The Ocean Has Been Breaking Heat Records. Marine Life Is Paying the Price
Record ocean heat is already changing marine life, from declining sardines and coral reefs to shifts in fish populations. Here is what the warming means for ecosystems and people.
A warming ocean is placing growing pressure on marine ecosystems, fisheries and coastal communities as global sea temperatures continue to reach record levels. Representational Image. Image credit: Ray Bilcliff/Pexels
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.
Global daily sea-surface temperatures from 2023 to 2026 show how recent years have remained well above the range recorded from 1982–2022, with 2026 reaching the highest levels shown. Source: Climate Central, using NOAA OISSTv2.1 data.
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.
Ocean warming and prolonged marine heat stress can cause corals to bleach, putting reef ecosystems at greater risk of damage and mortality. Representational image. Image credit: Zir YU/Pexels
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.
EP Staff is the editorial team at EdPublica, an independent media organisation focused on science, education, environment and public policy. The team produces evidence-based news, features, explainers and analysis on issues that shape society and everyday life.
Cyclone Arnab Makes Landfall in Andhra Pradesh, Uproots Trees and Disrupts Power Supply
Cyclone Arnab hits Andhra Pradesh with strong winds and heavy rainfall, disrupting transport and electricity supply as authorities evacuate vulnerable coastal communities.
Strong winds and rough seas pose risks to coastal communities during cyclonic weather. Representational image. Image credit: Atlantic Ambience/ Pexels
Cyclone Arnab crossed the Andhra Pradesh coast in the early hours of Wednesday, October 28, bringing destructive winds and heavy rainfall to coastal districts. Trees were uprooted, electricity infrastructure was damaged and transport services were disrupted as authorities continued emergency operations in vulnerable areas. The last major cyclone to hit Andhra Pradesh before Cyclone Arnab was Cyclone Montha, which made landfall near Kakinada on October 28–29, 2025. It struck almost exactly a year before Arnab’s landfall on October 28, 2026.
The India Meteorological Department (IMD) had forecast that the very severe cyclonic storm would cross the Andhra Pradesh–Yanam coast between Bapatla and Visakhapatnam, close to Yanam, with sustained winds of 125–135 kmph and gusts reaching 150 kmph. The landfall process began early on Wednesday and was expected to continue for several hours.
Officials reported peak winds of up to 185 kmph during the storm, while warning that dangerous weather would persist across coastal Andhra Pradesh and parts of neighbouring Odisha even as the system weakened over land. The IMD’s subsequent bulletins will be important for establishing the storm’s observed intensity and movement.
What Does the Name Arnab Mean?
The name Arnab was proposed by Bangladesh and is included in the official list of tropical cyclone names maintained under the World Meteorological Organization (WMO) and the United Nations Economic and Social Commission for Asia and the Pacific (UN ESCAP) regional system.
Pronounced “Ornab”, the name is commonly associated with the Bengali word for the ocean or sea. The official naming list confirms Bangladesh as the country that proposed it, although the list itself does not provide a formal definition of the word.
Satellite imagery of Very Severe Cyclonic Storm Arnab over the Bay of Bengal, located at 16.0°N and 84.3°E, off India’s eastern coast. Source: IMD
The regional naming system includes 13 countries: Bangladesh, India, Iran, the Maldives, Myanmar, Oman, Pakistan, Qatar, Saudi Arabia, Sri Lanka, Thailand, the United Arab Emirates and Yemen. Each country contributes names to a shared list, which meteorological agencies use in sequence as cyclones develop over the Arabian Sea and Bay of Bengal.
Andhra Pradesh Bears the Immediate Impact
Coastal Andhra Pradesh experienced the most immediate effects as the cyclone approached and crossed the coast. Reports from Kakinada described uprooted trees and damaged electrical infrastructure. In Visakhapatnam, strong winds and rain brought down trees, obstructing traffic along Beach Road and in Seethammadhara.
