Response of the HadGEM2 Earth System Model to Future Greenhouse Gas Emissions Pathways to the Year 2300*

Abstract A new ensemble of simulations from the Earth System configuration of the Hadley Centre Global Environmental Model, version 2 (HadGEM2-ES), is used to evaluate the response to historical and projected future greenhouse gas forcings that follow Representative Concentration Pathways (RCPs). In addition to the projected changes during the twenty-first century, extended simulations to the year 2300 allow an investigation into inertia in the climate system post-2100 that may occur even if atmospheric CO2 concentrations have stabilized. Projections of temperature, precipitation, sea level, permafrost, heat waves, and compatible carbon emissions are analyzed. The low emissions scenario RCP2.6 is the only scenario considered here that is approximately consistent with a 2°C global warming limit, though there are regions where local changes in temperature are projected to considerably exceed 2°C, particularly over northern high-latitude areas. An aggressive mitigation approach, represented here by RCP2.6, could contribute to avoiding the larger-magnitude future climate changes projected under higher emissions scenarios. Despite these benefits, changes should still be expected under an aggressive mitigation pathway and may require adaptation.