A city can draw up a climate adaptation plan quickly. Changing what people experience on its streets takes years. Across Europe, local governments are investing in measures meant to make urban areas more resilient to rising temperatures, flooding and other climate risks. The 2026 Europe Cities Report by the Lancet Countdown recorded 1,519 planned or implemented adaptation actions across more than 850 cities. These include green infrastructure, flood defences, ecological restoration and community engagement.

There are signs that some of these interventions are making a difference. Summer surface urban heat-island intensity declined in 88% of the cities analysed, with an average reduction of 0.7°C. But progress is uneven. Nearly one-third of the cities reported financial and technical constraints as major barriers to adaptation. For residents, the value of these measures is ultimately measured at a much smaller scale: a shaded road, a cooler neighbourhood, a bus stop protected from direct sun or a safer route to work and school.

Climate Adaptation: Where the Trees are Matters

Trees are one of the most visible ways cities can respond to heat, but the amount of urban tree cover varies widely across Europe. Swedish cities had average tree cover equivalent to 41.6% of urban land in 2020. Eleven of the 14 cities studied had at least 30% tree cover. Bulgaria’s average was 22%, while Spain recorded 13.2%, France 9.2% and Ireland 3.4%. The figures do not establish a direct link between tree cover and a city’s overall heat risk. They do, however, show how different the urban environments are in which people are exposed to a warming climate.

Dr Rita Issa, a family medicine and climate-health consultant at WHO, identifies green spaces as an intervention that can support physical and mental health while helping cities respond to environmental pressures. She also points to low-emission zones as an example of a policy that can produce health benefits alongside environmental gains.

But where greenery is placed matters. A park at the edge of a neighbourhood may offer little protection to someone walking along a treeless road or waiting at an exposed bus stop. Trees lining routes used by children, older people and pedestrians can affect heat exposure much more directly.

Adaptation Measured by its Impact

The 1,519 adaptation actions in the report cover a broad range of interventions. Community engagement accounted for 8.1% of the actions, green infrastructure for 6.4%, flood defence for 5.1% and ecological restoration for 4.5%.

Of these actions, 596, or 39.2%, reported public-health co-benefits. That provides a useful way of looking at urban adaptation. Infrastructure is only part of the story. What matters is whether an intervention reduces exposure or produces measurable benefits for residents. Francesca de’Donato of ASL Roma 1 says city-level indicators can help connect scientific evidence with local policy while allowing health co-benefits to be measured and monitored.

That approach shifts the focus from the number of projects completed to what they achieve. A city can count the trees it has planted or the flood barriers it has built. It is more useful to know whether those measures have reduced heat exposure, improved air quality or made vulnerable neighbourhoods safer.

Heat Changes Cities’ Movement

Transport is closely tied to this question. The cities studied in Sweden and Spain recorded an average sustainable transport score of 5.3 out of 10. Ireland scored 5.2, France 5 and Bulgaria 4.6. Access to public transport also differed. Only 23% of urban areas in the Swedish cities studied were within 250 metres of a public transport stop. The corresponding figures were 32% in Spain, 31% in Ireland and 30% in France.

Then there is the question of shade. Trees covered 27.7% of cycling and shared cycling-pedestrian paths in the Swedish cities studied. The proportion fell to 9.4% in Spain and 8.3% in Ireland.

These indicators are presented as measures of transport infrastructure, but they also say something about exposure to heat. A journey that is manageable in moderate weather can become difficult when temperatures rise and the route offers little shade. Jordi Jové of the Barcelona Metropolitan Area links sustainable mobility with lower emissions, cleaner air and healthier urban environments. For cities facing more frequent heat, how people move around the urban environment becomes part of the climate-health equation.

The Cost of Adaptation Remains a Constraint

The biggest obstacle may not be a lack of possible solutions. Nearly one-third of the cities in the report identified financial and technical constraints as major barriers to adaptation. Many measures also require continued investment after they are built. Trees need space and maintenance. Public transport systems require long-term funding. Heat-health measures depend on cooperation between municipal authorities, health services and communities. The 596 adaptation actions reporting public-health co-benefits point to one way of making these investments work harder. A single intervention can address several problems.

A greener street can provide shade and improve the surrounding environment. Better public transport can reduce emissions and traffic-related pollution. Streets designed for walking can make everyday journeys easier while reducing dependence on cars. The difficulty is ensuring that these benefits do not remain concentrated in parts of a city that already have better infrastructure.

