The vast ice sheets that cover Greenland and Antarctica have the potential to trigger catastrophic sea level rise as the climate warms.
But the ice-sheet models that scientists use to project future changes underestimate how fast sea levels are rising now and how much they have risen in the past.
This suggests the models are missing important processes driving ice-sheet retreat.
New research suggests that melting at grounding zones – where the ice transitions from sitting on land to floating on water – could be the missing piece of the puzzle.
And it is potentially a big piece. For example, when one study on the Thwaites glacier in west Antarctica included these processes, its projections of ice-sheet loss more than doubled.
In this guest post, we unpack the latest research on grounding-zone mechanisms and why they suggest that current global projections of sea level rise may be substantially underestimated.
Ice sheets are shrinking faster than models project
Scientists use ice-sheet models to project how fast – and by how much – the Earth’s ice sheets will shrink as global temperatures rise.
These models, developed by scientists at universities and national research institutes, represent physical real-world processes using sets of equations. By solving these equations, scientists gain understanding how the physical system will respond to different scenarios. There are around 20 ice sheet models in use around the world today.
The models capture what we know about how ice sheets flow and deform. Projections using these models suggest that ice sheets will contribute 10s of centimetres to sea level rise by the end of the century.
However, it increasingly looks like these models underestimate the true sensitivity of ice sheets to climate change.
First, we can look at sea level rise from ice sheets over the past 20-25 years. Over this period, we have detailed satellite observations to compare to model predictions.
The figure below shows the spread in projections from models (blue shading) for Greenland’s contribution to sea level rise compared to the satellite data (blue line). This spread is generated by a range of factors, such as how different models describe ice flow, how fine of a resolution they use to represent the real system and the initial state used for model runs. Sea levels are presented relative to 2015, as this was chosen as a benchmark year.
It is clear that the majority of models underestimated the rate of Greenland melt.
Next, we can consider whether models have succeeded in reproducing ice sheet loss from historical warm periods.
For example, proxy records, such as reconstructions of previous shorelines, indicate that during the Pliocene (5.3-2.6m years ago) sea levels were between six and 40 metres higher than today.
This extreme sea level rise would have required a substantial contribution from the world’s ice sheets. However, models are largely unable to reproduce these values, with almost all failing to even attain lower bounds.
Finally, from a different standpoint, we can ask how much climate forcing is required to reproduce current ice sheet retreat rates. Models of the west Antarctic ice sheet typically require ice shelves, which restrain the flow of grounded ice, to be melted very rapidly in order to reproduce current rates. However, recent observations of melting in these regions suggest it is in fact far smaller than models require.
Together, this evidence suggests that ice-sheet models are not entirely capturing what is going on: they should be more sensitive to changes in the climate than they currently are. Two recent papers have suggested that what happens in so-called “grounding zones” could be the missing piece of this puzzle.
Grounding zones
Ice sheets are not static; they spread out like a very thick liquid. The majority of ice in the world’s ice sheets sits on top of land, above sea level. As the ice spreads out and thins, it begins to float, transitioning into a floating ice shelf.
The boundary between ice on land and floating ice shelves – shown in the figure below – is known as the “grounding zone”.
The classical picture of grounding zones is as distinct boundaries between floating and grounded ice. It was previously thought that they migrate on annual-to-decadal timescales as ice sheets retreat and advance, and that little melting took place there.
Recently, however, a different picture has emerged, where grounding zones are actually highly dynamic regions.
In particular, two independent mechanisms – called “tidal intrusion” and “porous intrusion” – are thought to be taking place in grounding zones.
Both of these mechanisms are thought to allow relatively warm ocean water to rush under ice sheets, enabling vigorous melting to take place there.
Tidal intrusion
Antarctica has one of the largest tidal ranges in the world, with sea levels fluctuating by up to seven metres each day.
As the tide rises, water pressure under ice shelves increases, lifting the ice and creating a new cavity in the grounding zone. As a result, this newly formed cavity, which can be up to 15km long, is rapidly filled with ocean water.
When the tide falls, the reverse happens: the ice settles back down and water flushes out of the cavity. This cyclic process – named “tidal intrusion” – occurs up to twice per day, driving rapid flows of warm ocean water into and out of the grounding zone, where it can melt the ice from below.
