During campaign stops throughout coal country, Donald Trump repeatedly promised to put miners back to work, vowing to reverse four decades of economic history.

In early May, speaking before a cheering West Virginia crowd filled with miners wearing hard hats or holding “Trump Digs Coal” signs, the then-Republican nominee pledged: “Get ready because you’re going to be working your asses off.”

With his upset victory last week, the president-elect now must make good on what many energy experts always saw as an empty promise—or, far more likely, explain in four years why he couldn’t.

Few doubt the Trump administration will move swiftly to unravel environmental rules that are wildly unpopular across the fossil fuel industry, allowing a dangerous rise in greenhouse gas emissions. But observers say no amount of regulatory rollbacks can bring the coal sector roaring back at this point.

That’s because regulations aren’t the industry’s real problem—market forces are. Coal’s true rival is cheap natural gas, which was freed in soaring volumes during the last decade through fracking. Coal’s economics meant it simply couldn’t compete.

Meanwhile, mining jobs have been in decline since a boom in the 1970s, falling even while production climbed, largely due to shifts toward highly mechanized and less labor-intensive methods like mountaintop removal and strip mining. There were more than a quarter of a million U.S. coal mining jobs in 1979. As of October, there were fewer than 54,000, according to the Bureau of Labor Statistics.

Of course, none of this fits with the coal industry’s preferred narrative, which is that battered companies and miners are victims of the Obama administration’s environmentally obsessed “war on coal.”

“If the industry had spent more time trying to innovate and solve their problems, instead of shaking their fist at the EPA, they might be in a better position to compete,” says James Van Nostrand, director of the Center for Energy and Sustainable Development at the West Virginia University College of Law.

Despite growing global demand for cleaner energy sources, the coal sector has so far made precious few research investments into the carbon capture and storage technologies necessary to make “clean coal” more than an empty slogan.

None of this is to say that a Trump administration won’t make a show of trying to help the coal industry, as part of its broader ideologically driven push to deregulate energy. Trump said that climate change is a hoax perpetuated by China, vowed to back out of the landmark Paris climate agreement, argued for eliminating the Environmental Protection Agency, and promised to kill the Clean Power Plan. His campaign energy positions call for ending President Obama’s moratorium on new coal leases and unleashing “hundreds of years in clean coal reserves,” presumably by loosening restrictions on potential mining sites.

To be sure, some of these policy shifts could help maintain coal extraction and energy generation levels, and may even protect a limited number of jobs. In particular, the now endangered Clean Power Plan, which would require states to cut energy sector emissions, was expected to substantially reduce coal production and accelerate closures of coal-fired plants, according to an Energy Information Administration analysis.

But all of Trump’s potential changes would still do little to stimulate new demand for coal given that natural gas is expected to remain cheap and plentiful for the foreseeable future. After all, Trump has also promised to ease regulations on fracking.

At best, the president-elect’s policies may help slow the coal sector’s decline, but they won’t return it to growth at this stage, says Chiza Vitta, a mining analyst with credit ratings firm Standard & Poor's.

Critically, even if all these efforts fail to revitalize the coal industry, they would still exact an enormous toll. Trump’s energy policies may allow billions of tons of additional emissions, narrowing already low odds that the globe will avoid critical warming thresholds that could lock in a cascading series of environmental disasters.