President Barack Obama on Monday nominated Gina McCarthy to lead the Environmental Protection Agency and MIT professor Ernest J. Moniz to serve as Energy secretary during his second term.

“They’re going to be making sure that we’re investing in American energy, that we’re doing everything that we can to combat the threat of climate change, that we’re going to be creating jobs and economic opportunity in the first place,” Obama said in introducing his nominees at a White House news conference. “They are going to be a great team. And these are some of my top priorities going forward.”

McCarthy, currently the agency’s assistant administrator for air and radiation, has worked for Democrats and Republicans alike in state governments. However, her role as the point person in developing rules limiting emissions from industrial sources like power plants and boilers is likely to make her a proxy during the confirmation process for the administration’s broader efforts to address climate change.

Under her tenure, the EPA moved to limit greenhouse gas emissions from power plants – standards that would effectively end future construction of coal-fired facilities without carbon capture and storage technology if finalized. She also oversaw tighter standards for mercury and soot pollution and stricter fuel economy standards for cars and trucks.

“Gina McCarthy will bring her bipartisan leadership to tackling climate change,” said Daniel J. Weiss, senior fellow at the liberal Center for American Progress Action Fund. “She designed the first carbon pollution standard for new power plants, which must be finalized.”

Moniz, a physicist, personifies the president’s “all of the above” energy policy that includes an expansion of domestic fossil fuel production. Some clean water groups are rallying opposition to Moniz, who served as the Energy Department’s undersecretary during the Clinton administration, because of his advocacy for the use of hydraulic fracturing techniques to exploit previously inaccessible oil and natural gas reserves. He also directs MIT’s Energy Initiative, which is funded largely by oil and gas companies and electric utilities.

But Moniz’s position on exploiting U.S. energy resources is considerably more nuanced. While an MIT analysis showed that natural gas will play a key role in weaning the United States off more carbon-intensive resources, Moniz told a Senate committee in 2011 that gas is still no substitute for zero-emission power.

“I do believe that for this decade, in my context of moving toward lower carbon, natural gas will be a major bridge but it is only a bridge to what I believe will be a required deployment of zero carbon options and we have to see what nuclear’s role is in there,” Moniz said.

The position leaves some environmentalists unconvinced.

“We’re concerned that, as energy secretary, Ernest Moniz may take a politically expedient view of harmful fracking and divert resources from solar, geothermal and other renewable energy sources vital to avoiding climate disaster,” said Bill Snape, senior counsel with the Center for Biological Diversity, in a statement earlier this month. “We’re also concerned that Moniz would be in a position to delay research into the dangers fracking poses to our air, water and climate.”

Moniz has also advocated for nuclear power, including a new generation of small modular reactors that proponents say hold great promise as a power source with fewer risks and costs than larger-scale reactors.

Obama insisted that the drive to develop domestic energy resources is not inconsistent with protecting the environment.

“Ernie knows that we can produce more energy and grow our economy, while still taking care of our air, our water and our climate,” he said.

Familiarity Won’t Preclude Debate

McCarthy led Connecticut’s Department of Environmental Protection and worked for GOP presidential nominee Mitt Romney when he was the governor of Massachusetts, completing the state’s first climate protection plan. At the EPA, she has been an architect of the administration’s clean air rules.

“As assistant EPA administrator, Gina’s focused on practical, cost-effective ways to keep our air clean and our economy growing,” Obama said. “She’s earned a reputation as a straight-shooter. She welcomes different points of views. I’m confident that she’s going to do an outstanding job leading the EPA.”

McCarthy won Senate confirmation for her current position in 2009. Oklahoma Republican Sen. James M. Inhofe, a vociferous EPA critic despite his affinity for former EPA Administrator Lisa P. Jackson, predicted in December that senators would largely defer to Obama’s choice and avoid filibustering the nomination.

Other lawmakers also have suggested that an EPA nominee who has already received Senate confirmation could see an easier path to assuming the agency’s top post.

But given Republicans’ vehement opposition to Defense secretary nominee Chuck Hagel— — a former GOP senator from Nebraska— McCarthy’s route to confirmation will likely be anything but easy.

And while environmentalists praise McCarthy for her past work, they will push for her to make proposing carbon pollution limits for the existing power plant fleet a priority.

Like Steven Chu, Moniz comes from a scientific background, serving as the head of MIT’s physics department and the current director of the school’s Laboratory for Energy and the Environment. He also leads MIT’s Energy Initiative, which is funded largely by oil and gas companies and electric utilities.

Moniz serves on the President’s Council of Advisors on Science and Technology, and has experience on corporate boards in the electric utility, natural gas and oil industries. He also served on an Obama-appointed panel to draw up recommendations for the long term, safe disposal of radioactive waste.