Trends of the thermal growing season in China, 1951-2007

Observed 20th century changes ill the length of the growing season (GS) across the Northern Hemisphere have been linked to increasing temperatures, associated with global warming. Past studies of GS changes in China have largely been based on phenological observations and satellite data, and little attention has been paid to changes in starting and ending dates of GS. Here we examine changes in the thermal GS over China from 1951 to 2007 based on observed daily surface air temperature. Using five indices, trends of three GS parameters, start, end and length, were determined at 114 high-quality stations over China. Our results show large spatial and temporal differences in the GS parameters in China, where the most prominent changes have Occurred in northern China relative to southern China. On average, from 1951 to 2007 the GS has been extended by 2.3 days/decade in northern China where most of these changes is due to an earlier onset of the GS in spring (-1.7 days/decade). In southern China, there is an average increase of GS by 1.3 days/decade with 0.6 days/decade earlier onsets in spring. Furthermore, most stations showing significant trends of GS changes are located in northern China. An extended GS in northern China indicates improved agricultural conditions due to warmer and longer GS. However, this effect may be counteracted by changes in the precipitation pattern. Copyright (C) 2009 Royal Meteorological Society