Former Texas Gov. Rick Perry pledged to advocate energy "in all forms" as well as protect and modernize the nation’s nuclear stockpile during his confirmation hearing Thursday for his Energy secretary nomination.

Donald Trump's pick to head the Energy Department also said, in hindsight, he regrets recommending the elimination of the department during his 2012 presidential bid.

"My past statements made over five years ago about abolishing the Department of Energy do not reflect my current thinking," Perry said in testimony to the Senate Energy and Natural Resources Committee Thursday. At a 2011 GOP primary debate, Perry infamously forgot the department was one of three agencies he wanted to eliminate.

The former three-term Republican governor covered a range of issues during Thursday's hearing. In his opening remarks, he touched on the global warming debate, saying he believes the climate is changing -- some of it, naturally, and some "man-made."

"The question is how do we address it in a thoughtful way that doesn't compromise economic growth, the affordability of energy or American jobs," he said.

Sen. Maria Cantwell, D-Wash., ranking member of the committee, told Perry she was "concerned" by his remarks that "we cannot compromise economic growth" in addressing climate change.

"I guarantee you, today, we are compromising economic growth by our dependance on fossil fuel," Cantwell said.

Perry, 66, also touted his record as governor and declared Texas the nation’s leading energy-producing state. Perry claimed climate and air quality improved in the state under his watch -- despite a fast-growing population and one of the largest petro-chemical refining industries in the world.

"Our power plants reduced their carbon output by 17 percent, sulfur dioxide by 56 percent and nitrous oxide by 66 percent," he said. "We decommissioned 137 older, dirtier power plants while providing incentives for clean technology, such as clean coal and carbon capture and underground storage."

Perry also pledged to advance the department's science and technology mission and carefully dispose of nuclear waste.

The Texas governor was for "all of the above" on energy production before President Obama embraced the strategy.

Years before the Democratic president endorsed all types of energy production -- from oil and gas to renewable sources like wind and solar power -- Perry was putting the policy into practice in Texas.

During Perry's tenure as governor, Texas maintained its traditional role as a top driller for oil and natural gas, while also emerging as the leading producer of wind power in the United States and a top 10 provider of solar power.

Democratic Sen. Joe Manchin of West Virginia introduced Perry, a rarity for one of Trump's Cabinet selections. Manchin called Perry a successful executive of a state with a diverse energy portfolio and a longtime friend. 

Neil Auerbach, CEO of Hudson Clean Energy Partners, an investment firm that specializes in renewable energy, called Perry's nomination a "hopeful signal" that Trump and congressional Republicans "will remain true to Republican orthodoxy about 'all of the above' as the mantra steering U.S. energy policy." 

Even as he maintains ties to oil and gas producers, a Perry-led Energy Department is likely to support renewable energy and the tax incentives that encourage its growth, Auerbach and other experts said. 

Perry left office in 2015 and then launched his second ill-fated bid for the GOP presidential nomination. He was a harsh critic of Trump, even calling the billionaire businessman a "cancer" on conservatism, but later endorsed the Republican nominee.

Democrats and environmental groups have derided Perry's nomination, calling him a steep drop-off from the two renowned physicists who preceded him as energy chief, Steven Chu and Ernest Moniz. Perry earned a bachelor's degree in animal science from Texas A&M University, where he was also a member of the Corps of Cadets and a Yell Leader.

FoxNews.com's Cristina Corbin and the Associated Press contributed to this report.