Washington (CNN) Scott Pruitt, Donald Trump's pick to lead the Environmental Protection Agency, broke with the President-elect Wednesday and said he doesn't believe climate change is a "hoax."

But in testimony before the Senate Committee on Environment and Public Works, Pruitt didn't indicate he would take swift action to address environmental issues that may contribute to climate change. Instead, the Oklahoma attorney general said there is still debate over how to respond.

"Science tells us the climate is changing and human activity in some matter impacts that change," Pruitt said. "The ability to measure and pursue the degree and the extent of that impact and what to do about it are subject to continuing debate and dialogue."

That stance puts Pruitt in line with the climate change views of several other Trump Cabinet picks, including Rex Tillerson and Ryan Zinke, who have acknowledged the issue but haven't committed to an aggressive response.

Trump once called climate change a "hoax" invented by the Chinese and, during his campaign for president, repeatedly questioned scientific conclusions that human activity has caused global warming. More recently, he has acknowledged "some connectivity" between human activity and climate change.

Pruitt, who has long viewed the EPA skeptically and has sued the agency repeatedly as Oklahoma attorney general, is a lightning rod of a pick. As the hearing got underway, protesters criticizing Pruitt for his ties to the oil industry outside the room were clearly audible. A handful of protesters were escorted out of the hearing.

Pruitt said the EPA serves a critical mission and detailed how the agency under his leadership would take a dramatically different approach than under President Barack Obama. He accused the agency under Obama of flouting congressional rules and ignoring the desires of states.

Pruitt said "rule of law matters" and that as EPA director he would "follow the law" and regulations set out by Congress, a suggestion that the current leadership has not done that.

Views on climate change

It is likely that Pruitt, despite views that are abhorrent to many Democrats, will be confirmed as the next head of the EPA. But Democrats want to make him pay for it and plan to push the Republican on some of his past comments about climate and his ties to energy companies.

Pruitt wrote last year that climate change scientists "continue to disagree" about whether climate change is real, despite the fact that 97% or more of climate scientists believe climate change is real and linked to human activity.

And lawyers with the Environmental Defense Fund tell CNN that Pruitt filed at least 12 lawsuits challenging environmental protections as attorney general. Pruitt, in particular, sued over the EPA's clean power plan, which seeks to curb carbon emissions from power plants and attempts to curb methane emissions from the oil and gas industry.

Bernie Sanders, the liberal Vermont senator who railed against the fossil fuel industry during his 2016 presidential campaign, hammered Pruitt for questioning the impact humans have on climate change.

Pruitt said his personal views on climate change are "immaterial" to whether he should lead the EPA, arguing that his prospective job is about following Congress' guidance, not his own personal beliefs.

"Really?" Sanders asked incredulously. "You are going to be the head of the agency to protect the environment and your personal feelings about whether climate change is caused by human activity and carbon emission is immaterial?"

Pruitt stood by the statement, telling Sanders that his job as administrator would be to "carry out statutes passed by this body."

Probed for ties to energy companies

He sought to beat back concerns about his ties to the energy industry by arguing it is wrong to say someone who is pro-energy is inherently anti-environment.

"First, we must reject the false paradigm that if you are pro-energy, you are anti-environment and if you are pro-environment, you are anti-energy," he said. "I utterly reject the narrative."

But environmental activists call Pruitt dangerous and Democrats on the committee will look to put his views of science and climate change on trial.

Sen. Tom Carper of Delaware, the top Democrat on the committee, has labeled the Oklahoma Republican "Polluting Pruitt" since his nomination was announced and argued that an EPA head that does not "recognize the damaging effects of climate change on our environment and economy" is not qualified for the job.

Sen. Sheldon Whitehouse, a Rhode Island Democrat, hammered Pruitt for his ties to a number of oil companies through his campaigns for attorney general, his super PACs and the Republican Attorneys General Association.

Whitehouse called some of his ties "a complete black hole" of money, alleging that Pruitt could be conflicted when dealing with some energy companies due to his fundraising.

Pruitt denied soliciting money from Koch Industries and others for the Rule of Law Defense Fund and noted that, as attorney general, he also sued energy companies.

According to the National Institute on Money in State Politics, Pruitt has received more than $300,000 from interests close to the fossil fuel industry since 2002.

Many Senate Republicans, however, see Pruitt as the right person to lead what they view as a wasteful agency that over-regulates, especially because Oklahoma is the biggest oil and natural gas-producing state in the nation.

Pledging action

Pruitt said he believes mistakes were made in the handling of lead poisoning in Flint, Michigan, blaming the Obama administration's EPA for not moving faster.

"As you know, the Clean Water Act and The Safe Drinking Water Act, if there is an emergency situation, the EPA can enter an emergency order to address those kind of concerns," Pruitt said. "I think there should have been a more fast response, a more rapid response to Flint, Michigan."

Pruitt's main argument during the start of his hearing has been that the states should have more power within the EPA, but on this issue, he argued that the federal government agency should have had more power to respond.

Sen. Ben Cardin, a Maryland Democrat, pressed Pruitt on his lawsuits against the EPA, charging the body with overreach in state matters.

Pruitt said on issues of air quality and water quality and inter-state issues, the EPA is particularly necessary.