Using satellite data, scientists have confirmed that a 2018 blowout turned a natural gas well in eastern Ohio into a “super-emitter,” leaking more methane in 20 days than all but three European nations emit over an entire year.

Methane, a potent greenhouse gas, escaped from the well at a rate twice as fast as the Aliso Canyon leak in California in 2015, a four-month incident that became the nation’s largest accidental release of methane, according to the group of 15 scientists.

The blowout in rural Ohio took place Feb. 15, 2018, at a well owned by XTO Energy, a subsidiary of ExxonMobil, and it took 20 days to get it under control. The well had been “fracked,” or hydraulically fractured, before the blowout took place. Workers had been completing the well, according to news reports at the time, a job made more difficult by heavy rains and a crane that collapsed when the explosion took place.

“We deeply regret this incident occurred and are committed to identifying and managing risks associated with our activities to prevent recurrence,” Julie King, a spokeswoman for ExxonMobil, said in an email.

The new report gauges that the mishap spewed 60 kilotons of methane into the atmosphere – five times the amount ExxonMobil estimated.

“We are eager to learn more about their study,” King said. “ExxonMobil is working with government laboratories, universities, NGOs and other industry participants to identify the most cost-effective and best-performing technology, including satellites, that can be adopted by all producers to detect, repair and accurately measure methane.”

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The accident shines a light on the use of natural gas, which has spread widely, especially in the United States, thanks to the sharp increase in fracking and to opposition to coal-fired power. Natural gas emits only half the greenhouse gas as coal at the point of combustion.

But leaks of methane throughout the production system can undercut the advantage of natural gas and can drive emissions back up to dangerous levels.

Methane is a powerful greenhouse gas, up to 25 times as potent, pound for pound, as carbon dioxide, according to Environmental Protection Agency estimates.

Major oil companies have said that they are improving their ability to capture methane and seal leaks, yet many environmental groups say difficult-to-detect leaks – from the wellhead to the processing plant to the distribution pipes – continue to offset the advantages of natural gas.

The blowout in Ohio was measured by the Tropospheric Monitoring Instrument, a satellite that at the time was doing a routine global survey of methane emissions, scientists said in an article published in the Proceedings of the National Academy of Sciences.

The satellite was able to observe the well on the 13th day of the blowout, and it calculated the changes in well pressure and the speed of emissions.

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“To combat climate change and build a low-carbon economy, being able to accurately monitor greenhouse gas emissions is an essential prerequisite,” the study said. Its authors said that the study shows how methane emissions “from large gas leakages due to accidents in the oil and gas sector can escape the greenhouse gas emission accounting system, adding a significant source of uncertainty to the annual estimates reported to the United Nations Framework Convention on Climate Change.”

“Satellite-based instruments that regularly scan the entire globe provide a means to detect and quantify methane emissions, which are challenging to measure,” said the article, whose lead author was Sudhanshu Pandey of the SRON Netherlands Institute for Space Research.

The group said its paper “highlights the importance of accidental emissions for regional and national-scale emission reporting and inventories, as the lack of incorporating such emissions can lead to significant underestimation of overall emissions.”