Critical role of low cloud feedback in irreversible sea level rise.

Abstract

Despite mitigation efforts, anthropogenic emissions are projected to cause a global mean sea level rise of approximately 0.44 m and sustained sea levels over human timescales (e.g., centuries). Even without glacial melting, sea level remains elevated for centuries due to the substantial thermal inertia of the ocean interior. However, mechanisms governing persistent sea level rise remain inadequately understood. Here, using a fully coupled climate model, we demonstrate that a distinct sea surface temperature pattern drives enhanced and prolonged sea level rise. This surface warming pattern enhances the absorption of shortwave radiation through climate feedbacks, such as low cloud and sea ice-albedo feedbacks, thereby sustaining ocean heat uptake, thermal expansion, and continued sea level rise. Atmosphere-only simulations confirm that the sea surface temperature pattern alone explains the increased shortwave radiation through the positive feedbacks. These findings underscore the importance of accurately representing surface warming patterns and associated cloud responses in future sea level rise projections.