PNNL

Abstract

Asian monsoon supplies the freshwater that a large population in Asia depends on, but how anthropogenic climate warming may change this key water source for Asia remains obscure. This is partly due to the prevailing point-wise assessment of climate projections, even though climate change patterns are inherently organized by the dynamics intrinsic to the climate system. This study evaluates the future change of the East Asian summer monsoon rainfall by projecting the precipitation from several large ensemble simulations onto the leading two dynamical modes of internal variability. The result reveals a remarkable consensus across the ensembles on the increasing trends and the daily variability in both dynamical modes. More specifically, the summer rainfall in the middle and lower reaches of Yangtze River valley, the southern Korean Peninsula, and southern Japan is projected to increase, with the projection pattern emerging as early as the late 2030s, despite the increasing internal uncertainty as climate warms. The increase of the daily variability of the modes harbingers more monsoon-related hydrological extremes over some identifiable East Asian regions in the decades to come.