Increased CO2 and anthropogenic aerosols (AAs) coexist in the atmosphere with opposite radiative effects. Their resultant climate responses may not fully offset each other, leading to some nonlinear changes, particularly in summer precipitation over East Asia (EA). However, how the coexistence of CO2 and AAs causes the nonlinear effect on EA precipitation remain unclear. Through analyses of fully coupled model simulations, this study shows that when both forcings are included, the precipitation over North China in July–August decreases less than the linear combination of the changes induced by individual forcings, indicating a nonlinear increase of precipitation. These nonlinear changes over EA likely originate from the Arctic and North Atlantic region. Specifically, the Arctic sea-ice sensitivity to the CO2-induced warming is higher than that to the AA-induced cooling, leading to a large increase of sea ice concentration over the East Siberian–Beaufort Seas in the nonlinear effect. This can excite an anomalous atmospheric Rossby wave propagating southeastward into the North Atlantic, which increases low cloudiness to cool the surface over the midlatitude North Atlantic. This cooling subsequently generates an anomalous Rossby wave train pattern across Eurasia with two branches propagating toward EA. The concurring circulation changes over EA ultimately result in nonlinear precipitation changes there. This study suggests that the nonlinear climate response in the high latitudes can remotely induce nonlinear changes in the lower latitudes and highlights the need to consider nonlinear effects in analyzing externally forced climate changes over EA.

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