English schools could exceed an “overheating” threshold of 26C for one-third of the academic year if global warming reaches 2C above pre-industrial temperatures, a new study finds.
The study, published in Climate Risk Management, assesses the risk of overheating in around 20,000 schools across England, using data on the schools’ location, the type of building and the climate.
The authors identify the indoor temperature of 26C as the upper “comfortable” limit in classrooms. While the average school would be expected to surpass this limit for more than one-third of the academic year under 2C of warming, it rises to half of the year for 4C of warming.
The authors also investigate a 35C threshold, above which “important health impacts” are seen. They find that, currently, schools only exceed this temperature threshold once every year, on average.
However, under 4C warming, the average school is expected to exceed this threshold around nine times per year, accounting for 5% of the academic year.
Newer schools are more likely to overheat than their older counterparts, the authors say, because they typically have better insulation and lower ceilings. They add that schools in the south and east of England, as well as London, are at greatest risk of overheating.
The study shows the need for adaptation measures such as improved ventilation, a scientist not involved in the study tells Carbon Brief. She adds that “school buildings need to be designed today with tomorrow’s climate in mind”.
Overheating schools
Over the past month, millions of children in the Philippines, Bangladesh and India stayed home as a record-breaking heatwave forced schools across southern Asia to shut.
However, schools in more temperate climates can also be affected by the heat. In July 2022, the UK experienced a record-breaking heatwave that saw temperatures exceed 40C for the first time on record. During this period, the UK put out its first red heat alert and many schools finished early or closed their doors entirely for the safety of their staff and students.
Extreme heat can be deadly. During a heatwave, the number of “heat-related deaths” – where exposure to heat either causes or significantly contributes to a death – tends to increase.
Children are particularly vulnerable to high temperatures. When it is hot, the human body produces sweat to cool itself down. However, children do not sweat as much as adults and are therefore less able to regulate their body temperature.
Even when temperatures do not reach headline-grabbing highs, any increase above the “optimal” temperature can be harmful. A recent World Bank report estimates that in “middle and high-income settings”, the ideal classroom temperature lies between 19.5C and 23.3C. The report says:
“In those settings, any temperature above 24C can compromise reaction time, processing speed and accuracy through changes in heart rate and respiratory rates…
“Across five experimental studies, high temperature produced declines in student performance ranging from 2 to 12% for each 1C increase in classroom temperature.”
Furthermore, when teachers work in classrooms that are too hot, they can become fatigued or lose concentration, making them more likely to put themselves and the children in their care at risk.
UK guidance suggests a minimum working temperature of 16C, if employees are not carrying out physical work. However, there are no legal maximum working temperatures for schools in the UK.
“Our children spend 30% of their lives in schools,” says Prof Lucelia Rodrigues – chair of sustainable and resilient cities at the University of Nottingham. Rodrigues, who was not involved in the study, tells Carbon Brief that it is “imperative that we provide them with comfortable, healthy environments to thrive and achieve their best”.
Newer buildings
The new study assesses how often English schools overheat, which schools are most at risk and how climate change could exacerbate the problem. The study authors define two temperature thresholds:
- 26C: The “upper limit of comfortable operative temperature in schools”.
- 35C: The temperature at which “important health impacts” are seen.
The authors use the open-access CLIMADA platform to simulate the risk of English schools overheating, combining information on hazard, exposure and vulnerability.
The authors use climate data from the UK Climate Projections 2018 (UKCP18) to determine annual variations in temperature across England over 1998-2017. They then model those temperatures in worlds with average global temperatures of 2C and 4C above pre-industrial levels. This provides the hazard data.
They then quantify exposure using data on the location of around 20,000 primary and secondary state schools in England. And vulnerability is assessed using “physics-based building models” to quantify the link between outdoor and indoor temperature for different types of buildings.
The plot below shows an example of the relationship between outdoor daily average temperature (blue) and indoors daily maximum temperature (red) in two different schools. The dashed and dotted lines indicate the 26C and 35C temperature thresholds, respectively.
The authors find that schools built before 1918 are generally most able to keep cool, while those built after 1967 overheat the most easily.
Dr Laura Dawkins – an “expert scientist” in climate risk and resilience at the UK Met Office, and lead author of the study – tells Carbon Brief that this is due to “differences in typical floor-to-ceiling heights”. Newer schools are typically built with lower ceilings, which cause the room to heat up more quickly, she explains.
Rodrigues adds that newer schools are built to “more stringent building regulations designed to reduce heating energy demand”, making them more airtight and well-insulated. Citing her 2010 study, she continues:
“In classrooms within schools built post-2010, overheating occurred for more than 40% of school hours, whilst in older schools with leakier and non-insulated envelopes overheating was rarely reported.”
