The state is vastly underestimating the amount of local pollution from methane, the primary component of natural gas and among the most potent of the greenhouse gases that causes climate change, according to a significant new study.
The long-term study, released Monday in the Proceedings of the National Academy of Sciences, found six times more methane leaking into the air around the Boston area than the most recent estimate issued three years ago by the state Department of Environmental Protection.
The study, led by scientists at Harvard University and Boston University, also found that despite state laws requiring utilities to spend billions of ratepayer dollars reducing leaks in their vast network of aging gas pipes, the methane appears to be flowing into the region’s air unabated.
With about 1,800 miles of pipes replaced in recent years in Massachusetts, the authors of the paper say their findings show that far greater amounts of methane are likely coming from stoves, furnaces, boilers, and other household appliances than was previously believed. Methane has more than 80 times the warming potential of carbon dioxide over a 20-year period.
“Our policy changes so far have not made a difference,” said Maryann Racine Sargent, the lead author and a research scientist at Harvard’s School of Engineering and Applied Sciences. “This study shows that we have a systemic problem and that the state is missing a big source of emissions. We need to figure out the source of those emissions, so we can meet our climate goals.”
State officials did not respond to requests for comment.
The study used laser spectrometers and other technology to measure methane concentrations at five sites throughout the metropolitan area between 2012 and 2020. By comparing the methane measured at two of those sites — one atop a tall building in Copley Square and another on a smaller building at Boston University — the authors of the study concluded that significant amounts of methane are likely coming from buildings and household appliances.
They did that by measuring emissions there during the shutdown in April 2020 as a result of the pandemic. They found that emissions were 42 percent lower at the Boston University building than the average of previous Aprils in the survey. By contrast, the emissions measured at the building in Copley Square were about the same as they were in the previous Aprils. That was the only April in which methane concentrations were greater at the Copley Square site than the one at Boston University.
The scientists concluded that the discrepancy reflected the reduced use of appliances at office buildings, restaurants, and in dorms on or around the university campus, they said. Unlike appliances, such as stoves or water heaters that release emissions when in use, the pressure in pipelines that April remained constant, and those emissions were likely picked up by the sensors atop the much taller building in Copley Square.
“The BU site was a ghost town, and clearly more influenced by what was happening in the immediate area,” said Lucy Hutyra, a professor of earth and environment at Boston University and one of the study’s authors.
She and other scientists said their study points to the need for states and the federal government to change the way they tabulate their emissions, which rely on complex calculations and estimates, rather than measurements. It also suggests they should be looking beyond pipelines for reducing methane leaks, they said.
“Leaking pipes are a bad thing, but that’s only part of the problem,” Hutyra said. “The policies that we have in place aren’t addressing the other sources.”
Charles Crews, president of the Northeast Gas Association, a trade group representing the utilities, defended the steps taken by gas companies and called reducing methane emissions “a priority for the Boston area.”
But he said, “the most effective and efficient way to reduce methane emissions from gas leaks is continued support of the replacement of leak-prone pipe.”
He noted that gas companies reduced 8 percent of leak-prone pipes in Massachusetts during the study period.
“The utilities have more work to do and are committed to reducing leak-prone pipes to help the state meet its efforts to reduce carbon,” he said.
But environmental advocates and others urged state officials to do more to look beyond spending billions of dollars replacing pipes to reduce leaks.
“Massachusetts has well-intentioned programs that are designed to reduce methane emissions, but this study shows that they may not be working,” said Erin Murphy, a senior attorney at the Environmental Defense Fund, a Washington-based advocacy group that specializes in energy regulation. “Utility regulators need to change course, require the use of methane detection technologies, and consider other ways to reduce emissions other than pipe replacement, such as pipe repair and retirement.”
The study, the longest of its kind, echoed the findings of similar studies in other cities, including Washington, D.C., Los Angeles, and New York. The authors estimated that as much as 36 percent of all lost methane is from the distribution and end use of the gas in urban areas.
In Boston, as much as 4.7 percent of the gas sent to residents is likely escaping into the atmosphere, the authors estimated.
While serving as President Barack Obama’s assistant director of the Office of Science and Technology Policy, Donald Wuebbles led a team that looked into how to improve emissions estimates. It concluded that measuring emissions directly in the atmosphere was needed to improve assessments and verify that governments are doing what they promised.
Wuebbles, a retired professor of atmospheric studies at the University of Illinois, called the study a “thorough analysis” and “unique” in identifying sources of methane concentrations in an urban environment.
“There’s a real problem with counting methane emissions, and it has serious policy ramifications,” he said.
Some state lawmakers said the time for cutting emissions is now, noting that Massachusetts’ new climate law requires the state to cut its greenhouse gases by 50 percent by the end of the decade.
“Keeping up the infrastructure is beginning to look like a hopeless job,” said Senator Mike Barrett, a Lexington Democrat and one of the climate bill’s lead negotiators. “There’s been little progress since 2014, and not for lack of trying. We may be better off walking away from the assets as soon as we can.”
Audrey Schulman, president of the Home Energy Efficiency Team, a Cambridge nonprofit, has been pressing the utilities to reduce their gas leaks for years.
But she said far more needs to be done to reduce the consumption of gas.
“I think this study is akin to having a teacher check our math,” she said. “We are far from the right answer here. We need to adjust our state’s accounting of emissions, while we also potentially consider moving as soon as we can to a non-emitting renewable [energy].”