Widespread warming of Earth's estuaries

Water temperature responses to climate change may vary across Earth's estuaries. To understand how climate change influences estuarine surface water temperature, we need global, long-term records of estuarine temperature. Here, we generated spatially explicit data of surface water temperature over 1,060 estuaries globally using Landsat 5, 7 and 8 from 1985 to 2022 and compared water warming rates with local air temperature warming rates. 47% of Earth's estuaries are warming, with a global average warming rate of 0.070 ± 0.004 degree Celsius/year (median = 0.060 degree Celsius/year). Estuaries at higher latitudes showed rapid warming. A 1 degree Celsius increase in air temperature could lead to a 0.81 degree Celsius increase in estuarine surface water warming, or 1.3 degrees Celsius in estuaries above 60.5 degrees North. We inferred the potential influences over estuarine warming based on distinct global spatial patterns in water and air warming, or lack of warming, and discussed implications for estuarine carbon cycling.