A mid-troposphere perspective on the East African climate paradox

Abstract The East African climate paradox—a term framing the observed precipitation decline in the March–May (MAM) wet season of East Africa from roughly 1980–2010, yet an increase in future climates simulated by global climate models (GCMs)—mostly relies on data representing sea level. Here we add a mid-troposphere perspective by combining in-situ meteorological measurements at ∼6000 m a.s.l. from Africa’s highest mountain summit and a carefully selected subset of GCMs through a machine-learning link. Temporal trends of the resultant six weather types do support a drier mountain climate in the recent past and a moister one in the course of the 21st century, and a key to understanding these contrasting trends materializes from the new dominance of changes in weather type frequency in the future climate. Importantly, however, the results also suggest that the trend reversal requires a strong external climate forcing. Hence, the forcing strength should be considered more systematically in forthcoming studies, to challenge the question whether equatorial East Africa’s MAM climate will indeed become wetter in all plausible future scenarios.