine ecosystems. Ecosystem variables that respond linearly to climate forcing will have become prone to much larger variations over the observational record, whereas ecosystem variables that respond nonlinearly to climate forcing will have become prone to more frequent "regime shifts." Thus, slowing down of North Pacific climate variability can help explain the large magnitude and potentially the quick succession of well-known abrupt changes in North Pacific ecosystems in 1977 and 1989. When looking ahead, despite model limitations in simulating mixed layer depth (MLD) in the North Pacific, global warming is robustly expected to decrease MLD. This could potentially reverse the observed trend of slowing down of North Pacific climate variability and its effects on marine ecosystems.

  4. Slowing down of North Pacific climate variability and its implications for abrupt ecosystem change

    PubMed Central

    Boulton, Chris A.; Lenton, Timothy M.

    2015-01-01

    Marine ecosystems are sensitive to stochastic environmental variability, with higher-amplitude, lower-frequency––i.e., “redder”––variability posing a greater threat of triggering large ecosystem changes. Here we show that fluctuations in the Pacific Decadal Oscillation (PDO) index have slowed down markedly over the observational record (1900–present), as indicated by a robust increase in autocorrelation. This “reddening” of the spectrum of climate variability is also found in regionally averaged North Pacific sea surface temperatures (SSTs), and can be at least partly explained by observed deepening of the ocean mixed layer. The progressive reddening of North Pacific climate variability has important implications for marine ecosystems. Ecosystem variables that respond linearly to climate forcing will have become prone to much larger variations over the observational record, whereas ecosystem variables that respond nonlinearly to climate forcing will have become prone to more frequent “regime shifts.” Thus, slowing down of North Pacific climate variability can help explain the large magnitude and potentially the quick succession of well-known abrupt changes in North Pacific ecosystems in 1977 and 1989. When looking ahead, despite model limitations in simulating mixed layer depth (MLD) in the North Pacific, global warming is robustly expected to decrease MLD. This could potentially reverse the observed trend of slowing down of North Pacific climate variability and its effects on marine ecosystems. PMID:26324900

  5. Characterization of Climate Change and Variability with GPS

    NASA Technical Reports Server (NTRS)

    Kursinski, R.

    1999-01-01

    influence of natural climate variability. S. Leroy concludes that the signal-to-noise ratio of global warming detection increases by unity approximately every 10 years if a single oceanic region is chosen. Less time for detection is likely when many global regions are considered simultaneously. GPS occultation constellations allow the possibility of detecting small changes in upper air temperature with inconsequential calibration errors, making occultation an ideal data type for global warming detection studies. Our initial study of a 22-GHz satellite-satellite occultation system predicts upper troposphere moisture sensitivities of 3-5 ppmv and 1-2 percent in the middle and lower troposphere. Additional information contained in original.

  6. Subseasonal climate variability for North Carolina, United States

    NASA Astrophysics Data System (ADS)

    Sayemuzzaman, Mohammad; Jha, Manoj K.; Mekonnen, Ademe; Schimmel, Keith A.

    2014-08-01

    Subseasonal trends in climate variability for maximum temperature (Tmax), minimum temperature (Tmin) and precipitation were evaluated for 249 ground-based stations in North Carolina for 1950-2009. The magnitude and significance of the trends at all stations were determined using the non-parametric Theil-Sen Approach (TSA) and the Mann-Kendall (MK) test, respectively. The Sequential Mann-Kendall (SQMK) test was also applied to find the initiation of abrupt trend changes. The lag-1 serial correlation and double mass curve were employed to address the data independency and homogeneity. Using the MK trend test, statistically significant (confidence level ≥ 95% in two-tailed test) decreasing (increasing) trends by 44% (45%) of stations were found in May (June). In general, trends were decreased in Tmax and increased in Tmin data series in subseasonal scale. Using the TSA method, the magnitude of lowest (highest) decreasing (increasing) trend in Tmax is - 0.050 °C/year (+ 0.052 °C/year) in the monthly series for May (March) and for Tmin is - 0.055 °C/year (+ 0.075 °C/year) in February (December). For the precipitation time series using the TSA method, it was found that the highest (lowest) magnitude of 1.00 mm/year (- 1.20 mm/year) is in September (February). The overall trends in precipitation data series were not significant at the 95% confidence level except that 17% of stations were found to have significant (confidence level ≥ 95% in two-tailed test) decreasing trends in February. The statistically significant trend test results were used to develop a spatial distribution of trends: May for Tmax, June for Tmin, and February for precipitation. A correlative analysis of significant temperature and precipitation trend results was examined with respect to large scale circulation modes (North Atlantic Oscillation (NAO) and Southern Oscillation Index (SOI). A negative NAO index (positive-El Niño Southern Oscillation (ENSO) index) was found to be associated with

  7. Variability of West African monsoon patterns generated by a WRF multi-physics ensemble

    NASA Astrophysics Data System (ADS)

    Klein, Cornelia; Heinzeller, Dominikus; Bliefernicht, Jan; Kunstmann, Harald

    2015-11-01

    The credibility of regional climate simulations over West Africa stands and falls with the ability to reproduce the West African monsoon (WAM) whose precipitation plays a pivotal role for people's livelihood. In this study, we simulate the WAM for the wet year 1999 with a 27-member multi-physics ensemble of the Weather Research and Forecasting (WRF) model. We investigate the inter-member differences in a process-based manner in order to extract generalizable information on the behavior of the tested cumulus (CU), microphysics (MP), and planetary boundary layer (PBL) schemes. Precipitation, temperature and atmospheric dynamics are analyzed in comparison to the Tropical Rainfall Measuring Mission (TRMM) rainfall estimates, the Global Precipitation Climatology Centre (GPCC) gridded gauge-analysis, the Global Historical Climatology Network (GHCN) gridded temperature product and the forcing data (ERA-Interim) to explore interdependencies of processes leading to a certain WAM regime. We find that MP and PBL schemes contribute most to the ensemble spread (147 mm month-1) for monsoon precipitation over the study region. Furthermore, PBL schemes have a strong influence on the movement of the WAM rainband because of their impact on the cloud fraction, that ranges from 8 to 20 % at 600 hPa during August. More low- and mid-level clouds result in less incoming radiation and a weaker monsoon. Ultimately, we identify the differing intensities of the moist Hadley-type meridional circulation that connects the monsoon winds to the Tropical Easterly Jet as the main source for inter-member differences. The ensemble spread of Sahel precipitation and associated dynamics for August 1999 is comparable to the observed inter-annual spread (1979-2010) between dry and wet years, emphasizing the strong potential impact of regional processes and the need for a careful selection of model parameterizations.

  8. Variable Production of African American English across Oracy and Literacy Contexts

    ERIC Educational Resources Information Center

    Thompson, Connie A.; Craig, Holly K.; Washington, Julie A.

    2004-01-01

    Many African American students produce African American English (AAE) features that are contrastive to Standard American English (SAE). The AAE-speaking child who is able to dialect shift, that is, to speak SAE across literacy contexts, likely will perform better academically than the student who is not able to dialect shift. Method: This…

  9. Solar variability and climate change: An historical perspective

    NASA Astrophysics Data System (ADS)

    Feldman, Theodore S.

    There is nothing new about the debate over the Sun's influence on terrestrial climate.As early as the late 18th century, widespread concern for the deterioration of the Earth's climate led to speculation about the Sun's role in climate change [Feldman, 1993; Fleming, 1990]. Drawing analogies with variations in the brightness of stars, the British astronomer William Herschel suggested that greater sunspot activity would result in warmer terrestrial climates. Herschel supported his hypothesis by referring to price series for wheat published in Adam Smiths Wealth of Nations [Hufbauer, 1991]. Later, the eminent American physicist Joseph Henry demonstrated by thermopile measurements that, contrary to Herschel's assumption, sunspots were cooler than the unblemished portions of the solar disk.

  10. Impacts of Climatic Variability on Vibrio parahaemolyticus Outbreaks in Taiwan.

    PubMed

    Hsiao, Hsin-I; Jan, Man-Ser; Chi, Hui-Ju

    2016-02-01

    This study aimed to investigate and quantify the relationship between climate variation and incidence of Vibrio parahaemolyticus in Taiwan. Specifically, seasonal autoregressive integrated moving average (ARIMA) models (including autoregression, seasonality, and a lag-time effect) were employed to predict the role of climatic factors (including temperature, rainfall, relative humidity, ocean temperature and ocean salinity) on the incidence of V. parahaemolyticus in Taiwan between 2000 and 2011. The results indicated that average temperature (+), ocean temperature (+), ocean salinity of 6 months ago (+), maximum daily rainfall (current (-) and one month ago (-)), and average relative humidity (current and 9 months ago (-)) had significant impacts on the incidence of V. parahaemolyticus. Our findings offer a novel view of the quantitative relationship between climate change and food poisoning by V. parahaemolyticus in Taiwan. An early warning system based on climate change information for the disease control management is required in future. PMID:26848675

  11. Climate change impacts on working people (the HOTHAPS initiative): findings of the South African pilot study

    PubMed Central

    Mathee, Angela; Oba, Joy; Rose, Andre

    2010-01-01

    Background It is now widely accepted that climate change is occurring as a result of the accumulation of greenhouse gases (GHG) in the atmosphere. With the prospect of a warmer world, increased attention is being devoted to the implications for worker well-being and work performance. Objectives The ‘high occupational temperature health and productivity suppression’ (HOTHAPS) programme is a multi-centre health research and prevention programme aimed at characterising and quantifying the extent to which working people are affected by, or adapt to, heat exposure while working. The main aim of the current South African pilot study was to look at the perceptions of outdoor workers regarding their work environment in hot weather and how this affected their health and productivity levels. Design A qualitative study utilising focus group discussions was employed in two sites, Johannesburg (which has a temperate climate) and Upington (located in the hottest part of South Africa). Results In summary, the pilot study demonstrated that especially in Upington, where daily maximum temperatures may reach +40°C, workers reported a wide range of heat-related effects, including sunburn, sleeplessness, irritability, and exhaustion leading to difficulty in maintaining work levels and output during very hot weather. Few, if any, measures were being undertaken by employers to protect health or improve worker comfort. Conclusion This pilot study has demonstrated that people working in sun-exposed conditions in hot parts of South Africa currently experience heat-related health effects, with implications for their well-being and ability to work and that further research is warranted. In this regard, the pilot study has proved valuable in informing the design, site, sample selection, and logistical planning for a proposed main study on the health and performance aspects of work in hot weather in South Africa. PMID:21139703

  12. Linking global climate and temperature variability to widespread amphibian declines putatively caused by disease.

    PubMed

    Rohr, Jason R; Raffel, Thomas R

    2010-05-01

    The role of global climate change in the decline of biodiversity and the emergence of infectious diseases remains controversial, and the effect of climatic variability, in particular, has largely been ignored. For instance, it was recently revealed that the proposed link between climate change and widespread amphibian declines, putatively caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), was tenuous because it was based on a temporally confounded correlation. Here we provide temporally unconfounded evidence that global El Niño climatic events drive widespread amphibian losses in genus Atelopus via increased regional temperature variability, which can reduce amphibian defenses against pathogens. Of 26 climate variables tested, only factors associated with temperature variability could account for the spatiotemporal patterns of declines thought to be associated with Bd. Climatic predictors of declines became significant only after controlling for a pattern consistent with epidemic spread (by temporally detrending the data). This presumed spread accounted for 59% of the temporal variation in amphibian losses, whereas El Niño accounted for 59% of the remaining variation. Hence, we could account for 83% of the variation in declines with these two variables alone. Given that global climate change seems to increase temperature variability, extreme climatic events, and the strength of Central Pacific El Niño episodes, climate change might exacerbate worldwide enigmatic declines of amphibians, presumably by increasing susceptibility to disease. These results suggest that changes to temperature variability associated with climate change might be as significant to biodiversity losses and disease emergence as changes to mean temperature.