The Real Measure of a Climate-ready City

The report presents a European urban landscape that is changing, but not at the same pace everywhere. Some cities have reduced their summer heat-island intensity. Others have extensive tree cover or are investing in transport, flood protection and ecological restoration. Yet many still face financial and technical limits. Lorna Benton of Pathfinder says city-level assessments can help cities understand the health risks they face and identify opportunities to build healthier, more resilient and lower-carbon urban environments.

The next step is whether that information changes decisions on the ground. For residents, adaptation is not experienced as a number in a municipal report. It is the shade on a walk to school, the temperature at a bus stop, the availability of a nearby green space or the ease of reaching a clinic without spending too long in the heat.

That is where the success of urban climate policy becomes tangible. European cities have started changing their streets, public spaces and transport systems. The larger challenge is to make those changes reach the neighbourhoods and people most exposed to a hotter climate.

In the waters around Jeju Island in South Korea, divers are watching coral colonies collapse. The soft corals around the island are showing a condition researchers call “slumping”. Instead of holding their usual shape, parts of the colonies are losing their structure as the water becomes warmer due to ocean warming and environmental stress increases. Researchers have found signs of deterioration across coral clusters, with some areas showing severe decline. The corals are important nurseries for other marine species, so their deterioration affects more than the organisms themselves.

The situation in Jeju is one small example of a much larger change taking place across the world’s oceans. For about 100 days this summer, global sea-surface temperatures outside the polar regions remained at record levels for the time of year. Climate Central‘s analysis of NOAA data found the record streak running from June 2 through September 10, 2026. The NOAA dataset reached 21.24°C on August 23.

Copernicus recorded a slightly different peak of 21.11°C because it uses another dataset and methodology. Its August average of 21.07°C was the highest August value in its record. The number itself is difficult to picture. Its consequences are easier to see.

Ocean Warming and Marine Animals

Consider the oil sardine, one of the most familiar fish along India’s coast. The species is particularly sensitive to changes in sea temperature. India’s Central Marine Fisheries Research Institute has warned that the El Niño-driven warming expected later this year could affect oil sardine availability in 2027. CMFRI says small pelagic fish such as oil sardines are among the species most vulnerable to marine heatwaves and ocean warming.

That makes the current global warming signal relevant to an Indian fishing household as well as to climate scientists. The same pattern is already visible elsewhere. Morocco’s sardine landings fell 46% in 2026. Warmer waters were identified as a major factor, along with overfishing, pollution and higher fuel costs. The decline contributed to an export ban on frozen sardines and shortages in European markets.

In Peru, the fishing sector fell 73% year on year in May. The country’s first anchovy fishing season produced only about 0.5 million tonnes, compared with 1.9 million tonnes a year earlier. Manufacturing connected to fishing fell 42%. The fish do not need to die for this to become an economic problem. If the water becomes uncomfortable for a species, it can move. A fishing fleet that has depended on finding that species in the same waters for generations may then have to travel farther, catch less or change what it fishes for.

A 2026 study examining more than 33,000 fish populations found that long-term ocean warming was associated with annual biomass declines of up to 19.8%. Marine heatwaves produced much sharper losses in some populations at the warmer edge of their range, reaching 43.4%.

Then There is the Coral That Cannot Move

This is where the damage becomes harder to reverse. Fish can follow cooler water. A coral reef cannot. When seawater remains too warm, corals expel the microscopic algae living inside their tissues. Those algae provide much of the coral’s energy and give it its colour. The result is coral bleaching. If the heat persists, the coral can die.

The Mesoamerican Reef has experienced this on a huge scale. Almost the entire reef was exposed to serious heat stress during 2023 and 2024. Around half of its corals were severely affected by bleaching. Between 2023 and 2025, the reef lost about half of its living coral, leaving live coral cover at only 17%.

That loss changes the habitat available to fish and other marine organisms. It also affects people who depend on reefs for fishing, tourism and protection from waves. The Mediterranean has seen another kind of biological upheaval. Repeated marine heatwaves have contributed to mass deaths of marine organisms, while coral populations in some areas have fallen sharply. The noble fan mussel, one of the Mediterranean’s largest shellfish, has been pushed close to extinction in recent years.

Some Animals Thrive: Hidden Trouble

Ocean warming does not kill everything equally. Some species benefit from warmer conditions or move into areas that were previously too cold for them. That can produce an unfamiliar mix of species and upset existing food chains.

British waters are already showing this shift. Warmer conditions have been associated with increasing numbers of warm-water species such as sunfish, sardines and anchovies, while cold-water species including cod have declined along parts of the southern coast. Octopus populations have increased in some areas, putting additional pressure on crab and lobster fisheries.

