Anthropogenic forcing drives equatorward migration of heatwave locations across continents

Heatwaves have increased in frequency, intensity, duration, and spatial extent, posing a serious threat to socioeconomic development, natural ecosystems and human health worldwide. Assessments of trends in heatwave locations (HWL) have been hindered by the distinct regional characteristics of heatwaves across continents. Here we identify a consistent striking equatorward migration in the average latitudinal location of heatwaves occurrence over the period 1979−2023 based on various datasets. The trends of HWL in each hemisphere illustrate equatorward migration at a rate of approximately one degree of latitude per decade, which falls well into the extent of the estimated rate in the observed intertropical convergence zone contraction and the contrast in soil moisture between tropics and subtropics. Our analyses suggest that anthropogenic contribution plays a dominant role in the equatorward trends. The equatorward migration, which has already occurred and is projected to continue in future scenarios, highlights that the risk of damages and disasters caused by heatwaves may increase at lower latitudes. This study shows that anthropogenic forcing has driven an equatorward migration of heatwave locations in both hemispheres in the past 40 years. Projections of future climate show even larger migration rates, suggesting a 'warm-get-warmer' tendency.