Human-Driven Ocean Heat, Not El Niño, Now Drives Global Coral Death

Scientists publishing in the journal Oceanography utilized a multi-model extreme event attribution method to isolate the impact of rising sea surface temperatures. By applying these findings to NOAA’s Coral Reef Watch models, the team determined that climate change consistently pushed ocean temperatures past the critical threshold required for bleaching. During the 2018-2025 event, for instance, researchers found that 70 out of 71 observed regions would have avoided bleaching entirely in a world without human-induced warming.

Andrew Pershing, lead author and Chief Program Officer at Climate Central, noted that bleaching would remain a rare, isolated phenomenon without the current trajectory of carbon emissions. The study indicates that the reliance of millions on coral reefs for food security and livelihoods is under direct threat as ecosystems face irreversible collapse. Projections for the ongoing 2026-2027 El Niño cycle show that human-driven heat will continue to trigger widespread damage across the southern Caribbean, Central and South American coasts, and eastern Asia.

Evidence suggests the gap between natural variability and human-driven impact is widening rapidly. Under current warming rates, the influence of anthropogenic heat will overshadow El Niño’s contribution in every coral-containing region globally by 2028. Without immediate and significant reductions in carbon emissions, the ability of these reefs to adapt to their changing environment is projected to fail, leading to the permanent loss of these vital marine habitats.