Why does Trump seem to tilt at windmills? Experts weigh in. The president claims wind turbines "cause cancer." Experts disagree.

President Donald Trump was getting strong bipartisan pushback Thursday over his strange criticism of wind turbines, which he railed against in a speech Tuesday and has a long history of publicly opining on, without much basis in wind energy facts.

Top Republican Sen. Chuck Grassley, known for his leadership in developing a wind energy tax credit in Iowa, called the comments "idiotic" in a conference call with reporters Wednesday, the AP reported, and House Speaker Nancy Pelosi echoed his comment in her weekly press conference Thursday.

"It just seems like every time you turn around there's another thing the president is saying -- wind power causes cancer, I associate myself with the remarks of Chairman Grassley -- it's an 'idiotic' statement," Pelosi said in her weekly news conference on Thursday.

The president made his latest claim about wind turbines in a speech on Tuesday at a Republican spring dinner.

"If you have a windmill anywhere near your house, congratulations, your house just went down 75 percent in value -- and they say the noise causes cancer," Trump said Tuesday, swinging his arm in a circle and making a cranking sound to imitate the noise of windmill blades. "And of course it's like a graveyard for birds. If you love birds, you never want to walk under a windmill. It’s a sad, sad sight."

Wind turbines are not, in fact, proven to have widespread negative impacts on property values, according to the Department of Energy's Office of Scientific and Technical Information in the largest study done so far in the U.S., and there is no peer-reviewed data to back up the claim that the noise causes cancer.

I am considered a world-class expert in tourism. When you say, 'Where is the expert and where is the evidence?' I say: I am the evidence.

It's true wildlife is affected by wind turbines -- particularly birds and bats. One study estimated between 140,000 and 328,000 birds are killed annually by collisions with turbines across the U.S. The U.S. Energy Information Administration estimated, however, that other human-related impacts also contribute to declines in population.

The wind industry works with biologists to find solutions to the impact of turbines on wildlife, and the Department of Energy awards grants each year to researchers addressing the issue. But, overall, scientists warn that climate change itself is a bigger threat to bird populations than wind turbines, according to the National Audobon Society.

The president, however, is not a fan of wind turbines, and he hasn't been for awhile: Since 2012, Trump has publicly referenced windmills at least 75 times in speeches, remarks, tweets and interviews, according to the data aggregation site Factbase.

But where does the president's public opposition to wind energy stem from?

It appears to date back to his days in the tourism business, and specifically, the recent development of his golf course opened in 2012 in Aberdeenshire, Scotland. When the city sought to install windmills nearby, Trump fought against the Scottish government, eventually taking legal action. His attempts ultimately failed and, in 2018, the newly installed windmills were generating enough electricity for at least 75 percent of all homes in the city of Aberdeen, according to Scottish First Minister Nicola Sturgeon.

In 2012, however, Trump took his fight against windmills before the Scottish Parliament, marking one of the first times Trump was publicly challenged on the evidence behind his opinions on wind turbines.

At the time, Trump said he spent "tremendous money" on what "many already consider to be the greatest golf course anywhere in the world," and he didn't want to see the property destroyed by "monstrosities." He also argued that installing them would put the entire country in "serious trouble."

"Almost most importantly -- other than the fact that the subsidies are enormous -- almost most importantly, is the fact that the windmills are so unattractive, so ugly, so noisy and so dangerous that, if Scotland does this, I think that Scotland will be in serious trouble," Trump said, repeating claims he continues to use in political rallies as president.

Immediately after Trump's testimony, he was reminded by a member of the Scottish Parliament that the hearing wasn't on any specific wind turbine developments and had nothing to do with his golf course. Scottish Parliament Member Chic Brodie also dove into Trump's multiple claims, pressing him for data to back them up.

Brodie cited research that refuted each of Trump's claims about Scotland, saying that surveying showed tourists would not be deterred from vacationing in Scotland, that 70 percent of Scots themselves supported wind power, that some wind turbine farms in Europe were known to actually draw tourists and that, despite Trump's concerns for the environment, the World Wildlife Fund of Scotland supported turbines.

Brodie then asked Trump for evidence. Twice.

"First of all, I am the evidence," Trump said to laughter in the parliament's chamber. Though it was four years before he would announce his run for president and make similar claims about wind energy at political rallies across the U.S., it would be a preview of his unwavering political style as president.

"You know what? I think that I am a lot more of an expert than the people who you would like me to hire, who are doing it to make a paycheck. I am considered a world-class expert in tourism," Trump said at the time. "When you say, 'Where is the expert and where is the evidence?' I say: I am the evidence."

The science behind wind energy

This year, Trump's repeated criticisms of wind turbines during otherwise unrelated speeches -- like on Tuesday at the National Republican Congressional Committee spring dinner -- are still points on which many experts push back.

Jeremy Firestone, director of the Center for Research in Wind at the University of Delaware, found one of the president's claims on wind turbines to be particularly striking: that wind turbines are not only linked to, but cause cancer.

"Other than hearing the president say it -- other than that -- I have not seen anything in the peer-reviewed literature ... to suggest that it causes cancer," said Firestone, who's been a professor at the University of Deleware's School of Marine Science and Policy for almost 20 years.

Beyond the repeated claims about property values and bird mortality -- both of which Firestone refuted based on evidence and literature he's studied -- Trump also recently said wind energy only works when the wind is blowing.

"If it doesn't blow you can forget about television for that night," Trump said at a rally in Michigan at the end of March. "Darling, I want to watch television. I'm sorry, the wind isn't blowing," he said to laughter from the crowd.

That's not exactly how energy storage works, said Firestone. Instead, wind energy can be stored in a battery or sent back to the larger electrical grid generating power for an interconnected network.

"It's like storing power in your cell phone, or the same thing is true of an electric vehicle," Firestone explained in a phone interview with ABC News. "You charge it, you take the electricity and you store it."

"So," Firestone added, "if I take power from a wind turbine when its blowing, and I store it in my battery in my electric vehicle, for example, I can use that stored energy to go somewhere when I want."

Though wind energy isn't perfect, it's significant to note that all energy sources have their flaws, Firestone said, and all human choices have consequences on the environment.

"Everything humans do has a footprint and that includes generating electricity," he said. "Ultimately, you've got to think about these things in a comparative fashion, including climate impacts and other effects to the planet."