1.5°C threshold: Year-round toll of record ocean warming revealed

A landmark new study has documented more than 200 marine ecosystem impact events during the first year global temperatures temporarily exceeded 1.5°C above pre-industrial levels – revealing disruption that is broader and more persistent than existing monitoring systems were designed to detect.

The study, published in One Earth and led by researchers at King Abdullah University of Science and Technology, catalogued 201 ecological impact events spanning coral bleaching, harmful algal blooms, species mortality, habitat disruption and fisheries impacts.

Data was drawn from scientific literature, government agencies, environmental monitoring programmes and observations compiled across 17 languages.

“This study provides a real-world snapshot of how marine ecosystems responded during an exceptional period of ocean warmth,” said Dr Shannon Klein, lead author and Research Scientist at KAUST. “One of the clearest findings was that impacts were not confined to traditional summer heat extremes. We found evidence of ecological disruption across seasons, which suggests that understanding and responding to ocean warming requires year-round monitoring and assessment.”

That finding challenges a central assumption in marine monitoring – that ecological risk is concentrated in summer months when sea surface temperatures peak. The study found widespread disruption throughout the year, suggesting that monitoring systems calibrated around seasonal extremes may be missing significant events occurring between them.