Social media posts circulating in recent weeks allege that a US military programme is being used to manipulate the weather, suggesting it is responsible for the heatwaves affecting Europe.To support the claim, several accounts have shared clips of journalists, scientists, and public figures discussing geoengineering (deliberate, large-scale interventions in Earth’s climate system), presenting them as evidence that weather events are being deliberately manipulated.One of the shared videos features French TV presenter Anne-Claire Coudray discussing geoengineering.”In response to climate change, more and more countries are exploring what’s known as geoengineering,” she said in the clip. “The idea is to intervene directly in the climate system to artificially cool the planet.” The clip has been presented online as proof that governments are actively manipulating the climate, but its original context does not support the claim.Published in late August 2025, the footage of Coudray comes from a news report explaining scientific research into geoengineering — a field that explores theoretical methods of reducing the effects of climate change.The report does not suggest that these technologies are currently being used to create or intensify heatwaves.Many of the posts also refer to HAARP, the High-frequency Active Auroral Research Program, a US research facility that has frequently been the subject of conspiracy theories.What is HAARP?Launched in the 1990s, HAARP was built to study the ionosphere, a layer of the Earth’s upper atmosphere. Scientists do this by transmitting high-frequency radio waves and measuring how electrically charged particles respond.According to the programme’s stated mission, the research was intended to improve understanding of the ionosphere and help develop communication and surveillance technologies. Since 2015, HAARP has been operated by the University of Alaska, which publicly documents its research activities.Frequent conspiracy theoryThe theory relies on a misunderstanding of how the atmosphere works.Weather systems, including heatwaves, develop in the troposphere and, to some extent, the stratosphere. HAARP’s experiments take place in the ionosphere, hundreds of kilometres above the Earth’s surface.The radio waves used by the facility do not interact with the lower layers of the atmosphere where weather forms.Scientists have repeatedly stated that there is no known mechanism through which HAARP could create or intensify weather events.According to climate scientists, the recent heat across Europe was driven by a persistent high-pressure system that trapped hot air over western parts of the continent.Researchers also say that human-induced climate change is making heatwaves more frequent, longer-lasting and more intense.