Effects of 0.5 °C less global warming on climate extremes in the contiguous United States

The Intergovernmental Panel on Climate Change (IPCC) suggests limiting global warming to 1.5 degrees C compared to 2 degrees C would avoid dangerous impacts of anthropogenic climate change and ensure a more sustainable society. As the vulnerability to global warming is regionally dependent, this study assesses the effects of 0.5 degrees C less global warming on climate extremes in the United States. Eight climate extreme indices are calculated based on Coupled Model Intercomparison Project-phase 5 (CMIP5), and North American-Coordinated Regional Climate Downscaling Experiments (NA-CORDEX) with and without bias correction. We evaluate the projected changes in temperature and precipitation extremes, and examine their differences between the 1.5 and 2 degrees C warming targets. Under a warming climate, both CMIPS and NA-CORDEX show intensified heat extremes and reduced cold extremes across the country, intensified and more frequent heavy precipitation in large areas of the North, prolonged dry spells in some regions of the West, South, and Midwest, and more frequent drought events in the West. Results suggest that the 0.5 degrees C less global warming would avoid the intensification of climate extremes by 32-46% (35-42%) for heat extremes intensity (frequency) across the country and, by 23-41% for heavy precipitation intensity in the North, South, and Southeast. The changes in annual heavy precipitation intensity are mainly contributed by winter and spring. However, impacts of the limited warming on the frequency of heavy precipitation, dry spell, and drought frequency are only evident in a few regions. Although uncertainties are found among the climate models and emission scenarios, our results highlight the benefits of limiting warming at 1.5 degrees C in order to reduce the risks of climate extremes associated with global warming.