Climate-dependency of Impact of Increased Carbon Dioxide on African
Monsoon Rainfall: Insights from model simulations
Abstract
Previous studies on future scenarios identified two key effects of
increasing CO2 on the African summer monsoon (ASM): Rising CO2 leads to
an enhancement in moisture supply, favoring an increase in ASM
precipitation (the thermodynamic effect). However, it also results in a
weakening in mean atmospheric flow, thus facilitating a dryness across
the ASM region (the dynamic effect). Therefore, the ultimate change in
ASM precipitation stems from the balance of both the thermodynamic and
dynamic effects. This study further examines the impact of rising CO2 on
ASM rainfall, by taking into account various climate states. Our results
suggest that an increase in CO2 during warm interglacial periods has a
stronger influence from thermodynamic factors than from dynamic factors,
resulting in an enhancement in ASM rainfall. In contrast, if CO2
increases under cold glacial climate backgrounds, its dynamic impact
dominates a reduction of rainfall in the ASM region.