In addition, the war in Ukraine has driven up gasoline prices, prompting Mr. Biden to take steps that are anathema to climate activists. He released a record amount of oil from the Strategic Petroleum Reserve, pleaded with oil and gas companies to do more drilling and temporarily loosened environmental rules to allow gasoline blended with ethanol to be sold during the summer months, when it is ordinarily banned because it can cause smog.
Those moves came as a landmark United Nations report was released in which top scientists from around the world warned that time is running out for nations to pivot away from fossil fuels or face a future of climate catastrophe.
One person described Ms. McCarthy as being in “beleaguered mode” and said she had been worried about the political and legal challenges facing the administration’s climate plans. Others said she had bemoaned the difficulties of traveling and being away from her husband.
Publicly, though, Ms. McCarthy has insisted that she remains optimistic about the chances that climate legislation will pass this year. At a recent event in Washington, she said she was “not naïve” about the challenges but added, “I think we will have a bill that will move this fall.”
When she worked in the Obama administration, Ms. McCarthy was a chief architect of the president’s historic and far-reaching climate change policies.
After the election of Donald J. Trump, Ms. McCarthy became head of the Natural Resources Defense Council, which sued the Trump administration more than 100 times as Mr. Trump countermanded much of Mr. Obama’s environmental legacy.
Under Mr. Biden, Ms. McCarthy was charged with leading a “whole-of-government” approach in which nearly every federal agency enacted new regulations designed to address climate change. She had also hoped to guide Congress toward passage of new climate laws that could not be rolled back by a future president, ensuring a steady drop in the nation’s greenhouse emissions.
Zolan Kanno-Youngs contributed reporting.