Experts said it’s difficult to make direct comparisons between President Trump’s various moves on regulations and their effect on rising temperatures. He’s weakened emissions rules on the power sector and, separately, oil and gas operations. He’s also threatened to remove the United States from the Paris climate agreement.

Now there’s reason to believe that yesterday’s move to halt car rules could be the most consequential in terms of putting more greenhouse gases in the atmosphere, several experts said.

“I think it’s fair to say that if they’re successful in rolling back the clean car and fuel economy standards, it would…