Impacts of Sea Surface Temperature Patterns on Global Radiative Response

Variations in sea surface temperature (SST) patterns significantly impact radiative fluxes at the top of the atmosphere (TOA). In this work, we explore the sensitivity of radiative feedbacks to SST patterns in idealized aquaplanet simulations using Community Atmospheric Model version 5 (CAM5), part of Community Earth System Model (CESM 1.2.1). We use a Green’s function approach where we prescribe delta function-like perturbations in SST in latitude bands, with SSTs kept fixed at climatological values everywhere else. We use 19 equidistant northern hemisphere ‘2K’ warming patches. We find that the radiative response is primarily driven by warming at the equator, primarily due to an increase in off-equatorial low clouds. Tropical surface warming spreads significantly both horizontally and vertically whereas extra-tropical warming leads to temperature responses confined within the lower tropospheric column. An interesting result is that the response to imposing multiple patches is strongly non-linear, except for near-equatorial patches. This test demonstrates that Green's function responses in the model are strongly linear only in the Intertropical Convergence Zone (ITCZ). These findings reveal significant nonlocal effects of SST variations on radiative feedback, a strong dominance of equatorial SSTs in moderating Earth’s energy budget, and a surprising degree of non-linearity.