African Lakes and Climate

Context

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Robust future projections of changes in rainfall in semi-arid regions of northern and southern Africa are critical in the assessment of vulnerability to climate-related hazards. These areas are thought to be particularly susceptible to climate change given the high proportions of the population employed in rainfed agriculture. State-of-the-art climate model simulations of the next century suggest that North and East Africa are projected to experience an increase in rainfall, while southern regions may become drier. Interannual variability and the frequency of extreme events such as heavy rainfall occurrences or droughts are broadly expected to increase. Uncertainty in these projections is large and complicated by the importance of evaporation and soil moisture for predicting impacts on water availability. 

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We know that there have been times in prehistory when there were also very different rainfall regimes to today in tropical and sub-tropical Africa. One particular well-documented event was the African Humid Period (AHP; roughly 14,000 to 6,000 years ago) when, due to enhanced monsoon rainfall, much of the Sahara was transformed into a region with extensive wetlands, savannahs, and large lakes, occupied by people and a variety of iconic animals, including hippos and crocodiles. But there is evidence of many such events across the whole continent occurring at various times. For example,  Lake Makgadikgadi in Botswana was at times a 'mega' lake (see right image), but is now a mostly dry saltpan.

What can the past dynamics of these highly changeable systems tell us about the dominant causal mechanisms and how sensitive they will be to future climate change? 

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