Contributions of natural and anthropogenic forcings to the summer cooling over eastern China: An AGCM study

We estimate the contributions of natural and anthropogenic forcings to the observed summer cooling over the Eastern China through a set of controlled experiments of an atmospheric general circulation model. The control run is forced by historical natural and anthropogenic agents, as well as by the Hadley Center global sea surface temperature. The model suggests a weak influence by the solar radiation change on this cooling, but a significant contribution by the sulfate aerosol to this cooling, through both dynamic and thermal processes. The inclusion of the sulfate aerosol induces a positive gradient of air temperature in the middle-upper troposphere, which results in a northward shift in the 200 hPa East Asian westerly jet stream and an increase of the East Asian summer monsoon, leading to more cloud cover and precipitation in the Eastern China therefore surface cooling over the region.