Coral bleaching caused by climate change not El Nino, study finds

A new study published in Oceanography and led by Climate Central shows that human-caused climate change, not El Nino, has driven every global coral bleaching event since 1998. Researchers used climate models to separate natural variability from fossil fuel warming and found that without human emissions, mass bleaching would be virtually absent. The ongoing 2018-2025 bleaching event would not have happened without climate change. The study analyzed 71 coral reef regions and found that global warming overtook El Nino as the dominant bleaching driver in most reefs by 1998. Today, with temperatures 1.35°C above pre-industrial levels, climate change outweighs El Nino in all but three reef regions. The authors warn that coral reefs could disappear without rapid emissions cuts, as ocean warming outpaces coral adaptation. The findings come as oceans continue to set temperature records. June 2026 was the warmest June ever recorded, and marine heatwaves affected 82% of the global ocean. The study also projects widespread bleaching during the current 2026-27 El Nino, driven primarily by background warming from carbon pollution.