Twitter accounts run by machines are a major source of climate change disinformation that might drain support from policies to address rising temperatures. “Twitter bots have been this growing force of evil over a half a decade now,” said John Cook, a professor at George Mason University’s Center for Climate Change Communication who was not involved with the study. “Twitter bots have been a part of that.”Marlow’s team measured the influence of bots on Twitter’s climate conversation by analyzing 6.8 million tweets sent by 1.6 million users between May and June 2017. But those bots accounted for 25% of the total tweets about climate change on most days. The bots were also more prevalent in discussions on climate research and news.