全球变暖减缓期陆地地表气温变化特征和CMIP5多模式的未来情景预估

2000年后全球气温的增温率显著下降,全球进入变暖减缓期.本文基于CRU(Climatic Research Unit) 观测资料,分析讨论了2000年后全球及欧亚中高纬度地区全球变暖的减缓特征,评估了CMIP5(Coupled Model Intercomparison Project Phase 5)试验多模式对全球变暖减缓的模拟及未来气温变化预估.结果表明,2000年后全球陆地平均地面气温的增温率大幅下降至0.14℃ (10 a)-1,仅为1976~1999年加速期增温率的一半.全球陆地13个区域中有9个地区的增温率小于2000年前,4个地区甚至出现了降温.其中以欧亚中高纬地区最为特殊.加速期(1976~1999年)增温率达到0.50℃ (10 a)-1,为全球陆地最大,2000年后陡降至-0.17℃ (10 a)-1,为全球最强降温区,为全球变暖的减缓贡献了49.13%.并且具有显著的季节依赖,减缓期冬季增温率下降了-2.68℃ (10 a)-1,而秋季升高了0.86℃ (10 a)-1,呈现反位相变化特征.CMIP5多模式计划中仅BCC-CSM1.1在RCP2.6情景下和MRI-ESM1模式在RCP8.5下的模拟较好地预估了全球及欧亚中高纬地区在2000年后增温率的下降以及欧亚中高纬秋、冬温度的反位相变化特征.BCC-CSM1.1在RCP2.6情景下预估欧亚中高纬地区2012年后温度距平保持在1.2℃左右,2020年后跃至2℃附近振荡.而MRI-ESM1在RCP8.5情景下预估的欧亚中高纬度温度在2030年前一直维持几乎为零的增温率,之后迅速升高.

Evolution of Surface Temperature during Global Warming Hiatus Based on Observations and CMIP5 Simulations

The rise in global surface temperature has significantly declined after 2000. In this study, the evolution of the surface temperature of the global land-mean and Eurasia middle-high latitudes during the global warming hiatus was analyzed based on CRU observations. Simulations and projections were also evaluated using the Coupled Model Intercomparison Project 5 (CMIP5). The results indicate that, in the global warming hiatus period, the trend of the global land-mean surface temperature is only 0.14℃ (10 a)-1, which is half that during 1976-1999. The trend is less than that before 2000 in nine of the 13 global land regions, and four of them show a decreasing trend. The Eurasia middle-high latitude region is the most interesting among all the regions. For 1976-1999, the Eurasia middle-high latitude region shows the largest warming among all the land regions and reaches 0.50℃ (10 a)-1. After 2000, the trend significantly declines to -0.17℃ (10 a)-1, the greatest cooling trend over land, globally, contributing 49.13% of the remarkable change in global land surface temperatures before and after 2000. Furthermore, the surface temperature of the Eurasia middle-high latitude region shows an opposite change in autumn and winter after 2000; the temperature of the former rises by 0.86℃ (10 a)-1, while the that of the latter decreases by 2.68℃ (10 a)-1. In CMIP5, only the simulation and projects in BCC-CSM1.1 under the RCP2.6 scenario and MRI-ESM1 under the RCP8.5 scenario reproduce the evolution of the global land-mean and Eurasia middle-high latitude surface temperature, as well as the opposite change between autumn and winter of the Eurasia middle-high latitude region, during the global warming hiatus. The temperature projection of the BCC-CSM1.1 under the RCP2.6 scenario for the Eurasia middle-high latitude remains flat, near 1.2℃, after 2012, and jumps to 2℃ after 2020. The change in the MRI-ESM1's projected temperature under the RCP8.5 scenario is close to zero before 2030; the temperature then rises remarkably, to ℃ (10 a)-1.