Climate change trend in China, with improved accuracy

Abstract

We have found that a spatial interpolation of mean annual temperature (MAT) in China can be accomplished using a global ordinary least squares regression model since the relationship between temperature and its environmental determinants is constant. Therefore the estimation of MAT does not very across space and thus exhibits spatial stationarity. The interpolation of mean annual precipitation (MAP), however, is more complex and changes spatially as a function of topographic variation. Therefore, MAP shows spatial non-stationarity and must be estimated with a geographically weighted regression. A statistical transfer function (STF) of MAT was formulated using minimized residuals output from a high accuracy and high speed method for surface modeling (HASM) with an ordinary least squares (OLS) linear equation that uses latitude and elevation as independent variables, abbreviated as HASM-OLS. The STF of MAP under a BOX-COX transformation is derived as a combination of minimized residuals output by HASM with a geographically weighted regression (GWR) using latitude, longitude, elevation, impact coefficient of aspect and sky view factor as independent variables, abbreviated as HASM-GWR-BC. In terms of HASM-OLS and HASM-GWR-BC, MAT had an increasing trend since the 1960s in China, with an especially accelerated increasing trend since 1980. Overall, our data show that MAT has increased by 1.44 °C since the 1960s. The warming rates increase from the south to north in China, except in the Qinghai-Xizang plateau. Specifically, the 2,100 °C · d contour line of annual accumulated temperature (AAT) of ≥10 °C shifted northwestward 255 km in the Heilongjiang province since the 1960s. MAP in Qinghai-Xizang plateau and in arid region had a continuously increasing trend. In the other 7 regions of China, MAP shows both increasing and decreasing trends. On average, China became wetter from the 1960s to the 1990s, but drier from the 1990s to 2000s. The Qinghai-Xizang Plateau and Northern China experienced more climatic extremes than Southern China since the 1960s.