Heat Exposure Projections

Heat exposure projections: interactive map

• For data included in this map, extreme heat days are defined as days with Wet Bulb Globe Temperatures (WBGT) of 30°C/86°F or higher. WBGT humid-heat temperatures incorporate both air temperatures and relative humidity, with more humid areas having higher values than less humid areas with the same air temperature. Thus, areas that are hot and humid are more hazardous to human and animal health.
• Person-days refers to the total number of days of extreme heat experienced in a year multiplied by the population in a given geography that experienced such heat. This number is divided by one million to provide million person-days per year, as used in this map.
   

About the data

• Selecting 2016 on the time slider at the top of the map will show observed heat exposure data averaged from 2007 to 2016 provided by the Climate Hazards Center Coupled Model Intercomparison Project Phase 6 (CHC-CMIP6). 
• Selecting 2030 or 2050 on the time slider at the top of the map will show projected data from the Climate Hazards Center Coupled Model Intercomparison Project Phase 6 (CHC-CMIP6).
  • Shared Socioeconomic Pathways (SSPs) refer to climate change scenarios of projected socioeconomic global changes up to 2100 as defined in the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report. SSPs are used to derive greenhouse gas emissions scenarios with different climate policies. 
  • SSP245 and SSP585 represent two different future emission scenarios. These scenarios have been used to drive two large sets of CMIP6 climate projections, each with varying degrees of severity. 
  • SSP245 uses a “middle of the road” emission set of assumptions to inform its heat projections, reflecting a more optimistic scenario. This scenario assumes an additional radiative forcing of 4.5 W/m² by the year 2100 and reflects a medium pathway of emission scenarios in current literature.
  • SSP585 uses higher emission assumptions and reflects a hotter, more pessimistic scenario. This scenario assumes an additional radiative forcing of 8.5 W/m² by the year 2100 and represents the highest emission scenarios in current literature. 
• Annual Extreme Days Count layers under each baseline and scenario map show the current and projected number of days that each area is expected to experience conditions that exceed the 30°C/86°F threshold. Areas where projections show less than one annual day of extreme heat can be interpreted as having a small proportion of the total area covered experiencing temperatures above this threshold.
• Climate Hazards Center Coupled Model Intercomparison Project Phase 6 (CHC-CMIP6) data supports the analysis of climate-related hazards over the recent past and in the near future. Support for the development of this dataset was provided by the Bill and Melinda Gates Foundation and USAID. This climate projection dataset contains global, daily gridded data for the observational (1983-2016) and projection (2030 and 2050) periods to be used in the identification and monitoring of hydroclimatic extremes. The dataset contains global daily high resolution (0.05°) grids of the Climate Hazards InfraRed Temperature with Stations (CHIRTS-daily) temperature product, the Climate Hazards InfraRed Precipitation with Stations (CHIRPS) precipitation product, and ERA5-derived relative humidity, from which Vapor Pressure Deficits (VPD) and maximum Wet Bulb Globe Temperatures (WBGTmax) were derived. The results presented here are based on WBGTmax.