Severe summer rainfall in China associated with enhanced global warming

Trends of extreme wet and dry conditions during recent decades-were examined using observed data for eastern China. Mean precipitation for the region has shown a significant downward trend from the 1950s to the mid-1970s, and a positive trend since the late 1970s. The change in trend since the late 1970s, i.e. the period during which enhanced global warming emerged, is most prominent. The linear trend of the mean summer rainfall anomalies over the 4 subregions studied was +7.5 % decade(-1). Changes in the trend of severe wet and dry events are not symmetrical. During the period 1977-1998, the number of severe wet stations increased at the rate of 20.3 decade(-1), but the trend far severe dry events was only -5.4 decade(-1). Similar rainfall changes can be found over many global land areas. The summer rainfall in eastern China showed only a negligible secular trend during the period 1880-1998. However, the decadal variations were clear. The mean rainfall in 1990-1998 was higher than for any other decade in the last 100 yr. The linear trend of the 33-station mean during 1977-1998 was +47.5 mm decade(-1); such a strong increase is unprecedented in the record since 1880. Decadal variations and global warming may both play important roles in the recent significant increase in summer rainfall. This paper also presents the results of greenhouse and/or aerosol forcing experiments, in which summer precipitation over eastern China is generally estimated to rise. There are many uncertainties, however, in the regional precipitation simulations. For example, the modeled rainfall is sensitive to whether aerosols are included or not. Further research is needed to determine whether there is a substantial relationship between the rainfall changes in China and global greenhouse warming.