Summary/Abstract
Heatwaves are becoming more frequent and intense under climate change, with prolonged periods of excessive heat that threaten human health, food and water security, energy systems, and ecosystems. Preparedness often focuses on heatwaves developing over land, yet dangerous heat can also originate over the ocean and propagate onto land, often becoming more severe than expected. Underestimating these oceanic heatwaves limits forecasting and leaves coastal and inland communities, as well as essential services, underprepared.
The authors show linkages between oceanic and continental heatwaves and find that 22% of continental and 43% of coastal heatwaves originate over the ocean, raising heat exposure in densely populated coastal areas and extending risks inland. Limiting global warming to 1.5°C above pre-industrial levels would reduce these risks. The findings can inform weather services and emergency managers to improve early-warning systems and guide heat mitigation and adaptation strategies.