Sen. Bernie Sanders (I-VT) joined climate change strikers outside of the Iowa Capitol Building in Des Moines as part of Friday’s global climate strike.

Sanders joined youth activists in Iowa on Friday as part of the climate strikes held by protesters across the globe and thanked those in attendance for being there and “understanding what the President of the United States does not understand.”

“And that is that climate change is not a hoax, but climate change is a terrible, terrible reality impacting our country and the entire world today,” Sanders said. “Not tomorrow, but today.”

He told the group of activists:

And the bad news is, that what the scientists have told us is that they have underestimated the severity and the degree to which climate change is ravaging our country and the entire world, and what they have told us — and unlike the President of the United States, we listen to science.

“And we know that if we’re going to save this planet … we have got to take on the fossil fuel industry, and we have got to transform our energy system away from fossil fuel,” he said, calling for “sustainable energy.”

He said the “very bad” and “scary” news is that we face a “global existential crisis.”

The good news, Sanders said, is “we can address this crisis if we have the courage to stand up to greedy and powerful special interests.”

“I’m proud to stand with young people in Iowa and around the world today in their climate strikes,” Sanders wrote alongside a video of his appearance at the event.

“This is about the future of the planet and we won’t accept a middle ground approach,” he added. “We need a Green New Deal”:

I'm proud to stand with young people in Iowa and around the world today in their climate strikes. This is about the future of the planet and we won't accept a middle ground approach. We need a Green New Deal. https://t.co/BsX9K7NHx2 — Bernie Sanders (@BernieSanders) December 6, 2019

On Thursday, Sanders declared that he is running a “climate campaign,” touting his $16 trillion Green New Deal proposal.

“Our Green New Deal is the only proposal put forth by any candidate that is bold enough to take on the crisis we face,” he wrote:

We are the climate campaign. Our Green New Deal is the only proposal put forth by any candidate that is bold enough to take on the crisis we face. Thank you to @sunrisemvmt for your leadership! https://t.co/gAptQcEMm8 — Bernie Sanders (@BernieSanders) December 5, 2019

“Trump’s ignorance threatens the lives and well-being of our kids and future generations. He must be defeated,” he wrote in another tweet:

While scientists tell us climate change is the great threat facing our planet, Trump thinks it is a "hoax." Trump's ignorance threatens the lives and well-being of our kids and future generations. He must be defeated. We must transform our energy system away from fossil fuels. — Bernie Sanders (@BernieSanders) December 5, 2019

Unlike Trump, I don't think climate change is a hoax. I believe the scientists and will do everything I can to pass a Green New Deal to take on this crisis. Thank you to all those who are striking around the world this week! pic.twitter.com/YlbsolZS8v — Bernie Sanders (@BernieSanders) December 5, 2019

As Breitbart News reported, Sanders’ multitrillion-dollar climate change proposal drastically expands existing entitlement programs and pledges $200 billion for the Green Climate Fund. He plans to pay for the proposal, in part, by “massively raising taxes on corporate polluters’ and investors’ fossil fuel income and wealth.”