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

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 by fall in pollution.”

The article was shared on social media by Richard Tice – deputy leader of the hard-right, climate-sceptic Reform UK party – along with a number of prominent rightwingcommentators

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 by falling pollution levels, researchers find.”

Scientists tell Carbon Brief that the framing of heatwaves being “caused” by declining air pollution is “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”

The extensive reporting around Europe’s heatwaves in recent months has often mentioned that Europe is the world’s fastest-warming continent. 

The new study in question aims to unpack why Europe’s summer temperatures are rising more quickly than other regions of the northern hemisphere’s mid and high latitudes. 

The research – published in Geophysical Research Letters – explores the role of air pollution and, specifically, how it affects circulation patterns in the atmosphere. 

(The study focuses on long-term trends in European summers and does not include the very recent heatwaves.)

Human-caused emissions of aerosols – tiny, light‑scattering particles produced mainly by burning fossil fuels – have long acted to “mask” global warming. 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 <a href="https://jiuniversity.com/new-student-visa-rule-will-have-significant-impact-on-international-students-harvard-says-news-the-harvard-crimson/” title=”New Student Visa Rule Will Have ‘Significant Impact’ On International Students, Harvard Says | News | The Harvard Crimson”>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, by letting more sunlight reach the land surface and, indirectly, by influencing the jet stream

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 by declining aerosols, it is “wrong” to say they are being “caused” by them, says Prof Erich Fischer, a climate scientist at ETH Zurich

Fischer, who was not involved in the study, tells Carbon Brief:

“Heatwaves are caused by high-pressure systems and are now much more frequent and intense because they are happening in a climate that is much warmer than 100 years ago as a result of greenhouse-gas-induced warming. 

“The paper shows that the greenhouse-gas-induced summer warming had been temporarily masked by air-polluting aerosols. The full extent for European summers only becomes visible now as the air-polluting aerosols have declined.”

Samset adds:

“Air pollution never causes or removes global warming, it only temporarily moderates it.”

Study lead author Dr Pedro Roldán‐Gómez, an associate researcher at the Barcelona Supercomputer Centre, is quoted in the Daily Telegraph saying that “most” of the “excess warming” in Europe, beyond that of comparable regions in the northern hemisphere, can be linked to declining aerosols

But, earlier in the article, the newspaper interprets this as, simply, “most of the extra heat experienced in Britain and Europe” is down to air pollution. 

GB News uses a similar phrasing, reporting that “much of the additional warming across Britain and western Europe since the 1980s is linked to the sharp decline in airborne particles known as aerosols”

This is “misleading”, says Fischer, while Roldan-Gomez tells Carbon Brief that this is a “tricky point”, which “could lead to wrong interpretations if not properly explained”. He adds:

“The contribution of greenhouse gases is, in any case, the most important factor.”

The Daily Telegraph’s article was seized upon by Reform’s Richard Tice to claim that “cleaner air” was causing higher temperatures, rather than CO2

This continued his position – refuted by long-established climate science – that CO2 does not drive global warming. 

Tice also claimed in his post that net-zero policies are “contributing to rising temperatures”. Tice appears to be linking declining air pollution to a shift from fossil fuels to renewable energy

Samset points out that net-zero became a goal “decades later” than the cumulative efforts to reduce air pollution since the 1980s and that it is “simply wrong” to link it to the study. 

“The scientific community will keep working to understand how greenhouse gas warming and air pollution interact,” he says, but “nothing we do will change the fact that the consequences of global warming are due to human-induced CO2 emissions”

Fischer adds:

“Let us not forget that cleaning up air-polluting aerosols is highly desirable. According to the World Health Organisation, 7 million people still die prematurely every year due to air pollution.”

Finally, the Daily Telegraph article and the study itself both attribute Europe’s declining air pollution from the 1980s onwards to the Montreal Protocol

This is a “glaring error”, Samset says, and it is “surprising that it wasn’t picked up” in the peer-review process for the study. He explains:

“The Montreal Protocol did not deal with air pollution. It dealt with ozone-depleting gases and has been an extremely successful multi-national effort against environmental damage. “

Clean air legislation was already in place in many European countries by the time the Montreal Protocol was signed in 1987, says Samset. 

In response, Roldán‐Gómez says that while the protocol did not target aerosols specifically, it “boosted the clean air policies”

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Source: www.carbonbrief.org