What did Donald Trump do today?

He promised to raise the amount of pollution cars can emit by about 54%.

Trump said today that he would roll back pollution emission standards for vehicles to what they were during his first term. The difference is dramatic: it would allow cars to emit 54% more greenhouse gases per mile traveled (204 grams per mile vs. 132) and SUVs and other light trucks to emit 52% more (284 g/mi vs. 187).

"It doesn't mean a damn bit of difference to the environment. It doesn't matter," he said of the regulations. Trump, who is 78, insists that climate change from the buildup of greenhouse gasses is a "hoax," and in fact may even believe it—although he's also taken every other position on the matter, too, depending on when he was asked.

In reality, climate change is a real and urgent problem, acknowledged by everyone from the United States military to Trump's own golf course in Ireland, and vehicle emissions contribute to it.

Trump claimed he would this as a favor to the American car industry, although they'll be unlikely to thank him for it. The existing standards are for models through the year 2026, which are already in production, and there wouldn't be much advantage to radically retooling later models that already have the fuel efficiency improvements spurred on by the current standards. 

It's more likely that Trump was caught flat-footed by the reporter who was asking him about his call with the CEO of Stellantis, the multinational company that makes Jeep, Chrysler, and Ram vehicles in the United States. The reporter asked if Stellantis executives had raised concerns about the massive tariffs Trump is about to impose on American car buyers—a subject on which the company has not been shy.

Trump denied it, and then insisted that the call had instead been about "trouble" that Stellantis had had with the environmental regulations all their cars and trucks already meet.

Why does this matter?

• Ignoring a problem doesn't make it go away.

• Scrapping environmental regulations to benefit industry isn't great, but if a president is going to do that, at the very least they should be regulations that industry wants to have scrapped.