"What really surprised us this year was to see a resurgence in language such as 'climate hoax' and 'climate scam' that deny the phenomenon of climate change," said Jennie King, head of civic action at the Institute for Strategic Dialogue, a London-based digital research group.
Popular topics included the false claims that CO2 does not cause climate change or that global warming is not caused by human activity, said Climate Action Against Disinformation (CAAD), a coalition of campaigners, in a report.
An analysis by Advance Democracy seen by AFP found the number of Twitter posts "using climate change denialism terms" more than tripled from 2021 to 2022, reaching over 900,000.
Another analysis of Twitter messages - carried out for AFP by two computational social scientists at City, University of London - counted 1.1 million tweets or retweets using strong climate-sceptic terms in 2022.
That was nearly twice the figure for 2021, said researchers Max Falkenberg and Andrea Baronchelli. They found climate denial posts peaked in December, the month after Tesla billionaire Musk took over the platform.
On TikTok, views of videos using hashtags associated with climate change denialism increased by 4.9 million, it said.
On YouTube, climate change denial videos got hundreds of thousands of views, with searches for them bringing up adverts for climate-denial products.
YouTube spokesperson Elena Hernandez told AFP that in response to the claim, certain climate-denial ads had been taken down.
TikTok and Twitter did not respond to requests for comment.
On Facebook, meanwhile, ADI found the number of such posts decreased compared to 2021, in line with overall climate change claims.
Use of the denialist hashtag #ClimateScam surged on Twitter from July, according to analyses by CAAD and the US-based campaign group Center For Countering Digital Hate (CCDH).
For weeks it was the top suggested search term on the site for users typing "climate".
CAAD said the reason for that was "unclear", though one major user of the term appeared to be an automated account, possibly indicating that a malignant bot was churning it out.
ADI noted that July saw US President Joe Biden secure support for a major climate spending bill -- subject of numerous "climate scam" tweets -- plus a heatwave in the United States and Europe.
Climate denial posts also peaked during the COP27 climate summit in November.
A quarter of all the strongly climate-sceptic tweets came from just 10 accounts, including Canadian right-wing populist party leader Maxime Bernier and Paul Joseph Watson, editor of conspiracy-theory website InfoWars, the City research showed.
CCDH pointed the finger at Musk, who reinstated numerous banned Twitter accounts and allowed users to pay for a blue tick -- a mark previously reserved for accredited "verified" users in the public eye.
"Elon Musk's decision to open up his platform for hate and disinformation has led to an explosion in climate disinformation on the platform," said Callum Hood, CCDH's head of research.
Musk himself tweeted in August 2022: "I do think global warming is a major risk."
Musk has also created a $100 million dollar prize for technology innovations shown to be effective in removing carbon dioxide from the atmosphere.