  13. Linking global climate and temperature variability to widespread amphibian declines putatively caused by disease.

    PubMed

    Rohr, Jason R; Raffel, Thomas R

    2010-05-01

    The role of global climate change in the decline of biodiversity and the emergence of infectious diseases remains controversial, and the effect of climatic variability, in particular, has largely been ignored. For instance, it was recently revealed that the proposed link between climate change and widespread amphibian declines, putatively caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), was tenuous because it was based on a temporally confounded correlation. Here we provide temporally unconfounded evidence that global El Niño climatic events drive widespread amphibian losses in genus Atelopus via increased regional temperature variability, which can reduce amphibian defenses against pathogens. Of 26 climate variables tested, only factors associated with temperature variability could account for the spatiotemporal patterns of declines thought to be associated with Bd. Climatic predictors of declines became significant only after controlling for a pattern consistent with epidemic spread (by temporally detrending the data). This presumed spread accounted for 59% of the temporal variation in amphibian losses, whereas El Niño accounted for 59% of the remaining variation. Hence, we could account for 83% of the variation in declines with these two variables alone. Given that global climate change seems to increase temperature variability, extreme climatic events, and the strength of Central Pacific El Niño episodes, climate change might exacerbate worldwide enigmatic declines of amphibians, presumably by increasing susceptibility to disease. These results suggest that changes to temperature variability associated with climate change might be as significant to biodiversity losses and disease emergence as changes to mean temperature. PMID:20404180

  14. Present and future precipitation variability over the East African region using CORDEX simulations (COSMO-CLM) and its relation with circulation patterns

    NASA Astrophysics Data System (ADS)

    Souverijns, Niels; Thiery, Wim; Demuzere, Matthias; van Lipzig, Nicole

    2015-04-01

    The East African region is highly dependent on precipitation due to its water-fed agricultural system. On the other hand the region experiences a high interannual variability regarding precipitation amounts during several months. Consequently, there is a strong need to predict how precipitation variability will evolve under climate change in this region. This requires a good understanding of the processes that influence this variability. This study tackles this issue via the use of circulation patterns, shown to strongly influence precipitation over the East African region. Changes in (the frequency of) circulation patterns towards the future are therefore the main drivers of changes in precipitation variability. To investigate this issue a classification of the different circulation patterns over the region was executed for a reference period (1981-2010) on ERA Interim data using the COST733class software. Different algorithms are tested and their performance over the study area is evaluated. This results in a weather atlas concerning the circulation patterns and their corresponding precipitation amounts that are currently present over the region. Furthermore, the classification will be executed on the COSMO-CLM CORDEX-Africa evaluation simulation for the same reference period. The model results are evaluated by comparing them with the classification results of the ERA Interim data and observational datasets. To predict how precipitation variability changes towards the future, a classification is also applied on the whole CORDEX-Africa ensemble for a present (1981-2010) and future period (2071-2100) under RCP 8.5. Comparing both classifications makes it possible to detect differences in the frequencies of circulation patterns and in the circulation patterns themselves. Particular attention is paid to the months that show a high interannual variability in precipitation amounts, since changes here are of most importance for the region. Finally, the different drivers

  15. Do Birds of a Feather Flock Together? The Variable Bases for African American, Asian American, and European American Adolescents' Selection of Similar Friends.

    ERIC Educational Resources Information Center

    Hamm, Jill V.

    2000-01-01

    Examined variability in adolescent-friend similarity in African American, Asian American, and European American adolescents. Found greatest similarity for substance use, modest for academic orientation, and low for ethnic identity. Found that compared with other groups, African Americans chose friends who were less similar in academic orientation…

  16. Estimating the climate variability of the last millennium on the East Antarctic plateau

    NASA Astrophysics Data System (ADS)

    Münch, Thomas; Laepple, Thomas

    2016-04-01

    Quantitative knowledge about the climate variability on the Antarctic continent is crucial to attribute and detect the anthropogenic influence, and to understand the past and future evolution of the Antarctic ice sheet. Isotope records from firn and ice cores provide information about Holocene climate variability but strong non-climate effects hamper their quantitative interpretation, especially in low-accumulation regions. So far, the magnitude and time-scale dependency of both the climate signal and the noise is largely unknown. Here, we combine 16 annually-resolved firn cores spanning the last 200 years, three records covering the last millennium as well as surface snow data from the Amundsenisen region on the East Antarctic plateau. By means of a spectral correction technique we can separate the climate signal from noise and derive, for the first time, a time-scale dependent estimate of East-Antarctic temperature variability. Our preliminary results indicate that, unlike the raw isotope data, the obtained temperature variability for our study region shows a scaling behavior with more variability on longer time scales, similar to estimates from marine SST records. The noise levels we find are in accordance with the independent surface snow sampling results from Kohnen station. An analysis of the variability in current climate models on the other hand suggests less variability on centennial time scales. The discrepancy between the model and data-based results indicates either deficiencies in the model simulations, or further unknown processes affecting the ice-core records. Our estimate of East-Antarctic climate variability thus highlights the importance of an improved understanding of Holocene climate and ice-core derived variability.

  17. Trends and Variability in Pastoral Resources in the West African Sahel

    NASA Astrophysics Data System (ADS)

    Hanan, N. P.

    2014-12-01

    The geography of water and nutrients in the savannas of West Africa has shaped the development of a system of migratory cattle movements ("transhumance") in which herds travel north during the rainy season to graze the nutritious grasslands of the Sahel and return south in the dry season to graze in fallow lands and on agricultural residue. Cattle in this system gain most of their body mass while grazing in the Sahel and frequently lose mass on their dry season range. The Sahel is, therefore, at the heart of extensive livestock production systems in West Africa. However, there is increasing concern regarding how climate change will impact the region, while human population growth and economic development require increased agricultural and livestock production. The future for pastoral production systems in West Africa is, therefore, uncertain. This presentation combines remote sensing of vegetation structure and phenology with a watershed-scale tree-grass ecohydrology model, to explore how key resources for Sahelian pastoralist communities (forage and surface water for livestock, woody biomass for fuel) respond to climate variability and extreme events, conditioned by human management of grazing, fire and fuel-wood harvest. Mortality of woody species and loss of herbaceous cover during the Sahelian droughts of the 1970's and 1980's significantly perturbed vegetation dynamics and ecohydrological interactions, perturbations from which the region is still recovering. The re-greening and reforestation of the Sahel reported by many authors is, in part, an expression of this recovery. Future trajectories of change in pastoral resources in the Sahel, in particular forage availability and drinking water, are explored using climate change ensembles.

  18. Molecular records of climate variability and vegetation response since the Late Pleistocene in the Lake Victoria basin, East Africa

    NASA Astrophysics Data System (ADS)

    Berke, Melissa A.; Johnson, Thomas C.; Werne, Josef P.; Grice, Kliti; Schouten, Stefan; Sinninghe Damsté, Jaap S.

    2012-11-01

    New molecular proxies of temperature and hydrology are helping to constrain tropical climate change and elucidate possible forcing mechanisms during the Holocene. Here, we examine a ˜14,000 year record of climate variability from Lake Victoria, East Africa, the world's second largest freshwater lake by surface area. We determined variations in local hydroclimate using compound specific δD of terrestrial leaf waxes, and compared these results to a new record of temperature utilizing the TEX86 paleotemperature proxy, based on aquatic Thaumarchaeotal membrane lipids. In order to assess the impact of changing climate on the terrestrial environment, we generated a record of compound specific δ13C from terrestrial leaf waxes, a proxy for ecosystem-level C3/C4 plant abundances, and compared the results to previously published pollen-inferred regional vegetation shifts. We observe a general coherence between temperature and rainfall, with a warm, wet interval peaking ˜10-9 ka and subsequent gradual cooling and drying over the remainder of the Holocene. These results, particularly those of rainfall, are in general agreement with other tropical African climate records, indicating a somewhat consistent view of climate over a wide region of tropical East Africa. The δ13C record from Lake Victoria leaf waxes does not appear to reflect changes in regional climate or vegetation. However, palynological analyses document an abrupt shift from a Poaceae (grasses)-dominated ecosystem during the cooler, arid late Pleistocene to a Moraceae-dominated (trees/shrubs) landscape during the warm, wet early Holocene. We theorize that these proxies are reflecting vegetation in different locations around Lake Victoria. Our results suggest a predominantly insolation-forced climate, with warm, wet conditions peaking at the maximum interhemispheric seasonal insolation contrast, likely intensifying monsoonal precipitation, while maximum aridity coincides with the rainy season insolation and the

  19. Skilful multi-year predictions of tropical trans-basin climate variability

    PubMed Central

    Chikamoto, Yoshimitsu; Timmermann, Axel; Luo, Jing-Jia; Mochizuki, Takashi; Kimoto, Masahide; Watanabe, Masahiro; Ishii, Masayoshi; Xie, Shang-Ping; Jin, Fei-Fei

    2015-01-01

    Tropical Pacific sea surface temperature anomalies influence the atmospheric circulation, impacting climate far beyond the tropics. The predictability of the corresponding atmospheric signals is typically limited to less than 1 year lead time. Here we present observational and modelling evidence for multi-year predictability of coherent trans-basin climate variations that are characterized by a zonal seesaw in tropical sea surface temperature and sea-level pressure between the Pacific and the other two ocean basins. State-of-the-art climate model forecasts initialized from a realistic ocean state show that the low-frequency trans-basin climate variability, which explains part of the El Niño Southern Oscillation flavours, can be predicted up to 3 years ahead, thus exceeding the predictive skill of current tropical climate forecasts for natural variability. This low-frequency variability emerges from the synchronization of ocean anomalies in all basins via global reorganizations of the atmospheric Walker Circulation. PMID:25897996

  20. The relationship between African easterly waves and daily rainfall over West Africa: observations and regional climate simulations

    NASA Astrophysics Data System (ADS)

    Crétat, Julien; Vizy, Edward K.; Cook, Kerry H.

