A major new study blows up the whole notion of natural gas as a short-term bridge fuel to a carbon-free economy.

Natural gas is mostly methane (CH4), a potent heat-trapping gas. If, as now seems likely, natural gas production systems leak 2.7% (or more), then gas-fired power loses its near-term advantage over coal and becomes more of a gangplank than a bridge. Worse, without a carbon price, some gas displaces renewable energy, further undercutting any benefit it might have had.

Fifteen scientists from some of the leading institutions in the world — including Harvard, NOAA and Lawrence Berkeley National Lab — have published a seminal study, “Anthropogenic emissions of methane in the United States.” Crucially, it is based on “comprehensive atmospheric methane observations, extensive spatial datasets, and a high-resolution atmospheric transport model,” rather than the industry-provided numbers EPA uses.

Indeed, the Proceedings of the National Academy of Sciences study by Scot Miller et al takes the unusual step of explicitly criticizing the EPA:

The US EPA recently decreased its CH4 emission factors for fossil fuel extraction and processing by 25–30% (for 1990–2011), but we find that CH4 data from across North America instead indicate the need for a larger adjustment of the opposite sign.

D’oh!

How much larger? The study found greenhouse gas emissions from “fossil fuel extraction and processing (i.e., oil and/or natural gas) are likely a factor of two or greater than cited in existing studies.” In particular, they concluded, “regional methane emissions due to fossil fuel extraction and processing could be 4.9 ± 2.6 times larger than in EDGAR, the most comprehensive global methane inventory.”

This suggests the methane leakage rate from natural gas production, which EPA recently decreased to about 1.5%, is in fact 3% or higher.

This broad-based look at methane emissions confirms the findings of 3 recent leakage studies covering very different regions of the country: