Europe's seas took the summer's heat, and the ocean gives it back slowly

The sea absorbed the summer

The World Weather Attribution group published a rapid analysis on Wednesday. It found that carbon pollution has driven a “massive expansion” of marine heatwaves around Europe this year [1]. In three of the four sea regions studied, this year’s hottest fortnight would have been “virtually impossible” in a preindustrial climate [1]. In the Celtic region, the water around Britain and Ireland, the peak heat was a once-a-century event in a world without human warming [1].

The added heat is roughly 2C in the Mediterranean, 1.4C along the Bay of Biscay and the Iberian coast, and 1.3C around Ireland and the Channel [1]. About two-thirds of the observed excess heat traces to climate change, the researchers said [1]. Last month the Mediterranean averaged 27C, the hottest July on record, and a buoy near Mallorca read 33C in early August [2].

The reach is wide. About 90% of the Bay of Biscay region and 80% of the western Mediterranean have been in marine heatwave conditions this year [1][2]. Strip the human warming out of the models and the numbers collapse. The expected heatwave area in the eastern Mediterranean falls from 70% to 9%, and in the Celtic region from 80% to 30% [1].

Hot seas matter on land too. Water cools far more slowly than ground does, so a warm sea holds coastal nights hot after dark [1][2]. It also kills the species that build habitat, such as corals and large seaweeds, and the fish and seabirds that live off them [1]. “We are rapidly approaching the absolute biological limits of adaptation for many species,” said John Bruno, a marine ecologist at the University of North Carolina [2]. The analysis has not yet been submitted for peer review [1].

A separate paper in Nature Climate Change sharpens why the ocean’s pace matters. It finds that the Atlantic overturning circulation, the great conveyor that carries warm water north, does not have a single temperature at which it breaks [6]. Its stability depends on how fast the push changes. Under a slow rise in carbon dioxide of 0.5 parts per million a year, the model circulation held together up to 5.5C of warming [6]. Under faster rises it collapsed at about 2C [6].

The Pacific is about to hand some heat back

The US Climate Prediction Center now puts the odds of a very strong El Nino at greater than 90% for the northern hemisphere autumn and winter [4]. El Nino is a periodic warming of the eastern Pacific sea surface, caused by trade winds weakening [4]. It arrives every two to seven years and usually runs nine to twelve months [4]. This one is on track to be the strongest in nearly 80 years of records [5].

The effects are already showing. Parts of Panama, normally one of the wettest countries on Earth, have had no major storm since early May [5]. Ethiopia’s highlands are in one of their driest summer stretches in four decades, and India had its fifth-driest June since modern rain records began in 1901 [5]. Around Christmas Island in Kiribati, the sea surface is 2C warmer than usual for this time of year, measured against the previous 30 years [3]. About 10% of corals appeared bleached in dives over recent days [3].

The World Food Programme estimates that 50 million more people could be pushed into hunger by the developing event [14]. Every strong El Nino of the past 55 years has cut cocoa output, according to the investment firm WisdomTree [4].

The bill on land

Heatwaves have killed more than 25,000 people across Europe this year, on Bloomberg’s estimate [7]. Triodos Bank forecasts they will cost the European Union 180 billion euros, about 1% of its output, largely because worker productivity falls once temperatures pass 25C [7]. Europe is warming at 0.6C per decade, faster than any other continent, yet only 23% of its households have air conditioning against 90% in the United States [7].

Very little of the damage is insured. Moody’s estimates last summer’s extreme weather cost Europeans 43 billion euros while generating only about 500 million euros of insured payouts [7][9]. “Heat in itself is not a traditionally insured risk,” said Swenja Surminski of the broker Marsh [9]. In Padua, a survey of about 600 hospitality businesses found more than 80% reporting turnover down around 20% during the recent heatwave, as the evening drink moved indoors [9].

That gap pushes the cost onto governments. The European Environment Agency puts weather and climate losses in the EU at an estimated 822 billion euros between 1980 and 2024 [8]. A quarter of that came in just the last four years [8]. Only a quarter of climate catastrophe losses in the bloc are insured, and coverage is below 5% in some countries [8]. Fitch’s Federico Barriga-Salazar said the problem is that such events are “becoming more recurrent” rather than one-off budget shocks [8].