Rodrigues says that ventilation is key, noting that it not only prevents buildings from overheating, but can also “improve air quality, which will have a significant impact on productivity” in pupils.
Mapping heat
The study’s findings include a series of maps to show where the most at-risk schools are located.
The maps below show the expected total number of days in an academic year that each school will cross the 26C (left) and 35C (right) temperature thresholds. The top row uses the climate of 1998-2017, the middle row a 2C-warmer world and the bottom row a 4C-warmer world. Darker red indicates more overheating days.
The authors assume 195 days in a school year, to account for weekends and holidays. The analysis does not include August – the hottest part of the year – because schools are typically closed for the summer holidays during this time.
The authors find that schools in south and east of England, as well as London, are at greatest risk of overheating. They add that this is largely due to the urban heat island effect – in which a combination of factors, such as buildings, reduced vegetation and high domestic energy use, cause urban areas to become hotter than more rural regions.
By combining the data from all 20,000 schools, the authors determine how many days the average school is expected to cross the 26C and 35C warming thresholds under different global warming levels. The authors also calculate values for “at-risk” schools – which rank in the highest 10% on their risk metric.
These results are shown in the table below.
| 26C threshold, average school | 26C threshold, at-risk school | 35C threshold, average school | 35C threshold, at-risk school | |
|---|---|---|---|---|
| Recent climate | 59 | 59 | 1 | 1 |
| 2C warming | 71 | 75 | 3 | 5 |
| 4C warming | 89 | 92 | 9 | 13 |
Number days during the academic year that “average” and “at-risk” schools are expected to cross the 26C and 35C warming thresholds under different global warming levels. Adapted from Dawkins et al (2024).
The average school currently exceeds the 26C threshold for 59 days – accounting for around one-third of the academic year – according to the study. However, the authors warn that this could rise to 71 and 89 days under the 2C and 4C scenarios, respectively.
Meanwhile, England’s most at-risk schools currently face one day per year of indoor temperatures above 35C. This could rise to five days per year under a 2C warming scenario, and 13 under a 4C scenario.
This study is “a first attempt at applying the novel spatial risk assessment framework to this real world problem”, according to Dr Dan Bernie climate resilience science manager and health science lead at the UK Met Office and an author on the study.
Bernie tells Carbon Brief that he is currently working on “generating more robust results using individual school building models and higher resolution climate projections”.
Prof David Bresch is a professor at the department of environmental systems science at ETH Zurich and is the founder and senior scientific advisor at CLIMADA. He tells Carbon Brief that the authors have used the platform well, providing a good “prototype” for this type of study.
The biggest “challenge” in the study is the team’s use of fixed temperature thresholds, he says. However, he calls the paper an “important contribution” to the literature, and says that it will allow schools and governments to start thinking about adaptation measures.
Bresch emphasises the importance of adaptation. He tells Carbon Brief that it is crucial to “take a forward looking view of risk”, adding that it comes with the win-win situation of limiting impacts and likely coming with a lower price tag than waiting for major impacts to hit.
Government plans
Every five years, the UK government publishes its Climate Change Risk Assessment (CCRA), which assesses the “current and future risks to and opportunities for the UK from climate change”.
The National Adaptation Programme (NAP) is published shortly afterwards, allowing administrations such as the Department of Education (DfE) to outline how they are planning to adapt to climate change.
In July 2023, the UK government published its third National Adaptation Programme (NAP3). In this report, the DfE recognised the “significant threat” of rising overheating in schools, and highlighted the need for further research to better understand this risk.
The new study was carried out partly in response to this call for research and has experts from both the UK Met Office and DfE in its author list. Bernie tells Carbon Brief that this study was a collaboration between “climate science, data science, building performance models and stakeholder insights”.
The DfE tells Carbon Brief that it has already allocated £138m to make education buildings more sustainable or more resilient to the impacts of climate change. The UK government’s “strategy for the education and children’s services systems” adds:
“All new school buildings delivered by DfE (not already contracted) will be net-zero in operation. They will be designed for a 2C rise in average global temperatures and future-proofed for a 4C rise, to adapt to the risks of climate change, including increased flooding and higher indoor temperatures.”
However, Rodrigues tells Carbon Brief that “there is still no requirement to design for future climate conditions, even though schools typically have at least a 50-year lifespan, with many occupied continuously for over 100 years”. She adds that “school buildings need to be designed today with tomorrow’s climate in mind”.
The DfE tells Carbon Brief that they are working with partners including the Met Office on the next iteration of this research and will provide more information about it later this year.
The post English schools face ‘overheating’ for one-third of year under 2C warming appeared first on Carbon Brief.
English schools face ‘overheating’ for one-third of year under 2C warming
A US biofuels producer that exports “green” aviation fuel to Britain and the European Union has purchased beef tallow from a Brazilian supply chain tied to illegal deforestation in the Amazon, shipping data and a court document show.
