World’s oceans hit hottest temperature on record on August 22

• The daily global average sea surface temperature (SST) has reached its highest level on record, exceeding the previous record set in March 2024. 

• The Copernicus Climate Change Service (C3S) confirmed the record, with a temperature of 21.1°C on August 22, exceeding the previous record of 21.09°C. 

• This milestone is consistent with the continued long-term warming of the global ocean and the emergence of an extreme El Nino event in the tropical Pacific.

• The timing of the record is particularly notable. Global ocean temperatures are typically highest in March and April, following the austral summer, yet this record has been reached in August. 

• It also exceeds the previous highest August value, recorded in 2023 at 20.98°C. 

• A strong El Nino is now developing in the tropical Pacific, adding further warmth to an ocean that has already been warming over many decades as a result of human-driven climate change. 

• According to the World Meteorological Organisation (WMO), El Nino is expected to strengthen during the coming months, while the C3S seasonal forecasting system suggests the event could reach levels not seen for several decades.

Consequences of rise in global sea temperatures

• The long-term rise in ocean temperatures has far reaching consequences for both communities and ecosystems. 

• A warmer ocean contributes to sea-level rise through thermal expansion, increasing risks for coastal communities and low-lying island nations. 

• Higher temperatures also increase the likelihood and intensity of marine heatwaves, which can damage key ecosystems, such as coral reefs and seagrass meadows, which in turn disrupt marine food webs and industries such as fisheries and aquaculture.

• Higher ocean temperatures also enhance the potential for extreme weather events. 

• A warmer ocean transfers more heat and moisture to the atmosphere, potentially intensifying rainfall and some storm systems. 

• In addition, a warmer ocean becomes less efficient at absorbing carbon dioxide from the atmosphere, potentially weakening one of the planet’s most important natural buffers against climate change.