The tidal opening and closing of grounding zone cavities can be observed using surface elevation and radar measurements from satellites. However, these observations – particularly in fast-changing regions – have typically been limited by how frequently the satellites pass over the same spot, which varies between weeks and months.
Recent research, published last month, has used a unique set of sub-daily satellite observations from the ICEYE constellation to show that tidal intrusion is widespread beneath Thwaites glacier.
This research indicates that warm water is able to intrude up to 6km beneath the Thwaites ice shelf during each high tide, where it could accelerate ice melt from below.
Thwaites – nicknamed the “doomsday glacier” – holds enough ice to raise global sea levels by up to 65cm and has long concerned scientists because of its rapid present retreat, potential for runaway ice loss and possibly important role as a keystone in the west Antarctic ice sheet.
This new research suggests that Thwaites may be even more vulnerable than previously thought.
Porous intrusion
Beneath ice sheets, there are networks of channels and tunnels, as well as porous sediments, through which meltwater from the bottom of ice sheets flows.
In grounding zones, this cold, fresh meltwater meets relatively warm, salty ocean water. The ocean water is denser, allowing it to intrude beneath the meltwater and into the grounding zone. This process is called “porous intrusion”.
Recent modelling has suggested that ocean water can intrude kilometres beneath ice sheets via this mechanism.
However, previous research has not considered how the geometry of these regions change in response to melting. In our new study, published in Nature Geoscience, we show that, when this effect is considered, the porous intrusion mechanism can be far more powerful.
In particular, we show that these systems display a tipping-point like behaviour, in which a small change in ocean temperatures can lead to a dramatic change in the distance that warm water is able to intrude through grounding zones.
We also show that the porous intrusion mechanism is not only applicable to ice shelves exposed to warm water or with high melt rates at a glacier’s base, such as Thwaites, but can also influence cold water ice shelves.
The susceptibility of a glacier to porous intrusion is linked to the slope of the seabed and how quickly melted ice is replaced. This is illustrated in the figure below; glaciers in the purple-shaded area are the most susceptible.
In fact, Thwaites appears to be relatively unsusceptible to porous intrusion – despite being highly vulnerable to tidal intrusion – because it flows very rapidly and ice is replaced very quickly.
Other ice shelves, such as the Ross and Ronne ice shelves, which sit in relatively cold water may, surprisingly, be amongst the most susceptible ice shelves.
Are grounding zones the missing piece?
The majority of ice-sheet models still represent grounding zones as a distinct transition between grounded and floating ice, with no melting there from either tidal or porous intrusion.
The only models able to attain anything resembling sea level rise values during past warm periods have included a grounding-zone melting mechanism or a similar mechanism that boosts their sensitivity to climate change.
These same models have also received much attention for their pessimistic future sea level rise projections. Capturing the past requires an increased sensitivity to climatic change, meaning that they predict much higher sea level rise in future.
So, grounding zone intrusion and melting might be the missing piece to reconcile observed and modelled sea level rise.
While scientists have yet to run model simulations with grounding-zone melting included for the whole of Antarctica, studies focusing on specific regions of the continent’s ice sheets project up to twice as much sea level rise.
Current global projections of sea level rise also do not include grounding-zone melting. This means that these projections – including those that inform the reports of the Intergovernmental Panel on Climate Change (IPCC) – may be substantial underestimates.
Ice-sheet models have “known unknowns” – things we know that we do not know perfectly, but can account for imperfect knowledge of. However, they also have “unknown unknowns” – things that we do not even know are happening and therefore cannot quantify the full effects of.
Although grounding-zone melting might result in higher sea level than we expected, at least we now know that it is happening and can begin to incorporate it into our models. The devil we know is better than the devil we don’t.
The post Guest post: The critical role of ‘grounding zones’ in the retreat of Earth’s ice sheets appeared first on Carbon Brief.
Guest post: The critical role of ‘grounding zones’ in the retreat of Earth’s ice sheets
Greenhouse Gases
Analysis: Constituency of Reform’s climate-sceptic Richard Tice gets £55m flood funding
The Lincolnshire constituency held by Richard Tice, the climate-sceptic deputy leader of the hard-right Reform party, has been pledged at least £55m in government funding for flood defences since 2024.
