The world's oceans absorbed a record amount of heat in 2025, an international team of scientists said Friday, further priming conditions for sea level rise, violent storms, and coral death.

The heat that has accumulated in the oceans last year increased by approximately 23 zettajoules—an amount equivalent to nearly four decades of global primary energy consumption.

This finding—published in the journal Advances in Atmospheric Sciences—was the highest reading of any year since modern record keeping began in the early 1950s, researchers said.

To derive these calculations, more than 50 scientists from 31 research institutions used multiple sources including a thousands-strong fleet of floating robots that track ocean changes to depths of 2,000 meters.

Peering into the depths, rather than fluctuations at the surface, provides a better indicator of how oceans are responding to "sustained pressure" from humanity's emissions, said study co-author Karina von Schuckmann.