CMIP5模式对21世纪全球和中国年平均地表气温变化和2℃升温阈值的预估

The 21st century annual mean surface air temperature change and the 2℃ warming threshold over the globe and China as projected by the CMIP5 models

中文关键词:  气候模式  地表气温  预估  不确定性

英文关键词:Climate model  Surface air temperature  Projection  Uncertainty

中文摘要:

      基于参加国际耦合模式比较计划第5阶段（CMIP5）的29个全球气候模式开展的历史气候模拟和3种典型浓度路径（RCP2.6、RCP4.5、 RCP8.5）下21世纪气候预估的结果，分析了单个模式和多模式集合平均（MME）的21世纪全球与中国年平均地表气温（ASAT）变化特征及2℃升温阈值的出现时间。多模式集合平均的结果显示：全球和中国年平均地表气温均将继续升高，21世纪末的升温幅度随着辐射强迫的增大而增大。RCP2.6情景下，年平均地表气温增幅先升高后降低，全球（中国）年平均地表气温在2056年（2049年）达到升温峰值，21世纪末升温1.74℃（2.12℃）；RCP4.5情景下，年平均地表气温在21世纪前半叶逐渐升高，之后升温趋势减缓，21世纪后期趋于平稳，21世纪末全球（中国）年平均地表气温增幅为2.60℃（3.39℃）；RCP8.5情景下，21世纪年平均地表气温快速升高，21世纪末全球（中国）年平均地表气温增幅为4.75℃（6.55℃）。全球平均的年平均地表气温增幅，在RCP2.6情景下没有超过2℃，RCP4.5和RCP8.5情景下分别在2047和2038年达到2℃。RCP2.6、RCP4.5和RCP8.5情景下中国年平均地表气温增幅连续5 a不低于2℃的时间分别在2032、2033和2027年，明显早于全球平均。任一典型浓度路径情景下，达到2℃升温的时间，北半球同纬度地区早于南半球，同半球高纬度地区早于低纬度地区，同纬度地区陆地早于海洋。3种不同典型浓度路径情景下21世纪全球和中国年平均地表气温将继续升高这一结果是可信的，RCP4.5和RCP8.5情景下全球和中国年平均地表气温增幅超过2℃的结果模式之间有较高的一致性。多模式预估的全球和中国年平均地表气温升幅和不同幅度升温的出现时间均存在一定的不确定性，预估结果的不确定性随预估时间的延长而增大；相同情景下，中国年平均地表气温预估的不确定性大于全球。

英文摘要:

      The paper examines the projected annual mean surface air temperature (ASAT) change characteristics and the occurrence time for 2℃ warming threshold over the globe and China in the 21st century under the three different Representative Concentration Pathways (RCPs) (RCP2.6, RCP4.5, RCP8.5) by the 29 coupled climate models participating the Coupled Model Intercomparison Project Phase 5 (CMIP5). The multi-model ensemble mean (MME) shows that the ASAT over the globe and China is projected to increase in the 21st century under the three RCPs, and the larger radiative forcing the higher the increment of ASAT by the late of the 21st century (2091-2100). MME projects an increase-peak-decrease process of ASAT over the globe (China) under RCP2.6, with the peak value in 2056 (2049) and 1.74℃ (2.12℃) warming by the late of the 21st century relative to 1871 to 1900 mean. Under RCP4.5, MME projects ASAT gradually increasing and then tending to slightly increase or to be stable with 2.60℃ (3.39℃) warming over the globe (China) by the late of 21st century. The ASAT is projected to fast increase under RCP8.5 with 4.75℃ (6.55℃) warming over the globe (China) by the late of 21st century. The global mean ASAT warming will unlikely reach 2℃ under RCP2.6, and will exceed 2℃ in 2047 and 2038 under RCP4.5 and RCP8.5 respectively by MME. The China-averaged mean ASAT warming will exceed 2℃ in 2032, 2033 and 2027 under RCP2.6, RCP4.5 and RCP8.5 respectively by MME, which are much earlier than those for the global means. For any RCP, there are obvious geographical differences in the occurrence time for 2℃ warming, and it is earlier in the Northern Hemisphere than in the Southern Hemisphere, earlier in higher latitudes than in the lower ones for the same hemisphere, and earlier over land than over ocean for the same latitude. It is reliable that the ASAT over the globe and China will increase in the 21st century under any RCP. There is much high consistence among the models for the occurrence of 2℃ warming during the 21st century under RCP4.5 and RCP8.5. There are also some uncertainties in ASAT change projection with the characteristics of the uncertainties increasing with the extension of the projected period, as well as larger for China than the global mean.