This investment in Boston and Skegness is the second-largest sum for a single constituency from a £1.4bn flood-defence fund for England, Carbon Brief analysis shows.
Flooding is becoming more likely and more extreme in the UK due to climate change.
Yet, for years, governments have failed to spend enough on flood defences to protect people, properties and infrastructure.
The £1.4bn fund is part of the current Labour government’s wider pledge to invest a “record” £7.9bn over a decade on protecting hundreds of thousands of homes and businesses from flooding.
As MP for one of England’s most flood-prone regions, Tice has called for more investment in flood defences, stating that “we cannot afford to ‘surrender the fens’ to the sea”.
He is also one of Reform’s most vocal opponents of climate action and what he calls “net stupid zero”. He denies the scientific consensus on climate change and has claimed, falsely and without evidence, that scientists are “lying”.
Flood defences
Last year, the government said it would invest £2.65bn on flood and coastal erosion risk management (FCERM) schemes in England between April 2024 and March 2026.
This money was intended to protect 66,500 properties from flooding. It is part of a decade-long Labour government plan to spend more than £7.9bn on flood defences.
There has been a consistent shortfall in maintaining England’s flood defences, with the Environment Agency expecting to protect fewer properties by 2027 than it had initially planned.
The Climate Change Committee (CCC) has attributed this to rising costs, backlogs from previous governments and a lack of capacity. It also points to the strain from “more frequent and severe” weather events, such as storms in recent years that have been amplified by climate change.
However, the CCC also said last year that, if the 2024-26 spending programme is delivered, it would be “slightly closer to the track” of the Environment Agency targets out to 2027.
The government has released constituency-level data on which schemes in England it plans to fund, covering £1.4bn of the 2024-26 investment. The other half of the FCERM spending covers additional measures, from repairing existing defences to advising local authorities.
The map below shows the distribution of spending on FCERM schemes in England over the past two years, highlighting the constituency of Richard Tice.
By far the largest sum of money – £85.6m in total – has been committed to a tidal barrier and various other defences in the Somerset constituency of Bridgwater, the seat of Conservative MP Ashley Fox.
Over the first months of 2026, the south-west region has faced significant flooding and Fox has called for more support from the government, citing “climate patterns shifting and rainfall intensifying”.
He has also backed his party’s position that “the 2050 net-zero target is impossible” and called for more fossil-fuel extraction in the North Sea.
Tice’s east-coast constituency of Boston and Skegness, which is highly vulnerable to flooding from both rivers and the sea, is set to receive £55m. Among the supported projects are beach defences from Saltfleet to Gibraltar Point and upgrades to pumping stations.
Overall, Boston and Skegness has the second-largest portion of flood-defence funding, as the chart below shows. Constituencies with Conservative and Liberal Democrat MPs occupied the other top positions.
Overall, despite Labour MPs occupying 347 out of England’s 543 constituencies – nearly two-thirds of the total – more than half of the flood-defence funding was distributed to constituencies with non-Labour MPs. This reflects the flood risk in coastal and rural areas that are not traditional Labour strongholds.
Reform funding
While Reform has just eight MPs, representing 1% of the population, its constituencies have been assigned 4% of the flood-defence funding for England.
Nearly all of this money was for Tice’s constituency, although party leader Nigel Farage’s coastal Clacton seat in Kent received £2m.
Reform UK is committed to “scrapping net-zero” and its leadership has expressed firmly climate-sceptic views.
Much has been made of the disconnect between the party’s climate policies and the threat climate change poses to its voters. Various analyses have shown the flood risk in Reform-dominated areas, particularly Lincolnshire.
Tice has rejected climate science, advocated for fossil-fuel production and criticised Environment Agency flood-defence activities. Yet, he has also called for more investment in flood defences, stating that “we cannot afford to ‘surrender the fens’ to the sea”.
This may reflect Tice’s broader approach to climate change. In a 2024 interview with LBC, he said:
“Where you’ve got concerns about sea level defences and sea level rise, guess what? A bit of steel, a bit of cement, some aggregate…and you build some concrete sea level defences. That’s how you deal with rising sea levels.”
