– The United States is on the verge of losing more than half of its low-carbon energy as the fight against climate change reaches a critical point — a reality the country hasn’t fully grappled with.

That’s according to findings recently published by researchers at the University of California, San Diego, Harvard University and Carnegie Mellon University in the journal Proceedings of the National Academy of Sciences.

The paper — “U.S. nuclear power: The vanishing low-carbon wedge” — paints a picture of an industry on the verge of collapse. Facing economic competition from cheap natural gas, a significant number of U.S. nuclear power plants could be retired in the coming years, the authors wrote.

“We’re asleep at the wheel on a very dangerous highway,” said Ahmed Abdulla, co-author and fellow at the School of Global Policy and Strategy at UC, San Diego. “We really need to open our eyes and study the situation.”

The U.S. now has a choice of abandoning nuclear power altogether or embracing the next generation of smaller, more cost-effective reactors, the report says.

However, researchers argue, the second option is unlikely because it would require accelerating the regulatory review process and a sizable infusion of public money.

“It’s really surprising that one of our best weapons in our fight against climate change is at risk of utter collapse because of the economic and political challenges and not the technical ones,” Abdulla said.

While it might be a long shot, the promise of nuclear power has captured the imagination of many younger academics in recent years.

More students are pursuing nuclear engineering degrees than at any time since the early 1980s, with graduation rates in the field tripling between 2001 and 2015, according to survey data from the Oak Ridge Institute for Science and Education.

“Where else are you going to get a job where you can tell your grandkids that you saved the world?” said Per Peterson, a professor in the University of California, Berkeley’s Department of Nuclear Engineering. “They don’t think they’re going to get rich.”

Still, environmental groups have remained skeptical about the value of nuclear energy, given anxiety about safety and cost. While advocacy groups have expressed concerns about replacing phased-out nuclear plants with fossil-fuel plants, many would rather focus on supporting renewable sources.

“The danger is that the amount of subsidy that nuclear would require would suck all the energy out of supporting the other renewables,” said Edwin Lyman, a physicist at the Union of Concerned ­Scientists.

Dan Jacobson, director of Environment California, echoed those concerns. “Nuclear power in its current form has been an incredibly expensive way to boil water,” he said. “If you’re really trying to decarbonize our grid, we would rather spend those billions on efficiency, conservation and renewables.”

Nuclear energy produces roughly 20 percent of the nation’s power supply, compared with about 17 percent for all renewables combined, according to the U.S. Energy Information Administration. Wind and solar, for example, produce about 7.6 percent.

While aggressive efforts continue to develop batteries for storing intermittent sources of electricity from solar and wind, utilities are embracing natural gas. The fossil fuel now produces nearly 32 percent of U.S. power.

Scientists question whether renewables would be able to offset the losses from retiring nuclear plants in time to stave off the worst consequences of climate change.

“The reality is you cannot actually replace 20 percent of the need with wind and solar, unless you want to wallpaper every square inch of many states,” said Christian Back, a vice president at General Atomics. “It’s not efficient enough.”