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
Drought and heatwaves occurring together – known as “compound” events – have “surged” across the world since the early 2000s, a new study shows.
Compound drought and heat events (CDHEs) can have devastating effects, creating the ideal conditions for intense wildfires, such as Australia’s “Black Summer” of 2019-20 where bushfires burned 24m hectares and killed 33 people.
The research, published in Science Advances, finds that the increase in CDHEs is predominantly being driven by events that start with a heatwave.
The global area affected by such “heatwave-led” compound events has more than doubled between 1980-2001 and 2002-23, the study says.
The rapid increase in these events over the last 23 years cannot be explained solely by global warming, the authors note.
Since the late 1990s, feedbacks between the land and the atmosphere have become stronger, making heatwaves more likely to trigger drought conditions, they explain.
One of the study authors tells Carbon Brief that societies must pay greater attention to compound events, which can “cause severe impacts on ecosystems, agriculture and society”.
Compound events
CDHEs are extreme weather events where drought and heatwave conditions occur simultaneously – or shortly after each other – in the same region.
These events are often triggered by large-scale weather patterns, such as “blocking” highs, which can produce “prolonged” hot and dry conditions, according to the study.
Prof Sang-Wook Yeh is one of the study authors and a professor at the Ewha Womans University in South Korea. He tells Carbon Brief:
“When heatwaves and droughts occur together, the two hazards reinforce each other through land-atmosphere interactions. This amplifies surface heating and soil moisture deficits, making compound events more intense and damaging than single hazards.”
CDHEs can begin with either a heatwave or a drought.
The sequence of these extremes is important, the study says, as they have different drivers and impacts.
For example, in a CDHE where the heatwave was the precursor, increased direct sunshine causes more moisture loss from soils and plants, leading to a drought.
Conversely, in an event where the drought was the precursor, the lack of soil moisture means that less of the sun’s energy goes into evaporation and more goes into warming the Earth’s surface. This produces favourable conditions for heatwaves.
The study shows that the majority of CDHEs globally start out as a drought.
In recent years, there has been increasing focus on these events due to the devastating impact they have on agriculture, ecosystems and public health.
In Russia in the summer of 2010, a compound drought-heatwave event – and the associated wildfires – caused the death of nearly 55,000 people, the study notes.
The record-breaking Pacific north-west “heat dome” in 2021 triggered extreme drought conditions that caused “significant declines” in wheat yields, as well as in barley, canola and fruit production in British Columbia and Alberta, Canada, says the study.
Increasing events
To assess how CDHEs are changing, the researchers use daily reanalysis data to identify droughts and heatwaves events. (Reanalysis data combines past observations with climate models to create a historical climate record.) Then, using an algorithm, they analyse how these events overlap in both time and space.
The study covers the period from 1980 to 2023 and the world’s land surface, excluding polar regions where CDHEs are rare.
The research finds that the area of land affected by CDHEs has “increased substantially” since the early 2000s.
Heatwave-led events have been the main contributor to this increase, the study says, with their spatial extent rising 110% between 1980-2001 and 2002-23, compared to a 59% increase for drought-led events.
The map below shows the global distribution of CDHEs over 1980-2023. The charts show the percentage of the land surface affected by a heatwave-led CDHE (red) or a drought-led CDHE (yellow) in a given year (left) and relative increase in each CDHE type (right).
The study finds that CDHEs have occurred most frequently in northern South America, the southern US, eastern Europe, central Africa and south Asia.
Threshold passed
The authors explain that the increase in heatwave-led CDHEs is related to rising global temperatures, but that this does not tell the whole story.
In the earlier 22-year period of 1980-2001, the study finds that the spatial extent of heatwave-led CDHEs rises by 1.6% per 1C of global temperature rise. For the more-recent period of 2022-23, this increases “nearly eightfold” to 13.1%.
The change suggests that the rapid increase in the heatwave-led CDHEs occurred after the global average temperature “surpasse[d] a certain temperature threshold”, the paper says.
This threshold is an absolute global average temperature of 14.3C, the authors estimate (based on an 11-year average), which the world passed around the year 2000.
Investigating the recent surge in heatwave-leading CDHEs further, the researchers find a “regime shift” in land-atmosphere dynamics “toward a persistently intensified state after the late 1990s”.
In other words, the way that drier soils drive higher surface temperatures, and vice versa, is becoming stronger, resulting in more heatwave-led compound events.
Daily data
The research has some advantages over other previous studies, Yeh says. For instance, the new work uses daily estimations of CDHEs, compared to monthly data used in past research. This is “important for capturing the detailed occurrence” of these events, says Yeh.
He adds that another advantage of their study is that it distinguishes the sequence of droughts and heatwaves, which allows them to “better understand the differences” in the characteristics of CDHEs.
Dr Meryem Tanarhte is a climate scientist at the University Hassan II in Morocco, and Dr Ruth Cerezo Mota is a climatologist and a researcher at the National Autonomous University of Mexico. Both scientists, who were not involved in the study, agree that the daily estimations give a clearer picture of how CDHEs are changing.