While climate adaptation is viewed as vital in a warming world, there are limits on how much societies can adapt and adaptation costs will continue to increase as emissions rise.
The post Analysis: Constituency of Reform’s climate-sceptic Richard Tice gets £55m flood funding appeared first on Carbon Brief.
Analysis: Constituency of Reform’s climate-sceptic Richard Tice gets £55m flood funding
Greenhouse Gases
Cropped 25 February 2026: Food inflation strikes | El Niño looms | Biodiversity talks stagnate
We handpick and explain the most important stories at the intersection of climate, land, food and nature over the past fortnight.
This is an online version of Carbon Brief’s fortnightly Cropped email newsletter.
Subscribe for free here.
Key developments
Food inflation on the rise
DELUGE STRIKES FOOD: Extreme rainfall and flooding across the Mediterranean and north Africa has “battered the winter growing regions that feed Europe…threatening food price rises”, reported the Financial Times. Western France has “endured more than 36 days of continuous rain”, while farmers’ associations in Spain’s Andalusia estimate that “20% of all production has been lost”, it added. Policy expert David Barmes told the paper that the “latest storms were part of a wider pattern of climate shocks feeding into food price inflation”.
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NO BEEF: The UK’s beef farmers, meanwhile, “face a double blow” from climate change as “relentless rain forces them to keep cows indoors”, while last summer’s drought hit hay supplies, said another Financial Times article. At the same time, indoor growers in south England described a 60% increase in electricity standing charges as a “ticking timebomb” that could “force them to raise their prices or stop production, which will further fuel food price inflation”, wrote the Guardian.
‘TINDERBOX’ AND TARIFFS: A study, covered by the Guardian, warned that major extreme weather and other “shocks” could “spark social unrest and even food riots in the UK”. Experts cited “chronic” vulnerabilities, including climate change, low incomes, poor farming policy and “fragile” supply chains that have made the UK’s food system a “tinderbox”. A New York Times explainer noted that while trade could once guard against food supply shocks, barriers such as tariffs and export controls – which are being “increasingly” used by politicians – “can shut off that safety valve”.
El Niño looms
NEW ENSO INDEX: Researchers have developed a new index for calculating El Niño, the large-scale climate pattern that influences global weather and causes “billions in damages by bringing floods to some regions and drought to others”, reported CNN. It added that climate change is making it more difficult for scientists to observe El Niño patterns by warming up the entire ocean. The outlet said that with the new metric, “scientists can now see it earlier and our long-range weather forecasts will be improved for it.”
WARMING WARNING: Meanwhile, the US Climate Prediction Center announced that there is a 60% chance of the current La Niña conditions shifting towards a neutral state over the next few months, with an El Niño likely to follow in late spring, according to Reuters. The Vibes, a Malaysian news outlet, quoted a climate scientist saying: “If the El Niño does materialise, it could possibly push 2026 or 2027 as the warmest year on record, replacing 2024.”
CROP IMPACTS: Reuters noted that neutral conditions lead to “more stable weather and potentially better crop yields”. However, the newswire added, an El Niño state would mean “worsening drought conditions and issues for the next growing season” to Australia. El Niño also “typically brings a poor south-west monsoon to India, including droughts”, reported the Hindu’s Business Line. A 2024 guest post for Carbon Brief explained that El Niño is linked to crop failure in south-eastern Africa and south-east Asia.
News and views
- DAM-AG-ES: Several South Korean farmers filed a lawsuit against the country’s state-owned utility company, “seek[ing] financial compensation for climate-related agricultural damages”, reported United Press International. Meanwhile, a national climate change assessment for the Philippines found that the country “lost up to $219bn in agricultural damages from typhoons, floods and droughts” over 2000-10, according to Eco-Business.
- SCORCHED GRASS: South Africa’s Western Cape province is experiencing “one of the worst droughts in living memory”, which is “scorching grass and killing livestock”, said Reuters. The newswire wrote: “In 2015, a drought almost dried up the taps in the city; farmers say this one has been even more brutal than a decade ago.”
