Intensification of the hydrological cycle expected in West Africa over the 21st century

This study uses the high-resolution outputs of the recent CORDEX-Africa climate projections to investigate the future changes in different aspects of the hydrological cycle over West Africa. Over the twenty-first century, temperatures in West Africa are expected to increase at a faster rate (+0.5 degrees C per decade) than the global average (+0.3 degrees C per decade), and mean precipitation is expected to increase over the Guinea Coast (+0.03 mm d(-1) per decade) but decrease over the Sahel (-0.005 mm d(-1) per decade). In addition, precipitation is expected to become more intense (+0.2 mm d(-1) per decade) and less frequent (-1.5 d per decade) over all of West Africa as a result of increasing regional temperature (precipitation intensity increases on average by +0.35 mm d(-1) degrees C-1 and precipitation frequency decreases on average by -2.2 d degrees C -1). Over the Sahel, the average length of dry spells is also expected to increase with temperature (+4 % d degrees C-1), which increases the likelihood for droughts with warming in this subregion. Hence, the hydrological cycle is expected to increase throughout the twenty-first century over all of West Africa, on average by +11 % degrees C-1 over the Sahel as a result of increasing precipitation intensity and lengthening of dry spells, and on average by +3 % degrees C-1 over the Guinea Coast as a result of increasing precipitation intensity only.