Cerezo-Mota adds that another major contribution of the study is its global focus. She tells Carbon Brief that in some regions, such as Mexico and Africa, there is a lack of studies on CDHEs:
“Not because the events do not occur, but perhaps because [these regions] do not have all the data or the expertise to do so.”
However, she notes that the reanalysis data used by the study does have limitations with how it represents rainfall in some parts of the world.
Compound impacts
The study notes that if CDHEs continue to intensify – particularly events where heatwaves are the precursors – they could drive declining crop productivity, increased wildfire frequency and severe public health crises.
These impacts could be “much more rapid and severe as global warming continues”, Yeh tells Carbon Brief.
Tanarhte notes that these events can be forecasted up to 10 days ahead in many regions. Furthermore, she says, the strongest impacts can be prevented “through preparedness and adaptation”, including through “water management for agriculture, heatwave mitigation measures and wildfire mitigation”.
The study recommends reassessing current risk management strategies for these compound events. It also suggests incorporating the sequences of drought and heatwaves into compound event analysis frameworks “to enhance climate risk management”.
Cerezo-Mota says that it is clear that the world needs to be prepared for the increased occurrence of these events. She tells Carbon Brief:
“These [risk assessments and strategies] need to be carried out at the local level to understand the complexities of each region.”
The post Heatwaves driving recent ‘surge’ in compound drought and heat extremes appeared first on Carbon Brief.
Heatwaves driving recent ‘surge’ in compound drought and heat extremes
Greenhouse Gases
DeBriefed 6 March 2026: Iran energy crisis | China climate plan | Bristol’s ‘pioneering’ wind turbine
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
Energy crisis
ENERGY SPIKE: US-Israeli attacks on Iran and subsequent counterattacks across the Middle East have sent energy prices “soaring”, according to Reuters. The newswire reported that the region “accounts for just under a third of global oil production and almost a fifth of gas”. The Guardian noted that shipping traffic through the strait of Hormuz, which normally ferries 20% of the world’s oil, “all but ground to a halt”. The Financial Times reported that attacks by Iran on Middle East energy facilities – notably in Qatar – triggered the “biggest rise in gas prices since Russia’s full-scale invasion of Ukraine”.
‘RISK’ AND ‘BENEFITS’: Bloomberg reported on increases in diesel prices in Europe and the US, speculating that rising fuel costs could be “a risk for president Donald Trump”. US gas producers are “poised to benefit from the big disruption in global supply”, according to CNBC. Indian government sources told the Economic Times that Russia is prepared to “fulfil India’s energy demands”. China Daily quoted experts who said “China’s energy security remains fundamentally unshaken”, thanks to “emergency stockpiles and a wide array of import channels”.
‘ESSENTIAL’ RENEWABLES: Energy analysts said governments should cut their fossil-fuel reliance by investing in renewables, “rather than just seeking non-Gulf oil and gas suppliers”, reported Climate Home News. This message was echoed by UK business secretary Peter Kyle, who said “doubling down on renewables” was “essential” amid “regional instability”, according to the Daily Telegraph.
China’s climate plan
PEAK COAL?: China has set out its next “five-year plan” at the annual “two sessions” meeting of the National People’s Congress, including its climate strategy out to 2030, according to the Hong Kong-based South China Morning Post. The plan called for China to cut its carbon emissions per unit of gross domestic product (GDP) by 17% from 2026 to 2030, which “may allow for continued increase in emissions given the rate of GDP growth”, reported Reuters. The newswire added that the plan also had targets to reach peak coal in the next five years and replace 30m tonnes per year of coal with renewables.
ACTIVE YET PRUDENT: Bloomberg described the new plan as “cautious”, stating that it “frustrat[es] hopes for tighter policy that would drive the nation to peak carbon emissions well before president Xi Jinping’s 2030 deadline”. Carbon Brief has just published an in-depth analysis of the plan. China Daily reported that the strategy “highlights measures to promote the climate targets of peaking carbon dioxide emissions before 2030”, which China said it would work towards “actively yet prudently”.
Around the world
- EU RULES: The European Commission has proposed new “made in Europe” rules to support domestic low-carbon industries, “against fierce competition from China”, reported Agence France-Presse. Carbon Brief examined what it means for climate efforts.
- RECORD HEAT: The US National Oceanic and Atmospheric Administration has said there is a 50-60% chance that the El Niño weather pattern could return this year, amplifying the effect of global warming and potentially driving temperatures to “record highs”, according to Euronews.
- FLAGSHIP FUND: The African Development Bank’s “flagship clean energy fund” plans to more than double its financing to $2.5bn for African renewables over the next two years, reported the Associated Press.
- NO WITHDRAWAL: Vanuatu has defied US efforts to force the Pacific-island nation to drop a UN draft resolution