- NOUVELLE VEG: New guidelines published under France’s national food, nutrition and climate strategy “urged” citizens to “limit” their meat consumption, reported Euronews. The delayed strategy comes a month after the US government “upended decades of recommendations by touting consumption of red meat and full-fat dairy”, it noted.
- COURTING DISASTER: India’s top green court accepted the findings of a committee that “found no flaws” in greenlighting the Great Nicobar project that “will lead to the felling of a million trees” and translocating corals, reported Mongabay. The court found “no good ground to interfere”, despite “threats to a globally unique biodiversity hotspot” and Indigenous tribes at risk of displacement by the project, wrote Frontline.
- FISH FALLING: A new study found that fish biomass is “falling by 7.2% from as little as 0.1C of warming per decade”, noted the Guardian. While experts also pointed to the role of overfishing in marine life loss, marine ecologist and study lead author Dr Shahar Chaikin told the outlet: “Our research proves exactly what that biological cost [of warming] looks like underwater.”
- TOO HOT FOR COFFEE: According to new analysis by Climate Central, countries where coffee beans are grown “are becoming too hot to cultivate them”, reported the Guardian. The world’s top five coffee-growing countries faced “57 additional days of coffee-harming heat” annually because of climate change, it added.
Spotlight
Nature talks inch forward
This week, Carbon Brief covers the latest round of negotiations under the UN Convention on Biological Diversity (CBD), which occurred in Rome over 16-19 February.
The penultimate set of biodiversity negotiations before October’s Conference of the Parties ended in Rome last week, leaving plenty of unfinished business.
The CBD’s subsidiary body on implementation (SBI) met in the Italian capital for four days to discuss a range of issues, including biodiversity finance and reviewing progress towards the nature targets agreed under the Kunming-Montreal Global Biodiversity Framework (GBF).
However, many of the major sticking points – particularly around finance – will have to wait until later this summer, leaving some observers worried about the capacity for delegates to get through a packed agenda at COP17.
The SBI, along with the subsidiary body on scientific, technical and technological advice (SBSTTA) will both meet in Nairobi, Kenya, later this summer for a final round of talks before COP17 kicks off in Yerevan, Armenia, on 19 October.
Money talks
Finance for nature has long been a sticking point at negotiations under the CBD.
Discussions on a new fund for biodiversity derailed biodiversity talks in Cali, Colombia, in autumn 2024, requiring resumed talks a few months later.
Despite this, finance was barely on the agenda at the SBI meetings in Rome. Delegates discussed three studies on the relationship between debt sustainability and implementation of nature plans, but the more substantive talks are set to take place at the next SBI meeting in Nairobi.
Several parties “highlighted concerns with the imbalance of work” on finance between these SBI talks and the next ones, reported Earth Negotiations Bulletin (ENB).
Lim Li Ching, senior researcher at Third World Network, noted that tensions around finance permeated every aspect of the talks. She told Carbon Brief:
“If you’re talking about the gender plan of action – if there’s little or no financial resources provided to actually put it into practice and implement it, then it’s [just] paper, right? Same with the reporting requirements and obligations.”
Monitoring and reporting
Closely linked to the issue of finance is the obligations of parties to report on their progress towards the goals and targets of the GBF.
Parties do so through the submission of national reports.
Several parties at the talks pointed to a lack of timely funding for driving delays in their reporting, according to ENB.
A note released by the CBD Secretariat in December said that no parties had submitted their national reports yet; by the time of the SBI meetings, only the EU had. It further noted that just 58 parties had submitted their national biodiversity plans, which were initially meant to be published by COP16, in October 2024.
Linda Krueger, director of biodiversity and infrastructure policy at the environmental not-for-profit Nature Conservancy, told Carbon Brief that despite the sparse submissions, parties are “very focused on the national report preparation”. She added:
“Everybody wants to be able to show that we’re on the path and that there still is a pathway to getting to 2030 that’s positive and largely in the right direction.”
Watch, read, listen
NET LOSS: Nigeria’s marine life is being “threatened” by “ghost gear” – nets and other fishing equipment discarded in the ocean – said Dialogue Earth.
