Carbon Pollution Drives 'Massive Expansion' of Marine Heatwaves Across Europe

Carbon pollution has triggered a dramatic increase in marine heatwaves across Europe this summer, with some sea regions recording temperatures up to 6°C higher than usual. A rapid analysis by World Weather Attribution suggests that the hottest two-week periods this year would have been "virtually impossible" in a pre-industrial climate in three of the four studied regions. In the Celtic region, which includes waters around the British Isles, temperatures reached levels previously expected only once a century.

## Climate Breakdown's Role in Rising Sea Temperatures

The study found that climate breakdown contributed to about two-thirds of the observed excess heat, raising sea temperatures by approximately 2°C in the Mediterranean, 1.4°C in the Bay of Biscay and Iberian Peninsula, and 1.3°C around Ireland and the Channel. The analysis, which has not yet undergone peer review, comes as Europe endures one of its hottest summers on record, marked by deadly heatwaves, crop failures, and widespread wildfires.

While marine heatwaves often go unnoticed, they pose severe threats to ecosystems, including the death of habitat-forming species like corals and macroalgae, leading to fish and seabird die-offs. They also exacerbate overnight heat in coastal areas, as oceans retain heat longer than land.

Claire Bergin, a scientist at Maynooth University and co-author of the report, emphasized the broader impacts: "While warmer waters may seem appealing to beachgoers, the consequences for marine life are far more serious. This could reshape ecosystems that coastal communities depend on for food and livelihoods, while also intensifying extreme weather on land."

## Marine Heatwaves and Extreme Weather

The study compared observed sea surface temperatures with climate model simulations to assess the role of global heating. It revealed a "massive expansion" of marine heatwaves in 2026, affecting 90% of the Bay of Biscay and Iberian coast region and 80% of the western Mediterranean. Without human-induced climate change, these figures would likely be half as large.

Removing the effects of climate breakdown reduced the expected marine heatwave area from 70% to 9% in the eastern Mediterranean and from 80% to 30% in the Celtic region.

Separate research published earlier this year linked marine heatwaves to more intense rainfall on land. Globally, 5-25% of extreme coastal rainfall events coincide with nearby marine heatwaves, with rainfall during such events increasing by 20-30%.

Jamie Atkins, a scientist at Utrecht University who studied the 2023 marine heatwave in northwest Europe, noted that the findings align with previous research, showing that current heat extremes in Europe are not unexpected. He warned that the impact of climate change on European seas is becoming increasingly severe, affecting not just isolated areas but broader regions.

## Europe's Warming Crisis and Policy Challenges

Europe, the fastest-warming continent, is facing growing consequences of its historical carbon emissions. Recent catastrophic weather events, worsened by climate breakdown, have underscored the urgency of reducing fossil fuel dependence. However, some governments continue to expand polluting fuel extraction and roll back climate policies.

Mohamed Adow, director of Power Shift Africa, criticized Europe's contradictory stance: "Europe cannot acknowledge climate science while expanding fossil fuels. Every new oil and gas project locks in more warming, pushing ecosystems toward irreversible damage."

The study highlights the urgent need for action, as marine heatwaves threaten both ecosystems and human communities, reinforcing the broader climate crisis.