The IMD reported exceptionally heavy rainfall at several locations in Anakapalli and Visakhapatnam districts. Rainfall exceeding 200 mm was recorded at some stations during the observation period extending from October 27 into the early hours of October 28. Such intense rainfall can overwhelm drainage systems, flood low-lying settlements and disrupt road connectivity.
Power disruptions and transport cancellations added to the difficulties faced by residents. Some train services were cancelled, while flight operations at airports in the region were reported suspended. Schools were closed in affected areas, and some school buildings were used as temporary shelters. The full extent of damage to houses, agricultural land, roads and public infrastructure was not yet clear in the initial post-landfall reports.
Thousands Evacuated: Authorities Prepare for Flooding
The scale of the evacuation operation reflected the exposure of coastal communities to strong winds and flooding. According to the Associated Press, at least 89,000 people had been evacuated from vulnerable areas in Andhra Pradesh by Wednesday morning.
Authorities had established more than 2,000 cyclone shelters across 20 districts, secured over 30,000 fishing boats and deployed nearly 1,100 medical teams for emergency assistance. The state’s disaster management authority said more than 12 million people lived along the cyclone’s projected path.
In neighbouring Odisha, authorities planned to evacuate approximately 48,000 people from areas expected to be affected. The IMD warned of heavy to extremely heavy rainfall in parts of southern Odisha, raising concerns about flooding and possible landslides in hilly districts. The evacuation figures describe the scale of preparedness and displacement, rather than the number of people confirmed to have suffered damage or injury.
Risks Continue After Landfall
A cyclone’s impact can persist after its centre crosses the coast. Heavy rainfall may continue as the system moves inland, while saturated soil and swollen rivers can increase flood risks. Strong winds can also delay the restoration of electricity and transport services.
Agriculture and fishing are among the livelihoods potentially exposed to the storm. Standing paddy crops may be damaged by strong winds and waterlogging, while rough seas and fishing restrictions can interrupt incomes for coastal communities. The actual losses to these sectors will depend on the storm’s subsequent movement and local damage assessments. At the time of the initial post-landfall reports, there were no immediate reports of casualties. This was an early assessment, and the situation required continued monitoring as emergency teams reached affected areas.
Kashmir’s Traditional Rice Varieties Hold Genetic Clues to Climate Resilience
A new study by SKUAST-Kashmir researchers identifies cold-tolerance genes in traditional rice varieties, highlighting their potential for climate-resilient crop breeding.
Traditional rice cultivation highlights the agricultural heritage that researchers are working to preserve as they investigate genetic resources for climate-resilient crops.Imagecredit:Pexels
For generations, farmers in Kashmir have cultivated traditional varieties of rice adapted to the region’s distinctive growing conditions. A new genomic study has found that these varieties retain genetic characteristics associated with cold tolerance and local adaptation, potentially offering valuable resources for developing climate-resilient crops.
Researchers at the Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir (SKUAST-Kashmir), Srinagar, analysed 142 rice germplasm samples to examine the genetic diversity and evolutionary history of rice cultivated in the region. Published in The Plant Genome in 2026, the study identified genetic signatures in traditional varieties that could help researchers develop rice better suited to environmental stress.
The findings are significant as climate change alters growing conditions and increases uncertainty for agricultural production. Preserving traditional crop varieties could give plant breeders access to genetic traits that may have become less common in modern cultivars.
Genes linked to cold tolerance
The study, titled Re-sequencing 142 rice genomes reveals the fine-scale population structure and phylogenetic affinities of landraces of Kashmir Valley: Evidence from domestication and adaptive signatures, used genomic analysis to investigate relationships among traditional landraces, modern varieties and other rice genetic resources.
The researchers found that Kashmir’s traditional varieties carried genetic signatures associated with temperate japonica rice, while many modern varieties showed stronger associations with indica lineages from subtropical India. This distinction points to differences in their genetic histories and adaptation to local growing environments.
Among the important findings was the identification of favourable variants of CTB4a and HAN1, two genes associated with cold tolerance in rice. The researchers also examined genetic variation linked to grain quality, plant development and other agricultural traits.
