Evaluation of the University of Victoria Earth System Climate Model version 2.10 (UVic ESCM 2.10)

The University of Victoria Earth system climate model of intermediate complexity has been a useful tool in recent assessments of long-term climate changes including paleo-climate modelling. Since the last official release of the UVic ESCM 2.9, and the two official updates during the last decade, a lot of model development has taken place in multiple groups. The new version 2.10 of the University of Victoria Earth System Climate Model (UVic ESCM), to be used in the 6th phase of the coupled model intercomparison project (CMIP6), presented here combines and brings together multiple model developments and new components that have taken place since the last official release of the model. To set the foundation of its use, we here describe the UVic ESCM 2.10 and evaluate results from transient historical simulations against observational data. We find that the UVic ESCM 2.10 is capable of reproducing well changes in historical temperature and carbon fluxes, as well as the spatial distribution of many ocean tracers, including temperature, salinity, phosphate and nitrate. This is connected to a good representation of ocean physical properties. For the moment, there remain biases in ocean alkalinity and dissolved inorganic carbon, which will be addressed in the next updates to the model

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