YouTube users interested in climate issues are just as likely to be directed to conspiracy theories as they are scientific content, new research has found.
And the Google-owned site's efforts to crack down on fake content appears to be struggling, with subscriber counts to channels promoting debunked nonsense still growing.
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Researchers in Germany took a look at what YouTube had to offer when it came to climate science, and were disturbed by what they found.
"Searching YouTube for climate-science and climate-engineering-related terms finds fewer than half of the videos represent mainstream scientific views," said Joachim Allgaier, sociologist at RWTH Aachen University.
"It's alarming to find that the majority of videos propagate conspiracy theories about climate science and technology."
About 54 percent of the clips YouTube served up at the top of the search rankings for terms like 'climate engineering', 'global warming' and climate modification' bucked the scientific consensus, which is that humans are the cause of an unprecedented spike in greenhouse gas emissions and temperatures.
The worst offender was the search term 'chemtrails'. Only 5 percent of clips presented the scientific consensus, and they weren't popular, only garnering 1.5 percent of views. Conspiracy videos accounted for 95 of videos and 98.5 percent of views.
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Dr Allgaier said what was most worrying is that conspiracy theorists have learned to present their claims in scientific language so it's not immediately clear the claims have no basis in reality.
"People searching for 'geoengineering' or 'climate modification' on YouTube won't find any information on these topics in the way they are discussed by scientists and engineers. Instead, searching for these terms results in videos that leave users exposed to entirely non-scientific video content."
YouTube earlier this year announced plans to cut down the number of conspiracy theory videos it recommended to its 2 billion users.
"We'll begin reducing recommendations of borderline content and content that could misinform users in harmful ways," the site said in a blog post in January, "such as videos promoting a phony miracle cure for a serious illness, claiming the Earth is flat, or making blatantly false claims about historic events like 9/11."
But a new investigation by The Huffington Post has found the change has had little impact on major purveyors of such nonsense. Tech reporter Jesselyn Cook analysed several channels and found while it appears to be preventing new channels from breaking through to a wider audience, subscriber counts are still growing for YouTubers who already had a big following before the change.
"If a creator has already started to grow an audience, that audience will seek out their content whether it’s going up in the algorithm or not," data researcher Becca Lewis told Cook.
In many cases, this change is too little, too late."
Dr Allgaier said YouTube needs to "take responsibility to ensure its users will find high-quality information if they search for scientific and biomedical terms, instead of being exposed to doubtful conspiracy videos".
"YouTube has an enormous reach as an information channel, and some of the popular science YouTubers are doing an excellent job at communicating complex subjects and reaching new audiences.
"Scientists could form alliances with science-communicators, politicians and those in popular culture in order to reach out to the widest possible audience. They should speak out publicly about their research and be transparent in order to keep established trustful relationships with citizens and society."
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Dr Allgaier's findings were released the same day two new studies detailed how climate change sceptics have misused historic climate data to claim the recent upswing in temperatures has nothing to do with humans.
His research was conducted between 2015 and December 2018, before YouTube announced its changes, which affected recommended videos but not search results.