Traditional varieties, including Mushq Budji, Kamad, Kaw Kreer, Nun Beoul and Zag, displayed distinctive genetic patterns. Their diversity could provide useful material for future crop-improvement programmes.
The findings do not establish that all these varieties are more resilient than modern cultivars under every environmental condition. Instead, they identify genetic resources that warrant further investigation through breeding programmes and field trials.
Earlier research explains the significance
Previous research provides a scientific basis for investigating the cold-tolerance genes identified in Kashmir’s traditional rice varieties.
A 2017 study published in Nature Communications examined CTB4a, a gene associated with cold tolerance during the booting stage of rice development, when reproductive structures form. The researchers found that a favourable variant improved cold tolerance and helped maintain pollen fertility and seed setting under low-temperature conditions.
Crops in a paddy field.Image credit:Pexels
Similarly, a 2019 study published in the Proceedings of the National Academy of Sciences investigated HAN1 and found that natural genetic variation in the gene contributes to chilling tolerance in temperate japonica rice. The findings helped explain how rice adapted to cooler climates.
These studies strengthen the case for investigating CTB4a and HAN1 variants in Kashmir’s rice germplasm. However, the presence of promising genetic variants does not automatically guarantee improved performance in farmers’ fields. Their effects can depend on the crop’s broader genetic background, the timing and intensity of temperature stress, and other environmental conditions.
Conserving agricultural diversity
The Kashmir study also offers insights into the region’s agricultural history. Its genetic analysis suggests links between traditional Kashmir rice varieties and temperate rice lineages associated with Northeast Asia. The researchers propose that these lineages reached the region after approximately 1500 BCE, although this historical reconstruction remains an interpretation of genetic and archaeological evidence.
Beyond their historical significance, traditional rice varieties may preserve traits useful for future agricultural challenges. Modern breeding programmes often prioritise yield and other selected characteristics, but genetic diversity within traditional varieties can provide additional options for addressing environmental stress and maintaining grain quality.
The findings underline the importance of conserving traditional rice germplasm in gene banks and supporting its continued cultivation where feasible. Such conservation helps prevent potentially valuable genetic material from disappearing as farming systems and crop preferences change.
As climate change places increasing pressure on agricultural systems, Kashmir’s traditional rice varieties offer researchers a valuable starting point for investigating crop adaptation. Their genetic diversity connects generations of farming knowledge with modern genomic research, potentially helping plant breeders develop rice varieties suited to changing environmental conditions while preserving the region’s agricultural heritage.
India’s Green Cover Declined by 5.6 Percentage Points in 25 Years as Summer Heat Intensified: Study
A new study links India’s declining green cover to rising summer temperatures, highlighting the importance of vegetation conservation for climate adaptation.
Vegetation helps regulate local temperatures through shade and evapotranspiration, highlighting the role of green cover in climate adaptation. Image credit:Unsplash
India’s green cover declined from approximately 36.95 per cent in 2001 to 31.35 per cent in 2025, while non-green surfaces expanded across the country, according to a new study by Climate Trends. The analysis found that non-green landscapes consistently recorded higher summer temperatures than vegetated areas, highlighting the role of green cover in moderating local heat.
The findings suggest that vegetation loss can contribute to local warming, although the study also identifies broader regional climate change as a factor influencing temperature trends. Protecting and restoring vegetation could help reduce local thermal stress, but it cannot independently offset the effects of global warming.
“Vegetation is not merely an ecological asset; it is an important component of India’s climate-adaptation infrastructure,” said Dr Palak Balyan, Research Lead at Climate Trends.
The study comes amid growing concerns over extreme heat and its implications for public health, livelihoods and infrastructure. The India Meteorological Department reported that 2024 was the country’s warmest year since records began in 1901, with the annual mean temperature 0.65°C above the 1991–2020 average.
Vegetation Loss and the Local Heat Effect
The Climate Trends analysis used land-cover information from the Moderate Resolution Imaging Spectroradiometer (MODIS) and ERA5-Land temperature data to assess changes between 2001 and 2025. It examined summer conditions during March, April and May to understand how land-cover transitions corresponded with temperature patterns.
