Uncertainty in the Regional Surface Warming under 2oC and 1.5oC Scenarios.

We evaluate the uncertainty in regional climate change projections using the MIT Integrated Global System Modeling (IGSM) framework, which links the Economic Projections and Policy Analysis (EPPA) model to the MIT Earth System Model (MESM) of intermediate complexity.

First, we carry out 400-member ensembles of climate simulations with the MESM under two emissions scenarios produced by EPPA, using our latest probabilistic distributions of climate parameters. These two scenarios were designed to ensure that global mean surface air temperature in year 2100 does not exceed 2^oC and 1.5^oC relative to 1861-1880 mean with no less than a 66% and 50% probability respectively. We then calculate regional distributions of surface warming using a statistical downscaling approach based on the geographical patterns obtained from climate simulations with 34 CMIP5 models. Finally, we estimate probability distributions of surface temperature increase for different regions of the world.