Whether large trends exist in pre-industrial control （PICTL） runs is critically important for evaluating simulations of present climate change. This study examined the long-term trends in PICTL surface air temperatu...Whether large trends exist in pre-industrial control （PICTL） runs is critically important for evaluating simulations of present climate change. This study examined the long-term trends in PICTL surface air temperature （SAT） in CMIP5 models. Small trends （〈0.06 ℃/100 year） in the globally averaged SAT （GASAT） exist in most CMIP5 models. Of these, positive （negative） trends result from positive （negative） net radiation fluxes at the TOA. This conclusion was further confirmed by the significant positive correlations between the TOA and the SAT tendency. The PICTL GASAT trends constitute less than 10% of the historical trends, indicating that such trends are of negligible importance in estimates of historical global warming in most models. Spatially, relative to the historical trends, the PICTL trends comprise a nontrivial fraction （〉20%） in the Southern Ocean between 50°S and 65°S and in the northern Atlantic and Pacific oceans north of 40°N, with large inter-model spread. The long-term behavior of SAT is significantly related to ocean circulation adjustment in the mid-high latitudes.展开更多
基金supported by the National Key Basic Research Program of China[grant numbers 2010CB950502 and 2013CB956204]the‘Strategic Priority Research Program-Climate Change:Carbon Budget and Related Issues’of the Chinese Academy of Sciences[grant number XDA05110302]the National Natural Science Foundation of China[grant numbers 41376019 and 41376039]
文摘Whether large trends exist in pre-industrial control （PICTL） runs is critically important for evaluating simulations of present climate change. This study examined the long-term trends in PICTL surface air temperature （SAT） in CMIP5 models. Small trends （〈0.06 ℃/100 year） in the globally averaged SAT （GASAT） exist in most CMIP5 models. Of these, positive （negative） trends result from positive （negative） net radiation fluxes at the TOA. This conclusion was further confirmed by the significant positive correlations between the TOA and the SAT tendency. The PICTL GASAT trends constitute less than 10% of the historical trends, indicating that such trends are of negligible importance in estimates of historical global warming in most models. Spatially, relative to the historical trends, the PICTL trends comprise a nontrivial fraction （〉20%） in the Southern Ocean between 50°S and 65°S and in the northern Atlantic and Pacific oceans north of 40°N, with large inter-model spread. The long-term behavior of SAT is significantly related to ocean circulation adjustment in the mid-high latitudes.
