Matthew England and Alex Sen Gupta of UNSW Sydney and Alistair Hobday of CSIRO discuss how the new El Niño is set to bring about unprecedented ocean heat records and extreme weather.
The world’s oceans are the hottest on record for June, pushing past records set during the 2023–24 El Niño years.
Right now, the average sea surface temperature is just under 21°C across the world’s tropical and temperate oceans. Before widespread industrialisation in 1870, the temperature was about 19.6°C.
That may not sound like a big difference. But heating the world’s oceans this much requires a truly enormous amount of energy. Of all the extra heat trapped by greenhouse gases from burning coal, gas and oil, more than 90pc has gone into the world’s oceans.
As a result, the oceans are getting rapidly warmer. In 2025, the heat added was the equivalent of about 12 Hiroshima-scale nuclear bombs exploding every second of every day.
