By Abdullahi Lukman
The global daily average sea surface temperature has reached a record 21.1°C, surpassing the previous high of 21.09°C recorded in March 2024, according to the Copernicus Climate Change Service (C3S).
The new record was recorded on Monday in the C3S ERA5 dataset, which provides reliable global observations from 1979 onward. The temperature also exceeded the previous highest August average of 20.98°C, recorded in 2023.
The record is particularly significant because global ocean temperatures typically peak around March and April following the Southern Hemisphere summer. Its occurrence in August points to persistent and unusually high ocean temperatures.
Scientists said the latest warming is being reinforced by a developing strong El Niño in the tropical Pacific, which is adding heat to oceans already experiencing decades of human-driven warming.
The World Meteorological Organisation expects El Niño to strengthen in the coming months, while the C3S seasonal forecasting system indicates that the event could reach levels not seen for several decades.
Samantha Burgess, Strategic Lead for Climate at the European Centre for Medium-Range Weather Forecasts (ECMWF), said the record was another indication of increasing stress on the global ocean.
She warned that rising ocean temperatures were increasing risks to marine ecosystems and coastal communities, noting that global marine heatwave days have more than tripled since the early 1990s.
Warmer oceans contribute to sea-level rise through thermal expansion and increase the frequency and intensity of marine heatwaves, which can damage coral reefs, seagrass ecosystems and other marine habitats.
The warming also threatens fisheries and aquaculture, while increasing the amount of heat and moisture transferred to the atmosphere, potentially intensifying heavy rainfall and some storms.
Scientists also warn that warmer seawater absorbs less carbon dioxide from the atmosphere, potentially weakening the ocean’s role as a major natural buffer against climate change.
ECMWF scientists working with C3S are continuing to monitor the record to determine whether the unusually high temperature is temporary or part of a longer-lasting trend. The daily observations are generated through the ERA5 reanalysis and monitored through C3S’s Climate Pulse platform.
