Abstract Earth System Models (ESMs) employed approximations to reduce computational costs, many of which were made decades ago when polar regions were not a modeling priority. However, the unique conditions and rapid climate changes in the Arctic challenge these assumptions. For instance, ESMs commonly treat surfaces as blackbodies and neglect cloud scattering in the longwave (LW) radiation, which is valid in humid environments but not in the drier polar atmosphere. Using the Department of Energy's Exascale Energy Earth System Model (E3SM) version 2, we examined the combined effect of surface spectral emissivity and ice‐cloud LW scattering on both the mean‐state climate and the response to quadrupling CO 2 , with a focus on Arctic warming. Including both processes increases the global mean surface air temperature by 1.05 K, with a more pronounced increase of 3.09 K in the Arctic. The effects from surface emissivity and ice‐cloud scattering are largely additive, except for a small nonlinearity in the polar region. Regarding climate response to quadrupling CO 2 , incorporating both processes reduces global warming by 3.8% and Arctic warming by 12.4%. Feedback analysis shows that the inclusion of both processes has little effect on the global mean total radiative feedback, as changes in individual feedback mechanisms largely offset each other. In the Arctic, however, the warming contributions from albedo and lapse‐rate feedback decrease by 14.36% and 28.76%, respectively.
Zhao et al. (Sun,) studied this question.
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