Joe Biden had a tense exchange with an Iowa climate activist and assumed the man supported Bernie Sanders.

"I'm going to support you if you win the nomination. We have to beat Trump, but what are we going to do about climate change?" Ed Fallon, a former Iowa state representative who works with climate activist group Bold Iowa, said to Biden at an event on Tuesday. "You say you're against pipelines, but then you want to replace these gas lines. That's not going to work."

"Go vote for someone else," Biden said as he put his hand on Fallon's chest. "You're not going to vote for me in the primary," he said, putting his finger on Fallon's chest.

"I'm going to vote for you in the general," Fallon said.

"Look, you ask for a picture with me, you're coming up to tell me you don't support me," Biden said. "I'm looking for a primary, in a caucus, that's what I'm looking for, OK? Now, you believe that Bernie could do something by 2030?"

"I'm actually supporting Tom Steyer," Fallon said.

"Well, that's good," Biden said. "You've got the right guy."

Fallon endorsed Tom Steyer, a billionaire former hedge fund manager-turned-climate activist and impeachment proponent, about a month ago. Bold Iowa led a demonstration in 2018 where they walked nearly 100 miles across the state to protest the Dakota Access Pipeline.

Steyer responded to the video on Tuesday, scolding Biden for how he treated Fallon.

"This is no way to treat an Iowan. He said he'd vote for the Dem in the general b/c he knows how important it is to beat Trump. We need immediate action on climate. If you don't agree, happy to talk @ debate," Steyer wrote.

Biden faced another confrontation about climate change on Saturday in New Hampshire.

"Not a single solitary scientist thinks it'd work," Biden told a woman who identified herself as Ann about Sanders's climate plan. "You can not get to zero emissions by 2030. It's impossible."