COMEBACK CAUSALITY: A Vox long-read looked at whether Costa Rica’s “payments for ecosystem services” programme helped the country turn a corner on deforestation.
HOMEGROWN GOALS: A Straits Times podcast discussed whether import-dependent Singapore can afford to shelve its goal to produce 30% of its food locally by 2030.
‘RUSTING’ RIVERS: The Financial Times took a closer look at a “strange new force blighting the [Arctic] landscape”: rivers turning rust-orange due to global warming.
New science
- Lakes in the Congo Basin’s peatlands are releasing carbon that is thousands of years old | Nature Geoscience
- Natural non-forest ecosystems – such as grasslands and marshlands – were converted for agriculture at four times the rate of land with tree cover between 2005 and 2020 | Proceedings of the National Academy of Sciences
- Around one-quarter of global tree-cover loss over 2001-22 was driven by cropland expansion, pastures and forest plantations for commodity production | Nature Food
In the diary
- 2-6 March: UN Food and Agriculture Organization regional conference for Latin America and Caribbean | Brasília
- 5 March: Nepal general elections
- 9-20 March: First part of the thirty-first session of the International Seabed Authority (ISA) | Kingston, Jamaica
Cropped is researched and written by Dr Giuliana Viglione, Aruna Chandrasekhar, Daisy Dunne, Orla Dwyer and Yanine Quiroz.
Please send tips and feedback to cropped@carbonbrief.org
The post Cropped 25 February 2026: Food inflation strikes | El Niño looms | Biodiversity talks stagnate appeared first on Carbon Brief.
Cropped 25 February 2026: Food inflation strikes | El Niño looms | Biodiversity talks stagnate
Rising temperatures across France since the mid-1970s is putting Tour de France competitors at “high risk”, according to new research.
The study, published in Scientific Reports, uses 50 years of climate data to calculate the potential heat stress that athletes have been exposed to across a dozen different locations during the world-famous cycling race.
The researchers find that both the severity and frequency of high-heat-stress events have increased across France over recent decades.
But, despite record-setting heatwaves in France, the heat-stress threshold for safe competition has rarely been breached in any particular city on the day the Tour passed through.
(This threshold was set out by cycling’s international governing body in 2024.)
However, the researchers add it is “only a question of time” until this occurs as average temperatures in France continue to rise.
The lead author of the study tells Carbon Brief that, while the race organisers have been fortunate to avoid major heat stress on race days so far, it will be “harder and harder to be lucky” as extreme heat becomes more common.
‘Iconic’
The Tour de France is one of the world’s most storied cycling races and the oldest of Europe’s three major multi-week cycling competitions, or Grand Tours.
Riders cover around 3,500 kilometres (km) of distance and gain up to nearly 55km of altitude over 21 stages, with only two or three rest days throughout the gruelling race.
The researchers selected the Tour de France because it is the “iconic bike race. It is the bike race of bike races,” says Dr Ivana Cvijanovic, a climate scientist at the French National Research Institute for Sustainable Development, who led the new work.
Heat has become a growing problem for the competition in recent years.
In 2022, Alexis Vuillermoz, a French competitor, collapsed at the finish line of the Tour’s ninth stage, leaving in an ambulance and subsequently pulling out of the race entirely.
Two years later, British cyclist Sir Mark Cavendish vomited on his bike during the first stage of the race after struggling with the 36C heat.
The Tour also makes a good case study because it is almost entirely held during the month of July and, while the route itself changes, there are many cities and stages that are repeated from year to year, Cvijanovic adds.
‘Have to be lucky’
The study focuses on the 50-year span between 1974 and 2023.
The researchers select six locations across the country that have commonly hosted the Tour, from the mountain pass of Col du Tourmalet, in the French Pyrenees, to the city of Paris – where the race finishes, along the Champs-Élysées.
These sites represent a broad range of climatic zones: Alpe d’ Huez, Bourdeaux, Col du Tourmalet, Nîmes, Paris and Toulouse.
For each location, they use meteorological reanalysis data from ERA5 and radiant temperature data from ERA5-HEAT to calculate the “wet-bulb globe temperature” (WBGT) for multiple times of day across the month of July each year.
