Feedback Attribution of the Land/Sea Warming Contrast in NCAR CCSM4 Global Warming Simulations

Tuesday, May 13, 2014 - 07:00
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One of the salient features in both observations and climate simulations is stronger warming over land than over sea. This paper provides a quantitative understanding of the main processes that give rise to such land/sea warming asymmetry in global warming simulations of the NCAR CCSM4. The CO2 forcing alone warms land and sea nearly the same. The evaporation feedback favors land warming by reducing warming mainly over oceans whereas the surface sensible heat flux feedback favors ocean warming by reducing warming mainly over land. However, their net effect favors a greater warming over ocean than over land. The water vapor and atmospheric dynamics feedbacks favor greater warming over ocean. A more substantial reduction of clouds over land compared to ocean leads to stronger warming over land as the shortwave effect of clouds dominates globally. The ocean heat storage also contributes positively to the land/sea warming asymmetry in a transient response.

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