Diamond Green Diesel (DGD), a major provider of sustainable aviation fuel (SAF) and renewable diesel, has sourced hundreds of thousands of tonnes of beef tallow from Brazil, alongside waste fats from other sources, over the last three years, as global demand for biofuel feedstocks soars.
Reporting by Unearthed and nonprofit investigative outlet Repórter Brasil reveals DGD’s connection to a rendering plant that has sourced supplies from a meatpacker fined for buying cattle from an illegally deforested Amazon reserve. A previous investigation by Reuters and Repórter Brasil found DGD had bought animal fat from two other rendering factories linked to supplies of cattle from illegal ranches.
The newly identified factory, Pacífico Indústria e Comércio de Óleos e Proteínas Ltda, which is based in Cacoal, a small city in the far-western Amazon state of Rondônia, has been supplied by Rondônia meatpacker DistriBoi, a 2022 court document shows.
DistriBoi was fined two years ago for illegally purchasing cattle from the state’s Jaci-Paraná conservation reserve, which has been ravaged by illegal ranching.
There is no suggestion that the companies involved were aware of deforestation at farm level. But the findings suggest a traceability gap in the supply chain of feedstocks for sustainable fuels, where cattle by-products are subject to less oversight than the primary commodities of the cattle industry, such as meat and leather.
Pristine rainforest blanketed the Jaci-Paraná reserve when it was created 30 years ago to protect traditional forest activities such as rubber tapping and nut harvesting.
Today, illegal ranching has devoured nearly 80% of its forest cover and it has become a notorious example of the devastation wrought by land grabbers in the world’s largest rainforest.
“The damage to biodiversity has been devastating,” said local Indigenous activist Neidinha Suruí, who featured in the 2025 Emmy Award-winning documentary “O Território”.
“It is sad to see what has been lost,” she said.
Greener air travel?
The “renewable diesel” and sustainable aviation fuel (SAF) that are being exported by DGD – a joint venture between US oil refiner Valero Energy Corp and Texas-based Darling Ingredients – are classed as “green” because they are made from feedstocks classified as waste, including tallow, which consists of fat separated from cattle carcasses.
Many governments and airlines are pinning their hopes for greener flying on SAF made with organic waste materials, including Britain which introduced a compulsory blending requirement last year.
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Air travel accounts for about 2.5% of global carbon emissions and in contrast to other transport sectors that can be electrified, shrinking aviation’s carbon footprint is much more difficult.
Waste products such as beef tallow and used cooking oil (UCO) are considered the greenest of viable SAF feedstocks on the grounds that they do not create competition with foodstuffs such as soy oil or palm oil, nor increase deforestation pressure.
But there is concern that the global rush to ramp up SAF use could indirectly exacerbate deforestation pressure by increasing demand for feedstocks such as tallow and UCO.
That could increase the profit margins of cattle ranches – including illegal ones – and have other unintended consequences, such as encouraging fraud in supply chains, as Climate Home News has reported.
An investigation published in March by Climate Home News and Swedish broadcaster SVT found that Finnish biofuels giant Neste is sourcing key ingredients for its SAF from an opaque supply chain that enables fresh palm oil to be passed off as used, waste oil.
Because tallow is classified as waste by regulators in markets including the UK and EU, the green fuel industry’s most widely used certification scheme – International Sustainability and Carbon Certification (ISCC) – does not assess whether forests were cleared to rear the cattle that produced it in the first place.
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This allows tallow from cattle to qualify as a sustainable feedstock for green fuels, even if they were raised on illegally deforested land.
“There is clearly an oversight within the rules if the products, in this case animal tallow, are originally coming from deforested land,” said Cian Delaney, a campaign coordinator at the clean transport and energy advocacy group Transport & Environment.
That means government SAF mandates aimed at stemming air travel emissions could help boost the earnings of cattle ranchers linked to illegal deforestation in Brazil, where ranching and other forms of agriculture have been the main driver of forest loss.
Land grabbers clear way for ranchers
Once covered by an unbroken rainforest canopy, Rondônia’s Jaci-Paraná reserve has been decimated by illegal deforestation driven by cattle ranching – a major cause of tree loss in the Amazon.
Land-grabbers have seized – often violently – and cleared more than three-quarters of its forest for pasture, as ranching has steadily advanced into the southern Amazon.
Suruí, the local Indigenous activist, said companies that buy products derived from illegal activities perpetuate environmental crimes in the rainforest.
“If there were no meat processors buying illegally sourced cattle, there would be no land grabbing and no deforestation,” Suruí told Repórter Brasil, which partnered on the new investigation with Unearthed, and a team of journalists supported by JournalismFund Europe.
