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This paper is among the first to report on the full integration of basin-scale models that include projections of the demand and supply of water and energy for residential, commercial, industrial, and agricultural sector users. We link two widely used regional planning models that allow one to study the impact of rising climate variability on water and electricity use in Sacramento, California. Historic data combined with the current energy and water system configuration was used to assess the implications of changes in temperature and precipitation. Climate simulations suggest that electricity imports to the region would increase during hot dry spells, when regional power production is most constrained. In particular, regional imports of electricity would increase over 35 % in hot dry years, assuming a 4 °C increase in average temperature and a 25 % decrease in average precipitation. [ABSTRACT FROM AUTHOR]

Little is known about climate change and its impacts for the arid coastal and mountainous regions in northern Chile. The Elqui river basin, part of the Norte Chico of Chile between 27ºS and 33ºS latitude, is located south of the hyper-arid Atacama desert. Despite water scarcity, agricultural development in this region has been enhanced by agronomic practices and the marketing of valuable products. This paper characterizes the actual climate conditions and presents an overview and analyses of past climate variability, and future possible climate trends, emphasizing those relevant to agriculture. Precipitation shows an important decrease during the first decades of the past century. Runoff shows decreasing trends for the first half of the past century and increases for 1960 to 1985. Drought appears to be increasing. Statistical downscaling was accomplished using the Long Ashton Research Station Weather Generator. Both future periods of 2011 to 2030 and 2046-65 showed trends to higher minimum and maximum temperature. The number of hot days (maximum temperature greater than or equal to 30°C) has a strong increasing trend during October to April. Even though the downscaled results for precipitation do not show trends, the continuation of the present trend of low amounts is a concern. We discuss some implications of climatic changes for agriculture and we emphasize the importance of adaptation, especially to deal with water scarcity. [ABSTRACT FROM AUTHOR]

Single- to multiple-year drought episodes posed significant challenges for agrarian communities across southern Africa during the nineteenth century and hence are widely recorded in a variety of historical documents. However, the ways in which droughts are articulated, and the focus of individual accounts, vary considerably between different authors and historical source types. This study draws on a range of documentary source types—specifically newspapers, letters, reports and diaries—to explore the varied narratives associated with three protracted droughts (those of 1861–1863, 1876–1879 and 1895–1897) that affected large areas of the subcontinent. The analysis spans four case study areas—present day KwaZulu-Natal (South Africa), Lesotho, Malawi and the southern Kalahari (Botswana and South Africa)—which were investigated as part of different interdisciplinary projects. We explore issues common to all case study areas, including (i) how specific drought events are framed and (ii) what is and is not reported about individual droughts across different source types. We conclude that different source types in the subcontinent may be more or less appropriate for addressing the specific objectives of historical climatology, particularly in relation to historical drought. Sources such as newspapers and weather diaries are rich in qualitative and quantitative observations suitable for the reconstruction of temporal and spatial patterns of weather and climate, as well as climate-related natural disasters. In contrast, letters, reports and personal journals, especially those written by missionaries, provide additional qualitative narratives through which to investigate the vulnerability of past societies and economies to climate variations, and to explore past discourses and social representations of climate. While studies of this kind have been published for European and American source types, this is the first systematic exploration of documentary sources for the historical climatology of Africa. It should therefore provide a guide for climate history studies elsewhere in the continent, or other regions where written records are absent prior to the arrival of European colonists. [ABSTRACT FROM AUTHOR]

Recent water resources planning studies have proposed climate adaptation strategies in which infrastructure and policy actions are triggered by observed thresholds or "signposts." However, the success of such strategies depends on whether thresholds can be accurately linked to future vulnerabilities. This study presents a framework for testing the ability of adaptation thresholds to dynamically identify vulnerable scenarios within ensemble projections. Streamflow projections for 91 river sites predominantly in the western USA are used as a case study in which vulnerability is determined by the ensemble members with the lowest 10% of end-of-century mean annual flow. Illustrative planning thresholds are defined through time for each site based on the mean streamflow below which a specified fraction of scenarios is vulnerable. We perform a leave-one-out cross-validation to compute the frequency of incorrectly identifying or failing to identify a vulnerable scenario (false positives and false negatives, respectively). Results show that in general, this method of defining thresholds can identify vulnerable scenarios with low false positive rates (< 10%), but with false negative rates for many rivers remaining higher than random chance until roughly 2060. This finding highlights the tradeoff between frequently triggering unnecessary action and failing to identify potential vulnerabilities until later in the century, and suggests room for improvement in the threshold-setting technique that could be benchmarked with this approach. This testing framework could extend to thresholds defined with multivariate statistics, or to any application using thresholds and ensemble projections, such as long-term flood and drought risk, or sea level rise. [ABSTRACT FROM AUTHOR]

The response of West African climate zones to anthropogenic climate change during the late 21st century is investigated using the revised Thornthwaite climate classification applied to ensembles of CMIP5, CORDEX, and higher-resolution RegCM4 experiments (HIRES). The ensembles reproduce fairly well the observed climate zones, although with some notable discrepancies. CORDEX and HIRES provide realistic fine-scale information which enhances that from the coarser-scale CMIP5, especially in the Gulf of Guinea encompassing marked landcover and topography gradients. The late 21st century projections reveal an extension of torrid climates throughout West Africa. In addition, the Sahel, predominantly semi-arid in present-day conditions, is projected to face moderately persistent future arid climate. Similarly, the Gulf of Guinea shows a tendency in the future to experience highly seasonal semi-arid conditions. Finally, wet and moist regions with an extreme seasonality around orographic zones become less extensive under future climate change. Consequently, West Africa evolves towards increasingly torrid, arid and semi-arid regimes with the recession of moist and wet zones mostly because of the temperature forcing, although precipitation can be locally an important factor. These features are common to all multimodel ensembles, a sign of robustness, with few disagreements in their areal extents, and with more pronounced changes in the higher-resolution RCM projections. Such changes point towards an increased risk of water stress for managed and unmanaged ecosystems, and thus add an element of vulnerability to future anthropogenic climate change for West African water management, ecosystem services and agricultural activities. [ABSTRACT FROM AUTHOR]