Donald Trump has finally gotten one of the longstanding wishes of his presidency: the weakening of an Obama-era fuel economy standard that made new cars more fuel efficient and more environmentally friendly. The National Highway Traffic Safety Administration and the Environmental Protection Agency announced a new rule on Tuesday that will take its place, one that will increase pollution while the world wrestles with a respiratory virus pandemic and a climate crisis.

Under the new rule, automakers will now have to increase the average fuel economy of their new vehicle fleets by 1.5 percent every year through their 2026 model year lineup, ultimately arriving at an average of around 40 miles per gallon. Under the previous rule — which the EPA under Obama found automakers were “over-complying” with in 2016 — automakers had to increase the average fuel economy of their fleets by 5 percent, with the goal of hitting 54 miles per gallon in the 2026 model year cars.

As the Natural Resources Defense Council (NRDC) points out, the Obama-era standard has already helped cut carbon dioxide emissions by half a billion metric tons, and saved drivers $86 billion in fuel costs, according to EPA’s own data. The new standard, meanwhile, is expected to release one billion metric tons more carbon dioxide into the atmosphere, increase gasoline consumption by around 80 billion gallons, and oil consumption by 2 billion barrels — all at a time when the transportation industry is already the world’s leading source of CO2 emissions.

“We’re watching, in real time, the crippling consequences of President Donald Trump’s weakening of our nation’s health and safety standards,” California attorney general Xavier Becerra said on a call with reporters Tuesday. “It’s become pretty obvious that his backsliding on so many important regulations that protect our health and our environment are having real consequences now.”

The Trump administration’s argument in support of the rollback is, essentially, this: New cars have gotten more expensive as they got more fuel efficient, which has forced more people to either buy used cars or stick with the ones they already own. Since older cars aren’t equipped with the kinds of modern safety features found on new ones, they’re less safe. Lowering the fuel economy standard will reduce the upfront cost of a new vehicle by around $1,000, meaning more people will be able to buy newer, safer cars.

It’s a flawed argument for a number of reasons. For one thing, the administration has given basically no consideration to the fact that average vehicle prices have risen in the US because automakers now heavily favor selling more expensive — and, crucially, more profitable — SUVs and trucks, to the point that many of them are practically removing sedans from their lineups altogether.

While most consumers would likely appreciate a cheaper sticker price, some experts believe that the new rule would ultimately cost them more over the life of these cars. Consumer Reports recently did an analysis that that showed that even if gas prices fall to $1.50 per gallon and stay there for the next 30 years, the rollback “would still increase new vehicle total cost of ownership for consumers.”

There also seems to be no guarantee that the lower cost of fuel economy technology required to meet the new standard will get passed onto consumers in the form of that $1,000 savings. When asked about this during a call with reporters, NHTSA’s acting administrator James Owens said it will basically be up to automakers to use that extra headroom to compete on price.

“We have the force of competition in our country, and at the end of the day, American families will make the their buying decisions based on many different factors, and our automakers will continue, we hope will continue, to compete for those sales,” he said.

The Trump administration has also given little consideration during this three-year process to the fact that, since newer cars now tend to be bigger vehicles, pushing more consumers into these vehicles will directly increase the risk to pedestrians, who have been dying at an alarming rate amid the boom of SUVs and trucks.

This should come as no surprise. Trump’s attempt to roll back the Obama-era standard has been built on flimsy and misleading arguments from the start. When the EPA first officially claimed the Obama-era standard was too aggressive in April 2018, for example, it based that argument on auto industry lobbyist talking points and (what was then) two-year old data.

“[EPA administrator Andrew Wheeler] issued a tweet saying that this new rule would save lives, and reduce pollution, and that it would provide significant benefits to the American economy. In each case, he’s wrong,” Becerra said Tuesday. “We’re prepared to debunk” that, he said.

The new rule announced by NHTSA and the EPA on Tuesday isn’t as harsh a rollback as Trump originally wanted. When the Trump EPA unveiled its first official proposed version of the rule in 2018, it suggested freezing the planned year-over-year gains in fuel economy at their 2020 levels, which would have capped the required gains at 37 miles per gallon.

While automakers started lobbying Trump to roll back the standard within days of him taking office, even they balked at a full freeze. They’ve since split in their alliances. Volkswagen, Ford, Honda, and BMW each struck a deal last year with California to commit to 3.7 percent year-over-year increases in average fuel economy, while General Motors, Toyota, and Fiat Chrysler filed support for the Trump administration concurrent attempt to revoke California’s authority to set its own vehicle emissions standards — standards that around a dozen other states already follow.

The rollback is now likely to face what could be a lengthy challenge in court from states and environmental groups.

“Gutting the clean car standards makes no sense. It will harm the air we breathe, stall progress in fighting the climate crisis and increase the cost of driving,” Gina McCarthy, who led the EPA under Obama and is now president of the NRDC, said in a statement. “I am hoping that automakers know better than to go along with this illegal, ill-conceived and dangerous rollback. The clean cars program helped them bounce back from the 2008 financial crisis and achieve record sales. They should join us in fighting back. We’ll be seeing the Trump administration in court.”

“We intend to make sure that the [Trump administration’s] backsliding doesn’t reach California’s doorstep,” Becerra said. “And we’ll try to make sure that, working with our allies and our coalition partners, we keep this from getting to America’s doorstep.”

Update March 31st, 1PM ET: Added quotes from California’s attorney general.