Climate Action Against Disinformation found that, in every month since COP27, the hashtag #climatescam generated more retweets and likes than #climatecrisis and #climateemergency on X, the platform formerly known as Twitter. The hashtag appeared in widely circulated posts that falsely blamed arson committed by migrants for wildfires or repeated debunked claims that television broadcasters were manipulating weather maps.

Researchers attributed much of #climatescam’s traction to a small group of influential accounts, which they said tended to be far more vocal about climate denial on X than on platforms like Facebook and Instagram. One account, which researchers said had originated as an anti-vaccine forum on Telegram before shifting to climate denial on X this year, had only a few hundred followers when it shared its first #climatescam post in March; it now has more than 250,000.

Some of the sites pushing climate disinformation made money from ads — a revenue stream that researchers said was enabled by more than 150 advertising exchanges owned by some of the largest tech companies. The marketplaces, which largely use automated auctions to buy and sell online ads, placed ads on at least 15 websites known for hosting climate denial content, according to the report. Doing so flouted policies set up by many of the exchanges to block climate denial content and other disinformation from being monetized.

Ads for McDonald’s and L.L. Bean appeared next to one opinion column this fall that described “an overbearing ‘climate change’ agenda” as “implementing socialism under the guise of saving the planet” by “tyrannical central planners around the globe.”

Some climate disinformation was spread by countries like Russia and China, which often target such content to parts of the world where they seek to wield influence at the expense of the United States and the rest of the West. The report found that Russian state media had framed emission-reduction plans as a form of “Western imperialism” engineered to undermine the development of the so-called global south, or the southern part of the world, which includes some of the poorest and least industrialized countries. (Experts say global warming is a financial threat to developing nations, which are more vulnerable to climate change shocks despite contributing a disproportionately small share of greenhouse gas emissions.)