The recent Sahel drought is real

Widely distributed proxy records indicate that the Medieval Climate Anomaly (MCA; *900-1350 AD) was characterized by coherent shifts in large-scale Northern Hemisphere atmospheric circulation patterns. Although cooler sea surface temperatures in the central and eastern equatorial Pacific can explain some aspects of medieval circulation changes, they are not sufficient to account for other notable features, including widespread aridity through the Eurasian sub-tropics, stronger winter westerlies across the North Atlantic and Western Europe, and shifts in monsoon rainfall patterns across Africa and South Asia. We present results from a full-physics coupled climate model showing that a slight warming of the tropical Indian and western Pacific Oceans relative to the other tropical ocean basins can induce a broad range of the medieval circulation and climate changes indicated by proxy data, including many of those not explained by a cooler tropical Pacific alone. Important aspects of the results resemble those from previous simulations examining the climatic response to the rapid Indian Ocean warming during the late twentieth century, and to results from climate warming simulations-especially in indicating an expansion of the Northern Hemisphere Hadley circulation. Notably, the pattern of tropical Indo-Pacific sea surface temperature (SST) change responsible for producing the proxy-model similarity in our results agrees well with MCA-LIA SST differences obtained in a recent proxy-based climate field reconstruction. Though much remains unclear, our results indicate that the MCA was characterized by an enhanced zonal Indo-Pacific SST gradient with resulting changes in Northern Hemisphere tropical and extra-tropical circulation patterns and hydroclimate regimes, linkages that may explain the coherent regional climate shifts indicated by proxy records from across the planet. The findings provide new perspectives on the nature and possible causes of the MCA-a remarkable, yet incompletely understood episode of Late Holocene climatic change.

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“…These trends parallel the decreasing trends in Sahel rainfall (e.g. Dai et al 2004) and increasing trends in Indian Ocean SSTs (Fig. 19).…”

Section: Discussionsupporting

confidence: 63%

Support for global climate reorganization during the “Medieval Climate Anomaly”

et al. 2010

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“…3). We applied the nonparametric statistical test of Pettitt (1979) These results correspond to the trends observed elsewhere in the Sahel of West Africa, with the start of the drought in the late 1960s (Dai et al, 2004;L'Hoˆte et al, 2002;Ozer, 2000) and wetter conditions in the early 1990s (Nicholson, 2005;Ozer et al, 2003).…”

Section: Resultsmentioning

confidence: 90%

“…Climate is characterized by a short rainy season, largely limited to the months of July-September, as well as the North-South gradient of the mean annual rainfall (Ozer, 2000). Over the last decades, the Sahel of West Africa has been affected by a severe drought (Dai et al, 2004;L'Hoˆte et al, 2002;Ozer, 2000). These long-time rainfall shortages have not only affected natural vegetation and stream flows but also socio-economical activities.…”

Section: Article In Pressmentioning

confidence: 99%

Fifty years of landscape evolution in Southwestern Mauritania by means of aerial photos

Niang

Ozer

2008

Journal of Arid Environments

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South-western Mauritania is located in a semi-arid environment exposed to large rainfall variations and affected by a severe drought since the mid-1960s. The studied area includes the right bank of the Senegal River and the southern extension of the Saharan sandy dunes and is based on the analysis of climatic data, field studies, and four aerial surveys realized since 1954.The climatic analysis shows that, after a strong decline of yearly rainfall started in the mid-1960s, a significant increase is observed from the early 1990s. In the meantime, dust storms frequency has dramatically increased while the threshold wind speed declined as a result of vegetation contraction. The comparison of the four mosaics of aerial photos reveals the major impact of both drought and human on recent environment changes with the strong decline of the forest, the reactivation of sandy soils and the apparition of large rice fields.If the increase of active dunes activity is likely to be a consequence of the persisting drought, forest decline is more likely to be attributed to fuel wood collection in a first time, then to the creation of rice fields since the late 1980s. Although the 2003 aerial photos show a timid return of vegetation in very limited and specific areas, field surveys show that wind erosion is still very important and water erosion is developing very rapidly because of the absence of vegetation cover. r

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“…This has led to contradictory results from climate trend studies at local and subregional scales. For instance, following the 1990s' report of the Sahelian drought (Sivakumar 1992;Le Barbé and Lebel 1997), several studies considered it either ended in the 1990s (Ozer et al 2003), continued (Hulme 2001;L'Hote et al 2002;Dai et al 2004) or even was simply an artifact of changing station networks (Chappell and Agnew 2008). The recent discovery of a precipitation gradient from eastern to western Sahel ) in addition to the north-south Inter Tropical Convergence Zone (ITCZ) influence on rainfall distribution is also a factor of importance for reliable hydrological predictions in West Africa.…”

Section: Introductionmentioning

confidence: 99%

Hydro-climatic changes in the Niger basin and consistency of local perceptions

et al. 2014

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Since the 1970s, the Niger basin has been characterized by hydro-climatic changes which have significant impacts on local populations. These changes are not well documented as a result of a decreasing observation network for hydro-climatic data. Indigenous peoples' knowledge has increasingly been considered an important component in addressing these data gaps. We evaluated the consistency of indigenous perceptions and adaptive responses with rainfall and river discharge observations in the Niger basin. Socioeconomic data were collected from 239 households in 30 communities across two settlements in the Niger basin. Data on historical rainfall and river discharge from 1950 to 2010 were analyzed and the consistency with local perceptions was assessed. Generally, there was a high agreement between observations and perceptions, but impacts of climate change in the communities were dependent on social and environmental factors that can introduce differences in perception despite identical observations. Indigenous perceptions gave good indication of the most vulnerable sectors as well as communities who also displayed the greatest willingness to combat climate change. These results suggest that integration of indigenous perceptions into climate change science, especially in data scarce regions, is highly valuable.

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The recent Sahel drought is real

Cited by 343 publications

References 33 publications

Support for global climate reorganization during the “Medieval Climate Anomaly”

Support for global climate reorganization during the “Medieval Climate Anomaly”

Fifty years of landscape evolution in Southwestern Mauritania by means of aerial photos

Hydro-climatic changes in the Niger basin and consistency of local perceptions

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