Factcheck: No, Europe’s heatwaves are not being ‘caused’ by declining air pollution

This summer has seen Europe suffer through a series of record-breaking heatwaves. Amid widespread media coverage of the number of deaths and the influence of climate change, the UK’s Daily Telegraph reported on new research with the incorrect headline: “Heatwaves caused .” The article was shared on social media – deputy leader of the hard-right, climate-sceptic Reform UK party – along with a number of prominent rightwing commentators. Tice claimed that “net stupid zero is contributing to rising temperatures, not helping”, adding that “we have been gaslit and lied to”. GB News followed up with its own article, incorrectly headlined: “Britain’s scorching heatwaves caused , researchers find.” Scientists tell Carbon Brief that the framing of heatwaves being “caused” “wrong”. While a drop in pollution has reduced the cooling impact it has had in the past, the scientists say, Europe’s summer heatwaves are primarily becoming more extreme “as a result of greenhouse-gas-induced warming”. Another scientist adds that “any attempt” to link this research to net-zero policies is “simply wrong”. This is largely because they absorb or reflect incoming sunlight and influence the formation and brightness of clouds.  To understand how the climate of Europe – or any region – is changing, scientists need to take into account a whole range of factors, says Prof Bjørn Samset, a research professor at Norway’s Center for International Climate Research (CICERO), who was not involved in the work. This includes “greenhouse gases, aerosols, land-use change, natural variability and how they all interact”, he says, adding: “The effects of air pollution on circulation, which is the topic here, has long been difficult to pin down.” As European countries improved their air quality through the second half of the 20th century, the cooling effect of aerosols has gradually been removed. This can boost heatwaves in two ways – directly, , indirectly, . Using hundreds of simulations from nine climate models, the new study finds that a decline in aerosols is resulting in more frequent “quasi-stationary Rossby waves”.  Rossby waves are huge meanders in the jet stream. Occasionally, they become slow-moving – or “quasi-stationary” – which allows weather systems to get stuck over one region, leading to prolonged heatwaves. These circulation changes have contributed to Europe’s rapidly warming summers. However, while Europe’s heatwaves are being influenced , it is “wrong” to say they are being “caused” by them, says Prof Erich Fischer, a climate scientist at ETH Zurich. Headline in the Daily Telegraph, .