The health picture is worse than assumed. A study in The Lancet Public Health, led by Stanford academics, looked at uncompensable heat stress, where the body loses the ability to cool itself [10]. It finds people aged 60 and over reach that point at about 1.5C of global warming, against 4C for younger adults [10]. Each additional degree of warming exposes roughly a million more people to at least 180 hours of it a year [10]. In Britain, the May and June heatwaves together caused 2,877 excess deaths, nearly double the 1,504 seen across summer 2025 [10].

Britain is also dry. Three-quarters of England and all of Wales are in drought, and five key reservoirs are described as exceptionally low [13]. Farm analysts think the country could see its worst cereal harvest in four decades, while grass growth for winter feed has stalled [12]. Water companies must write emergency drought plans, but the government will not publish them, citing security [13].

East Asia had its own summer. Yangsan in South Korea reached 42.5C on 2 August, the highest since records began in 1904 [11]. The heat has been blamed for at least 31 deaths, 900,000 dead livestock and 1.4 million dead farmed fish [11]. Japan logged its first “cruelly hot day”, a category introduced this year for temperatures above 40C, and Hong Kong hit 36.9C, its highest since 1884 [11]. Japan’s Weather Attribution Centre calculated that July’s heat there would have been virtually impossible without global warming, a once-in-10,000-year event otherwise [11].

Two energy systems, pulling opposite ways

Solar crossed 3 terawatts of installed capacity, according to BloombergNEF, an energy research firm [15]. The first terawatt took about ten years from 100 gigawatts in 2012, the second under three years, the third under two [15]. Seventy-four countries had at least a gigawatt installed in 2025, up from 42 in 2020 [15]. Last year the world added 600 terawatt-hours of solar generation, enough to power Canada for a year, and the first time a renewable led global supply growth [16]. In May, US solar beat coal’s monthly share of power for the first time [16].

The build shows in the plant list. Of 368 grid-scale US plants that came online in the first half of this year, 207 were solar and 95 were batteries [17]. Only three were large combined-cycle gas plants, the big always-on kind [17]. In Europe, wind and solar are on track to out-generate gas for the longest stretch on record this year [18]. Their capacity climbed from under 20 gigawatts to nearly 750 over 25 years, while gas went from 250 to about 400 [18]. Coalburn 1, a 500 megawatt battery built on a former coal-mine site near Glasgow, is now the largest operating battery in Europe [19].

Cars are moving too, pushed by the oil shock. A record 29% of new cars sold worldwide this year are expected to be electric or plug-in hybrid, up from 4% in 2020 [20]. Brent crude, the global oil benchmark, is up more than a quarter since the Iran war began in February [20]. Electric sales have roughly doubled in Australia, Brazil, India and South Korea [20].

The other direction is just as real. China turned away 360 terawatt-hours of clean power from January to June, up 49% on the year and enough to run Mexico for a year [21]. Its grids simply ran out of room to carry it. Throwing power away like this is called curtailment. “Curtailment in China is structural, not a temporary bottleneck,” said Yuan Ren of Wood Mackenzie [21]. New Chinese solar installations have fallen 66% this year [21]. Beijing’s new five-year coal plan, published on 10 August, declines to name a year for coal use to peak [24]. Coal still supplied under half of China’s power in the first half of 2026 [24]. In India, new mine proposals last year would add 2.5 billion tonnes a year to global supply, up 11%, driven almost entirely by Jharkhand and Odisha [23]. And in the United States, data-centre developers are commissioning their own gas plants, a shift Bloomberg reports will sharply raise power-sector emissions [22].

One genuine easing. Emissions from land-use change, mostly deforestation, are down about 32% from their 2000s average, with preliminary 2025 figures at 4.1 billion tonnes of carbon dioxide [25]. Fossil-fuel and cement emissions hit a record 38.1 billion tonnes over the same period [25].

The quiet one: money for dry ground

The UN’s desertification talks opened in Ulaanbaatar on Monday and run to 28 August [14]. Negotiators are working out how to spend more than $12bn pledged over seven years to 74 countries hit by drought and land degradation [14]. The UNCCD, the UN body that handles drought and land degradation, estimates that repairing degraded land needs about $2.6tn cumulatively by the end of this decade [14]. Saudi Arabia, which has blocked fossil-fuel language at the climate talks, is one of the fund’s most enthusiastic backers [14]. The United States remains a member despite leaving the Paris agreement [14].