Understanding the regional pattern of projected future changes in extreme precipitation

Regional projections of daily extreme precipitation are uncertain, but can be decomposed into thermodynamic and dynamic contributions to improve understanding. While thermodynamics alone uniformly increase extreme precipitation, dynamical processes introduce regional variations. Changes in extreme precipitation are among the most impact-relevant consequences of climate warming 1 , yet regional projections remain uncertain due to natural variability 2 and model deficiencies in relevant physical processes 3 , 4 . To better understand changes in extreme precipitation, they may be decomposed into contributions from atmospheric thermodynamics and dynamics 5 , 6 , 7 , but these are typically diagnosed with spatially aggregated data 8 , 9 or using a statistical approach that is not valid at all locations 10 , 11 . Here we decompose the forced response of daily regional scale extreme precipitation in climate-model simulations into thermodynamic and dynamic contributions using a robust physical diagnostic 8 . We show that thermodynamics alone would lead to a spatially homogeneous fractional increase, which is consistent across models and dominates the sign of the change in most regions. However, the dynamic contribution modifies regional responses, amplifying increases, for instance, in the Asian monsoon region, but weakening them across the Mediterranean, South Africa and Australia. Over subtropical oceans, the dynamic contribution is strong enough to cause robust regional decreases in extreme precipitation, which may partly result from a poleward circulation shift. The dynamic contribution is key to reducing uncertainties in future projections of regional extreme precipitation.