Leading source and constraint on the systematic spread of the changes in East Asian and western North Pacific summer monsoon
With ongoing global warming, the changes in EA-WNPSM rainfall—feeding over two billion people in East Asia and the Indochina Peninsula—projected by theCoupledModel Intercomparison Project Phase 5 (CMIP5)models show remarkable and unidentified inter-model spread.Here, we reveal the leading inter-model spread of EA-WNPSMchanges in 28CMIP5models is related to a ‘dry north–wet south’ dipole in East Asia and awet Indochina andWNP. This spread pattern of EA-WNPSMchanges is induced by the spread of sea surface temperature changes in the equatorial western Pacific, and can be further traced back to an apparent discrepancy among the state-of-the-artmodels in simulating the tropical Pacific rainfall. An air-sea coupling processes involvedwith summer background circulation contribute to this robust spread pattern of EA-WNPSMchanges.We can constrain the EA-WNPSM rainfall changes based on the current-future relationship and observation that there should bemore rainfall increase inNorthChina and theKorean Peninsula and less increase in SouthChina, the Indochina Peninsula andWNP, relative to previousmulti-model ensemble projections.