Climate Change Drives Global Coral Bleaching, Study Finds
A recent study published in Oceanography concludes that almost every global coral bleaching episode recorded over the last four decades would not have occurred without human-induced climate change.
Although El Niño is frequently identified as the main trigger of widespread bleaching events—including those in 1998, 2010, 2014–2017, and 2018–2025—the research shows that the underlying cause is the long-term rise in ocean temperatures driven by greenhouse gas emissions from fossil fuels. Scientists employed a multi-model extreme event attribution approach to determine the contribution of climate change to sea surface temperature increases. These findings were then integrated with NOAA’s Coral Reef Watch bleaching risk model, revealing a strong connection between anthropogenic climate change and elevated coral bleaching risk.
For the 2018–2025 global bleaching event, the study found that widespread bleaching would have been virtually absent in a world without human-caused climate change. Among the 71 regions where bleaching occurred, only one would have experienced even a moderate level of bleaching risk under natural climate conditions. Similar conclusions were reached for previous global bleaching events, indicating that climate change consistently pushed ocean temperatures beyond the threshold at which corals begin to bleach.
Andrew Pershing, Chief Program Officer at Climate Central and the study’s lead author, emphasized that coral bleaching would otherwise remain an uncommon and localized occurrence rather than a global phenomenon. He warned that millions of people depend on healthy coral reefs for food security, coastal protection, and economic livelihoods, yet continued carbon emissions are causing extensive degradation of these ecosystems. According to Pershing, rapid reductions in greenhouse gas emissions are essential to prevent the widespread loss of coral reefs.
The researchers also applied the same analytical framework to assess bleaching risks associated with the ongoing 2026–2027 El Niño event. While El Niño alone may generate limited bleaching in certain regions, the combination of El Niño and human-driven ocean warming is expected to produce extensive bleaching worldwide. Areas considered particularly vulnerable include the southern Caribbean, the Pacific and Atlantic coasts of Central and South America, and the coastal waters of eastern Asia.
The study further highlights that global coral bleaching has often been linked primarily to El Niño, whereas the dominant influence of long-term climate change has received less attention. The analysis indicates that, if current warming trends continue, the effect of human-induced ocean warming will surpass the influence of El Niño across all coral reef regions by 2028.
Overall, the findings reinforce growing evidence that coral reefs are facing increasing threats despite their limited capacity to adapt to rising temperatures. Without significant reductions in carbon emissions and effective climate action, continued ocean warming could result in the irreversible decline and eventual disappearance of coral reef ecosystems worldwide.
Although El Niño is frequently identified as the main trigger of widespread bleaching events—including those in 1998, 2010, 2014–2017, and 2018–2025—the research shows that the underlying cause is the long-term rise in ocean temperatures driven by greenhouse gas emissions from fossil fuels. Scientists employed a multi-model extreme event attribution approach to determine the contribution of climate change to sea surface temperature increases. These findings were then integrated with NOAA’s Coral Reef Watch bleaching risk model, revealing a strong connection between anthropogenic climate change and elevated coral bleaching risk.
For the 2018–2025 global bleaching event, the study found that widespread bleaching would have been virtually absent in a world without human-caused climate change. Among the 71 regions where bleaching occurred, only one would have experienced even a moderate level of bleaching risk under natural climate conditions. Similar conclusions were reached for previous global bleaching events, indicating that climate change consistently pushed ocean temperatures beyond the threshold at which corals begin to bleach.
Andrew Pershing, Chief Program Officer at Climate Central and the study’s lead author, emphasized that coral bleaching would otherwise remain an uncommon and localized occurrence rather than a global phenomenon. He warned that millions of people depend on healthy coral reefs for food security, coastal protection, and economic livelihoods, yet continued carbon emissions are causing extensive degradation of these ecosystems. According to Pershing, rapid reductions in greenhouse gas emissions are essential to prevent the widespread loss of coral reefs.
The researchers also applied the same analytical framework to assess bleaching risks associated with the ongoing 2026–2027 El Niño event. While El Niño alone may generate limited bleaching in certain regions, the combination of El Niño and human-driven ocean warming is expected to produce extensive bleaching worldwide. Areas considered particularly vulnerable include the southern Caribbean, the Pacific and Atlantic coasts of Central and South America, and the coastal waters of eastern Asia.
The study further highlights that global coral bleaching has often been linked primarily to El Niño, whereas the dominant influence of long-term climate change has received less attention. The analysis indicates that, if current warming trends continue, the effect of human-induced ocean warming will surpass the influence of El Niño across all coral reef regions by 2028.
Overall, the findings reinforce growing evidence that coral reefs are facing increasing threats despite their limited capacity to adapt to rising temperatures. Without significant reductions in carbon emissions and effective climate action, continued ocean warming could result in the irreversible decline and eventual disappearance of coral reef ecosystems worldwide.
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