Reduced heat exposure by limiting global warming to 1.5 °C

Since the Paris Agreement was reached in December 2015 there has been a drive in the scientific community to understand the impacts of global warming at the target levels of 1.5 °C and 2 °C above pre-industrial levels. A Special Report on the pathways to limiting global warming to 1.5 °C, and the associated implications of this target, is being prepared by the IPCC. Research has so far focused on changes indifferent types of climate extremes globally or regionally, developing and utilizing model experiments to infer differences between the two warming targets, or the emissions and warming trajectories associated with meeting or breaching the 1.5 °C target. Here we approach the question of how different a 1.5 °C world and a 2 °C world are through the lens of human population exposure to historically unprecedented heat extremes warmer than those observed since 1950 in Europe. We show that the proportion of the population exposed to hot summers above the current record increases dramatically from 1.5 °C of warming to 2 °C. In the past, record summer heat in Europe has been associated with severe heatwaves resulting in thousands of excess deaths, albeit with high variability in impacts between events — in part due to non-climatic factors. Nonetheless, global warming must be limited to reduce human exposure to historically unprecedented heat.