Increased interannual variability of Sahel rainfall under greenhouse warming.

The Sahel is home to tens of millions of people in developing regions and is frequently influenced by extreme events such as drought and floods. Multi-model mean projections indicate an increase in Sahel mean rainfall under greenhouse warming, but how Sahel rainfall interannual variability and extreme seasons might change is unclear. Using the latest generation of climate models, here we find that under a high emission scenario, Sahel rainfall variability increases, featuring a higher frequency of both extreme wet and dry seasons. The increase of rainfall interannual variability is stronger in the central-eastern Sahel than in the western Sahel. The increase in variability is due to several factors, including a projected increase in El Niño-Southern Oscillation variability, which leads to a stronger impact on low-level wind and moisture flux over the Sahel resulting in more extreme seasons, and a higher mean rainfall over the Sahel favoring large anomalies. Thus, the Sahel is likely to experience more extreme wet and dry seasons relative to its warmer and wetter mean climate.