Oceanic heat sources exacerbate continental heatwaves

Anthropogenic climate warming is anticipated to intensify heatwaves worldwide, posing growing risks to society and ecosystems. Yet the impacts of oceanic heatwaves (OHWs) on continental heatwaves (CHWs) remain insufficiently understood. This lack of understanding hinders the accurate prediction and effective mitigation of heatwave disasters. Here, we employ a Lagrangian tracking method and reveal that 22% of CHWs can be attributed to OHWs, 43% of heatwaves occurring in coastal regions globally can be ascribed to OHWs. We show that anthropogenic greenhouse forcing has increased the likelihood of landfalling OHWs by a factor of nine. Notably, under the Shared Socioeconomic Pathway (SSP)245 (SSP370) scenario, limiting warming to 1.5°C rather than 2°C above pre-industrial levels could avoid 17% (20%) landfalling OHW exposure, safeguard 21% (32%) of the population, and preserve 36% (42%) of economic status. Our findings underscore the significant role of OHWs in contributing to CHWs and emphasize the urgent benefits of stringent climate targets.