中文摘要：

中上新世是古气候研究领域的重要时期，研究此时期气候能为理解地球气候系统和预估未来气候变化提供帮助。利用美国国家大气研究中心研发的通用气候系统模式的平板海洋模式组件CCSM4-SOM，模拟了相对于工业革命前期，大气CO2浓度、地形和地表类型改变对中上新世气候增暖的不同影响。结果表明，地形改变对全球年平均地表气温影响较小，但在地形降低较大区域其增温效果十分明显；大气CO2浓度增加导致全球年均地表气温显著增加，而且全球各纬度均有增温，由于海冰反馈作用，两半球高纬海域增温更为显著；地表类型改变在北半球高纬增温效应最为明显，部分地区增温幅度已超过大气CO2浓度增加所引起的增幅。总体来看，大气CO2浓度增加所引起的增温效应在全球年平均和全年纬向平均上表现显著，但在高纬局地区域，它的影响并没有地形和地表类型改变的影响大。

英文摘要：

The Middle Pliocene is an important period in paleoclimate research field, and studying this period can improve our understanding of earth climate system and future climate change. Using the Community Climate System Model version 4.0 with slab ocean model,the individual climate effects of atmospheric CO2 concentration, topography and land cover change on climate warming in the Middle Pliocene relative to the pre-industrial period have been evaluated. The results show that the global annual mean surface air temperature（SAT） increases by 2.49K in the Middle Pliocene relative to the pre-industrial period. The topography change has a weak effect on the global annual mean SAT change, with the global annual mean SAT increases only by 0.26K, but in the areas where the topography decreases significantly,the warming effect is obvious. The increase of atmospheric CO2 concentration from 280ppm to 405ppm leads to a warming of 1.85K in the global annual mean SAT change, and the warming appears at all latitudes. Due to the sea ice feedback, the warming in high latitudes is more obvious. The land cover changes make the global annual mean SAT increase by 0.67K, and have the largest warming effect in northern high latitudes, with the largest warming by 6K. In general,the warming effect of atmospheric CO2 concentration increase is obvious in the global and zonal annual mean SAT change, but in the local area in high latitudes, its influence is not stronger than the effects produced by the topography and land cover changes.