U.S. leader Donald Trump is poised to replace former President Barack Obama’s plan to slash power plant greenhouse gas emissions with a substitute that could actually increase them.

The move, combined with a rollback of automobile efficiency mandates proposed earlier this month, represents a significant retreat from the fight against climate change by a president who’s already vowed to pull the U.S. out of the Paris agreement. Transportation and electric generation are the biggest sources of heat-trapping gas emissions in the U.S., accounting for 56 percent of the total in 2016, according to the Environmental Protection Agency. “The administration is taking aim at the two most significant climate protections that our nation has put in place to address the threat of climate change,” said Tomas Carbonell, director of regulatory policy at the Environmental Defense Fund.

Where Obama envisioned sweeping changes across the nation’s electric grid, Trump’s replacement focuses on boosting efficiency at coal-fired power plants, according to people familiar with the proposal who asked not to be identified describing an internal document. Those efficiency gains could encourage utilities to run their power plants more often, undercutting environmental benefits. The release of the new plan, expected within days, comes during a summer dominated by wildfires and hotter-than-normal weather. Northern Europe has withered in a deadly heat wave. California recorded its hottest July on record as its forests burned on an unprecedented scale. At least 116 people in Japan have died this summer, with the country posting its highest-ever temperatures in July. Meanwhile, parts of India are dealing with the worst flooding in a century.

Obama’s Clean Power Plan aimed to cut emissions from U.S. energy production 32 percent by 2030 relative to 2005 levels. It did that by looking beyond individual power plants and encouraging broad changes such as shutting down coal plants that are responsible for 67 percent of power sector emissions, using more cleaner-burning natural gas and boosting renewable electricity.

Obama’s approach — trying to compel broad changes in the nation’s electricity mix rather than regulating just what comes out of the smokestacks at power plants — sparked legal challenges from opponents who said it overstepped the EPA’s authority under federal law. The U.S. Supreme Court put the plan on hold in February 2016. “It’s a fact that the power market is changing, but EPA doesn’t have any authority to speed that up or to slow that down,” said Jeff Holmstead, a former assistant EPA administrator now at Bracewell LLP. “Its authority under this section of the Clean Air Act is to minimize emissions from individual plants.”

The Trump administration’s proposal takes a narrow view of what technology should be employed at individual facilities. For instance, it would not prescribe big changes such as forcing individual power plants to employ carbon capture technology or switch to cleaner fuels. Instead, the plan would encourage coal plants to make heat-rate improvements — or efficiency gains — that translate into fewer carbon dioxide emissions per unit of generated electricity. Such changes — such as adding automation or replacing worn turbine seals — would yield at most a 6 percent gain in efficiency, along with a corresponding fall in greenhouse gas emissions, according to EPA modeling under Obama.

Representatives of the EPA didn’t respond to an email seeking comment.

Analysts and environmental activists say that if the Trump administration requirements allow plants to generate more power with each ton of coal, they would produce cheaper electricity and better compete with natural gas. And coal plant owners would be inspired to run them more. This rebound effect from generating more power (and corresponding emissions) could eclipse any gains from paring the carbon dioxide generated along with each unit of electricity.

“You have a lower operating cost and you can run more,” said John Larsen, director of the Rhodium Group, a research firm. “All the modeling I’ve seen suggests emissions might actually rise if you’re forcing everybody to get more efficient, because they are more efficient and cost effective.”

The Trump administration’s drafted proposal also would give states more flexibility to write their own requirements and consider “the remaining useful life” of power plants — a benchmark in federal law. That approach reflects the bounds of the Clean Air Act, and the fact that there’s no national ambient air standard for carbon dioxide, Holmstead said.

But critics say that state departures and variances would undercut already modest requirements. “Without national standards, you get a race to the bottom,” said David Doniger, senior strategic director of the Natural Resources Defense Council’s Climate and Clean Energy Program. “There are some states that would be inclined to give their sources a break just because they don’t care,” and others that might feel pressure from neighboring states to do the same thing.

Once hailed as transformational, the ambitions of Obama’s Clean Power Plan have appeared more modest in hindsight. Even without its requirements in effect, the U.S. is on track to reduce carbon dioxide emissions 28 percent below 2005 levels by 2030, according to a forecast from the government’s Energy Information Administration.

But the plan offered a guarantee that those emissions reductions would be preserved, while creating a long-term framework for achieving further progress, Carbonell said.

And environmentalists say weakening the Obama rule now, while also freezing vehicle emissions standards at 2020 levels, as the administration proposes, could mean lost momentum in an urgent crusade against climate change.

The EPA and National Highway Traffic Safety Administration jointly proposed Aug. 2 to cap fuel economy requirements at a fleet average of 37 miles per gallon (59 kilometers per gallon) starting in 2020. Under the regulation put in place by Obama, the requirements are set to rise gradually to roughly 47 mpg (75 kpg) by 2025.

“We have an existential threat if we don’t deal with this,” Doniger said. “If the marketplace alone is reducing power plant carbon pollution, but not enough to meet the climate crisis, then we should be strengthening the Clean Power Plan now, not junking it.”