Record-breaking temperatures swept across Europe in May, triggering a wave of online claims that climate scientists say are not only misleading but also contribute to a hostile environment for researchers. The posts, circulating on platforms like X, echo familiar climate-change denial narratives, attempting to cast doubt on established science.
One widely viewed post on X argued that historic heatwaves in London during the summers of 1976 and 1921 prove current high temperatures are nothing unusual. Other posts allege that temperature records are unreliable due to the urban heat island effect—a real phenomenon where cities are warmer than surrounding rural areas—or through outright manipulation.
Climate scientists, however, stress that these arguments misunderstand how climate change influences extreme weather. Sonia Seneviratne, professor of climate science at ETH Zurich, told Euronews' fact-checking team, The Cube, that she has personally experienced hostile reactions linked to her work. "Every once in a while, I would get emails or some letters," she said, noting that it was particularly visible on social media. "At some point, I realised on Twitter (now X), it got quite bad." Seneviratne added that she had seen climate change denial messaging appear within seconds of posting, which she suspects could be bot activity.
Zeke Hausfather, climate research lead at Stripe and research scientist at Berkeley Earth, reported similar experiences. "The most I've got in terms of harassment is people hurling invectives at me online, thankfully, but many of my colleagues (particularly female ones) have experienced much worse," he said. Bart Verheggen, senior climate advisor at the Dutch meteorological institute KNMI, also encountered hostility. "In the past, I have frequently encountered verbal abuse and harassment, but not intimidation or threats," he told The Cube.
Misinformation at the Core
Verheggen said misinformation remains an important factor in public discussions about climate change, and its nature has evolved. "The science is getting clearer and clearer and increasingly accepted by a larger group in the middle," he said. "At the same time, the forces that work against these policies seem to have hardened their stance." According to Verheggen, climate denial has shifted from disputing whether the planet has warmed to questioning the consequences of climate change and the policies designed to mitigate it.
These experiences are not isolated. In January, Spanish authorities described an uptick in online abuse directed at climate scientists and meteorologists, calling the increase "alarming." Many of the hostile messages were found on X. Environment experts receiving harassment is far from new; for example, climate scientist Michael E. Mann previously described receiving threats and being targeted by campaigns aimed at discrediting his work on unprecedented global warming in 1998. The US-based Union of Concerned Scientists documented efforts by fossil-fuel-linked groups to attack and undermine Mann.
Verheggen noted that these dynamics are not unique to climate science. "Science denialism is a proven way of stalling policies (going all the way back to the tobacco wars)," he said. "So yes, misinformation and disinformation play a large role."
Familiar False Arguments Follow Heatwave
Climate scientists say that several false claims about the heatwave follow familiar narratives. Posts claiming that heatwaves in 1921 and 1976 show extreme temperatures occurred long before modern climate change concerns misunderstand how climate change influences extreme weather. Seneviratne said that while heatwaves like the one in 1976 were severe, today's events are more frequent, affect larger areas, and reach levels that would have been highly unlikely without human-induced climate change. "We start experiencing heatwaves that are so extreme in recent years that some of them would have had a near-zero probability of occurrence without human-induced climate change," she said.
Other posts allege that global temperature records are unreliable because cities are warmer than surrounding rural areas—the urban heat island effect. According to Seneviratne, this effect can "further amplify temperatures locally but does not explain the global observed trends." Other scientists confirm that the effect is well-documented and already accounted for in long-term temperature data. Hausfather added, "We now have nine different groups of scientists from the US, UK, EU, Japan, and China that all separately provide global temperature records, and they all agree quite well despite using different datasets and approaches. There are few things in science as well validated as the temperature record."
As Europe grapples with more frequent and intense heatwaves, the need for accurate information becomes ever more critical. The lack of cooling infrastructure in many EU homes exacerbates the health risks, while the UN has called for an accelerated clean energy transition in response to the May heatwave. Misinformation not only undermines public understanding but also threatens the safety of those who communicate the science.
