An Overview of China Climate Change over the 20th Century Using UK UEA/CRU High Resolution Grid Data

Abstract

The operational observations in China started in 1951.The availabity of instrumental observations is poor in the first half of the 20th century.Therefore,it is difficult to use them in discussing long-term climate change issue.Although a number of proxy data could be used,the deficiencies are apparent,such as the coarse temporal and spatial resolution,etc.The University of East Anglia recently released the latest version of high resolution grid dataset,named as CRU-TS2.1.It is a completely covered monthly dataset of surface climatic variables.Compared with domestic observations,it has some merits concerning China climate change over the 20th century.Firstly,this dataset provides new information of the climate change over western China before 1950.Although it should be noted that the records are interpolated from observations,the results show significant correlation with the observation in the second half of the 20th century.Secondly,CRU dataset provides monthly mean fields,while domestic century-scale series is just annual mean or seasonal mean data in the first half of the 20th century.Moreover,there are not any proxy data included in the construction of this dataset,which can bring noise and uncertainty.Hence,comparison between the CRU dataset and domestic observations is the way to verify the characteristics of China climate change during the 20th century and to validate the quality of the dataset in both China and UK. The results are as follows:(1) The interannual temperature variation is identical in both datasets.Their positive correlation coefficient is 0.84.They slightly differ from each other in the 1920s,when CRU underestimates the warming change in China,and therefore overestimates the warming trend of the whole century.(2) Even in the given 10 regional scales,both CRU and domestic data exhibit good consistency,apart from Tibet and Xinjiang areas.About one celsius degree bias is estimated by CRU in Tibet during the 1920s,which is the major difference from the reconstructed record.(3) The seasonal variability of precipitation over eastern China is identical in both series.The highest correlation coefficient(0.93) for 100 years among the four seasons is in autumn,while winter is the season that their correlation is the lowest one(0.77).(4) CRU data exhibits appropriate interdecadal variation of temperature and precipitation as shown in China records.Particularly,CRU dataset also presents some primary features before 1951,especially in western China,where and when no observational data can be available.Therefore,CRU high resolution grid data present a more complete picture of climate change in China over the 20th century.