    2015-01-01

    The relationship between summer African easterly waves (AEWs) and daily rainfall is assessed in West Africa for 1998-2008 using various reanalyses, satellite-derived rainfall products, and a regional climate model (RCM) run at 90- and 30-km resolutions. 3-5 and 6-9 day AEWs are extracted by filtering daily 700 hPa meridional wind time series at 1°W and 11.5°N, and 1°W and 17.5°N, respectively. Both observed and simulated rainfall anomalies are of larger magnitude over West Africa during 3-5-d than 6-9-d AEWs. The RCM simulates larger rainfall rates in phase with the 3-5-d wave trough instead of ahead, unlike the observations, and overestimates the intensity and spatial coverage of rainfall associated with 6-9-d AEWs. The observed and simulated co-variability between 3-5-d (6-9-d) AEW activity and daily rainfall is strong (weak) and mostly located south (north) of 15°N. However, the RCM overestimates the spatial coverage of the AEW-rainfall relationship in the longitudinal (latitudinal) direction in the case of 3-5-d (6-9-d) AEWs. Observed and simulated daily intense rainfall events, extracted using a percentile threshold approach, are mostly located south of 15°N during summer. The observed relationship between their frequency of occurrence and active 3-5-d AEWs is maximal west of 8°E, while extends up to southern Chad in both RCM simulations. Their magnitude is also largely overestimated by the RCM, indicating an exaggerated coupling between the wave activity and the convection. Finally, observed and simulated 3-5-d AEWs establish the most favorable synoptic conditions for the development of intense rainfall events over West Africa.

  1. Role of climate variability in the heatstroke death rates of Kanto region in Japan

    NASA Astrophysics Data System (ADS)

    Akihiko, Takaya; Morioka, Yushi; Behera, Swadhin K.

    2014-07-01

    The death toll by heatstroke in Japan, especially in Kanto region, has sharply increased since 1994 together with large interannual variability. The surface air temperature and humidity observed during boreal summers of 1980-2010 were examined to understand the role of climate in the death toll. The extremely hot days, when the daily maximum temperature exceeds 35°C, are more strongly associated with the death toll than the conventional Wet Bulb Globe Temperature index. The extremely hot days tend to be associated with El Niño/Southern Oscillation or the Indian Ocean Dipole, suggesting a potential link with tropical climate variability to the heatstroke related deaths. Also, the influence of these climate modes on the death toll has strengthened since 1994 probably related to global warming. It is possible to develop early warning systems based on seasonal climate predictions since recent climate models show excellent predictability skills for those climate modes.

  2. Role of climate variability in the heatstroke death rates of Kanto region in Japan.

    PubMed

    Akihiko, Takaya; Morioka, Yushi; Behera, Swadhin K

    2014-07-10

    The death toll by heatstroke in Japan, especially in Kanto region, has sharply increased since 1994 together with large interannual variability. The surface air temperature and humidity observed during boreal summers of 1980-2010 were examined to understand the role of climate in the death toll. The extremely hot days, when the daily maximum temperature exceeds 35 °C, are more strongly associated with the death toll than the conventional Wet Bulb Globe Temperature index. The extremely hot days tend to be associated with El Niño/Southern Oscillation or the Indian Ocean Dipole, suggesting a potential link with tropical climate variability to the heatstroke related deaths. Also, the influence of these climate modes on the death toll has strengthened since 1994 probably related to global warming. It is possible to develop early warning systems based on seasonal climate predictions since recent climate models show excellent predictability skills for those climate modes.

  3. Impacts of Sea Surface Salinity Bias Correction on North Atlantic Ocean Circulation and Climate Variability in the Kiel Climate Model

    NASA Astrophysics Data System (ADS)

    Park, Taewook; Park, Wonsun; Latif, Mojib

    2016-04-01

    We investigated impacts of correcting North Atlantic sea surface salinity (SSS) biases on the ocean circulation of the North Atlantic and on North Atlantic sector mean climate and climate variability in the Kiel Climate Model (KCM). Bias reduction was achieved by applying a freshwater flux correction over the North Atlantic to the model. The quality of simulating the mean circulation of the North Atlantic Ocean, North Atlantic sector mean climate and decadal variability is greatly enhanced in the freshwater flux-corrected integration which, by definition, depicts relatively small North Atlantic SSS biases. In particular, a large reduction in the North Atlantic cold sea surface temperature (SST) bias is observed and a more realistic Atlantic Multidecadal Variability (AMV) simulated. Improvements relative to the non-flux corrected integration also comprise a more realistic representation of deep convection sites, sea ice, gyre circulation and Atlantic Meridional Overturning Circulation (AMOC). The results suggest that simulations of North Atlantic sector mean climate and decadal variability could strongly benefit from alleviating sea surface salinity biases in the North Atlantic, which may enhance the skill of decadal predictions in that region.

  4. Intra-interglacial climate variability: model simulations of Marine Isotope Stages 1, 5, 11, 13, and 15

    NASA Astrophysics Data System (ADS)

    Rachmayani, Rima; Prange, Matthias; Schulz, Michael

    2016-03-01

    Using the Community Climate System Model version 3 (CCSM3) including a dynamic global vegetation model, a set of 13 time slice experiments was carried out to study global climate variability between and within the Quaternary interglacials of Marine Isotope Stages (MISs) 1, 5, 11, 13, and 15. The selection of interglacial time slices was based on different aspects of inter- and intra-interglacial variability and associated astronomical forcing. The different effects of obliquity, precession, and greenhouse gas (GHG) forcing on global surface temperature and precipitation fields are illuminated. In most regions seasonal surface temperature anomalies can largely be explained by local insolation anomalies induced by the astronomical forcing. Climate feedbacks, however, may modify the surface temperature response in specific regions, most pronounced in the monsoon domains and the polar oceans. GHG forcing may also play an important role for seasonal temperature anomalies, especially at high latitudes and early Brunhes interglacials (MIS 13 and 15) when GHG concentrations were much lower than during the later interglacials. High- versus low-obliquity climates are generally characterized by strong warming over the Northern Hemisphere extratropics and slight cooling in the tropics during boreal summer. During boreal winter, a moderate cooling over large portions of the Northern Hemisphere continents and a strong warming at high southern latitudes is found. Beside the well-known role of precession, a significant role of obliquity in forcing the West African monsoon is identified. Other regional monsoon systems are less sensitive or not sensitive at all to obliquity variations during interglacials. Moreover, based on two specific time slices (394 and 615 ka), it is explicitly shown that the West African and Indian monsoon systems do not always vary in concert, challenging the concept of a global monsoon system on astronomical timescales. High obliquity can also explain

  5. Characterization of climatic zones, variability and trend in northern Africa

    NASA Astrophysics Data System (ADS)

    Djomou, Zéphirin Yepdo; Monkam, David; Chamani, Roméo

    2015-03-01

    Using precipitation data from the Climatic Research Unit and the cluster analysis method, the northern Africa (0-30°N; 20°W-40°E) was sub-divided into four homogenous climatic zones for the base period (P0) 1901-1940. The four climatic zones were distributed into Saharan, Sahelian, wet tropical and equatorial climate types. The application of a segment of 15 years with overlap going from 1901-1940 (P0) and 1961 to 2000 (P4) throughout the periods 1916-1955 (P1), 1931-1970 (P2) and 1946-1985 (P3), shows important spatio-temporal modifications of rainfall zones south of 15°N . The semiarid lands (Sahelian) which govern the dynamics of this zone doubled at the end of the twentieth century, while the wet tropical and equatorial zones decreased at the half. Temperature trends have a magnitude of up to 1.5 K per century in all the four climatic zones. This warming was mainly observed during the last three decades. During these same three decades, regional precipitation trends were less significant. The extreme conditions in temperature and the precipitation were analysed in terms of their persistence. The sporadic long-lasting extreme conditions appear for several years to over 10 years during the last century.

  6. Intraseasonal Variability in the Atmosphere-Ocean Climate System. Second Edition

    NASA Technical Reports Server (NTRS)

    Lau, William K. M.; Waliser, Duane E.

    2011-01-01

    Understanding and predicting the intraseasonal variability (ISV) of the ocean and atmosphere is crucial to improving long-range environmental forecasts and the reliability of climate change projections through climate models. This updated, comprehensive and authoritative second edition has a balance of observation, theory and modeling and provides a single source of reference for all those interested in this important multi-faceted natural phenomenon and its relation to major short-term climatic variations.

  7. Sub-decadal North Atlantic Oscillation variability in observations and the Kiel Climate Model

    NASA Astrophysics Data System (ADS)

    Reintges, Annika; Latif, Mojib; Park, Wonsun

    2016-07-01

    The North Atlantic Oscillation (NAO) is the dominant mode of winter climate variability in the North Atlantic sector. The corresponding index varies on a wide range of timescales, from days and months to decades and beyond. Sub-decadal NAO variability has been well documented, but the underlying mechanism is still under discussion. Other indices of North Atlantic sector climate variability such as indices of sea surface and surface air temperature or Arctic sea ice extent also exhibit pronounced sub-decadal variability. Here, we use sea surface temperature and sea level pressure observations, and the Kiel Climate Model to investigate the dynamics of the sub-decadal NAO variability. The sub-decadal NAO variability is suggested to originate from dynamical large-scale air-sea interactions. The adjustment of the Atlantic Meridional Overturning Circulation to previous surface heat flux variability provides the memory of the coupled mode. The results stress the role of coupled feedbacks in generating sub-decadal North Atlantic sector climate variability, which is important to multiyear climate predictability in that region.

  8. Climate variability has a stabilizing effect on the coexistence of prairie grasses

    PubMed Central

    Adler, Peter B.; HilleRisLambers, Janneke; Kyriakidis, Phaedon C.; Guan, Qingfeng; Levine, Jonathan M.