Lawsuits and linked supply chains
Brazilian President Luiz Inácio Lula da Silva has pledged to end all deforestation in the country by 2030, in part by strengthening environmental enforcement in the world’s biggest rainforest.
In Rondônia, authorities have launched more than 50 lawsuits related to land-grabbing and deforestation in the Jaci-Paraná reserve alone. Local slaughterhouse DistriBoi is named in 31 of the lawsuits, including the 2024 case in which it was fined.
According to the 2022 court document, which concerned an unrelated labour dispute, lawyers for Pacífico refer to DistriBoi as the rendering plant’s “largest supplier of raw materials”.
US-based DGD received almost 15,000 tonnes of tallow from Pacífico from 2023 to 2025 at its Texas refinery, as well as used cooking oil from various countries and sources, according to trade database Panjiva.
Darling Ingredients is also a parent company of Pacífico since its 2022 acquisition of Brazilian rendering company FASA Group.
A spokesperson for Darling Ingredients denied that Pacífico had sourced beef residues from DistriBoi’s Ji-Paraná slaughterhouse – one of two that the meatpacker operates in Rondônia.
“The rendering plant Pacífico does not source any materials from the slaughterhouse Distriboi in Ji-Paraná,” the spokesperson said in an emailed response, without providing evidence or commenting directly on the content of the 2022 court document.
Darling did not respond to a follow-up question about Distriboi’s other slaughterhouse in the region, which, according to cattle transfer documents, has also bought from a farm that has illegally cleared forest within the extractive reserve.
“Our relationships are typically with the slaughterhouse, several levels removed from cattle ranchers. Regardless, we are committed to ensuring our raw materials are deforestation free. We expect our raw material suppliers to abide by our supplier code of conduct. In addition, we are in the process of requiring all [the] raw materials to attest that their material is deforestation free,” the spokesperson said in a statement.
DistriBoi said in an apparent reference to the pending Jaci-Paraná lawsuits that “the matters mentioned … are already under review, including by higher courts”. It has previously denied wrongdoing. The company’s statement did not address a question about its commercial ties to Pacífico.
Valero Energy, the major refiner that co-owns DGD with Darling Ingredients, did not respond to requests for comment, nor did DGD itself.
From slaughterhouse to SAF
In an effort to rein in carbon emissions from air travel, regulators in Britain and the EU have mandated progressively increasing SAF blending quotas in the years ahead, creating a new market for feedstocks including beef tallow.
Brazil’s exports of tallow to the US have risen sharply in recent years, up from less than 10,000 tonnes in 2021 to almost 400,000 tonnes last year, according to Panjiva, reflecting growing demand for biofuels like SAF.
In the UK, Europe’s biggest aviation market by seat capacity, jet fuel was required to contain 2% SAF by the end of 2025, rising to 10% by 2030 and 22% by 2040.
DGD shipped 134,000 tonnes of SAF worth nearly $90 million from Texas to the UK in 2025, according to trade data from Panjiva. The company also exported smaller amounts of renewable diesel to Britain.
The EU received biofuels, including small quantities of SAF, worth over $1.1 billion from DGD’s Texas refinery last year, figures show.
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Unearthed’s investigation could not identify which airlines or airports buy DGD’s SAF once it arrives in Britain.
Valero, DGD’s other parent company, is positioning itself as a key player in the transition to lower-carbon fuels in the UK, where it markets its renewable diesel under the Texaco brand.
It has been an active participant in SAF policy discussions and has criticised the government’s planned cap on waste fat sources in SAF, calling them “the world’s most cost-effective production route for SAF” in a submission to parliament.
Helping to cut emissions?
Even tighter oversight over SAF feedstocks is crucial to ensure that blending mandates such as Britain’s are effectively lowering emissions, said Anna Krajinska, a director at Transport & Environment UK.
Forests store vast amounts of carbon; when they are cut down or burned this carbon is released into the atmosphere.
“If there’s tallow coming from land that’s been deforested, then those emissions might be so high that you might not be getting to the greenhouse gas reduction threshold,” Krajinska said.
But as the world’s appetite for flying keeps on growing, some experts say SAF is the only viable means to reduce aviation emissions at present.
Referring to the deforestation links identified in Unearthed’s investigation, Wouter Dewulf, an aviation economist at Belgium’s University of Antwerp, said it “would be important to assess how large this infraction is”.
“I’m quite sure you have aberrations,” Dewulf added. “But biofuels are the best alternative for the moment.”
T&E’s Delaney said there needs to be less opacity and better oversight from regulatory authorities. “Right now, there are just too many blindspots,” he added.
The post UK imports of “green” jet fuel linked to Amazon deforestation appeared first on Climate Home News.
UK imports of “green” jet fuel linked to Amazon deforestation
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