Almost 15 percent of US citizens believe the science that explains climate change is a hoax, according to a new Michigan University study.
It found Republican voters and those living in central and southern parts of the US had the highest levels of denialism.
Researchers analysed more than 7 million tweets on X, formerly Twitter, between 2017 and 2019, using artificial intelligence.
Joshua Newell, environment and sustainability professor at Michigan University, said over half the tweets denied climate change was real.
"It wasn't surprising but it was disappointing, I would hope that more and more Americans would believe in climate change and the importance of addressing it," Dr Newell said.
Using a large language model, the researchers assessed tweets from about 1.3 million individual users. The posts were sorted by geocode (location) and classified as 'for' or 'against' climate change.
Former US president Donald Trump is described as a key influence on climate deniers. Two of his most-engaging tweets were about a cold snap in Texas in 2017, along with his dismissal of the 2018 IPCC report.
Well-known people like Trump are influential "when they use these events to trigger disbelief in climate change", Dr Newell said.
Past studies have found similar results.
A 2023 Yale University survey estimated 16 percent of US citizens don't believe climate science is real. The belief that climate change is real is common along the country's west and east coasts, where a higher proportion of people are Democratic voters.
But there are exceptions, such as Shasta county in California, where deniers make up 52 percent, versus 12 percent across the whole state.
Michael Mann, climatologist and geophysicist at Pennsylvania University, said there's a small but vocal minority that still deny the "overwhelming evidence of human-caused warming".
He said scientists have a duty to rebut misinformation and disinformation on social media, and that social media platforms should do the same, to address what researchers call "knowledge vulnerability".
AI can help researchers sort through millions of social media posts rapidly and at a fraction of the cost of doing it manually. But there's still concern over the ethics of using AI in research.
Dr Mann described AI as an "intriguing new tool" but warned "its limitations must be kept in mind" as it continues to evolve.
Dr Newell said social media companies have started to monitor and act on disinformation, mentioning Trump's ban from X after the insurrectionist attack on the US Capitol on January 6, 2021.
"These very powerful social media companies should consider similar strategies for misinformation regarding climate change," he said.