    2006-01-01

    How expected increases in climate variability will affect species diversity depends on the role of such variability in regulating the coexistence of competing species. Despite theory linking temporal environmental fluctuations with the maintenance of diversity, the importance of climate variability for stabilizing coexistence remains unknown because of a lack of appropriate long-term observations. Here, we analyze three decades of demographic data from a Kansas prairie to demonstrate that interannual climate variability promotes the coexistence of three common grass species. Specifically, we show that (i) the dynamics of the three species satisfy all requirements of “storage effect” theory based on recruitment variability with overlapping generations, (ii) climate variables are correlated with interannual variation in species performance, and (iii) temporal variability increases low-density growth rates, buffering these species against competitive exclusion. Given that environmental fluctuations are ubiquitous in natural systems, our results suggest that coexistence based on the storage effect may be underappreciated and could provide an important alternative to recent neutral theories of diversity. Field evidence for positive effects of variability on coexistence also emphasizes the need to consider changes in both climate means and variances when forecasting the effects of global change on species diversity. PMID:16908862

  9. Cenozoic Landscape evolution of the South-African Plateau around the Orange Valley: tectonic and climate coupling

    NASA Astrophysics Data System (ADS)

    Dauteuil, Olivier; Bessin, Paul; Guillocheau, François

    2014-05-01

    The plateaus form the key geomorphic element of the African relief with the occurrence of the South African (or Kalahari) Plateau, extending from South Africa to southern Congo (Fig. 1). The origin and evolution of this large relief with a mean elevation ranging 1 to 2 kilometres were largely debated. This work discussed the landscape growth of the South African plateau on both sides of the Orange valley in term of planation process, incision, deformation and climate change. This work is mainly based on a geomorphic analysis done from DEM and field data. First, we proposed a new typology of planation surfaces based on their genetic process (weathering versus erosion), and not depending the elevation, as previously. Five types of planation surfaces were retained: etchplain, peneplain, pediplain, top-weathering surface and wav-cut platform. Using this approach to determine the evolution of Orange valley, we recognised three planation surfaces of which origin is not controlled by the lithology: a top weathering surface recorded the end of Eocene weathering period, a first etchplain-to-pediplain formed during the Oligocene and finally a pediplain initiated after a deformation event during the Miocene. This event reorganised completely the drainage network and the catchment of the Orange River that became similar to the current one. It corresponds to a regional tilting of the southern part of the plateau with a elevation of 200 m at least. Afterwards, global eustatic variations driven the landscape evolution because the Orange River gained the current stream connected to the sea level. Thus the landscape growth of the South African plateau results in a change in planation processes driven by a first climate change occurring during a slow uplift, then a regional tilting and at least by eustasy. Thus, an accurate and detail geomorphic analysis allows discriminating the tectonic to climatic processes causing the current landscape.

  10. The Use of Spanish Historical Archives to Reconstruct Climate Variability.

    NASA Astrophysics Data System (ADS)

    García Herrera, Ricardo; García, Rolando R.; Rosario Prieto, M.; Hernández, Emiliano; Gimeno, Luis; Díaz, Henry F.

    2003-08-01

    Spanish historical archives contain a vast store of information about Spain and its former colonies in America and Asia. Some searches for climate-related information within these archives have been undertaken recently, but they have been by no means exhaustive. This paper discusses the principal archives and shows, by means of several examples, that they exhibit a high potential for inferring past climate over a wide range of timescales and geographical areas. Extraction of such information is often time consuming, and requires a combination of archival, historical, and climatological expertise, and the development of individualized methodologies to fit each situation and type of data. In spite of these difficulties, the archives can be particularly useful in many cases where there are no alternative sources of climate data. Thus, the complexities of the multidisciplinary effort required should not discourage other researchers from undertaking similar studies.

  11. Nonlinear detection of large-scale transitions in Plio-Pleistocene African climate

    NASA Astrophysics Data System (ADS)

    Donges, J. F.; Donner, R. V.; Trauth, M. H.; Marwan, N.; Schellnhuber, H. J.; Kurths, J.

    2011-12-01

    Potential paleoclimatic driving mechanisms acting on human development present an open problem of cross-disciplinary scientific interest. The analysis of paleoclimate archives encoding the environmental variability in East Africa during the last 5 Ma (million years) has triggered an ongoing debate about possible candidate processes and evolutionary mechanisms. In this work, we apply a novel nonlinear statistical technique, recurrence network analysis, to three distinct marine records of terrigenous dust flux. Our method enables us to identify three epochs with transitions between qualitatively different types of environmental variability in North and East Africa during the (i) Mid-Pliocene (3.35-3.15 Ma BP (before present)), (ii) Early Pleistocene (2.25-1.6 Ma BP), and (iii) Mid-Pleistocene (1.1-0.7 Ma BP). A deeper examination of these transition periods reveals potential climatic drivers, including (i) large-scale changes in ocean currents due to a spatial shift of the Indonesian throughflow in combination with an intensification of Northern Hemisphere glaciation, (ii) a global reorganization of the atmospheric Walker circulation induced in the tropical Pacific and Indian Ocean, and (iii) shifts in the dominating temporal variability pattern of glacial activity during the Mid-Pleistocene, respectively. A statistical reexamination of the available fossil record demonstrates a remarkable coincidence between the detected transition periods and major steps in hominin evolution. This suggests that the observed shifts between more regular and more erratic environmental variability have acted as a trigger for rapid change in the development of humankind in Africa.

  12. Shifts in Climate Foster Exceptional Opportunities for Species Radiation: The Case of South African Geraniums

    PubMed Central

    Martínez-Cabrera, Hugo I.; Peres-Neto, Pedro R.

    2013-01-01

    Climate change is often assumed to be a major driver of biodiversity loss. However, it can also set the stage for novel diversification in lineages with the evolutionary ability to colonize new environments. Here we tested if the extraordinary evolutionary success of the genus Pelargonium was related to the ability of its species to capitalize on the climate niche variation produced by the historical changes in southern Africa. We evaluated the relationship between rates of climate niche evolution and diversification rates in the main Pelargonium lineages and disentangled the roles of deep and recent historical events in the modification of species niches. Pelargonium clades exhibiting higher ecological differentiation along summer precipitation (SPP) gradients also experienced higher diversification rates. Faster rates of niche differentiation in spatially structured variables, along with lower levels of niche overlap among closely related species, suggest recent modification in species niches (e.g. dispersal or range shift) and niche lability. We suggest that highly structured SPP gradients established during the aridification process within southern Africa, in concert with niche lability and low niche overlap, contributed to species divergence. These factors are likely to be responsible for the extensive diversification of other lineages in this diversity hot spot. PMID:24358250

  13. Enhanced insights into late Quaternary African hydroclimate dynamics using a water-isotope enabled climate model

    NASA Astrophysics Data System (ADS)

    Singarayer, Joy; Holloway, Max

    2016-04-01

    The climate of intertropical Africa is strongly governed by the dynamics of the tropical rainbelt, which is often associated with the Intertropical Convergence Zone (ITCZ). On millennial time-scales the primary drivers of variation in the rainbelt include orbital configuration changes to insolation seasonality and high-latitude forcing (e.g. Heinrich events). The spatial pattern of precipitation variability in tropical and subtropical Africa over the late Quaternary is complex and has long been debated. Stable water isotopes from inland lakes and off-shore ocean core records have provided longitudinal records, variously interpreted as changes to precipitation intensity or changes to moisture source location due to atmospheric circulation changes (or a combination of several factors). In this preliminary study we have used a global climate model, HadCM3, in which water isotopes are interactively coupled to produce snapshots at 1000-year intervals covering the last deglaciation (21kyr to pre-industrial). In conjunction with a comparison to available palaeodata, this enables us to better elucidate the connections between precipitation and other climate factors with changes to the water isotope signature, as well as how this varies regionally and through time.

  14. Shifts in climate foster exceptional opportunities for species radiation: the case of South african geraniums.

    PubMed

    Martínez-Cabrera, Hugo I; Peres-Neto, Pedro R

    2013-01-01

    Climate change is often assumed to be a major driver of biodiversity loss. However, it can also set the stage for novel diversification in lineages with the evolutionary ability to colonize new environments. Here we tested if the extraordinary evolutionary success of the genus Pelargonium was related to the ability of its species to capitalize on the climate niche variation produced by the historical changes in southern Africa. We evaluated the relationship between rates of climate niche evolution and diversification rates in the main Pelargonium lineages and disentangled the roles of deep and recent historical events in the modification of species niches. Pelargonium clades exhibiting higher ecological differentiation along summer precipitation (SPP) gradients also experienced higher diversification rates. Faster rates of niche differentiation in spatially structured variables, along with lower levels of niche overlap among closely related species, suggest recent modification in species niches (e.g. dispersal or range shift) and niche lability. We suggest that highly structured SPP gradients established during the aridification process within southern Africa, in concert with niche lability and low niche overlap, contributed to species divergence. These factors are likely to be responsible for the extensive diversification of other lineages in this diversity hot spot. PMID:24358250

  15. Linking the uncertainty of low frequency variability in tropical forcing in regional climate change

    SciTech Connect

    Forest, Chris E.; Barsugli, Joseph J.; Li, Wei

    2015-02-20

    The project utilizes multiple atmospheric general circulation models (AGCMs) to examine the regional climate sensitivity to tropical sea surface temperature forcing through a series of ensemble experiments. The overall goal for this work is to use the global teleconnection operator (GTO) as a metric to assess the impact of model structural differences on the uncertainties in regional climate variability.

  16. Novel Modeling Tools for Propagating Climate Change Variability and Uncertainty into Hydrodynamic Forecasts

    EPA Science Inventory

    Understanding impacts of climate change on hydrodynamic processes and ecosystem response within the Great Lakes is an important and challenging task. Variability in future climate conditions, uncertainty in rainfall-runoff model forecasts, the potential for land use change, and t...

  17. Land use and climate variability amplify carbon, nutrient, and contaminant pulses: a review with management implications

    EPA Science Inventory

    Nonpoint source pollution from agriculture and urbanization is increasing globally at the same time that climate extremes have increased in frequency and intensity. We review over 160 studies and show how the interaction between land use and climate variability alters the magnit...

  18. Changes in climate variability with reference to land quality and agriculture in Scotland

    NASA Astrophysics Data System (ADS)

    Brown, Iain; Castellazzi, Marie

    2015-06-01

    Classification and mapping of land capability represents an established format for summarising spatial information on land quality and land-use potential. By convention, this information incorporates bioclimatic constraints through the use of a long-term average. However, climate change means that land capability classification should also have a dynamic temporal component. Using an analysis based upon Land Capability for Agriculture in Scotland, it is shown that this dynamism not only involves the long-term average but also shorter term spatiotemporal patterns, particularly through changes in interannual variability. Interannual and interdecadal variations occur both in the likelihood of land being in prime condition (top three capability class divisions) and in class volatility from year to year. These changing patterns are most apparent in relation to the west-east climatic gradient which is mainly a function of precipitation regime and soil moisture. Analysis is also extended into the future using climate results for the 2050s from a weather generator which show a complex interaction between climate interannual variability and different soil types for land quality. In some locations, variability of land capability is more likely to decrease because the variable climatic constraints are relaxed and the dominant constraint becomes intrinsic soil properties. Elsewhere, climatic constraints will continue to be influential. Changing climate variability has important implications for land-use planning and agricultural management because it modifies local risk profiles in combination with the current trend towards agricultural intensification and specialisation.

