Heat index historical trends and projections due to climate change in the Mediterranean basin based on CMIP6

Abstract

Air temperature and relative humidity can be considered as two essential meteorological parameters in the determination of heat stress. The heat index (HI) includes both of them and it is appropriate for determining the thermal conditions of different climates. We investigated potential changes in the HI for the Mediterranean basin using simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) climate models under two future scenarios (Shared Socio-economic Pathways: SSP2-4.5 and SSP5-8.5) over the period 2020–2099. Results reveal an important increase of HI at the end of the 21st century for both scenarios, with greater changes for the SSP5-8.5 scenario all over the basin. Strong significant upwards trends (around 1 °C per decade; significance level computed at 5%) are expected in the entire area and for all months at the end of the century, with greatest values during the summer months (close to 1.5 °C per decade) along the coastal areas of the basin. Many areas of the Southern Mediterranean basin (Africa and Arabian Peninsula) will be strongly affected with dangerously high heat index values (higher than 41 °C) during summer months by the end of the 21st century. A northward extension of these dangerous conditions is also expected including several areas of southern Europe.