After Greta Thunberg spoke out about the war between Israel and Hamas in October 2023, social media users shared a video purportedly showing the Swedish activist calling for the use of "biodegradable missiles" and "vegan hand grenades." But experts say the clip is a deepfake fabricated using artificial intelligence (AI) -- and the original BBC interview predates the conflict by months.

"BBC: @GretaThunberg calls on Hamas to prioritize the reduction of their carbon footprint when murdering, raping, beheading, mutilating, and kidnapping civilians," said Eli David, co-founder of the cybersecurity firm Deep Instinct, in an October 24, 2023 post on X, formerly known as Twitter.

The post has since been deleted, but similar claims have circulated on other platforms.

"Talk about STUPIDITY IN ACTION," says an October 24 post on Facebook. "SERIOULY?? (sic) She wants Electris (sic) planes / Tanks ?  Vegan Hand Grenades ??"

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The narrative spread after Hamas gunmen stormed across the border from the Gaza Strip into Israel and carried out the deadliest attack since the country was created in 1948.

During the Palestinian Islamist group's surprise October 7 attack, throngs of fighters killed more than 1,400 people -- mostly civilians -- and kidnapped some 200 more, according to Israeli officials.

Israel has retaliated with relentless strikes that Gaza's Hamas-run health ministry said October 26 had killed more than 7,000 people, also mainly civilians -- a toll expected to rise substantially if Israeli troops massed near the border thrust across.

Many celebrities and public figures have expressed their horror over the violence in the Middle East, including Thunberg, who is a regular target of misinformation.

"Today we strike in solidarity with Palestine and Gaza," she said in an October 20 post on X (archived here). "The world needs to speak up and call for an immediate ceasefire, justice and freedom for Palestinians and all civilians affected."

But claims that she called for a more climate-friendly conflict are inaccurate -- they stem from a manipulated BBC interview originally shared in jest.

In the clip, which has circulated on X, TikTok and Reddit, the 20-year-old environmentalist appears to say: "War's always bad, specifically for the planet. If we want to continue fighting battles like environmentally conscious humans, we must make the change to sustainable tanks and weaponry."

The posts credit the video to the X account @snicklink, which originally published the footage October 20 with #israel and #satire (archived here).

Hany Farid, a professor and digital forensics expert at the University of California-Berkeley, said the video is "a classic lip-sync deepfake in which the mouth region is replaced to be consistent with a new audio track."

"Throughout the video you can see both a de-synchronization between the mouth and audio (as in a dubbed movie from one language to another) and occasionally a misshapen mouth and teeth, which occurs when the AI generation fails to properly synthesize the mouth," Farid said October 25.

Kimberly Ton Mai, a PhD candidate at the University College of London who researches machine learning, agreed, saying October 25 that "other than the actual content of the video, the lips do not match up completely with the audio and are less sharp than the rest of the face."

Heather Cooper, an AI educator and consultant, added that Thunberg's neck and hands appear blurry at times.

"AI-generated video is improving, but it's simple to identify if you pay attention to the mouth, hands and body movements," she said October 25.

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The BBC published the original, unaltered interview November 1, 2022 on YouTube (archived here). In it, Thunberg describes the first actions she took to fight climate change:

AFP contacted @snicklink for comment on the deepfake, but a response was not forthcoming.

Digitally altered picture

Social media users have misrepresented other visuals of Thunberg amid the Israel-Hamas war.

A photo circulating on X purportedly shows the activist brandishing the flag of the Islamic State jihadist group and wearing a Hamas headband. But the image is an altered version of a picture Thunberg shared in a now-deleted October 20 X post, which featured no such paraphernalia.

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AFP has fact-checked other misinformation about the Israel-Hamas war here.