In the final minutes of the 90-minute long showdown, moderator Kristen Welker turned to climate change and asked each candidate how they planned to tackle the crisis.
President Trump, who has repeatedly called climate change a “hoax”, said he planned for a “trillion trees” before touting America’s “clean air”, “clean water” and lower carbon emissions (all of which are, at best, misleading, as The Independent has reported).
The president then pivoted to an attack on clean energy, taking particular issue with windmills.
“He thinks wind causes cancer. Windmills,” Mr Biden noted.
"I know more about wind than you do," Mr Trump replied, before going on to say windmills are extremely expensive, “kill all the birds” and “the fumes coming up, if you’re a believer in carbon emission … for these massive windmills is more than anything we’re talking about with natural gas which is very clean”.
Trump climate plan: Beware of the fumes from the scary windmills!
— Senator Jeff Merkley (@SenJeffMerkley) October 23, 2020
Mr Biden quipped: “Find me a scientist who will say that.”
The statement was met with immediate derision. Democratic Senator Jeff Merkley, from Oregon, tweeted: “Trump climate plan: Beware of the fumes from the scary windmills!”
Cory Booker’s chief of staff, Matt Klapper, wrote: “Trump has done the most of any President to stop windmills from causing cancer since Abraham Lincoln.”
“BTW, Trump said ‘windmills kill all the birds’ as if he cares? His administration has (illegally) rolled back the 100-year Migratory Bird Treaty Act, gutting protections for hundreds of migratory bird species. #Debates2020” tweeted Emily Gertz, senior editor at WeAreDrilled.
The president has repeatedly lied about windmills. "There is no evidence that wind turbines cause cancer, FactCheck.org reported last year, quoting The American Cancer Society which said it is “unaware of any credible evidence linking the noise from windmills to cancer.”