  19. Changes in climate variability with reference to land quality and agriculture in Scotland.

    PubMed

    Brown, Iain; Castellazzi, Marie

    2015-06-01

    Classification and mapping of land capability represents an established format for summarising spatial information on land quality and land-use potential. By convention, this information incorporates bioclimatic constraints through the use of a long-term average. However, climate change means that land capability classification should also have a dynamic temporal component. Using an analysis based upon Land Capability for Agriculture in Scotland, it is shown that this dynamism not only involves the long-term average but also shorter term spatiotemporal patterns, particularly through changes in interannual variability. Interannual and interdecadal variations occur both in the likelihood of land being in prime condition (top three capability class divisions) and in class volatility from year to year. These changing patterns are most apparent in relation to the west-east climatic gradient which is mainly a function of precipitation regime and soil moisture. Analysis is also extended into the future using climate results for the 2050s from a weather generator which show a complex interaction between climate interannual variability and different soil types for land quality. In some locations, variability of land capability is more likely to decrease because the variable climatic constraints are relaxed and the dominant constraint becomes intrinsic soil properties. Elsewhere, climatic constraints will continue to be influential. Changing climate variability has important implications for land-use planning and agricultural management because it modifies local risk profiles in combination with the current trend towards agricultural intensification and specialisation.

  20. Disease and thermal acclimation in a more variable and unpredictable climate

    NASA Astrophysics Data System (ADS)

    Raffel, Thomas R.; Romansic, John M.; Halstead, Neal T.; McMahon, Taegan A.; Venesky, Matthew D.; Rohr, Jason R.

    2013-02-01

    Global climate change is shifting the distribution of infectious diseases of humans and wildlife with potential adverse consequences for disease control. As well as increasing mean temperatures, climate change is expected to increase climate variability, making climate less predictable. However, few empirical or theoretical studies have considered the effects of climate variability or predictability on disease, despite it being likely that hosts and parasites will have differential responses to climatic shifts. Here we present a theoretical framework for how temperature variation and its predictability influence disease risk by affecting host and parasite acclimation responses. Laboratory experiments conducted in 80 independent incubators, and field data on disease-associated frog declines in Latin America, support the framework and provide evidence that unpredictable temperature fluctuations, on both monthly and diurnal timescales, decrease frog resistance to the pathogenic chytrid fungus Batrachochytrium dendrobatidis. Furthermore, the pattern of temperature-dependent growth of the fungus on frogs was opposite to the pattern of growth in culture, emphasizing the importance of accounting for the host-parasite interaction when predicting climate-dependent disease dynamics. If similar acclimation responses influence other host-parasite systems, as seems likely, then present models, which generally ignore small-scale temporal variability in climate, might provide poor predictions for climate effects on disease.

  1. Effect of Climate Change on Invasion Risk of Giant African Snail (Achatina fulica Férussac, 1821: Achatinidae) in India.

    PubMed

    Sarma, Roshmi Rekha; Munsi, Madhushree; Ananthram, Aravind Neelavara

    2015-01-01

    The Giant African Snail (Achatina fulica) is considered to be one the world's 100 worst invasive alien species. The snail has an impact on native biodiversity, and on agricultural and horticultural crops. In India, it is known to feed on more than fifty species of native plants and agricultural crops and also outcompetes the native snails. It was introduced into India in 1847 and since then it has spread all across the country. In this paper, we use ecological niche modeling (ENM) to assess the distribution pattern of Giant African Snail (GAS) under different climate change scenarios. The niche modeling results indicate that under the current climate scenario, Eastern India, peninsular India and the Andaman and Nicobar Islands are at high risk of invasion. The three different future climate scenarios show that there is no significant change in the geographical distribution of invasion prone areas. However, certain currently invaded areas will be more prone to invasion in the future. These regions include parts of Bihar, Southern Karnataka, parts of Gujarat and Assam. The Andaman and Nicobar and Lakshadweep Islands are highly vulnerable to invasion under changed climate. The Central Indian region is at low risk due to high temperature and low rainfall. An understanding of the invasion pattern can help in better management of this invasive species and also in formulating policies for its control. PMID:26618637

  2. Effect of Climate Change on Invasion Risk of Giant African Snail (Achatina fulica Férussac, 1821: Achatinidae) in India

    PubMed Central

    Rekha Sarma, Roshmi; Munsi, Madhushree; Neelavara Ananthram, Aravind

    2015-01-01

    The Giant African Snail (Achatina fulica) is considered to be one the world’s 100 worst invasive alien species. The snail has an impact on native biodiversity, and on agricultural and horticultural crops. In India, it is known to feed on more than fifty species of native plants and agricultural crops and also outcompetes the native snails. It was introduced into India in 1847 and since then it has spread all across the country. In this paper, we use ecological niche modeling (ENM) to assess the distribution pattern of Giant African Snail (GAS) under different climate change scenarios. The niche modeling results indicate that under the current climate scenario, Eastern India, peninsular India and the Andaman and Nicobar Islands are at high risk of invasion. The three different future climate scenarios show that there is no significant change in the geographical distribution of invasion prone areas. However, certain currently invaded areas will be more prone to invasion in the future. These regions include parts of Bihar, Southern Karnataka, parts of Gujarat and Assam. The Andaman and Nicobar and Lakshadweep Islands are highly vulnerable to invasion under changed climate. The Central Indian region is at low risk due to high temperature and low rainfall. An understanding of the invasion pattern can help in better management of this invasive species and also in formulating policies for its control. PMID:26618637

  3. Effect of Climate Change on Invasion Risk of Giant African Snail (Achatina fulica Férussac, 1821: Achatinidae) in India.

    PubMed

    Sarma, Roshmi Rekha; Munsi, Madhushree; Ananthram, Aravind Neelavara

    2015-01-01

    The Giant African Snail (Achatina fulica) is considered to be one the world's 100 worst invasive alien species. The snail has an impact on native biodiversity, and on agricultural and horticultural crops. In India, it is known to feed on more than fifty species of native plants and agricultural crops and also outcompetes the native snails. It was introduced into India in 1847 and since then it has spread all across the country. In this paper, we use ecological niche modeling (ENM) to assess the distribution pattern of Giant African Snail (GAS) under different climate change scenarios. The niche modeling results indicate that under the current climate scenario, Eastern India, peninsular India and the Andaman and Nicobar Islands are at high risk of invasion. The three different future climate scenarios show that there is no significant change in the geographical distribution of invasion prone areas. However, certain currently invaded areas will be more prone to invasion in the future. These regions include parts of Bihar, Southern Karnataka, parts of Gujarat and Assam. The Andaman and Nicobar and Lakshadweep Islands are highly vulnerable to invasion under changed climate. The Central Indian region is at low risk due to high temperature and low rainfall. An understanding of the invasion pattern can help in better management of this invasive species and also in formulating policies for its control.

  4. Untapped genetic variability in Herefords: implications for climate change

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Global climate change (CC) has the potential to significantly alter US cattle productivity. As a result, the creation of genetic resources for a specific environment may be necessary, given that genetic-environmental interactions are present and may become more important. Molecular evaluation of a s...

  5. Rainfall variability and extremes over southern Africa: assessment of a climate model to reproduce daily extremes

    NASA Astrophysics Data System (ADS)

    Williams, C.; Kniveton, D.; Layberry, R.

    2009-04-01

    It is increasingly accepted that that any possible climate change will not only have an influence on mean climate but may also significantly alter climatic variability. A change in the distribution and magnitude of extreme rainfall events (associated with changing variability), such as droughts or flooding, may have a far greater impact on human and natural systems than a changing mean. This issue is of particular importance for environmentally vulnerable regions such as southern Africa. The subcontinent is considered especially vulnerable to and ill-equipped (in terms of adaptation) for extreme events, due to a number of factors including extensive poverty, famine, disease and political instability. Rainfall variability and the identification of rainfall extremes is a function of scale, so high spatial and temporal resolution data are preferred to identify extreme events and accurately predict future variability. The majority of previous climate model verification studies have compared model output with observational data at monthly timescales. In this research, the assessment of ability of a state of the art climate model to simulate climate at daily timescales is carried out using satellite derived rainfall data from the Microwave Infra-Red Algorithm (MIRA). This dataset covers the period from 1993-2002 and the whole of southern Africa at a spatial resolution of 0.1 degree longitude/latitude. The ability of a climate model to simulate current climate provides some indication of how much confidence can be applied to its future predictions. In this paper, simulations of current climate from the UK Meteorological Office Hadley Centre's climate model, in both regional and global mode, are firstly compared to the MIRA dataset at daily timescales. This concentrates primarily on the ability of the model to simulate the spatial and temporal patterns of rainfall variability over southern Africa. Secondly, the ability of the model to reproduce daily rainfall extremes will

  6. Long-term successional forest dynamics: species and community responses to climatic variability

    SciTech Connect

    Kardol, Paul; Todd Jr, Donald E; Hanson, Paul J; Mulholland, Patrick J

    2010-01-01

    Question: Are tree dynamics sensitive to climatic variability, and do tree species differ in their responses to climatic variability? Hence, is vulnerability of forest communities to climatic variability depending on stand composition? Location: Mixed young forest at Walker Branch Watershed near Oak Ridge, East-Tennessee, USA. Methods: Using a long-term data set (1967-2006), we analyzed temporal forest dynamics at the tree and species level, and we analyzed community dynamics for forest stands that different in their initial species composition (i.e., Chestnut Oak, Oak-Hickory, Pine, and Yellow poplar stands). Using summer drought and growing season temperature as defined climate drivers, we evaluated relationships between forest dynamics and climate across levels of organization. Results: Over the 4-decade studied period, forest communities underwent successional change and substantially increased their biomass. Variation in summer drought and growing season temperature contributed to temporal biomass dynamics for some tree species, but not for others. Stand-level responses to climatic variability were shown to be related to responses of specific component species; however, not for Pine stands. Pinus echinata, the dominant species in stands initially identified as Pine stands, decreased over time due to periodical outbreaks of the pine bark beetle (Dendroctonus frontalis). The outbreaks on Walker Branch could not be directly related to climatic conditions. Conclusions: Our results imply that vulnerability of developing forests to predicted climate conditions is stand-type dependent, and hence, is a function of species composition. Autogenic successional processes (or insect outbreaks) were found to prevail over climatic variability in determining long-term forest dynamics for stands dominated by sensitive species, emphasizing the importance of studying interactions between forest succession and climate change.

