A ‘Nerve Center’ for Climate in the Biden White House

One of Ms. Aggarwal’s areas of expertise is the development of a clean energy standard — that is, the percentage of non-fossil fuel sources that utilities must reach in their power generation and sales. By setting a standard without a source-by-source prescription, the policy is supposed to allow businesses and utilities to determine the most efficient way of meeting the targets. With the Senate now controlled by Democrats, even with a razor thin margin, the possibility of passing such a mandate could be within reach.

Maggie Thomas, who served in climate adviser roles in the presidential campaigns of Governor Jay Inslee of Washington and Senator Elizabeth Warren of Massachusetts, will serve as Ms. McCarthy’s chief of staff.

Jahi Wise, who was a policy director for the Coalition for Green Capital, a nonprofit group that works to drive investment in clean energy, will be a senior adviser for climate policy and finance.

The expansive White House team, which is not subject to Senate confirmation, has provoked consternation among Republicans. Senator John Barrasso of Wyoming, who will be the top Republican on the Senate Energy Committee, said he believed increased energy innovation and “not the appointment of countless unchecked czars” would be best for both the economy and the environment.

James P. Pfiffner, an emeritus professor of public policy at George Mason University and an expert on the presidency, noted that presidents have increasingly centralized control in the White House by creating special positions around policies of high importance, with mixed results.

A new White House climate office staffed with at least five people is a lot, he said, and a White House “czar” like Ms. McCarthy would have her challenges.

“White House staffers do not have the authority to make decisions on spending or personnel,” he said. “Certainly, they can be powerful, but only to the extent that their policy area is of primary importance to the president.”

Christopher Flavelle contributed reporting.