Research reveals that climate-driven ocean heatwaves are more frequent, longer, and hotter, devastating marine life and intensifying storms.

The climate crisis has caused ocean heatwaves to triple in length, supercharging storms and destroying vital marine ecosystems, a new study reveals. As the world’s oceans heat up, their temperature spikes have become not only more frequent but also significantly more intense, with some regions experiencing an average rise of 1°C—and even as much as 5°C in places like the Mediterranean.

The comprehensive study, led by Dr. Marta Marcos of the Mediterranean Institute for Advanced Studies in Mallorca, Spain, assessed the impact of climate change on ocean heatwaves since 1940. It found that half of all marine heatwaves since 2000 would not have occurred without human-induced global heating, largely driven by fossil fuel consumption. The rising ocean temperatures have not only harmed sea life but also exacerbated extreme weather events such as powerful storms and floods.

Dr. Marcos highlighted the extreme changes taking place in the Mediterranean, where some marine heatwaves have reached temperatures 5°C above normal. “It looks like soup when you go swimming,” she said, describing the disturbing conditions. These heatwaves threaten underwater ecosystems, from kelp forests to coral reefs, and destroy essential habitats for marine life.

The impact extends far beyond the oceans. “Warmer oceans provide more energy for powerful storms that affect coastal and inland areas,” said Marcos. A stark example is the catastrophic flooding in Libya in 2023, where intense rainfall linked to higher Mediterranean temperatures killed 11,000 people. This storm, fueled by 5.5°C warmer waters, was 50 times more likely due to global heating.

Ocean heatwaves also disrupt critical carbon absorption by the seas, worsening the overall climate crisis. As oceans warm, they become less effective at soaking up carbon dioxide, which in turn accelerates the rate of global warming.

The study’s findings underline the growing urgency for climate action. “The only solution is cutting the burning of fossil fuels,” said Dr. Marcos. “More than 90% of extra heat from greenhouse gas emissions is stored in the ocean. If we stop warming the atmosphere, we’ll stop warming the oceans.”

Recent high-profile marine heatwaves illustrate the dire situation. In 2014-15, an extraordinary heatwave in the Pacific caused massive marine mortality. The 2015-16 heatwave in the Tasman Sea and record sea temperatures in the UK and Mediterranean in 2023 further highlighted the destructive effects. Scientists have warned that these events are becoming increasingly common, with heatwaves now killing marine life at the rate of “wildfires that burn vast areas of forest.”

Dr. Zoe Jacobs from the UK’s National Oceanography Centre, who was not involved in the study, emphasized the economic fallout of ocean heatwaves. “They pose significant risks to society, causing millions of dollars in losses across the fishing, aquaculture, and tourism industries,” she said. Moreover, these heatwaves exacerbate land heatwaves and amplify extreme weather like hurricanes.

The study, published in the Proceedings of the National Academy of Sciences, used a model to compare sea surface temperatures from before the climate crisis to current measurements. The analysis revealed that the global average number of extreme heat days per year has surged from 15 in the 1940s to nearly 50 days today. In some areas like the Indian Ocean and tropical Atlantic, heatwaves now last for up to 80 days a year, making them an almost daily occurrence.

Regions like the Mediterranean and North Sea, once considered cooler, have also seen heatwave intensity rise. As temperatures continue to climb, scientists warn that marine heatwaves will become even more frequent and severe, with irreversible damage to the oceans if urgent action is not taken.