Not only have there been no large increases in U.S. methane emissions over the last decade, but previous studies have significantly overestimated these emissions from U.S. oil and natural gas production, according to a new peer-reviewed study from the National Oceanic and Atmospheric Administration. As CIRES research scientist and study lead author Xin Lan told E&E News:

“We analyzed a decade’s worth of data and while we do find some increase in methane downwind of oil and gas activity, we do not find a statistically significant trend in the U.S. for total methane emissions.”

The study, which was conducted by researchers at NOAA’s Boulder, Colo., office in collaboration with the University of Colorado and published in Geophysical Research Letters, analyzed atmospheric methane (CH4) measurements from 20 North American sites that included both airplane and surface samples found in the NOAA Global Greenhouse Gas Reference Network (GGGRN) from 2006 to 2015. The researchers determined:

“Our estimated increases in North American ONG CH4 emissions (on average ~ 3.4 ± 1.4 % yr-1 for 2006-2015, ±σ) are much smaller than estimates from some previous studies and below our detection threshold for total emissions increases at the east coast sites that are sensitive to U.S. outflows. We also find an increasing trend in ethane/methane emission ratios which has resulted in major overestimation of oil and gas emissions trends in some previous studies.” (emphasis added)

Methane Emissions Below Detection Levels

From 2006 to 2015 U.S. natural gas production increased significantly from about 18.5 trillion cubic feet (tcf) to nearly 26.6 tcf. Despite a roughly 46 percent increase in production, the NOAA study finds that there was “no increase of total [U.S.] methane emissions” and only a “modest increase in oil and gas methane emissions” that is “much lower than some previous studies suggest.”

In fact, as E&E News reported,

“Recent studies showing increases of methane emissions from oil and gas production have overestimated their volume by as much as 10 times, according to the research.” (emphasis added)

According to the study, a major flaw in the previous estimations – that has fueled an assumption that the “significant” increase in global methane emissions after 2006 was caused by U.S. oil and natural gas operations – is that these studies relied on ethane measurements to estimate methane. From E&E News:

“Instead, according to Lan and other researchers, the spike in methane is more likely to have been caused by natural emissions whose sources can include the digestive tracts of cows, rotting vegetable matter and the activities of termites.”

Previous Methane Studies Flawed

One such ethane study that this latest NOAA and CU study specifically mentions was conducted by University of Colorado Associate Professor Detlev Helmig. In his previous research, Helmig was attempting to pair ethane (another gas that can be emitted during oil and natural gas production) with methane. His 2016 study claimed that ethane emissions had risen dramatically. Notably, the conclusion of his own work undermined his original thesis by stating that it is also released naturally via seepage of fossil fuel deposits, volcanic activity and wildfires, as well as biomass burning.

And as the NOAA study explains, the inconsistencies of using ethane as an estimate of methane emissions go even deeper because the ratio isn’t always the same depending on where in the United States the production is taking place and the time measurements are taken:

“Although [ethane] are appropriate indicative tracers for [oil and natural gas] emissions, [oil and natural gas methane] trends cannot be accurately estimated from [ethane]. Thus any conclusion of a large fossil CH4 increase in the past decade from studies that have used the constant ER assumption is unreliable.” (emphasis added)

As Lan told E&E News,

“What this means is if you want to track methane, you have to measure methane.”

Helmig also more recently attempted to connect ethane and methane emissions with increased ground-level ozone, despite publicly-available data showing that oil and gas production is not a significant contributor to ozone levels.

But that and other data didn’t stop Helmig from blaming ozone levels on oil and gas production. As EID reported at the time, Helmig still suggested that his team’s finding that methane and ethane emissions have increased 4.2 percent annually since 2009 is contributing to spikes in ground-level ozone. In absence of significant real-world evidence, the researchers made this determination by using an atmospheric chemical transport model to forecast significant increases in ground-level ozone throughout the U.S.

It is telling that Helmig presented this research alongside groups like New Yorkers Against Fracking and Physicians for Social Responsibility during a “Keep It In the Ground” February medical symposium in Colorado.

U.S. Methane Emissions Intensity Declining

While the NOAA study only analyzed data through 2015, a recent EID analysis of publicly available federal data demonstrates that U.S. oil and natural gas methane emissions have declined – both in intensity and total emissions – through 2017 in America’s largest producing basins.

The analysis found that methane emissions from onshore U.S. oil and natural gas production fell 24 percent, while oil and natural gas production rose 65 percent and 19 percent, respectively, from 2011 to 2017, according to data from the U.S. Environmental Protection Agency and the Energy Information Administration.

The Permian Basin – the largest oil producing region in the world – saw a 57 percent reduction in methane emissions intensity (emissions per unit of production) as production increased 125 percent from 2011 to 2017. Annual methane emissions from Permian production fell from 4.8 million metric tons (MMT) to 4.6 MMT from 2011 to 2017.

And the Appalachian Basin – America’s largest natural gas producing region and the world’s third largest – experienced a 379 percent increase in production and 82 percent decrease in methane emissions intensity during the same time period. Methane emissions from production in the basin fell from 5.3 MMT to 4.7 MMT.


This latest study from NOAA provides important context as various states like New Mexico, Colorado and Pennsylvania are evaluating methane emissions trends and regulations. Studies such as the ones highlighted by NOAA that have overestimated emissions have also been tools to bolster Democratic presidential hopefuls to campaign on platforms that call for total or partial bans on oil and gas development and for new legislative initiatives to introduce duplicative federal regulations on an industry that is already reducing emissions.