Quantifying Projected Hydroclimate Changes per Degree of Global Warming over the Contiguous United States

Abstract

Quantifying projected changes in local hydroclimate characteristics as a function of degree of global warming (DGW) is difficult due to the coarse resolution of global climate models and internal variability necessitating large ensembles to isolate climate change signals. Alternatively, thermodynamic global warming (TGW) simulations remove internal variability by using historical boundary conditions, adjusted for warmer temperatures and can be run at relatively fine resolution over regional domains. Most TGW experiments only include one historical and one “future climate” simulation, but this study leverages a dataset with eight TGW simulations to quantify changes in local temperature, precipitation, precipitation minus evapotranspiration, and 1-m soil moisture as a function of DGW over the contiguous United States. We find values generally ranging from 0.5 to 1.5°C, ± 60 mm yr −1 , ± 40 mm yr −1 , and ± 10 mm per degree Celsius of global warming, respectively. By examining changes in the seasonal water cycle, we explore mechanisms driving these changes in cases of particularly strong trends. In many regions, driving factors include a transition to ephemeral snow regimes in areas with historically seasonal snowpacks and changes to summer rainfall frequency and intensity.