PARIS • Global emissions of the potent greenhouse gas methane may be double current estimates, posing an added challenge in the fight against climate change, according to a new study.
The study was published on Wednesday, the same day the United Nations announced that the landmark Paris climate pact will come into force next month.
"Both emissions inventories and atmospheric studies have underestimated methane emissions from fossil fuel development," said Dr Stefan Schwietzke, a scientist at the US National Oceanic and Atmospheric Administration and lead author of the study.
Emissions from industry and natural geological sources combined "are 60 to 110 per cent greater than current estimates", he added.
The study, published in the peer- reviewed journal Nature, is based on a database 100 times larger than previous ones, and uses a methodology that avoids debatable assumptions underlying earlier models. Within the figure, the methane leaked during the production and use of natural gas, oil and coal is 20 per cent to 60 per cent higher than previously thought.
The new findings may have serious implications for efforts to cap global warming at "well under" 2 deg C, the target laid down in the Paris Agreement, experts say.
"Emissions scenarios used for climate prediction need to be reassessed taking into account revised values for anthropogenic (or human-generated) methane emissions," said Professor Grant Allen of the University of Manchester, commenting on the study.
Reaching the UN-backed temperature target, in other words, could be harder than once thought.
While not as abundant or long- lived as carbon dioxide, methane is 28 times more efficient at trapping heat in Earth's atmosphere over a 100-year time span. It is the second-largest contributor to global warming after carbon dioxide.
Methane concentrations in the atmosphere started to soar in 2007. Experts disagree as to why, but fossil fuels are apparently not to blame, the study said.
"Methane emissions from fossil fuel development have been dramatically underestimated," said Dr Schwietzke. "But they're not responsible for the increase in total methane emissions observed since 2007."