Hindcast Body Temperature Reveals Sites of Amplified Thermal Risk in Global Coastlines

Abstract Identifying regions where organisms are most (and least) vulnerable to climate change remains a key focus in ecological research. However, accurately capturing the thermal stress experienced by many, if not most, organisms is challenging because body temperature, which determines physiological performance, is driven by multiple environmental factors. We hindcasted hourly body temperatures of intertidal mussels globally using a modified heat budget model and assessed thermal risks (extreme temperatures and heatwaves) and hotspots based on body temperature. Results indicated that 98.34% of global coastal mussel populations faced at least one thermal risk factor, and 45.14% are subjected to the compounding effects of four or more thermal risk factors. Regions such as the Mediterranean coast and the northeastern coast of South America face a high and stacking thermal risk. Most thermal risk metrics exhibited a patchy, mosaic distribution. Semi‐enclosed topography and western boundary currents are thermal risk amplifiers, making organisms in these regions more vulnerable than those in other regions of the same latitude. Our research demonstrates the utility of hindcast body temperature in integrating multiple thermal metrics to assess global thermal risks.