This week’s natural gas headlines are awfully gloomy: “U.S. to Slash Marcellus Shale Gas Estimate 80%,” writes Bloomberg. “Geologists Sharply Cut Estimate of Shale Gas,” declares the New York Times. The stories, based on a new report from the U.S. Geological Survey, all suggest that the United States might have far, far less natural gas — which is expected to provide a cheap, abundant energy source in the decades to come — than previously thought. Terrible news, right?

Well, hold up. As it turns out, some of those stories may have been somewhat premature — and appear to be based on a slight misunderstanding of the USGS survey.

(The Washington Post)

Now along comes Tuesday’s USGS survey with a new topline number: 84 trillion cubic feet. That’s a lot of gas, by any measure. But it’s also far less than 410 trillion or 489 trillion. So doesn’t this vindicate earlier (and oft-criticized) reporting by Ian Urbina of the New York Times that both the government and the gas industry have been exaggerating shale gas resources?

A few caveats. As Brenda Pierce, program coordinator for the USGS energy resources program told me, it’s important to do an apples-to-apples comparison here. The USGS and EIA aren’t measuring the same thing, exactly: The USGS offered an estimate of undiscovered resources that can be recovered with current technology, whereas the EIA report looked at both “active” and “undeveloped” reserves together. “Ours is additive to what’s already in production,” explains Pierce.

So the USGS only surveyed a subset of what the EIA had been measuring. Although the comparison isn’t perfect, USGS’s figure of 84 trillion cubic feet can be lined up against the EIA’s 232 trillion cubic feet of “undeveloped” reserves. What’s more, Pierce notes, the 84 trillion cubic feet is a mean estimate—the USGS survey’s estimates ranged from 43 trillion to 144 trillion cubic feet. So the downward revision could end up being less stark than early media reports implied. Currently, USGS and EIA are working to reconcile the two studies, which will take a few weeks, and we’ll have to await the end result.

Meanwhile, Penn State’s Terry Engelder says that the new USGS report wasn’t necessarily incompatible with his own research. “They have only included part of the sum, so of course it’s going to be smaller,” he says. He also pointed to differences in modeling for how production at gas wells decline over time: Engelder’s study uses a more optimistic curve than the USGS’s conservative model. “It’s important to note that gas yield production is still very immature. We don’t know for sure what the truth is here,” Engelder explains. “It’s possibly between the optimistic and conservative projections.”

In any case, there’s a lot more work to be done in figuring out just how much gas is out there — and how much can be drilled at a profit (the USGS focused on how much gas could technically be extracted, not how much gas could be profitably extracted, an important distinction). Estimating reserves is a rough art, and the New York Times has raised sharp questions about how the government calculates its numbers. And it’s crucial that those numbers are as firm as possible, given the giant role shale gas is likely to play in energy policy for years to come.

(Meanwhile, there’s the separate — but no less controversial — question of whether hydraulic fracturing can be pursued in a safe and ecologically sound manner. Bryan Walsh recently wrote a nice piece on that topic in Time.)