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Boston and other older cities in the Northeast are responsible for as much as twice the amount of methane — among the most potent of greenhouse gases — than previously estimated by federal authorities, a new study found.

The combined emissions of the six cities, which include Providence, New York, Philadelphia, and Washington, D.C., exceed those from some of the nation’s largest producers of natural gas, including the Four Corners region in the West and the Bakken Shale in the Dakotas, according to the study, which included researchers from Harvard University.

To call attention to the worst of the leaks — those responsible for a disproportionate amount of the state’s methane emissions — about 100 climate activists in neon-colored vests gathered Wednesday in downtown Boston around one 13-year-old gusher across the street from the state’s Executive Office of Energy and Environmental Affairs.

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That leak is one of the so-called “super-emitters,” which make up an estimated 7 percent of all the state’s gas leaks but are responsible for about half of the overall methane emissions. Methane, the principal component of natural gas, is significantly more potent than carbon dioxide at trapping heat in the atmosphere over a shorter period.

Before walking onto Cambridge Street, where a dead tree on the median marked the location of the leak, Debbie New demanded that the state hold utilities accountable for plugging the larger leaks. She and others accused the state of failing to enforce a state law passed last year requiring utilities to fix the larger leaks, which the law defines as those having a “significant environmental impact.”

“The state needs to pass regulations that follow the intent and wording of the legislation,” said New, one of the protest’s organizers. “We’re here to hold the utilities accountable — to do what they promised to do.”

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The protesters say the state has violated the spirit of the law by allowing utilities to choose how they plug the leaks, including a cheaper method that they say fails to do the job adequately. In particular, they’ve raised concerns about National Grid using an alternative method that they say has failed to fully stem the largest leaks.

At the end of 2018, the utilities reported more than 16,000 non-hazardous leaks throughout the state, which include an estimated 1,100 super-emitters. The state requires that other leaks be repaired immediately.

In a statement, a spokesman for National Grid defended their method of reducing large leaks, saying the company has repaired 100 of them so far this year. He added that the company plans to use the activists’ preferred method next year.

“Our commitment to reduce greenhouse gas emissions remains the same, and deferring the leak extent method is only temporary,” said Bob Kievra, the company’s spokesman.

State environmental officials defended their implementation of the law. They noted that the rules now require utilities to repair large leaks within one to three years, depending on their environmental impact, and that state has hired an independent contractor to assess the safety of the state’s pipelines.

“As part of its commitment to holding utilities accountable and ensuring the state’s natural gas distribution system is operated in a safe and reliable manner, the Baker-Polito administration was proud to develop regulations supported by environmental stakeholders that establish stricter requirements for timely repairs and ensure the newest technologies can be used to detect leaks,” said Katie Gronendyke, a spokeswoman for the Executive Office of Environmental Affairs.

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But environmental advocates said the rules provide wiggle room for utilities to avoid expediting and accurately locating all of the large leaks.

While they commended some utilities, such as Eversource and Columbia Gas, for using the method they favor to repair the large leaks, they said National Grid has avoided such action. “We want to make it clear to National Grid that methane emission reduction must be a priority,” said Zeyneb Magavi, research director for Home Energy Efficiency Team, or HEET, a Cambridge nonprofit that has sought to reduce gas leaks. “We are in a climate crisis … and slow or delayed action is unacceptable.”

She noted that while carbon dioxide remains the largest source of greenhouse gases, reducing methane emissions could have a significant impact on reducing the threat of global warming. While methane persists in the atmosphere for less time, it’s considered about 86 times more powerful than carbon dioxide at trapping gasses during that period.

She and others at the protest cited the recent study of emissions in Boston and elsewhere — which appears in the journal Geophysical Research Letters — as a source of a concern.

The study relied on data capture by an aircraft equipped with sensors that measured methane and other gases in the atmosphere over Boston and the other cities. The federal inventory of greenhouses gases relies on estimates.

In addition to Harvard researchers, the study was compiled by scientists from the University of Michigan, and the National Oceanic and Atmospheric Administration. The report attributed the source of the methane mainly to natural gas leaks. They did that by identifying the presence of another gas, ethane, which is present in natural gas.

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In all, the researchers found that the cities’ combined methane emissions have totaled about 890,000 metric tons a year — more than twice the existing estimates by the Environmental Protection Agency.

At the protest, members of groups including Mothers Out Front, Gas Leaks Allies, and the Sierra Club, formed a circle around the gas leak on Cambridge Street and held signs with large letters that spelled #FIXBIGGASLEAKS.

Addressing the protesters, Boston City Councilor Matt O’Malley promised he would press utilities to make repairs a priority. “This is not only an environmental issue,” he said. “This is a social justice issue. This is a public health issue.”


David Abel can be reached at dabel@globe.com. Follow him on Twitter @davabel.