A former coal lobbyist Donald Trump has nominated to run the Environmental Protection Agency on Wednesday touted rolling back pollution standards and declined to identify climate change as a crisis requiring unprecedented action from the US.

Andrew Wheeler, the deputy administrator who took over when his predecessor Scott Pruitt resigned after months of controversy, said in his confirmation hearing that he is carrying out the president’s “regulatory reform agenda”. Wheeler called the US the “gold standard for environmental progress”.

Protesters interrupted Wheeler’s remarks, with two escorted out by security and more chanting outside: “Shut down Wheeler, not the EPA.” Most EPA staffers are furloughed and all but the agency’s most critical functions are on hold as the partial government shutdown continues.

Democrats said Wheeler’s policies have been as damaging to the environment as Pruitt’s, just without the high-profile scandals.

Although Wheeler is likely to be confirmed, they sought to pin him down on climate change, in a show of how the environment could become a top issue in the 2020 presidential race.

Protesters are arrested outside the confirmation hearing of Andrew Wheeler, nominee to be Environmental Protection Agency administrator. Photograph: Nicholas Kamm/AFP/Getty Images

The Vermont senator Bernie Sanders said it was Wheeler’s job to lead on climate, noting that some Republican senators do not believe humans are causing rising temperatures.

Asked if he agreed with the president’s past statements that climate change is a Chinese “hoax”, Wheeler said he would “not use the hoax word, myself”.

But Wheeler said he would “not call it the greatest crisis”.

“I consider it a huge issue that has to be addressed globally,” Wheeler added.

Wheeler also told the New Jersey senator Cory Booker, a likely presidential contender, that he is “still examining” a November report from US government scientists showing the country will suffer from heat-related deaths, coastal flooding and infrastructure damage.

Booker said Wheeler’s regulatory changes “fly in the face” of that science, and the Massachusetts senator Ed Markey called it “unacceptable” that Wheeler would seek confirmation without being familiar with the report.

Wheeler has said the report was based on the “worst-case scenario”, although the analysis considered what might happen if emissions slow down or continue to grow.

Wheeler’s predecessor, Pruitt, frequently questioned climate science but ultimately resigned not because of his policies but because months of reporting revealed he rented a condo from lobbyists, spent millions on security and travel and asked aides to help his wife get a job.

Republicans defended Wheeler, saying he had been unfairly vilified for his industry experience and was rewriting regulations that the EPA did not have the authority to propose.

Bernie Sanders said it was Wheeler’s job to lead on climate. Photograph: Nicholas Kamm/AFP/Getty Images

The panel’s Republican chairman, John Barrasso of Wyoming, asked Wheeler how the EPA will help support technology to reduce greenhouse gas pollution from fossil fuels.

“One thing that’s important on a regulatory side is that we don’t try to tip the scale one way or another on, for example, energy sources.” Wheeler said.

Wheeler is easing a rule that would have effectively required any new coal plants to capture carbon. He is also replacing carbon standards for the current power fleet with far weaker efficiency goals for coal plants.

Wheeler was a lobbyist at Faegre Baker Daniels, where he represented coal company Murray Energy until August 2017. Murray Energy wrote the administration a list of rule changes that would help the industry, and they are largely under way.

Wheeler is recused from certain interactions with his former employers, but he is coordinating rollbacks that benefit coal companies, including on climate change rules and the legal findings that underpin restrictions on toxic mercury pollution.

Senator Kevin Cramer, a North Dakota Republican, defended Wheeler’s background, saying that no one would prevent a banker from running the Federal Reserve or a doctor from leading the health department.