(Reuters) - Methane leaking out of the more than 4 million abandoned oil and gas wells in the United States and Canada is a far greater contributor to climate change than government estimates suggest, researchers from McGill University said on Wednesday.
Canada has underestimated methane emissions from its abandoned wells by as much as 150%, while official U.S. estimates are about 20% below actual levels, the study, published in Environmental Science and Technology, found.
The U.S. Environmental Protection Agency and Environment and Climate Change Canada did not immediately respond to a request for comment on the study.
More than a century of oil and gas drilling has left behind millions of abandoned wells around the globe, posing a serious threat here to the climate that governments are only starting to understand, according to a Reuters special report last year.
Methane has more than 80 times the warming potential of carbon dioxide in its first 20 years in the atmosphere.
In 2019, methane emissions from abandoned wells were included for the first time in U.S. and Canadian greenhouse gas inventories submitted to the United Nations.
But the McGill study found there are about 500,000 wells in the United States that are undocumented along with about 60,000 in Canada. It also found that the EPA and ECCC had come up with emissions estimates that were far too low - a conclusion the researchers said was based on their own analysis of emissions levels from different types of abandoned wells in seven U.S. states and two Canadian provinces.
Emissions measurements were also not available from major oil and gas-producing states and provinces like Texas and Alberta, adding to uncertainty around the official data, the study said.
The study was co-authored by McGill professor Mary Kang, who in 2014 was the first to measure methane emissions from old drilling sites in Pennsylvania.
Reporting by Nichola Groom; Editing by Marguerita Choy
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