WBGT is a heat-stress index that takes into account temperature, humidity, wind speed and direct sunlight.
Although there is “no exact scientific consensus” on the best heat-stress index to use, WBGT is “one of the rare indicators that has been originally developed based on the actual human response to heat”, Cvijanovic explains.
It is also the one that the International Cycling Union (UCI) – the world governing body for sport cycling – uses to assess risk. A WBGT of 28C or higher is classified as “high risk” by the group.
WBGT is the “gold standard” for assessing heat stress, says Dr Jessica Murfree, director of the ACCESS Research Laboratory and assistant professor at the University of North Carolina at Chapel Hill.
Murfree, who was not involved in the new study, adds that the researchers are “doing the right things by conducting their science in alignment with the business practices that are already happening”.
The researchers find that across the 50-year time period, WBGT has been increasing across the entire country – albeit, at different rates. In the north-west of the country, WBGT has increased at an average rate of 0.1C per decade, while in the southern and eastern parts of the country, it has increased by more than 0.5C per decade.
The maps below show the maximum July WBGT for each decade of the analysis (rows) and for hourly increments of the late afternoon (columns). Lower temperatures are shown in lighter greens and yellows, while higher temperatures are shown in darker reds and purples.
Six Tour de France locations analysed in the study are shown as triangles on the maps (clockwise from top): Paris, Alpe d’ Huez, Nîmes, Toulouse, Col du Tourmalet and Bordeaux.
The maps show that the maximum WBGT temperature in the afternoon has surpassed 28C over almost the entire country in the last decade. The notable exceptions to this are the mountainous regions of the Alps and the Pyrenees.
The researchers also find that most of the country has crossed the 28C WBGT threshold – which they describe as “dangerous heat levels” – on at least one July day over the past decade. However, by looking at the WBGT on the day the Tour passed through any of these six locations, they find that the threshold has rarely been breached during the race itself.
For example, the research notes that, since 1974, Paris has seen a WBGT of 28C five times at 3pm in July – but that these events have “so far” not coincided with the cycling race.
The study states that it is “fortunate” that the Tour has so far avoided the worst of the heat-stress.
Cvijanovic says the organisers and competitors have been “lucky” to date. She adds:
“It has worked really well for them so far. But as the frequency of these [extreme heat] events is increasing, it will be harder and harder to be lucky.”
Dr Madeleine Orr, an assistant professor of sport ecology at the University of Toronto who was not involved in the study, tells Carbon Brief that the paper was “really well done”, noting that its “methods are good [and its] approach was sound”. She adds:
“[The Tour has] had athletes complain about [the heat]. They’ve had athletes collapse – and still those aren’t the worst conditions. I think that that says a lot about what we consider safe. They’ve still been lucky to not see what unsafe looks like, despite [the heat] having already had impacts.”
Heat safety protocols
In 2024, the UCI set out its first-ever high temperature protocol – a set of guidelines for race organisers to assess athletes’ risk of heat stress.
The assessment places the potential risk into one of five categories based on the WBGT, ranging from very low to high risk.
The protocol then sets out suggested actions to take in the event of extreme heat, ranging from having athletes complete their warm-ups using ice vests and cold towels to increasing the number of support vehicles providing water and ice.
If the WBGT climbs above the 28C mark, the protocol suggests that organisers modify the start time of the stage, adapt the course to remove particularly hazardous sections – or even cancel the race entirely.
However, Orr notes that many other parts of the race, such as spectator comfort and equipment functioning, may have lower temperatures thresholds that are not accounted for in the protocol, but should also be considered.
Murfree points out that the study’s findings – and the heat protocol itself – are “really focused on adaptation, rather than mitigation”. While this is “to be expected”, she tells Carbon Brief:
“Moving to earlier start times or adjusting the route specifically to avoid these locations that score higher in heat stress doesn’t stop the heat stress. These aren’t climate preventative measures. That, I think, would be a much more difficult conversation to have in the research because of the Tour de France’s intimate relationship with fossil-fuel companies.”
The post Dangerous heat for Tour de France riders only a ‘question of time’ appeared first on Carbon Brief.
Dangerous heat for Tour de France riders only a ‘question of time’
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