Although the E.P.A.’s own staff scientists recommended tightening the current emissions rule, Mr. Wheeler said the scientific evidence was insufficient to merit doing so.

Douglas Buffington, the deputy attorney general of West Virginia, said the rule “represents a big win for West Virginia coal.”

“If they had been tightening it could have been a huge blow to the coal industry,” he said

Already, president-elect Joseph R. Biden Jr. is planning to move forward quickly in his first months in office to reinstate and strengthen many of the environmental rules rolled back by Mr. Trump

“We’re starting to see evidence that long-term exposure to air pollution — which disproportionately affects communities of color & low-income communities — is linked to COVID-19 death rates.”

Mr. Biden’s environmental policy proposals include a pledge to “prioritize strategies and technologies that reduce traditional air pollution in disadvantaged communities.

PM 2.5 pollution contributes to tens of thousands of premature deaths annually, and that even a slight tightening of controls on fine soot could save thousands of American lives

“There is a growing body of evidence that it is linked to neurological damage. And there is a growing body of evidence linking exposure of PM 2.5 to elevated levels of increased Covid morbidity.”

“The arguments against this rule are strong,” he said. “Even before that Harvard study there was very strong scientific evidence that stronger controls are merited. The Covid crisis reinforced that, but we didn’t need the Covid crisis to tell us that.”

The new rule retains a standard enacted in 2012, during the Obama administration. That rule limited the pollution of industrial fine soot particles — each about 1/30th the width of a human hair, but associated with heart attacks, strokes and premature deaths — to 12 micrograms per cubic meter

When E.P.A. scientists conducted that mandatory review, many concluded that if the federal government tightened that standard to about nine micrograms per cubic meter, more than 10,000 American lives could be saved a year.

The scientists wrote that if the rule were tightened to nine micrograms per cubic meter, annual deaths would fall by about 27 percent, or 12,150 people a year.

After the publication of that report, numerous industries, including oil and coal companies, automakers and chemical manufacturers, urged the Trump administration to disregard the findings and not tighten the rule

In September, the world entered La Niña, a phase of the climate pattern that also brings El Niño and affects weather across the world. La Niña is marked by cooler-than-normal sea surface temperatures in the eastern and central tropical Pacific Ocean.

2020 was on track to be one of the three warmest years ever, the organization’s secretary-general, Petteri Taalas, said that La Niña’s cooling effect “has not been sufficient to put a brake on this year’s heat.”

“Something to keep in mind is that the average global temperature is increasing at an unprecedented rate due to human influences,” she said. “That’s the main factor here.”

The Copernicus service scientists said the warm conditions in the Arctic last month had slowed the freeze-up of ice in the Arctic Ocean. The extent of sea-ice coverage was the second lowest for a November since satellites began observing the region in 1979. A slower freeze-up could lead to thinner ice and thus more melting in the late spring and summer.

Other sectors less directly affected by public health concerns — industries that were at recessionary levels just a few months ago — kept improving. They are not necessarily back to pre-pandemic levels, but on track to get there before much longer.

The list of sectors fitting that basic pattern — still at levels consistent with a recession but clawing their way back steadily — is long,

But as corporate executives make their capital spending plans and as consumers make their spending decisions, surging stocks do tend to have a positive effect. That would imply that the positive effects of new market highs over recent weeks should start to show up as public health concerns recede.

The December employment numbers cover a period before Congress reached a compromise pandemic aid package worth $900 billion. Among other things, the bill includes enhanced unemployment benefits that will help the hundreds of thousands of workers whose jobs disappeared in December, as well as $600 checks that should strengthen consumer spending in the months ahead

Moreover, the Democratic victories in Georgia this week and the resulting Senate majority make it more likely that those checks will grow to $2,000 per person

Mr. Barr, 70, is the strongest proponent of presidential power to hold the office of attorney general since Watergate.

He managed to heal fissures between the White House and the Justice Department that broke open when the president learned that his campaign was under investigation related to Russia’s interference in the 2016 election.

But weeks after taking office, Mr. Barr released a summary of the report by the special counsel, Robert S. Mueller III, that a judge later called distorted and misleading

And after the election, Mr. Barr opened the door to politically charged election fraud investigations, authorizing federal prosecutors to investigate “specific allegations” of voter fraud before results were certified.

Mr. Barr soon asked John H. Durham, the U.S. attorney in Connecticut, to open an investigation into the Russia inquiry itself to seek out any wrongdoing under the Obama administration

Pairing the Durham announcement with that revelation was widely seen as an effort to placate Mr. Trump, who was said to be enraged that Mr. Barr had publicly contradicted him.

Throughout the presidential campaign, Mr. Barr was among the loudest voices warning that mail-in ballots would result in mass election fraud. He routinely claimed in speeches and interviews that the potential for widespread voter fraud was high and posed a grave danger. Mr. Barr’s claims were sometimes false or exaggerated and were widely refuted.

“I don’t have empirical evidence other than the fact that we’ve always had voting fraud. And there always will be people who attempt to do that,” Mr. Barr said in September. He called his conclusions “common sense.”

In October, he secretly appointed Mr. Durham a special counsel assigned to seek out any wrongdoing in the course of the Russia investigation.

Mr. Barr broke his silence a few days later, telling The Associated Press that he had not seen evidence of election fraud on a scale that would have changed the fact that Mr. Biden won.

“To date, we have not seen fraud on a scale that could have effected a different outcome in the election,” he said.