The 2026 World Cup is the “biggest” in history: 48 teams, 16 cities, 104 matches stretched from Vancouver to Mexico City between 11 June and the final in New York on 19 July. The demand is huge: FIFA logged more than 500 million ticket requests in the random-selection phase alone and has now sold over 6 million tickets . So how does this split out by climate impact (both the negatives and positives)? Slice 1: the heat is no longer just weather A 2014 study that found measurable performance declines above 28°C, Climate Central estimates that warming has raised the likelihood of performance-impairing heat in 97 of the tournament’s 104 matches: and that 49 of them carry at least a 50% chance of those conditions. The single worst case is the 26 June meeting of Uruguay and Spain in Guadalajara, where a 70% chance of performance-sapping heat is some 37 percentage points higher than it would have been without climate change. Host cities now run about 0.7°C warmer than at the last US World Cup in 1994, and Climate Central finds that fossil-fuel pollution accounts for roughly 49% of extremely hot June–July days at host stadiums since 1970. What’s the impact on the actual football? The research is genuinely mixed: total running distance and high-intensity output tend to fall, yet peak sprint speed can rise by around 4% and successful passes and crosses by 8–9% in hot conditions, as players ration effort and slow the tempo. One striking finding links anomalously high temperatures to the frequency of penalty shootouts in the first knockout round (a correlation of r = 0.82). Heat, in other words, is quietly becoming a tactical input: something coaches rotate, substitute and game-plan around. By the stricter wet-bulb measure that combines heat, humidity and sun, World Weather Attribution expects around 26 matches in serious heat stress (nine of them in uncooled stadiums) versus roughly 21 (and six uncooled) had 1994’s climate held. And then there is everyone who isn’t a 23-year-old athlete! Of the matches expected in punishing conditions, about 17 are in stadiums with cooling : but cooling has its own history of failure (players at Qatar 2022 reported feeling ill and blamed the air conditioning), and scientists have called FIFA’s three-minute hydration breaks too short to matter, with 21 of them urging at least double . The quieter risk sits in the stands: older fans, hours in the sun, underlying heart conditions. Kansas City’s host-city medical lead has noted that hot days and early kick-offs have historically meant more spectators needing treatment. With matches now averaging around 63,000 fans , the most vulnerable person in the stadium may be the one in the seat, not on the pitch. Slice 2: leveraging existing stadium infrastructure, but lots of travel time! Unlike Qatar, which built seven stadiums from scratch, 2026 uses existing venues: and that genuinely works on its own terms. By Greenly’s accounting , infrastructure makes up just 3% of this tournament’s footprint, against roughly 24.6% for Qatar. If construction were the whole story, this would be the responsible World Cup. The same analysis puts spectator travel at around 87% of the total: because the format that avoided new concrete also guarantees a continent’s worth of flying. The average international fan now faces a round trip of roughly 19,400 km, against about 13,000 km for Qatar, where Europe, Africa and South Asia were all relatively short hops. From the UK that’s nearly 15,000 km return; from Saudi Arabia about 24,600 km; from India almost 28,000 km. And the load is concentrated: international fans are expected to be about 35% of attendance but roughly 74% of travel emissions . The decision that looks sustainable (don’t build) and the decision that drives the footprint (spread across three countries) are the same decision. A tournament can truthfully say it built almost nothing and still be on course to be the most carbon-intensive on record. So what is the carbon number? Nobody agrees Good Vision puts it at about 3.7 million tonnes of CO2e: only just above Qatar’s 3.63 million, and well above Brazil 2014 (2.72m) or Russia 2018 (2.16m). Greenly lands at 7.8 million , roughly the annual emissions of Sierra Leone. Scientists for Global Responsibility reach around nine million : equivalent, they reckon, to 6.5 million British cars driven for a year. That’s more than a twofold gap between serious analysts looking at the same tournament. The variance obviously comes from different assumptions: how much spectator travel do you attribute to the event versus trips people would have taken anyway? Which emission scopes count? How do you treat accommodation, offsets, and the baseline you compare against? climatecup.org frames the tournament as about 92% above the 2010–2022 average; others call it nearly double. And yet: the joy! Football is the most-watched thing humans do together: over five billion people will touch this tournament, and FIFA is on track to break 1994’s all-time attendance record of 3.5 million , with as many as 6.5 million through the turnstiles by 19 July. That is the uncomfortable centre of the whole carbon conversation. The emissions are large because the love is large: you don’t run these numbers on events nobody turns up to, and a World Cup nobody flew to wouldn’t be the World Cup. So the honest position isn’t to want less football, but rather for the fans to have 1) options to decarbonise their travel and, preferably, 2) for decarbonisation to be baked in to everything they do across travel and beyond. So this is the posture the newsletter wants to hold: clear-eyed about the heat, very aware of the travel impact that the World Cup instigates: and still, unembarrassedly, glad it exists! The question was never “should we love football less.” It’s whether a sport this big can grow up about its costs without losing what made five billion people fall for it in the first place. We’ll be watching. Probably from the sofa: which, it turns out, is also the lowest-carbon seat in the house!