In 2018, when the United States, Canada and Mexico bid to host the World Cup, their pitch included a climate promise: the bid committee said it would strive to deliver a carbon-neutral event.
The bid’s environmental assessment, a 97-page report by the consultancy Arup, estimated a footprint of 3.7 million tonnes of carbon dioxide equivalent (CO₂e) across 80 matches.
Eight years later, the tournament – which ended on Sunday with Spain beating Argentina 1-0 in the final – was far larger than the bid described.
It had swelled to 104 matches. Nearly seven million spectators attended – almost double the 1994 record when the US last hosted.
Throughout the tournament and at the time of writing, FIFA has published no updated emissions estimate.
We decided to build a computer model to analyse the event’s carbon footprint.
FIFA’s 2022 promise that did not deliver
Ahead of the Qatar World Cup in 2022, FIFA declared the event would be “fully carbon-neutral”.
But in June 2023, the Swiss Commission for Fairness – the advertising watchdog in FIFA’s home country – found the governing body had neither measured the emissions by accepted methods nor shown how it had offset them.
Carbon Market Watch also claimed stadium construction for the Qatar tournament counted at a fraction of a fair figure.
For 2026, FIFA moved to safer ground. Its only pledge was to “reduce emissions by 50% by 2030 and reach net zero by 2040”.
While the 2026 bid committee said it would aim for a carbon-neutral World Cup, FIFA had no actual climate target for the event.
A typical fan’s carbon footprint
Let’s imagine one England supporter who went the distance to support their team at the 2026 tournament.
Their journey started in Dallas, then moved to Boston, New Jersey, Atlanta, Mexico City, Miami, Atlanta, then back to Miami for a third-place playoff win against France.
That’s about 10,126 kilometres in the air – without counting return travel from the United Kingdom.
We priced those internal flights at about 1.6 tonnes of CO₂e, or 4.3 tonnes including the return from the UK.
Now, consider how many people travelled around North America during the World Cup. This is why almost nine in ten tonnes of this tournament’s carbon footprint came from travel.
Scientific disagreement
From a year before kickoff, two outside forecasts feared the event would far exceed the bid’s emissions estimate.
Scientists for Global Responsibility (SGR), an independent UK-based organisation that promotes ethical science, design and technology, predicted 9 million tonnes of CO₂e.
Greenly, a global carbon consultancy, predicted 7.8 million tonnes of CO₂e. Both these predictions were made before the tournament, and both assumed fans would pour in from overseas: up to 87.8% travelling internationally.
For SGR to be correct, every fan ticket at the World Cup would need to carry a bigger carbon cost than a ticket in Qatar – a tournament that built seven stadiums and flew almost everyone in.
This World Cup required no new stadiums.
To work out who would be correct, we used a computer simulation based on what happened on the ground.
Our model analysed attendances, match schedules and the journeys of all 48 squads.
It returned not a verdict but a contradiction. Despite the growth of the event, our model predicted an overall emissions of about 3.2 million tonnes of CO₂e – below the bid estimate and much lower than the green groups’ estimates.
Those pre-tournament forecasts predicted it could be the dirtiest sporting event ever staged.
But measured per spectator at the event, the World Cup may in fact have been surprisingly clean.
Why the emissions weren’t massive
All 16 stadiums for this World Cup already existed, which is why even SGR scored construction emissions at zero. The schedule helped too, as 14 of the 96 team journeys between group matches covered no major distance.
Using the aviation warming method FIFA used for Qatar, our model puts tournament emissions at almost 3.2 million tonnes of CO₂e.
In comparison, Qatar 2022 generated 3.8 million tonnes, while Russia 2018 reported 2.2 million tonnes.
The 2026 event drew almost double Qatar’s crowds but their individual emissions were lower.
Our model shows the carbon emissions of each Qatar ticket was equal to driving a petrol car about 6,500 kilometres. The figure for spectators at the 2026 tournament was about 2,900km (calculated using greenhouse gas reporting conversion factors).
Why the predictions disagree
The gap between Arup’s estimate of 3.7 million tonnes of CO₂e and SGR’s of 9 million tonnes is not a measurement dispute.
Two choices, made before counting began, decided it: how aviation’s wider warming is weighted and how many supporters are assumed to have crossed oceans.
Flights leave more than carbon dioxide behind. They also leave contrails and nitrogen oxides, which drive the majority of aviation’s warming. These white trails can trap heat and their true climate impact is hard to calculate.
If we only considered CO₂ emissions, our estimate would be reduced from 3.2 million tonnes to almost 1.9 million.
The second choice is how many fans crossed an ocean.
FIFA has published only a list of its top ticket-buying countries. Reading this data, our model estimated 42% of fans who attended the event travelled internationally.
Our highest total estimated emission showed 4.8 million tonnes of CO₂e on that basis.
This single unknown factor is the key to a final number.
The verdict arrives in August
The decisive evidence is spectator data, which US, Canada and Mexico border agencies will release from August onward.
If it shows a mostly North American crowd, our estimate stands.
If it shows mass long-haul travel, the total climbs toward SGR’s warning – the most polluting event in sporting history.
That is why August is important. It is when the argument moves from modelling to proof.
