In the New York Times, Joe Nocera says that natural-gas fracking is inevitable and just needs a few tweaks, like plugging methane leaks from wells. But that’s not as simple as it sounds. Recent research suggests that fracking could be disastrous, climate-wise, if those leaks aren’t fixed.

Working at a hydraulic fracturing site in South Montrose, Pennsylvania. (Spencer Platt/Getty)

Modeling studies have suggested that if more than 2 percent of the methane from natural-gas production is escaping out into the air, then natural gas’ climate advantage over coal starts to vanish. One recent paper, led by Tom Wigley of the National Center for Atmospheric Research, found that switching from coal to natural gas could, in some cases, prove worse for the planet if leakage rates are above that level. (Michael Levi of the Council on Foreign Relations offers some caveats on Wigley’s study, noting that this isn’t as pressing a concern if natural gas use is phased out in fairly short order. But that’s not a given.)

So how much methane is actually escaping from shale-gas wells? That’s a tricky question, since industry groups tend not to share their data. Officially, the EPA pegs the leakage rate at around 2 percent. One hotly debated study from Cornell’s Robert Howarth, meanwhile, found that the leakage rate could be as high as 7.8 percent, which would make natural gas considerably more effective at cooking the planet than coal. A more recent study led by researchers at the National Oceanic and Atmospheric Administration sampled the air over natural-gas wells in the Denver-Julesburg Basin and estimated the methane leakage at around 4 percent (that didn’t include any possible leaks from distribution pipelines).

Now, there’s still a lot of uncertainty in these estimates — it would help if industry data were more readily available. And it’s true, as Nocera says, that companies are experimenting with cost-effective ways to capture this methane and plug these leaks, though it’s conceivable that regulations would be needed to force their adoption. (See here for a rundown of some of these technologies.) But for now, a major environmental rationale behind natural gas — that it’s a cleaner way to generate electricity than coal — partly depends on these leakage rates. And those remain a big question mark.

Meanwhile, Nocera’s column oddly neglected one of the fiercest controversies around fracking — namely, whether the drilling process itself contaminates nearby water supplies. So far, the evidence that fracking (in which drillers inject underground shale wells with water, chemicals, and sand to extract gas) poses serious risks to human health is fairly scant and much disputed. For example, one study found that drinking wells near the Marcellus Shale contained 17 times as much methane as those half a mile away, but it’s still unclear whether the methane came from the fracking site itself or from other, shallower deposits.

Still, this is a major reason why fracking has run into so much opposition in parts of Pennsylvania and New York, and it’s a big reason why environmentalists have soured on natural gas in recent years. Bill McKibben has a long, comprehensive essay charting the green disillusionment with natural gas in the New York Review of Books, and Pete Aldhous has a piece in New Scientist looking at the public-health science that surrounds fracking. Aldhous notes that, although the evidence on this subject is still patchy, concerns about water contamination “could even bring the shale gas bandwagon to a halt.”