Numerical Simulation Study On Climate Change Over Global And China During The Last Millennium

In this paper, the climate change over Global and China during the last millennium (1000-1999A.D.) were investigated using the fully coupled climate model CCSM2.0.1. Six experiments of 1000-yr simulation have been performed with the model driven by different forcing factors(orbital parameter, solar radiation, volcanic activity and greenhouse gas concentration). Firstly, we analyse the characteristic of temperature over Global and China during the last millennium based on simulated data that resulted from each experiment and the reconstructed temperature data, and we discuss the effect of forcing factor on the temperature of the last millennium. Then we discuss the characteristic of precipitation and atmospheric circulation over the Eastern China in the last millennium. The main conclusions are as follows:(1)There are significant positive correlation between the simulated temperature data resulted from SVGM experiment and the reconstructed temperature data. In particular, for the simulated temperature over Northern Hemisphere and China, there are three typical climatic period, namely Medieval Warm Preiod(1000～1250A.D.), Little Ice Age period(1250-1850A.D.) and 20th century warm period, there are some difference in starting and ending time of each typical climatic period between the simulated data and reconstructed data, but all of them show that 20th century warm period is warmer than Medieval Warm Period, and 20th century is warmest in the last millennium.(2)The effect of orbital parameter on temperature variation in the last millennium is very small, the Medieval Warm Period and Little Ice Age period attribute to the change of solar radiation, volcanic activity enhances the cooling of the Little Ice Age period, and increasing concentration of greenhouse gas plays a key role on the rapid warming in the 20th century warm period.(3)Under the influences of nature and anthropic activity forcing factors, there is a significant positive correlation between the precipitation and temperature over Eastern China, where the correlation coefficient is 0.46 with a 95%confidence level. The Empirical Orthogonal Function (EOF) analysis shows that the change of precipitation in north of the Yangtze River is opposite to that in the south during the Medieval Warm Period and the 20th century warm period. While in the Little Ice Age period, the change in the reaches of the Yangtze River is opposite to that in the north and south of China. The Morlet wavelet analysis indicates the prominent inter-annual (2-8 years), multi-decadal (16-32 years), inter-decadal (64 years) and over 100-year periodicity variations (i.e.100 years,200 years and 256 years). The analysis of the circulation characteristics illustrates that there are some similarities between Medieval Warm Period and 20th century warm period and a significant difference in Little Ice Age period.