Republican presidential candidate Donald Trump puts on a miners hard hat during a rally in Charleston, W.Va., Thursday, May 5, 2016. (AP Photo/Steve Helber)

If coal and energy issues are at the top of the list of things you care about, you had to sit through a lot of other stuff during last night’s presidential debate, but eventually you heard from Republican Donald Trump and Democrat Hillary Clinton on this issue.

It was the next-to-last question from an audience member:

What steps will your energy policy take to meet our energy needs, while at the same time remaining environmentally friendly and minimizing job loss for fossil power plant workers?

Over at West Virginia MetroNews,  Brad McElhinny ran through their responses in a piece posted earlier this morning. Brad also cited “fact-check” stories by the Los Angeles Times and the Associated Press. They mostly focused on the question of whether Secretary Clinton wants to put all of the nation’s coal miners out of work, an issue that is more political theater than policy or reality (see my previous analysis of this whole question here).

The thing that really needs fact-checked from this whole exchange is this from Mr. Trump:

There is a thing called clean coal. Coal will last for 1,000 years in this country.

Coal will last for 1,000 years in this country? Really? Wow.

Remember this from four years ago? That time that then-GOP presidential nominee Mitt Romney said, in an ad attacking President Obama’s “war on coal”, said: “We have 250 years of coal, why wouldn’t we use it?”

After looking into it at the time, here’s what we published in the Gazette:

In new campaign ads criticizing the Obama administration’s coal policies, Republican presidential candidate Mitt Romney cites an estimate of the nation’s remaining coal reserves that has been increasingly questioned as overly optimistic.One of two new Romney ads includes footage of his visit last month to an Ohio coal mine, with a voiceover of a Romney speech where he says, “We have 250 years of coal, why wouldn’t we use it?”

Various industry publications have cited that same estimate, saying, “The United States has more than a 250-year-supply of coal if it continues using coal at the same rate at which it uses coal today.”

But in a major report five years ago, the National Academy of Sciences concluded that the best estimate it could confirm was that U.S. coal reserves would last less than half that long.

“The United States is endowed with a vast amount of coal,” said the report, written by a panel of geologists, engineers and industry officials for the National Academy’s National Research Council.

“Despite significant uncertainties in generating reliable estimates of the nation’s coal resources and reserves, there are sufficient economically mineable reserves to meet anticipated needs through 2030,” said the report, written at the request of the late Sen. Robert C. Byrd, D-W.Va. “Further into the future, there is probably sufficient coal to meet the nation’s needs for more than 100 years at current rates of consumption,” the report said. “However, it is not possible to confirm the often-quoted suggestion that there is a sufficient supply of coal for the next 250 years.”

Republican presidential nominee Donald Trump points at Democratic presidential nominee Hillary Clinton as he speaks during the second presidential debate at Washington University in St. Louis, Sunday, Oct. 9, 2016. (Saul Loeb/Pool via AP)

This sort of wild overstatement, while certainly not unusual coming from Mr. Trump — or the coal industry for that matter — is important, especially in the context of Mr. Trump’s promises over and over that he’s going to get the nation’s (and especially West Virginia’s) coal miners back to work.

When fact-checking that Romney ad, I checked out several scientific journal articles on the subject and interviewed their authors, and here’s more of what was published in the paper:

Questions about coal reserve figures and future production forecasts are important, especially in the Appalachian coalfields. A variety of factors have the region’s mine operators struggling and miners losing their jobs, and experts project major production declines during the next quarter century.Along with stiff competition from low-priced natural gas and from other coal basins, experts have long warned of an impending downturn in Central Appalachian coal because much of the region’s highest quality and easiest-to-produce coal has been mined out.

“In general, the remaining reserve potential is in thinner, deeper coal beds that are of poorer general quality than the coal that has already been mined,” Robert C. Milici, a geologist with the U.S. Geological Survey, wrote a dozen years ago in the International Journal of Coal Geology.

(In an updated paper in 2013, Milici and others wrote this:  “In spite of its large endowment of coal resources, recent studies have indicated that United States coal production is destined to reach a maximum and begin an irreversible decline sometime during the middle of the current century. However, studies and assessments illustrating coal reserve data essential for making accurate forecasts of United States coal production have not been compiled on a national basis. As a result, there is a great deal of uncertainty in the accuracy of the production forecasts.”)

In addition, that story on Gov. Romney’s ads reported:

The 250-year-supply estimate the Romney campaign repeated is based at least in part on 2006 U.S. Department of Energy projections that put the nation’s recoverable coal reserves at about 267 billion tons and on current projection levels of about 1 billion tons a year.

But when it examined that estimate, the National Research Council warned that, “a combination of increased rates of production with more detailed reserve analyses that take into account location, quality, recoverability, and transportation issues may substantially reduce the estimated number of years supply.”

Finally:

Tad Patzek, chairman of the Department of Petroleum and Geosystems Engineering at the University of Texas at Austin, has written about how estimates of world coal reserves could be greatly inflated, at least if you want to use them to project future production capabilities.

In a paper published two years ago by the journal “Energy,”  Patzek warned that society is likely to more quickly use up not necessarily all of the available coal, but chip away at the reserves that are easiest to reach and of highest quality. It’s possible industry developments could make thinner and deeper seams more economical to mine, but there’s no way for sure to predict such changes, that paper said.”When people refer to 250 years, there are a lot of assumptions about a lot of things,” Patzek said this week. “My hunch is that we are just way, way too optimistic.”

So if Mitt Romney’s 250-year figure was “way too optimistic,” what is the world is Donald Trump’s 1,000 years?