Projected changes in Northern Hemisphere permafrost in temperature stabilization and overshoot scenarios

Achieving the Paris Agreement goal of “holding the increase in global temperature to well below 2°C above pre-industrial levels” is increasingly challenging. Overshoot trajectories, which assume that a temperature target is reached after temporarily exceeding it, are becoming prominent in policy discussions. This thesis explores the long-term response of northern permafrost in temperature overshoot and stabilization scenarios used for the 6th Phase of the Coupled Model Intercomparison Project (CMIP6). The University of Victoria Earth System Climate Model, an Earth System model of intermediate complexity, is forced with a range of CMIP6 scenarios. Results suggest that permafrost recovery lags the decrease in surface air temperature associated with overshoot scenarios. Depending on the scenario, 15-30% of permafrost area is lost at the time temperature is restored to the level prior to the overshoot. Furthermore, in high temperature stabilization scenarios permafrost continues to thaw after global mean temperature is stabilized.