  7. Validation of China-wide interpolated daily climate variables from 1960 to 2011

    NASA Astrophysics Data System (ADS)

    Yuan, Wenping; Xu, Bing; Chen, Zhuoqi; Xia, Jiangzhou; Xu, Wenfang; Chen, Yang; Wu, Xiaoxu; Fu, Yang

    2015-02-01

    Temporally and spatially continuous meteorological variables are increasingly in demand to support many different types of applications related to climate studies. Using measurements from 600 climate stations, a thin-plate spline method was applied to generate daily gridded climate datasets for mean air temperature, maximum temperature, minimum temperature, relative humidity, sunshine duration, wind speed, atmospheric pressure, and precipitation over China for the period 1961-2011. A comprehensive evaluation of interpolated climate was conducted at 150 independent validation sites. The results showed superior performance for most of the estimated variables. Except for wind speed, determination coefficients ( R 2) varied from 0.65 to 0.90, and interpolations showed high consistency with observations. Most of the estimated climate variables showed relatively consistent accuracy among all seasons according to the root mean square error, R 2, and relative predictive error. The interpolated data correctly predicted the occurrence of daily precipitation at validation sites with an accuracy of 83 %. Moreover, the interpolation data successfully explained the interannual variability trend for the eight meteorological variables at most validation sites. Consistent interannual variability trends were observed at 66-95 % of the sites for the eight meteorological variables. Accuracy in distinguishing extreme weather events differed substantially among the meteorological variables. The interpolated data identified extreme events for the three temperature variables, relative humidity, and sunshine duration with an accuracy ranging from 63 to 77 %. However, for wind speed, air pressure, and precipitation, the interpolation model correctly identified only 41, 48, and 58 % of extreme events, respectively. The validation indicates that the interpolations can be applied with high confidence for the three temperatures variables, as well as relative humidity and sunshine duration based

  8. The Influence of Negative School Climate Factors on African American Adolescent Males' Academic Outcomes: The Mediating Role of Internalizing and Externalizing Behaviors

    ERIC Educational Resources Information Center

    Herring, Melvin H.

    2013-01-01

    This study explores the relationship between negative school climate factors (i.e., teacher neglect, peer rejection, discrimination) and academic outcomes amongst a sample of adolescent African American males. Specifically, this study directly examines a) the influence of negative school climate perceptions on the students' academic…

  9. Vegetation response to climate variability in India from 2001 to 2010

    NASA Astrophysics Data System (ADS)

    Hashimoto, H.; Milesi, C.; Wang, W.; Ganguly, S.; Michaelis, A.; Nemani, R.

    2011-12-01

    Food supply in India is a critical issue in sustaining a large population, and more accurate predictability of agricultural productivity is necessary for policy makers. After the Green revolution, the productivity in India has increased dramatically, but the leveling-off of the productivity was expected in the near future. Decreasing of ground water was already observed and some climate models predict a higher frequency of drought in the 21st century. For a better understanding of vegetation response to climate change, we analyzed the satellite images of India from 2001 to 2010. MODIS satellite imagery shows high spatial variability in vegetation indices in response to climate variability. In this study we scrutinize the cause and mechanism of the spatial variability in vegetation growth in India. First, we tried to find the corresponding climate variability from re-analysis data (MERRA and NCEP-NCAR reanalysis data) and satellite imagery such as TRMM, GIMMS, and MODIS, as well as interpolated climate observation data (CRU). Although the precipitation variability due to ENSO has the strongest impact on vegetation growth, the other climate variability, such as shortwave radiation, also perturbed the vegetation response to climate changes. Second, we proved our hypothesis explaining the vegetation growth trend by running the Terrestrial Observation and Prediction System (TOPS) model. The model results were compared with satellite images and showed reasonable spatial pattern of net primary production to explain the observed vegetation growth variability to climate change. Those results can contribute to a more profound understanding of the mechanism of vegetation growth in India toward future prediction in food supply.

  10. Utilizing Satellite Precipitation Products to Understand the Link Between Climate Variability and Malaria

    NASA Astrophysics Data System (ADS)

    Maggioni, V.; Mousam, A.; Delamater, P. L.; Cash, B. A.; Quispe, A.

    2015-12-01

    Malaria is a public health threat to people globally leading to 198 million cases and 584,000 deaths annually. Outbreaks of vector borne diseases such as malaria can be significantly impacted by climate variables such as precipitation. For example, an increase in rainfall has the potential to create pools of water that can serve as breeding locations for mosquitos. Peru is a country that is currently controlling malaria, but has not been able to completely eliminate the disease. Despite the various initiatives in order to control malaria - including regional efforts to improve surveillance, early detection, prompt treatment, and vector management - malaria cases in Peru have risen between 2011 and 2014. The purpose of this study is to test the hypothesis that climate variability plays a fundamental role in malaria occurrence over a 12-year period (2003-2014) in Peru. When analyzing climate variability, it is important to obtain high-quality, high-resolution data for a time series long enough to draw conclusion about how climate variables have been and are changing. Remote sensing is a powerful tool for measuring and monitoring climate variables continuously in time and space. A widely used satellite-based precipitation product, the Tropical Rainfall Measuring Mission (TRMM) Multi-satellite Precipitation Analysis (TMPA), available globally since 1998, was used to obtain 3-hourly data with a spatial resolution of 0.25° x 0.25°. The precipitation data was linked to weekly (2003-2014) malaria cases collected by health centers and available at a district level all over Peru to investigate the relationship between precipitation and the seasonal and annual variations in malaria incidence. Further studies will incorporate additional climate variables such as temperature, humidity, soil moisture, and surface pressure from remote sensing data products and climate models. Ultimately, this research will help us to understand if climate variability impacts malaria incidence

  11. Pacific Decadal Variability and Central Pacific Warming El Niño in a Changing Climate

    SciTech Connect

    Di Lorenzo, Emanuele

    2015-02-27

    This research aimed at understanding the dynamics controlling decadal variability in the Pacific Ocean and its interactions with global-scale climate change. The first goal was to assess how the dynamics and statistics of the El Niño Southern Oscillation and the modes of Pacific decadal variability are represented in global climate models used in the IPCC. The second goal was to quantify how decadal dynamics are projected to change under continued greenhouse forcing, and determine their significance in the context of paleo-proxy reconstruction of long-term climate.

  12. Causes of Decadal Climate Variability over the North Pacific and North America.

    PubMed

    Latif, M; Barnett, T P

    1994-10-28

    The cause of decadal climate variability over the North Pacific Ocean and North America is investigated by the analysis of data from a multidecadal integration with a state-of-the-art coupled ocean-atmosphere model and observations. About one-third of the low-frequency climate variability in the region of interest can be attributed to a cycle involving unstable air-sea interactions between the subtropical gyre circulation in the North Pacific and the Aleutian low-pressure system. The existence of this cycle provides a basis for long-range climate forecasting over the western United States at decadal time scales. PMID:17793457

  13. Causes of decadal climate variability over the North Pacific and North America

    SciTech Connect

    Latif, M. ); Barnett, T.P. )

    1994-10-28

    The cause of decadal climate variability over the North Pacific Ocean and North America is investigated by the analysis of data from a multidecadal integration with a state-of-the-art coupled ocean-atmosphere model and observations. About one-third of the low-frequency climate variability in the region of interest can be attributed to a cycle involving unstable air-sea interactions between the subtropical gyre circulation in the North Pacific and the Aleutian low-pressure system. The existence of this cycle provides a basis for long-range climate forecasting over the western United States at decadal time scales. 17 refs., 5 figs.

  14. Crop models capture the impacts of climate variability on corn yield

    NASA Astrophysics Data System (ADS)

    Niyogi, Dev; Liu, Xing; Andresen, Jeff; Song, Yang; Jain, Atul K.; Kellner, Olivia; Takle, Eugene S.; Doering, Otto C.

    2015-05-01

    We investigate the ability of three different crop models of varying complexity for capturing El Niño-Southern Oscillation-based climate variability impacts on the U.S. Corn Belt (1981-2010). Results indicate that crop models, irrespective of their complexity, are able to capture the impacts of climate variability on yield. Multiple-model ensemble analysis provides best results. There was no significant difference between using on-site and gridded meteorological data sets to drive the models. These results highlight the ability of using simpler crop models and gridded regional data sets for crop-climate assessments.

  15. Anxiety Disorders in Caucasian and African American Children: A Comparison of Clinical Characteristics, Treatment Process Variables, and Treatment Outcomes

    PubMed Central

    Gordon-Hollingsworth, Arlene T.; Becker, Emily M.; Keeton, Courtney; Compton, Scott N.; Birmaher, Boris B.; Sakolsky, Dara J.; Piacentini, John; Albano, Anne M.; Kendall, Philip C.; Suveg, Cynthia M.; March, John S.

    2014-01-01

    This study examined racial differences in anxious youth using data from the Child/Adolescent Anxiety Multimodal Study (CAMS) [1]. Specifically, the study aims addressed whether African American (n = 44) versus Caucasian (n = 359) children varied on (1) baseline clinical characteristics, (2) treatment process variables, and (3) treatment outcomes. Participants were ages 7–17 and met DSM-IV-TR criteria for generalized anxiety disorder, social phobia, and/or separation anxiety disorder. Baseline data, as well as outcome data at 12 and 24 weeks, were obtained by independent evaluators. Weekly treatment process variables were collected by therapists. Results indicated no racial differences on baseline clinical characteristics. However, African American participants attended fewer psychotherapy and pharmacotherapy sessions, and were rated by therapists as less involved and compliant, in addition to showing lower mastery of CBT. Once these and other demographic factors were accounted for, race was not a significant predictor of response, remission, or relapse. Implications of these findings suggest African American and Caucasian youth are more similar than different with respect to the manifestations of anxiety and differences in outcomes are likely due to treatment barriers to session attendance and therapist engagement. PMID:25293650

  16. The Impact of Climate and Its Variability on Crop Yield and Irrigation

    NASA Astrophysics Data System (ADS)

    Li, X.; Troy, T.

    2014-12-01

    As the global population grows and the climate changes, having a secure food supply is increasingly important especially under water stressed-conditions. Although irrigation is a positive climate adaptation mechanism for agriculture, it has a potentially negative effect on water resources. It is therefore important to understand how crop yields due to irrigation are affected by climate variability and how irrigation may buffer against climate, allowing for more resilient agricultural systems. Efforts to solve these barely exposed questions can benefit from comprehending the influence of climate variability on crop yield and irrigation water use in the past. To do this, we use historical climate data,irrigation water use data and rainfed and irrigated crop yields over the US to analyze the relationship among climate, irrigation and delta crop yields, gained by subtracting rainfed yield from irrigated yield since 1970. We find that the increase in delta crop yield due to irrigation is larger for certain climate conditions, such that there are optimal climate conditions where irrigation provides a benefit and other conditions where irrigation proves to have marginal benefits when temperature increased to certain degrees. We find that crop water requirements are linked to potential evapotranspiration, yet actual irrigation water use is largely decoupled from the climate conditions but related with other causes. This has important implications for agricultural and water resource system planning, as it implies there are optimal climate zones where irrigation is productive and that changes in water use, both temporally and spatially, could lead to increased water availability without negative impacts on crop yields. Furthermore, based on the exposed relationship between crop yield gained by irrigation and climate variability, those models predicting the global harvest will be redress to estimate crop production in the future more accurately.