Vegetation helps regulate surface temperatures through shading and evapotranspiration, the process by which plants release water vapour into the atmosphere. Trees reduce the amount of solar radiation reaching the ground, while vegetation and soil moisture influence how energy is absorbed and released. When green landscapes are replaced by built-up areas, exposed ground or sparsely vegetated surfaces, these cooling mechanisms may weaken.
Dr Balyan said the persistent temperature difference between green and non-green landscapes demonstrated the importance of vegetation in regulating local thermal conditions.
“Protecting existing natural vegetation should therefore be treated as an adaptation priority, particularly in regions experiencing simultaneous green-cover loss and rising summer temperatures,” she said.
The findings are consistent with the Intergovernmental Panel on Climate Change’s assessment of nature-based cooling measures, which identifies urban trees, vegetation and green infrastructure as potential ways to reduce heat exposure. However, the extent of cooling depends on local climate, vegetation type, water availability and the surrounding built environment.
Regional Differences Require Targeted Action
The study found that green-cover loss was concentrated in parts of western India, the Indo-Gangetic Plain, central India and the peninsula. Localised gains were identified in portions of the northeastern states, the Himalayan foothills and scattered areas of southern and eastern India.
Temperature changes also varied geographically. Warming was particularly evident across northwestern and northern India, while localised cooling occurred in parts of central and southern India. These variations indicate that national averages can obscure differences in local land-use patterns and climate conditions.
The findings have implications for urban planning, particularly in rapidly expanding cities where construction can replace trees, open spaces and other vegetated landscapes. Protecting mature trees, retaining existing green spaces and integrating vegetation into streets and public areas could help reduce heat exposure, particularly in vulnerable neighbourhoods.
However, restoration must be planned around local ecological conditions. Newly planted trees cannot immediately provide the shade offered by mature canopies, and their survival depends on suitable species, soil conditions, water availability and long-term maintenance. Protecting established vegetation is therefore an important complement to new planting initiatives.
Green Cover Cannot Replace Broader Climate Action
The study emphasises that land-cover changes are not the only drivers of summer temperatures. Both green and non-green landscapes experienced warming during the study period, indicating the continuing influence of broader climatic conditions.
Dr S K Dhaka, Professor of Atmospheric Physics at the University of Delhi, cautioned against treating vegetation restoration as a standalone solution.
“Vegetation restoration can reduce local thermal stress, but it should not be viewed as a substitute for broader climate action,” he said.
Temporal variation in green and non-green land cover across India
He added that warming observed even in areas that remained continuously green showed that large-scale climatic forces continued to influence regional temperatures.
“India therefore needs a dual strategy: prevent further loss of established vegetation while implementing scientifically targeted restoration in heat-vulnerable regions, alongside stronger action on water management, urban planning and greenhouse-gas emissions,” Dr Dhaka said.
The distinction is important because increasing vegetation alone cannot eliminate heat risks associated with rising background temperatures. Effective adaptation requires combining nature-based measures with emissions reduction, appropriate urban design and improved water management.
Aarti Khosla, Founder-Director of Climate Trends, said the study highlighted the practical consequences of losing vegetation.
“The study puts a number on something we’ve long argued, that vegetation is not a biodiversity afterthought, but a climate-adaptation infrastructure,” she said.
“Where green cover has disappeared, temperatures have risen with it, and that is a cost India’s communities are already paying for,” Khosla added.
She also pointed to international biodiversity commitments, including the target of restoring 30 per cent of degraded ecosystems by 2030, arguing that the gap between commitments and implementation has consequences for climate resilience.
The study recommends protecting existing vegetation, preventing avoidable green-cover loss and promoting ecological restoration as part of sustainable land management.
Its central message is that green cover should be considered more than an environmental amenity. While vegetation cannot prevent all forms of warming, conserving it can help moderate local temperatures and reduce thermal stress. As India faces increasing heat risks, integrating vegetation protection into climate adaptation and development planning could help build more resilient communities.