That is not necessarily a sign that the ecosystem is becoming healthier. An ecosystem works through relationships between species. Change one part and others can be affected. A new predator, a disappearing prey species or a fish moving into unfamiliar waters can alter what other animals eat and where they survive. A 2026 study of Western Mediterranean ecosystems found that marine heatwaves were associated with declines in commercially important fish and invertebrates, with catch reductions exceeding 10% in some areas.

The Smallest Organisms Matter

There is another change taking place much lower in the food chain. Phytoplankton are tiny organisms that use sunlight to produce energy in the ocean. They form the base of many marine food webs. When ocean temperatures and nutrient conditions change, their productivity can change as well.

ISRO’s Oceansat-3 observations found a marked decline in surface chlorophyll-a concentrations in the equatorial Pacific in June 2026, consistent with reduced marine productivity as El Niño developed. Chlorophyll-a is commonly used as an indicator of the amount of microscopic plant life in the water. ([The Indian Express][6])

That matters because the effects can move upward through the food chain. Less food for tiny organisms can mean less food for small fish. That can affect larger fish, seabirds and marine mammals. During past marine heatwaves, the consequences have been dramatic. The 2014–16 “Blob” in the northeast Pacific contributed to the starvation of thousands of sea lion pups and the deaths of about four million common murres, according to the factsheet.

The bird deaths were not simply a story about birds struggling with hot water. The heatwave altered the marine food web, making it harder for them to find enough suitable food.

The Ocean can Change What Happens on Land

This is where the story moves from marine biology into everyday life. Warm seawater can supply additional heat and moisture to weather systems. Marine heatwaves have been linked with stronger storms, extreme rainfall and heatwaves over land. One study cited in the factsheet found that 22% of continental heatwaves and 43% of coastal heatwaves began as marine heatwaves.

Storm Daniel, which killed nearly 6,000 people in 2023, was fuelled by unusually warm Mediterranean waters. Climate change made the storm 50 times more likely and increased its intensity by 50%, according to the attribution analysis cited in the factsheet. Cyclone Gabrielle, which struck New Zealand in 2023, formed over abnormally warm seas and caused NZ$14 billion in damage. Climate change increased the intensity of its rainfall.

The connection is not as simple as saying “warm ocean equals stronger storm”. Storms depend on several atmospheric and ocean conditions. But a warmer ocean changes the conditions available to those weather systems.

Warming is not a One-year Event

El Niño is contributing to the current heat. It explains part of the unusually high temperatures in 2026, particularly in the Pacific. The larger trend is much older. The ocean has absorbed about 93% of the excess heat trapped by the warming atmosphere. Around 104 zettajoules of energy have entered the ocean during the past decade. The rate of warming during the last 20 years has been more than twice that of the preceding 40 years.

That is why today’s “cool” La Niña years are still warmer than El Niño years from earlier decades. After the previous El Niño ended in May 2024, sea temperatures remained close to or above previous records through 2025 and early 2026. The ocean is essentially carrying the accumulated heat of a warming planet.

What 21.24°C Really Means

A global ocean temperature is an average. It does not mean every part of the sea is 21.24°C. Tropical waters are much warmer; polar waters are far colder. What matters is the departure from the conditions marine ecosystems have evolved around, and how long that departure lasts.

In July 2026, 37% of the world’s ocean was experiencing a marine heatwave, according to NOAA. That ranked second among all months since 1991. NOAA’s forecast also points to potentially even greater marine heatwave coverage during the northern-hemisphere winter of 2026–27. For a coral colony, that can mean bleaching. For a sardine, it can mean moving into different waters. For a fishing community, it can mean a smaller catch. For a seabird, it can mean less food. For a country dependent on fisheries, it can mean lost revenue.

And for people living on the coast, changes in the ocean can eventually arrive as a storm, a disrupted livelihood or a higher food bill. The most important number in the 2026 ocean record may therefore not be 21.24°C. It is the roughly 100 days that the ocean stayed at record warmth. Marine ecosystems can sometimes recover from a short shock. Repeated or prolonged heat gives them much less time to do so. That is what makes a hot ocean worth watching even for people who rarely see the sea.

In Perpignan, a city on France’s Mediterranean coast, the number of heat-related deaths has risen dramatically. Between 1991–2000 and 2015–2024, the rate increased by 1,184%. Perpignan is not an isolated case. Haskovo in Bulgaria recorded a 697% increase and Castellón de la Plana in Spain 553.5%. In Umeå, Sweden, the increase was 142%. Dublin recorded a 104.6% rise. The numbers come from the first Europe-wide city-level assessment of climate change and health by the Lancet Countdown.

