Improved estimation of average warming trend of China from 1951-2010 based on satellite observed land-use data

This paper provides new evidence of regional warming trends from local Chinese observations covering the period 1951-2010. We used satellite-derived land data and weighted urban and rural temperature records (a weighted method) and estimate the regional warming trend, which involves natural climate change and human impact. The annual warming rate over the whole of China is 0.21 +/- 0.02 A degrees C/decade. The seasonal warming is 0.30 A +/- 0.05 A degrees C/decade (Winter), 0.24 A degrees C A +/- 0.03 A degrees C/decade (Spring); 0.16 A +/- 0.02 A degrees C/decade (Summer) and 0.21 A +/- 0.03 A degrees C/decade (Autumn). The mean warming trend is lower than previous estimates (e.g. NMIC, CRU-China) using un-weighted methods (arithmetic average of all records). The warming difference between the weighted and un-weighted accounts for 27 % (12 %) of the NMIC (CRU-China) un-weighted estimate on the total warming. This indicates that previous estimations overestimated a regional warming trend. The differences can be partly attributed to the weighting of the urban effect which is taken into consideration in this study, resulting in a much slower temperature increase. Spatially, the northern part of China shows a larger difference than the south especially for winter and spring. We argue that it is of importance to take into consideration the influence of urban land-use change to improve the physical understanding of surface warming in China over past decades.