Ocean heatwaves now last three times longer due to fossil fuel-driven climate change
The climate crisis has significantly intensified marine heatwaves, which are now more frequent, last longer, and are destroying ecosystems from coral reefs to kelp forests.
Damian Carrington reports for The Guardian.
In short:
- Ocean heatwaves have nearly tripled in length since the 1980s, with half of all such events since 2000 linked directly to human-caused global warming.
- These prolonged marine heatwaves are weakening ocean carbon absorption, fueling powerful storms, and decimating underwater habitats like seagrass meadows and coral reefs.
- Some regions, such as the Mediterranean, are experiencing marine heat events 5°C above normal, with up to 80 days of extreme heat per year — roughly one in five days.
Key quote:
“More than 90% of the extra heat [trapped by greenhouse gas emissions] is stored in the ocean. If you stop warming the atmosphere, you will stop warming the ocean.”
— Marta Marcos, Mediterranean Institute for Advanced Studies
Why this matters:
As the oceans absorb the vast majority of excess heat caused by greenhouse gas emissions, they have become increasingly unstable. Marine heatwaves impact entire ecosystems and economies. Warmer seas supercharge hurricanes, flood coastal communities, and intensify inland rainfall; they also stress fisheries, undermine food security, and weaken the ocean's role as a carbon sink, creating a vicious feedback loop. The destruction of habitats like kelp forests and coral reefs reduces biodiversity and leaves coastlines more vulnerable to erosion. These heatwaves have become a silent force reshaping the planet’s climate system and threatening both human and ecological health.
Related EHN coverage: Surprise! Unexpected ocean heat waves are becoming the norm
