Greta Thunberg, at age 16, has quickly become one of the most visible climate activists in the world. Her detractors increasingly rely on ad hominem attacks to blunt her influence.

Thunberg gained prominence after she began skipping some days of school to protest climate inaction outside Swedish parliament. She spearheaded the school walkouts that saw more than a million children across the globe leaving their classrooms to demand action on global warming.

She has addressed world and U.N. leaders and has been nominated for the Nobel Peace Prize. Later this month, she'll sail across the Atlantic Ocean in a 60-foot yacht powered by solar panels and underwater turbines on her way to participate in the U.N. climate talks in New York (see related story).

But the success of Thunberg — who describes herself on Twitter as a "16 year old climate activist with Asperger" — remains a sore point for those who reject mainstream climate science and some who have helped shape or encourage the Trump's administration rollback of climate policy.

They frequently point to Thunberg's autism, claim she is used by her parents and compare her call to young people on climate change to "Hitler Youth." They have pointed to her "monotone voice" and framed her as a "millenarian weirdo" with the "look of apocalyptic dread in her eyes."

A recent opinion piece in The New York Times prompted an outcry among climate hawks and Thunberg's allies, who said the newspaper was validating these types of personal attacks on the teenage activist.

Experts say relying on ad hominem attacks has significant collateral damage in that they dissuade people with intellectual and developmental disabilities from speaking publicly. While the language of describing someone as a "puppet" or abused by adults may appear coded, it's clearly a dog whistle that signals her words should be discounted because her mind works differently, said Steve Silberman, author of "NeuroTribes: The Legacy of Autism and the Future of Neurodiversity."

"It's classic autism bashing," he said. "They feel at liberty to do it because autism has been framed as a pathology for decades, so they feel like they don't have to hold back, than just 'other' her, turn her into a freak when she's actually making more sense than 95% of the adults who have addressed this issue for the last 30 years."

Patrick Moore, chairman of the board of directors of the CO2 Coalition, which promotes the benefits of carbon dioxide, wrote on Twitter that "Greta=Evil." In an interview with E&E News, Moore denied that his numerous mentions of Thunberg's autism in media appearances and on social media were attacks on her disability but that he instead was "comparing her masters to Hitler."

He said that Thunberg's public speeches were written for her, that she was a "puppet" and that she was unable to answer questions in interviews because her ideas were not her own.

"They aren't her ideas," he said. "There's a reason why 16-year-olds don't vote, don't drink, don't drive, don't whatever. At that age, she is not an adult, and therefore she has no right to influence people in a political process."

Moore's group has been increasingly active on Capitol Hill and in the Trump administration. CO2 Coalition co-founder Will Happer is now serving on the National Security Council at the White House and spearheaded a shelved plan to conduct an "adversarial" review of climate science. Moore was recently invited by congressional Republicans to downplay an alarming U.N. extinction report.

Earlier this year, Trump enthusiastically tweeted a quote from a Moore performance on Fox News in which Moore said climate science was "fake news" and that more carbon dioxide would be good for humanity.

Moore said he was seeking to show Thunberg "is a full-blown tool of adults."

"She is being abused by her parents, by Al Gore, by society at large that is on side with this ideology as if there is a climate emergency," he said. "What a nonsensical, stupid concept, there is no climate emergency, I think you know, otherwise people would be fleeing from it."

While her critics claim to attack Thunberg for ideas, critiques that mention her personal traits are harmful and reliant on "prejudiced ideas about autistic people," said Zoe Gross, a spokeswoman for the Autistic Self Advocacy Network. People are quick to label autistic traits, including tone of voice and facial expressions, as "creepy." She said criticism of Thunberg that highlights the way she speaks, answers questions and displays emotions is clearly an attempt to belittle her.

"Some people may be making assumptions out of ignorance ... but others are explicitly saying that autistic people are not worth listening to," Gross wrote in an email response to questions. "It's upsetting to see any person being belittled because of their disability, especially a child. People with all kinds of disabilities can form and express opinions, speak up for ourselves and others, and become advocates and leaders."

Thunberg's critics include those who have been close to the Trump EPA.

Steve Milloy, who served on the Trump administration's EPA transition team and has pushed to restrict the use of science at the agency, has referred to Thunberg as an "adult-exploited empty-headed child."

"She's ignorant, maniacal and is being mercilessly manipulated by adult climate bedwetters funded by Putin," he wrote recently on Twitter.

At his congressional hearing, Moore testified alongside Marc Morano, who works for the conservative Committee for a Constructive Tomorrow and has a blog that misrepresents and attacks climate science. Morano has been invited by the Trump administration to EPA events weakening the role of science at the agency; he was photographed giving his book "The Politically Incorrect Guide to Climate Change" to former EPA Administrator Scott Pruitt. Morano's blog describes Thunberg as an "autistic prophet." In his Twitter feed, Morano retweets criticisms of her that center on her autism.

"She hasn't been called a mascot. Which; is really what she is. She'll get a Nobel Prize and a wanna-be Ph.d. from Harvard. For being autistic and not going to school," wrote one follower retweeted by Morano.

Conservative media have also begun using Thunberg's character traits in an attempt to minimize her words. A columnist at The Federalist, for instance, recently wrote that Thunberg's struggles with autism while growing up "bred in her an absolutist attitude that is far from attractive." An editor of the right-wing British magazine Spiked, which receives funding from the Koch brothers network, called Thunberg a "weirdo" and wrote that "there is something chilling and positively pre-modern about Ms Thunberg."

Andrew Bolt, a Sky News host, recently wrote a column that called Thunberg "deeply disturbed."

"I have never seen a girl so young and with so many mental disorders treated by so many adults as a guru," he wrote. "But Thunberg has something very rare as well: a sense of absolute certainty. She shows not the slightest doubt and forgives not the slightest compromise. This allows followers who are tormented with doubt and burden of freedom to relax into her totalitarian certainty. And in Thunberg's case, that certainty comes from what normally would be seen as a disability."

In the New York Times opinion piece, The Weekly Standard editor Christopher Caldwell called Thunberg a "complicated adolescent."

"Intellectually, she is precocious and subtle," Caldwell wrote. "She reasons like a well-read but dogmatic student radical in her 20s. Physically, she is diminutive and fresh-faced, comes off as younger than her years, and frequently refers to herself as a 'child' — about the last thing the average 16-year-old would ever do."

Thunberg's autism actually informs her activism and motivates her to speak out against the falsehoods spouted by climate deniers, said Silberman, the author of "NeuroTribes." He said she doesn't pay any attention to the false notion of a "debate" in climate science.

Thunberg speaks like "one of the few people who has woken up out of this fever dream of bullshit that's spread by these right-wing politicians and oil company misinformation," Silberman said.

"Unlike most neurotypical people, she can't just shrug off the fact that of course oil company executives are going to lie and politicians who are beholden to them are going to lie," he said. "She can't abide that, it bothers her almost viscerally."

For her part, Thunberg has said that autism is "not a 'gift'" but that it "CAN be a superpower."

"I've had my fair share of depressions, alienation, anxiety and disorders," she wrote in a Facebook post in April. "But without my diagnosis, I would never have started school striking. Because then I would have been like everyone else."

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at www.eenews.net.