Changes in climate extremes, fresh water availability and vulnerability to food insecurity projected at 1.5°C and 2°C global warming with a higher-resolution global climate model

Abstract

We project hydrological and ecological impacts in transient climate simulations at global warming of 1.5°C and 2°C relative to pre-industrial, using impacts models driven by new, higher-resolution (approximately 40km – 60km resolution) global atmospheric General Circulation Models driven by patterns of sea surface temperatures and sea ice from selected members of the 5th Coupled Model Intercomparison Project (CMIP5) ensemble, forced with the RCP8.5 concentration scenario. The projections for weather extremes indices and biophysical impacts quantities support expectations that the magnitude of change is generally larger for 2°C global warming than 1.5°C. Temperature-related warm extremes become even warmer, while precipitation-related extremes show more geographical variation with some increases and some decreases in both heavy precipitation and drought. Hydrological impacts generally point towards wetter conditions, with increased river flooding risk and less severe low flows. However, there are regional uncertainties due to different climate models producing different outcomes, and even when a majority model consensus indicates higher low flows, decreased low flows are still simulated by some models. Risk assessments should therefore consider both wetter and drier outcomes. For terrestrial ecosystems, a key factor may be the level of CO2 concentration that accompanies a specific level of global warming.