  17. Characterization of the impact of land degradation in the Sahel on the West African monsoon using an ensemble of climate models from the WAMME project

    NASA Astrophysics Data System (ADS)

    Boone, A. A.; Xue, Y.; Ruth, C.; De Sales, F.; Hagos, S.; Mahanama, S. P. P.; Schiro, K.; Song, G.; Wang, G.; Koster, R. D.; Mechoso, C. R.

    2014-12-01

    There is increasing evidence from numerical studies that anthropogenic land-use and land-cover changes (LULCC) can potentially induce significant variations on the regional scale climate. However, the magnitude of these variations likely depends on the local strength of the coupling between the surface and the atmosphere, the magnitude of the surface biophysical changes and how the key processes linking the surface with the atmosphere are parameterized within a particular model framework. One key hot-spot which has received considerable attention is the Sahelian region of West Africa, for which numerous studies have reported a significant increase in anthropogenic pressure on the already limited natural resources in this region, notably in terms of land use conversion and degradation. Thus, there is a pressing need to better understand the impacts of potential land degradation on the West African Monsoon (WAM) system. One of the main goals of the West African Monsoon Modeling andEvaluation project phase 2 (WAMMEII) is to provide basic understandingof LULCC on the regional climate over West Africa, and to evaluate thesensitivity of the seasonal variability of the WAM to LULCC. Theprescribed LULCC is based on recent 50 year period which represents amaximum feasible degradation scenario. In the current study, the LULCCis applied to five state of the art global climate models over afive-year period. The imposed LULCC results in a model-average 5-7%increase in surface albedo: the corresponding lower surface netradiation mainly results in a significant reduction in surfaceevaporation (upwards of 1 mm per day over a large part of the Sahel)which leads to less convective heating of the atmosphere, lowermoisture convergence, increased subsidence and reduced cloud coverover the LULCC zone. The overall impact can be characterized as asubstantial drought effect resulting in a reduction in annual rainfallof 20-40% in the Sahel and a southward shift of the monsoon. In

  18. Annual and Interannual Streamflow Variability for Mountainous Coastal Catchments in a Mediterranean Climate in Relation to Land Use Change and Climate Variability

    NASA Astrophysics Data System (ADS)

    Beighley, R. E.; Melack, J. M.; Dunne, T.

    2002-12-01

    Annual and interannual streamflow variability is of particular importance along the southern coast of California because of the Mediterranean climate, the hydrologic impacts of both El Nino and La Nina conditions, and the impacts of both runoff quantity and quality on coastal ecosystem. The Mediterranean climate provides annual variability with a seasonal rainfall pattern that accounts for approximately 80 percent of the annual rainfall in four months: December though March. Combining El Nino and La Nina conditions with seasonal rainfall produces significant interannual streamflow variability. Over the 14-year period, 9/1/1988 though 8/31/2002, 10-20 percent of the cumulative discharge occurred in only a few days. A conceptual rainfall-runoff model was developed to simulate streamflow from three sources of runoff: surface, steep shallow soils, and groundwater, as part of the Santa Barbara Channel - Long Term Ecologic Research project. Using simulated streamflow for the 14-year period, which contained 4 El Nino, 4 La Nina, and 6 normal years, and three different land use conditions: pre-development, current development, and projected future urbanization, the impacts of urbanization and climatic conditions were determined. Urbanization is shown to increase peak discharges and runoff while decreasing annual and inter-annual streamflow variability. In all cases, the interannual variability is dependent on climatic conditions with the maximum 10 days of flow from El Nino years producing 5-20 percent of the cumulative 14-year discharge compared to La Nina years that produce only 1-5 percent in 10 days. Regardless of land use conditions, the temporal distribution of runoff is clearly dominated by only a few annual events, with the percentage of annual runoff occurring in 1 day ranging from 20-50 percent. Additionally, the effects of streamflow variability from water years 2001 (wet) and 2002 (dry) are presented in terms of nutrient export from several coastal watersheds

  19. Planning for Production of Freshwater Fish Fry in a Variable Climate in Northern Thailand

    NASA Astrophysics Data System (ADS)

    Uppanunchai, Anuwat; Apirumanekul, Chusit; Lebel, Louis

    2015-10-01

    Provision of adequate numbers of quality fish fry is often a key constraint on aquaculture development. The management of climate-related risks in hatchery and nursery management operations has not received much attention, but is likely to be a key element of successful adaptation to climate change in the aquaculture sector. This study explored the sensitivities and vulnerability of freshwater fish fry production in 15 government hatcheries across Northern Thailand to climate variability and evaluated the robustness of the proposed adaptation measures. This study found that hatcheries have to consider several factors when planning production, including: taking into account farmer demand; production capacity of the hatchery; availability of water resources; local climate and other area factors; and, individual species requirements. Nile tilapia is the most commonly cultured species of freshwater fish. Most fry production is done in the wet season, as cold spells and drought conditions disrupt hatchery production and reduce fish farm demand in the dry season. In the wet season, some hatcheries are impacted by floods. Using a set of scenarios to capture major uncertainties and variability in climate, this study suggests a couple of strategies that should help make hatchery operations more climate change resilient, in particular: improving hatchery operations and management to deal better with risks under current climate variability; improving monitoring and information systems so that emerging climate-related risks are known sooner and understood better; and, research and development on alternative species, breeding programs, improving water management and other features of hatchery operations.

  20. Planning for Production of Freshwater Fish Fry in a Variable Climate in Northern Thailand.

    PubMed

    Uppanunchai, Anuwat; Apirumanekul, Chusit; Lebel, Louis

    2015-10-01

    Provision of adequate numbers of quality fish fry is often a key constraint on aquaculture development. The management of climate-related risks in hatchery and nursery management operations has not received much attention, but is likely to be a key element of successful adaptation to climate change in the aquaculture sector. This study explored the sensitivities and vulnerability of freshwater fish fry production in 15 government hatcheries across Northern Thailand to climate variability and evaluated the robustness of the proposed adaptation measures. This study found that hatcheries have to consider several factors when planning production, including: taking into account farmer demand; production capacity of the hatchery; availability of water resources; local climate and other area factors; and, individual species requirements. Nile tilapia is the most commonly cultured species of freshwater fish. Most fry production is done in the wet season, as cold spells and drought conditions disrupt hatchery production and reduce fish farm demand in the dry season. In the wet season, some hatcheries are impacted by floods. Using a set of scenarios to capture major uncertainties and variability in climate, this study suggests a couple of strategies that should help make hatchery operations more climate change resilient, in particular: improving hatchery operations and management to deal better with risks under current climate variability; improving monitoring and information systems so that emerging climate-related risks are known sooner and understood better; and, research and development on alternative species, breeding programs, improving water management and other features of hatchery operations.

  1. Cropping frequency and area response to climate variability can exceed yield response

    NASA Astrophysics Data System (ADS)

    Cohn, Avery S.; Vanwey, Leah K.; Spera, Stephanie A.; Mustard, John F.

    2016-06-01

    The sensitivity of agricultural output to climate change has often been estimated by modelling crop yields under climate change scenarios or with statistical analysis of the impacts of year-to-year climatic variability on crop yields. However, the area of cropland and the number of crops harvested per growing season (cropping frequency) both also affect agricultural output and both also show sensitivity to climate variability and change. We model the change in agricultural output associated with the response of crop yield, crop frequency and crop area to year-to-year climate variability in Mato Grosso (MT), Brazil, a key agricultural region. Roughly 70% of the change in agricultural output caused by climate was determined by changes in frequency and/or changes in area. Hot and wet conditions were associated with the largest losses and cool and dry conditions with the largest gains. All frequency and area effects had the same sign as total effects, but this was not always the case for yield effects. A focus on yields alone may therefore bias assessments of the vulnerability of agriculture to climate change. Efforts to reduce climate impacts to agriculture should seek to limit production losses not only from crop yield, but also from changes in cropland area and cropping frequency.

  2. Variation in Rubisco content and activity under variable climatic factors.

    PubMed

    Galmés, Jeroni; Aranjuelo, Iker; Medrano, Hipólito; Flexas, Jaume

    2013-11-01

    The main objective of the present review is to provide a compilation of published data of the effects of several climatic conditions on Rubisco, particularly its activity, state of activation, and concentration, and its influence on leaf gas exchange and photosynthesis. The environmental conditions analyzed include drought, salinity, heavy metals, growth temperature, and elevated [O3], [CO2], and ultraviolet-B irradiance. The results show conclusive evidence for a major negative effect on activity of Rubisco with increasing intensity of a range of abiotic stress factors. This decrease in the activity of Rubisco is associated with down-regulation of the activation state of the enzyme (e.g., by de-carbamylation and/or binding of inhibitory sugar phosphates) in response to drought or high temperature. On the contrary, the negative effects of low temperature, heavy metal stress (cadmium), ozone, and UV-B stress on Rubisco activity are associated with changes in the concentration of Rubisco. Notably, in response to all environmental factors, the regulation of in vivo CO2 assimilation rate was related to Rubisco in vitro parameters, either concentration and/or carboxylation, depending on the particular stress. The importance of the loss of Rubisco activity and its repercussion on plant photosynthesis are discussed in the context of climate change. It is suggested that decreased Rubisco activity will be a major effect induced by climate change, which will need to be considered in any prediction model on plant productivity in the near future.

  3. 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.

