Colorado oil and gas industry leaders are highlighting a study led by Boulder researchers that found methane emissions from drilling haven’t made large increases despite big boosts in energy production across the country over a decade.

The probe, led by scientists at the National Oceanic and Atmospheric Administration and University of Colorado Boulder, also found some previous studies showing significant hikes in methane emissions overestimated the amount of pollution coming from oil and gas activity, by as much as 10-fold in some cases.

“The assumption of a time‐constant relationship between methane and ethane emissions has resulted in major overestimation of an oil and gas emissions trend in some previous studies,” the paper stated.

That’s because some previous studies have failed to observe that ethane-to-methane ratios are increasing, causing major overestimations of oil and gas emission trends, a news release stated.

“What this means is if you want to track methane, you have to measure methane,” the paper’s lead author Xin Lan stated in the release.

But emissions of methane — a greenhouse gas that is the second-largest contributor to human-caused global climate change behind carbon dioxide, according to the release — related to oil and gas activity are still increasing at about 3.4% on average each year, with a plus-or-minus margin of 1.4%, the paper stated.

It was published last month by Geophysical Research Letters and included examinations made from 2006 to 2015 of 20 regional sites across North America that were selected because they capture air masses that are well-mixed and represent influences of emissions from large areas, five of which were heavily impacted by oil and natural gas development.

At three of those five sampling sites, methane emissions moderately increased, the study found. A post by Energy In Depth, a project of the Independent Petroleum Association of America, pointed to Environmental Protection Agency estimates that natural gas production was up 51% and oil production up 80% from 1990 through 2017 without emissions increasing as steadily, suggesting recent extraction projects have avoided polluting as much as those of the past.

But the study did find emissions of ethane and propane — also greenhouse gases — at the sites “are substantially larger on a relative basis than increases in oil and natural gas (methane) emissions.”

Overall, methane concentrations in air samples were shown by the study to be growing at the same rate as the global background, a news release on the paper stated.

Colorado Oil and Gas Association CEO Dan Haley took the study’s results as a sign that government regulations and industry efforts aimed at curbing drilling emissions are working.

“Colorado’s oil and natural gas companies are actively cooperating with the state health department’s task force efforts around pneumatic (meaning operated by pressurized air or gas) devices and the Statewide Hydrocarbon Emission Reduction program, as well as implementing many best management practices in the field to reduce emissions,” Haley stated through a spokesman. “While leaks may occur, that is exactly why Colorado’s first-in-the-nation air rules were put in place in 2014, requiring leak detection and repair practices and requiring operators to install technology that captures 95% of emissions. In Colorado, that commitment has resulted in significant emission reductions by industry, particularly methane and volatile organic compounds.”

Lan, the study’s author, noted the probe did not analyze health impacts of oil gas development for residents living nearby drilling operations, which other recent research has suggested is too difficult to meaningfully gauge due to uncertainties about the effects of simultaneous short and long-term exposures to multiple potentially harmful substances that can be emitted from oil and gas sites.