Individual feedback contributions to the seasonality of surface warming

Using the climate feedback response analysis method, the authors examine the individual contributions of the CO₂ radiative forcing and climate feedbacks to the magnitude, spatial pattern, and seasonality of the transient surface warming response in a 1% yr⁻¹ CO₂ increase simulation of the NCAR Community Climate System Model, version 4 (CCSM4). The CO₂ forcing and water vapor feedback warm the surface everywhere throughout the year.

The tropical warming is predominantly caused by the CO₂ forcing and water vapor feedback, while the evaporation feedback reduces the warming. Most feedbacks exhibit noticeable seasonal variations; however, their net effect has little seasonal variation due to compensating effects, which keeps the tropical warming relatively invariant all year long. The polar warming has a pronounced seasonal cycle, with maximum warming in fall/winter and minimum warming in summer.