WILL NATURAL GAS HINDER the fight against global warming?

America’s abundant supplies of unconventional gas have the potential to be a rich economic and environmental blessing. New extraction techniques — hydraulic fracturing, or “fracking” — make the country’s vast reserves accessible at low cost. The fact that burning natural gas produces about half the carbon emissions as coal means the fuel could be an attractive, affordable alternative, giving lower-carbon energy options more time to become less expensive.

But extracting and transporting all that natural gas, which is mostly methane, also results in fuel leaks. When methane leaks, it has a shorter-lived but much stronger global warming effect as the carbon dioxide released when the same amount of methane is burned. Particularly on relatively short time frames of 10 or 20 years, too much methane leakage can make the fuel less attractive than even dirty old coal, some critics warn.

A new study published in the Proceedings of the National Academy of Sciences estimates when using natural gas results in sustained climate benefits — and when it doesn’t. Assuming the Environmental Protection Agency’s estimate of the industry’s methane leakage rate — 2.4 percent — is accurate, choosing to build a new gas power plant instead of a new coal plant produces immediate greenhouse emissions benefits, and that would be the case even if the leakage rate were nearly a point higher. Replacing old, inefficient coal plants with new natural gas facilities would presumably produce larger benefits. But using natural gas to run cars wouldn’t reduce net climate impacts for 80 years. Fueling heavy-duty trucks with natural gas wouldn’t result in greenhouse emissions benefits for 300 years.

These results undercut the environmental rationale for the proposed Natural Gas Act, which would provide federal support for converting America’s heavy-truck fleet to run on natural gas. But they underscore the appeal of rules about to be finalized at the EPA, which would require natural gas producers to prevent leaks from wells, pipelines, storage tanks and other infrastructure. The rules are designed to reduce the release of volatile organic compounds that form dangerous smog, but the EPA estimates that they would also result in the collection of 3.4 million tons of methane annually, a quarter of current methane emissions from the sector. On top of environmental benefits, gas producers would have more product to sell. Reducing leaks might not be a money-making proposition at every well — and the industry naturally claims the government is off in its figures — but the EPA reckons that, overall, new standards will save the industry about $30 million a year.

The Obama administration must issue the final regulations by Tuesday. As long as regulators have a reasonable confidence that drillers will have enough time to deploy the necessary equipment, the rules will help ensure that natural gas contributes to the fight against climate change inexpensively, and perhaps mightily. Congress, meanwhile, should not go out of its way to push natural gas into the transportation sector any more than market forces already are.