  4. Capturing subregional variability in regional-scale climate change vulnerability assessments of natural resources.

    PubMed

    Buotte, Polly C; Peterson, David L; McKelvey, Kevin S; Hicke, Jeffrey A

    2016-03-15

    Natural resource vulnerability to climate change can depend on the climatology and ecological conditions at a particular site. Here we present a conceptual framework for incorporating spatial variability in natural resource vulnerability to climate change in a regional-scale assessment. The framework was implemented in the first regional-scale vulnerability assessment conducted by the US Forest Service. During this assessment, five subregional workshops were held to capture variability in vulnerability and to develop adaptation tactics. At each workshop, participants answered a questionnaire to: 1) identify species, resources, or other information missing from the regional assessment, and 2) describe subregional vulnerability to climate change. Workshop participants divided into six resource groups; here we focus on wildlife resources. Participants identified information missing from the regional assessment and multiple instances of subregional variability in climate change vulnerability. We provide recommendations for improving the process of capturing subregional variability in a regional vulnerability assessment. We propose a revised conceptual framework structured around pathways of climate influence, each with separate rankings for exposure, sensitivity, and adaptive capacity. These revisions allow for a quantitative ranking of species, pathways, exposure, sensitivity, and adaptive capacity across subregions. Rankings can be used to direct the development and implementation of future regional research and monitoring programs. The revised conceptual framework is equally applicable as a stand-alone model for assessing climate change vulnerability and as a nested model within a regional assessment for capturing subregional variability in vulnerability. PMID:26796918

  5. Capturing subregional variability in regional-scale climate change vulnerability assessments of natural resources.

    PubMed

    Buotte, Polly C; Peterson, David L; McKelvey, Kevin S; Hicke, Jeffrey A

    2016-03-15

    Natural resource vulnerability to climate change can depend on the climatology and ecological conditions at a particular site. Here we present a conceptual framework for incorporating spatial variability in natural resource vulnerability to climate change in a regional-scale assessment. The framework was implemented in the first regional-scale vulnerability assessment conducted by the US Forest Service. During this assessment, five subregional workshops were held to capture variability in vulnerability and to develop adaptation tactics. At each workshop, participants answered a questionnaire to: 1) identify species, resources, or other information missing from the regional assessment, and 2) describe subregional vulnerability to climate change. Workshop participants divided into six resource groups; here we focus on wildlife resources. Participants identified information missing from the regional assessment and multiple instances of subregional variability in climate change vulnerability. We provide recommendations for improving the process of capturing subregional variability in a regional vulnerability assessment. We propose a revised conceptual framework structured around pathways of climate influence, each with separate rankings for exposure, sensitivity, and adaptive capacity. These revisions allow for a quantitative ranking of species, pathways, exposure, sensitivity, and adaptive capacity across subregions. Rankings can be used to direct the development and implementation of future regional research and monitoring programs. The revised conceptual framework is equally applicable as a stand-alone model for assessing climate change vulnerability and as a nested model within a regional assessment for capturing subregional variability in vulnerability.

  6. Evaluating historical simulations of CMIP5 GCMs for key climatic variables in Zhejiang Province, China

    NASA Astrophysics Data System (ADS)

    Xuan, Weidong; Ma, Chong; Kang, Lili; Gu, Haiting; Pan, Suli; Xu, Yue-Ping

    2015-12-01

    Assessing the regional impact of climate change on agriculture, hydrology, and forests is vital for sustainable management. Trustworthy projections of climate change are needed to support these assessments. In this paper, 18 global climate models (GCMs) from the fifth phase of the Coupled Model Intercomparison Project (CMIP5) are evaluated for their ability to simulate regional climate change in Zhejiang Province, Southeast China. Simple graphical approaches and three indices are used to evaluate the performance of six key climatic variables during simulations from 1971 to 2000. These variables include maximum and minimum air temperature, precipitation, wind speed, solar radiation, and relative humidity. These variables are of great importance to researchers and decision makers in climate change impact studies and developing adaptation strategies. This study found that most GCMs failed to reproduce the observed spatial patterns, due to insufficient resolution. However, the seasonal variations of the six variables are simulated well by most GCMs. Maximum and minimum air temperatures are simulated well on monthly, seasonal, and yearly scales. Solar radiation is reasonably simulated on monthly, seasonal, and yearly scales. Compared to air temperature and solar radiation, it was found that precipitation, wind speed, and relative humidity can only be simulated well at seasonal and yearly scales. Wind speed was the variable with the poorest simulation results across all GCMs.

  7. Perspectives of non-gaussianity in large scale weather and climate Variability

    NASA Astrophysics Data System (ADS)

    Hannachi, Abdel; Sura, Philip

    2014-05-01

    Understanding non-Gaussian statistics of weather and climate variability has important consequences in the atmospheric and ocean sciences not least because weather and climate risk assessment depends on knowing and understanding the exact shape of the system's probability density function. While there is no doubt that many atmospheric variables exhibit non-Gaussian statistics on many time (and spatial) scales a full and complete understanding of this phenomenon remains a challenge. Various mechanisms behind the observed non-Gaussian statistics have been proposed but remain, however, multifaceted and scattered in the literature. Given the importance of this subject for climate research, and in an attempt to contribute to this topic a thorough review and discussion of the different mechanisms that lead to non-Gaussian weather and climate variability are presented in this paper and an outlook is given.

  8. Assessing the future of crop yield variability in the United States with downscaled climate projections (Invited)

    NASA Astrophysics Data System (ADS)

    Lobell, D. B.; Urban, D.

    2010-12-01

    One aspect of climate change of particular concern to farmers and food markets is the potential for increased year-to-year variability in crop yields. Recent episodes of food price increases following the Australian drought or Russian heat wave have heightened this concern. Downscaled climate projections that properly capture the magnitude of daily and interannual variability of weather can be useful for projecting future yield variability. Here we examine the potential magnitude and cause of changes in variability of corn yields in the United States up to 2050. Using downscaled climate projections from multiple models, we estimate a distribution of changes in mean and variability of growing season average temperature and precipitation. These projections are then fed into a model of maize yield that explicitly factors in the effect of extremely warm days. Changes in yield variability can result from a shift in mean temperatures coupled with a nonlinear crop response, a shift in climate variability, or a combination of the two. The results are decomposed into these different causes, with implications for future research to reduce uncertainties in projections of future yield variability.

  9. Long-range variability and predictability of the Ozark Highlands climate elements

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Won

    Interannual variations and intraannual variation of regional-scale and global-scale climate variables are characterized by principal component analysis (PCA). Climate consistency is detected among the entire United States, the North Central states, and the Ozark Highlands (OZHI). The regional-scale modes of the OZHI climate are classified as the predictands of the statistical climate model. Characteristic patterns and time coefficients are examined in global-scale climate variables as the predictor of the models. Relationships between regional-scale and global-scale climate variables are identified by the month lead cross- correlation analysis. The OZHI temperatures in January and July are highly correlated to lead time global-scale climate variables in the tropical and subtropical Pacific and Atlantic and those of lead time in the eastern subtropical and midlatitude Pacific, respectively. The OZHI precipitation levels in January and May are highly correlated to lead time global-scale climate variables in the western tropical Pacific and in the western tropical Indian, and South Pacific Convergence Zone (SPCZ), respectively. From multiple linear regression (MLR) and principal components regression (PCR) analysis, the predictability of OZHI regional temperature and precipitation are discussed with model diagnostics and measurements of forecasting performance. This study suggests that PCR can clearly eliminate the multicollinearity among predictors. For the purpose of building the statistical climate model, the sensitivities of the main predictors (i.e., temperature and precipitation) are investigated, and relatively long-memory and short-memory predictors are uncovered. The sea surface temperatures have a relatively long-memory effect.

  10. From Lake Malawi Drilling: East African Climate May Have Caused Major Evolutionary Turnover in Mammalian Species During MIS 14

    NASA Astrophysics Data System (ADS)

    Johnson, Thomas; Werne, Josef

    2016-04-01

    Hominin evolution underwent important changes in the last 1.3 million years, including the extinction of Paranthropus at about 1.2 Ma, leaving Homo as the sole hominin genus. Our genus experienced a major increase in cranial capacity at about 500 ka, and our species, H. sapiens, first appeared at ~200 ka. There was a major turnover in mammalian species in East Africa between 540 and 400 ka, favoring descendants of smaller size and less specialized diet. An understanding of what drove evolution in these directions is fundamental to understanding the development of modern H. sapiens. Climate certainly played a role, for it is the principal factor that influences the distribution of vegetation and habitability on the landscape. We present a 1.3 million year record of temperature and hydroclimate in the basin of Lake Malawi, the second deepest lake in Africa, derived from a 380 m sediment sequence taken from a water depth of 590 m by the Lake Malawi Drilling Project. Seismic reflection profiles used to select the site portray an undisturbed sedimentary section that was not impacted by erosion, turbidity currents or mass wasting events. Sediment samples were analyzed to produce records of temperature (TEX86) and aridity (Ca content and leaf wax δ13C). The temperature record displays progressively larger amplitude glacial-interglacial variations from MIS 13 (~500 ka) to MIS 5 (~125 ka). Intervals of low Ca abundance, which reflect lake high stands, correlate with times of depleted δ13Cwax and relatively warm temperatures. The Malawi basin experienced warm, wet interglacials and cooler (by about 2 - 4°C), dry glacial periods, with roughly a 100 ky periodicity since the Mid-Pleistocene Transition (MPT), about 900 ka. The paleoclimate record from Lake Malawi sediments portrays a transition from a highly variable and predominantly arid climate prior to 900 ka to a progressively more humid environment after the MPT dominated by 100 ky cycles consisting of warm, wet

  11. Modeling effects of inter-annual variability in meteorological and land use conditions on coupled water and energy cycling in the cultivated African Sahel

    NASA Astrophysics Data System (ADS)

    Velluet, C.; Demarty, J.; Cappelaere, B.; Braud, I.; Boulain, N.; Favreau, G.; Charvet, G.; Ramier, D.; Issoufou, H.; Boucher, M.; Mainassara, I.; Chazarin, J.; Oï, M.; Yahou, H.; Benarrosh, N.; Ibrahim, M.

    2012-12-01

    In the dry tropics in general and in the African Sahel in particular, hydro-ecosystems are very sensitive to climate variability and land management. In the Niamey region of South-West Niger, a severe multi-decadal drought together with large-scale vegetation clearing coincided with an unexpected increase in surface and ground water resources. Such an apparent paradoxical situation illustrates the complex way in which climate and land cover interactions control the Sahelian water cycle dynamics. This stresses the importance of understanding and reliably modeling water/energy transfers in the local soil-plant-atmosphere system, under contrasted meteorological and surface conditions. This study investigates the effects of the inter-annual variability of meteorological and land use conditions on the coupled water and energy cycles in the cultivated Sahel over a 5-year period. This is based on a comprehensive multi-year field dataset acquired for a millet crop field and a fallow savannah, the two main land cover types of South-West Niger (Wankama catchment in the mesoscale AMMA-CATCH Niger observatory, part of the French-initiated RBV network). It includes atmospheric forcing, seasonal course of vegetation phenology, soil properties and model validation variables (net radiation, turbulent fluxes, soil heat/water profiles), for the two fields. The study area is typical of Central Sahel conditions, with 400-600 mm annual rainfall concentrated in the 4-5 month wet season. Soils are mainly sandy and prone to surface crusting, leading to a strong vertical contrast in hydrodynamic properties. The SiSPAT process-based model used solves the 1D mass and heat transfer system of equations in the soil, including vapor phase and coupled with a two-component (bare soil and vegetation) water and energy budget at the surface-atmosphere interface. The study explores whether such a model can be accurately calibrated and validated for the two sites using realistic-parameter values. The

  12. The Women's Role in the Adaptation to Climate Variability and Climate Change: Its Contribution to the Risk Management

    NASA Astrophysics Data System (ADS)

    Quintero Angel, M.; Carvajal Escobar, Y.; Garcia Vargas, M.

    2007-05-01

    Recently, there is evidence of an increase in the amount of severity in extreme events associated with the climate variability or climate change; which demonstrates that climate in this planet is changing. There is an observation of increasing damages, and of social economical cost associated with these phenomena's, mostly d