Seminar: Climate model projections from the Scenario Model Intercomparison Project (ScenarioMIP) of CMIP6

The Scenario Model Intercomparison Project (ScenarioMIP) defined and coordinated the main set of future climate projections, based on concentration-driven simulations, within the Coupled Model Intercomparison Project phase 6 (CMIP6). In this talk, I will present a range of its outcomes by synthesizing results from the participating global coupled Earth system models. Importantly, however, I will precede the description of these geophysical outcomes with a succinct overview of the process leading to the development of scenarios of future greenhouse gas emissions and other external, anthropogenic forcings. This process involved the adoption of a formal framework to organize the exploration of socio-economic futures, and then the actual computation – through integrated assessment models (IAMs) of a range of future trajectories of emissions, that form the CMIP6 scenarios climate models have used as forcings. I will therefore describe the concept of shared socio-economic pathways (SSPs) and sketch the way scenario modelers went from qualitative storylines of the future to spatially and temporally resolved forcing input to our climate model simulations of the 21st century.

In the second half of the talk, I will focus on temperature and precipitation projections under the main SSPs chosen by the ScenarioMIP experimental design. I will show results of the multi-model ensemble that participated in CMIP6 ScenarioMIP. In terms of global time series and spatial patterns from the models’ most recent simulations, and compare them to their CMIP5 predecessors, for a number of scenarios meant to be comparable (with some important caveats). I will briefly touch on the issue of high climate sensitivity in the CMIP6 ensemble, and, also, show some of the results related to the crossing of policy-relevant thresholds, like 1.5C and 2.0C.