Vehicles and power plants are by far the biggest producers of greenhouse gases in Colorado, contributing roughly 50% of all planet-warming emissions in our atmosphere, according to recent state estimates.

Oil and gas wells, which leak the greenhouse gas methane into the air, are thought to be a distant fourth on the list of top emitters, contributing about 12%.

But in fact, no one really knows how much oil and gas operations are adding to greenhouse gas levels.

State monitoring and inspection of wells is flawed, as The Story Group reported in The Colorado Independent in April. The state’s method for tracking methane emissions is murky. Some estimates indicate oil and gas emissions are rising. Other data indicates they’re likely falling.

To get a more accurate picture, state environmental regulators are considering requiring oil and gas operators to routinely measure and report their methane emissions as early as June of 2020.

The data would use used as part of the state’s greenhouse gas inventory, which the Colorado Department of Public Health and Environment updated last week with more recent estimates. The report, issued every five years, tracks the emissions of greenhouse gases, including carbon dioxide, methane and nitrous oxide, from sources ranging from livestock to coal mines. These heat-trapping gases are the main sources of global warming, as opposed to volatile organic compounds, or VOCs, which lead to increases in ozone levels and create poor air quality.

The greenhouse gas inventory is key to gauging the state’s progress toward meeting its ambitious climate goals: cutting greenhouse gas emissions 50% by 2030 and 90% by 2050, compared to 2005 levels.

But as it stands, some of the data in that inventory can be misleading. One issue, experts say, is the state bases its methane emissions estimates on models using federal data rather than measuring them directly.

As a result, the state may have been underestimating historical emissions from oil and gas drilling, said Garry Kaufman, deputy director of the Colorado Department of Public Health and Environment’s Air Pollution Control Division.

“That is something that we need to sort out. The whole inventory is not an exact science,” Kaufman said.

The state’s nine-member Air Quality Control Commission, which oversees Colorado’s air quality programs, will decide whether it will require drillers to do the additional reporting and monitoring later this summer.

The Colorado Independent sought comment from oil and gas industry representatives, but they did not respond in time for publication.

The Air Quality Control Commission will consider the new reporting requirements because Democratic lawmakers passed a bill in May requiring it. The legislation also gives the Colorado Department of Public Health and Environment money to hire new staff to help develop and implement the new rules.

The state first took an inventory of greenhouse gas emissions in 2014 by executive order of former Gov. Bill Ritter. That same year, new rules went into effect requiring drillers to find and repair methane leaks, among other regulations. Whether the repairs reduced emissions is unknown, because the state doesn’t regularly track the effect of the repairs. Critics point to this as another flaw in the emissions estimate.

State officials and industry groups argue the 2014 regulations have reduced emissions from oil and gas operations. But the state does not have comprehensive data to support the claims.

The latest emissions inventory report estimates greenhouse gases peaked in 2010 and will decline slightly through 2030. But the report projects that the state still will produce twice as much greenhouse gas as the new climate goals call for in 2030.

“This is sort of a glass-half-full, glass-half-empty piece of data,” said Kaufman, of the Colorado Department of Public Health and Environment. “We have a long way to go before we are going to meet the goals that are set for us.”

In addition to more stringent reporting requirements by drillers, some environmental advocates argue the state needs to include in its calculations emissions from fossil fuels that are exported to heat homes and power cars out of state.

Jeremy Nichols, director of the climate and energy program at environmental advocacy group WildEarth Guardians, said burning fossil fuels releases far more greenhouse gases than are created during the extraction process.

“I think it’s time to demand a more thorough accounting,” Nichols said. “How can you ignore the fact that you are just exporting all these fossil fuels?”