AMOC tipping slows permafrost carbon release during overshoot

Abstract Overshooting global warming targets risks irreversible Earth system changes. However, uncertainties remain in how critical Earth system components such as permafrost and the Atlantic Meridional Overturning Circulation (AMOC) respond to and interact under warming. Here, we use three climate models of varying complexity to assess the permafrost carbon response under climate mitigation scenarios. We find that permafrost loses 11–21 PgC of carbon per 100 degree-years of time-integrated warming exposure during overshoot in a robust linear relationship. This relationship also holds true under relative Northern Hemisphere cooling from a temporary AMOC slowdown during overshoot. The AMOC weakening induces a negative feedback, reducing permafrost carbon loss by 30% per 100 degree-years of AMOC-induced relative cooling, partly offsetting climate change impacts on permafrost. These results underscore the importance of including both destabilizing and stabilizing Earth system feedbacks when assessing overshoot impacts, critical for informing carbon budgets, net-zero planning, and climate change reversibility.