在工业革命以来全球长期增暖趋势背景下,全球平均表面气温还同时表现出年代际变化特征,二者叠加在一起使得全球平均气温在某些年份增暖相对停滞(如1999～2008年)或者增暖相对较快(如1980～1998年).利用中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室(LASG)发展的耦合气候模式FGOALS-s2历史气候和典型路径浓度(RCPs)模拟试验结果研究了可能造成全球增暖的年代际停滞及加速现象的原因,特别是海洋环流对全球变暖趋势的调制作用.该模式模拟的全球平均气温与观测类似,即在长期增暖趋势之上,还叠加了显著的年代际变化.对全球平均能量收支分析表明,模拟的气温年代际变化与大气顶净辐射通量无关,意味着年代际表面气温变化可能与能量在气候系统内部的重新分配有关.通过对全球增暖加速和停滞时期大气和海洋环流变化的合成分析及回归分析,发现全球表面气温与大部分海区海表温度(SST)均表现出几乎一致的变化特征.在增暖停滞时期,SST降低,更多热量进入海洋次表层和深层,使其温度增加；而在增暖加速时期,更多热量停留在表层,使得大部分海区SST显著增加,次表层海水和深海相对冷却.进一步分析表明,热带太平洋表层和次表层海温年代际变化主要是由于副热带—热带经圈环流(STC)的年代际变化所致,然后热带太平洋海温异常可以通过风应力和热通量强迫作用引起印度洋、大西洋海温的年代际变化.在此过程中,海洋环流变化起到了重要作用,例如印度尼西亚贯穿流(ITF)年代际异常对南印度洋次表层海温变化起到关键作用,而大西洋经圈翻转环流(AMOC)则能直接影响到北大西洋深层海温变化.%Along with the long-term global warming trend since the industrial revolution, observations of global averaged surface air temperature have also shown a decadal variability. Superimposing the climate variations with two time scales above can result in reduced or no warming in some decades such as 1999-2008 and increased warming in other decades such as 1980-1998. The main goal of this study was to explore the reasons that may cause the warming hiatus or accelerated warming periods by using a coupled global climate model (GCM) FGOALS-s2, developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (LAP), Beijing, China. The model reproduces not only the long-term warming trend, but also significant decadal variability. The global mean energy budget analysis indicates that the decadal variability of the global mean surface temperature is independent of the net top-of-atmosphere (TO A) radiation flux, implying that it may be associated with the re-distribution of heat in the climate system. Using composite analysis and regression analysis, the decadal characteristics of the global surface temperature and sea surface temperature (SST) were very similar in most regions: during the hiatus period, the SST decreased, and more heat flux penetrated into the subsurface or deep ocean; during the acceleration period, more heat was trapped in the upper ocean and the SST increased. Furthermore, on a decadal timescale, the climate variability of the Subtropical-Tropical meridional Cells (STC) played a crucial role in modulating the SST and the subsurface temperature in the Pacific Ocean. Remote responses of the anomaly wind stress and the net surface heat flux to the SST anomalies in the tropical Pacific can induce the decadal changes of sea temperature in the Indian Ocean and the Atlantic Ocean. In the processes associated with decadal variability, ocean circulations also play important roles, e.g., the Indonesian Throughflow (ITF) has a great impact on the changes of the subsurface sea temperature in the South Indian Ocean at decadal time scales, and the deep-ocean temperature in the Atlantic can be directly affected by the Atlantic Meridional Overturning Current (AMOC).
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