The world has crossed its first major climate tipping point, scientists say, as coral reefs enter an irreversible decline caused by human-driven global warming. A sweeping new study released Friday warns that the collapse of these ecosystems-home to nearly a quarter of all marine life-marks the first threshold crossed in what researchers call the "cascade" of planetary tipping points.
The second Global Tipping Points Report, authored by 160 researchers across Europe and released ahead of November's COP30 climate summit in Brazil, concluded that warm-water coral reefs are now "passing their tipping point." The report, led by Professor Tim Lenton of the University of Exeter, said global marine heatwaves have pushed corals beyond recovery, with mass die-offs now unfolding worldwide. "We are rapidly approaching multiple Earth system tipping points that could transform our world, with devastating consequences for people and nature," Lenton said.
The researchers estimate that coral reefs reached their tipping point around 1.2 degrees Celsius of global warming and are now collapsing as global temperatures hover around 1.5 degrees above pre-industrial levels. "This has caused marine heatwaves that have led to severe bleaching impacts on 80% of the world's coral reefs," Lenton said. "It has also become clear that the world will inevitably exceed 1.5 degrees... Therefore, we conclude that coral reefs have passed a tipping point where a majority of them are suffering widespread dieback."
The report cites extensive coral bleaching in regions like the Great Barrier Reef, where mass mortality events have occurred six times since 2002. Terry Hughes, a coral scientist at James Cook University in Australia, said that "arguably, we passed the tipping point for coral reefs decades ago." He noted that "the transition from historical coral reefs to a different type of ecosystem is already well underway," adding that there are now "almost no unbleached reefs left anywhere in the world."
Other researchers warned of the far-reaching consequences of coral loss. "Coral reefs support the livelihoods of half a billion people," Lenton said in an email. They provide ecosystem services valued at over $2 trillion per year, including fisheries and vital coastal protection from storm surges and rising sea levels.
The tipping point designation underscores how rapidly climate change is altering natural systems. Global temperatures have warmed by 1.3 to 1.4 degrees Celsius, making the last two years the warmest on record, according to U.N. and EU science agencies. Marine heatwaves in that time have stressed 84% of reefs, leaving many on the brink of extinction. "The new report makes clear that each year there is an increase in the scope and magnitude of the negative impacts of climate change," said Pep Canadell, a senior scientist at Australia's CSIRO Climate Science Centre.
While the report highlights grim findings, it also notes progress in the global energy transition. For the first time this year, renewable energy sources generated more electricity than coal, data from think tank Ember show. "Nobody wants to be just traumatized and disempowered," Lenton said. "We still have some agency."