Covering more than 850 cities, the 2026 report shows how differently climate change is being experienced within the same continent. Southern European cities recorded a 160.6% increase in heat-related mortality when 2015–2024 is compared with 1991–2000.

The map of Europe, in other words, does not tell the whole story. The street where a person lives, the amount of shade around them and the heat retained by the buildings around them can all change what a hot summer means. Pierre Masselot, assistant professor in the Environment and Health Modelling Lab at the London School of Hygiene & Tropical Medicine, said the report reinforces evidence that “the health impacts of climate change are increasing faster than our efforts to adapt”.

Heat-related Deaths: Cities Trap Heat for Much Longer

A hot day in a city is not necessarily the same as a hot day outside it. Roads, buildings and other hard surfaces absorb heat during the day and release it slowly. The result is an urban heat island, where temperatures remain higher than in surrounding rural areas. The difference between cities can be striking. Granada experienced temperatures more than 1.5°C above its surrounding rural areas on an average of 118 days each summer between 2003 and 2020. The Spanish urban average was 12.3 days.

Sofia recorded 109 such days a summer against a Bulgarian urban average of 12.5. In France, Chambéry averaged 90 days, Annecy 78 and Nancy 75, while the national urban average was 12. In Göteborg, the figure was 19.3 days, more than three times Sweden’s urban average of about six. These differences help explain why the health burden of heat cannot be reduced to a European average.

Older people and children are particularly vulnerable. So are outdoor workers and people living in poorer neighbourhoods, where access to shade, cooling and green space may be limited. The report identifies these groups among those facing disproportionate climate-related health risks. For someone working outdoors or an older person living alone, the difference between a city cooling after sunset and one that holds onto the day’s heat can be consequential.

The Heat is Changing More Than Mortality

Heat is the most visible part of the story, but it is not the only one. In eastern European cities, the climatic suitability for dengue transmission increased by 369.3% in 2015–2024 compared with 1982–2010. Pollen concentrations with allergenic potential more than doubled in southern and eastern cities. In southern Europe, wildfire danger increased by 7% between 2003 and 2023.

For doctors, these are not abstract indicators. Miriam Meschede of the Centre for Planetary Health Policy said rising temperatures, worsening wildfire conditions, changing infectious disease risks and greater exposure to pollen are already affecting people’s lives and putting additional pressure on health.

Dr Courtney Howard, an emergency physician and president-elect of the Canadian Medical Association, said more frequent and intense heat, wildfire smoke and changing infectious disease risks can aggravate existing health conditions and contribute to premature deaths. Large-scale extreme events can also put health services under pressure when many people need care at once. That makes the city itself part of the health story. The places where people live, work, travel and seek relief from heat increasingly shape their exposure.

Cleaner Cities, Hotter Summers

There is another side to the European picture, and it complicates any simple account of climate failure. Several countries have made substantial progress in cutting emissions and pollution. Swedish cities reduced greenhouse gas emissions per person by 20% between 2000 and 2024. Residential emissions fell by 78.5% and energy-sector emissions by 62.5%. Premature mortality linked to PM2.5 from dirty-fuel use fell by 68.6% between 2000 and 2023.

France cut city-level greenhouse gas emissions per person by 42.6% over the same broad period, while premature mortality attributable to PM2.5 from power generation fell by 82%. Ireland recorded a 35.3% reduction in city-level emissions per person and a 69% decline in premature mortality attributable to dirty-fuel PM2.5. Those are meaningful public-health gains. Cleaner energy means cleaner air, and cleaner air saves lives.

But the heat numbers keep moving in the other direction. That is the uncomfortable part of the European story. A city can become cleaner without becoming cool enough. Cutting emissions slows the warming that lies ahead; it does not erase the heat already built into the urban environment.

What Happens at Street Level

The report offers some evidence that cities are beginning to respond. Eighty-eight percent of the cities analysed recorded a reduction in summer surface urban heat-island intensity, with an average reduction of 0.7°C. The researchers associate these changes mainly with expanded green space and changes in surface characteristics. But a citywide average can hide a great deal.

A tree-lined street and a heavily built-up neighbourhood may belong to the same municipality while offering very different levels of protection from heat. The same is true of access to public transport, shaded walking routes and places where people can escape extreme temperatures. Masselot argues that cities need to put public health closer to the centre of urban planning, including through greening, cleaner air and stronger protection for vulnerable residents.

Europe has spent years measuring emissions and setting climate targets. The city-level evidence suggests another measure deserves equal attention: what happens to the people living there when the temperature rises. That may be where the success or failure of urban climate policy is ultimately felt.