Methane shock

| 20th February 2020
Tiny bubbles of methane trapped in lake ice in Norway
Methane emissions from fossil fuels owing to human activity is around 25 percent to 40 percent higher than thought

If we can reduce our emissions, it's going to have more of an impact.

Scientists have been vastly underestimating the amount of methane humans are emitting into the atmosphere through fossil fuels, according to research.

Analysis published in the journal Nature shows methane emissions from fossil fuels owing to human activity is around 25 percent to 40 percent higher than thought.

But researchers believe their findings offer hope, saying stricter regulations to curb methane emissions could help reduce future global warming to "a larger extent than previously thought".

Ice core

Benjamin Hmiel, a professor of earth and environmental science at the University of Rochester and one of the study authors, said: "I don't want to get too hopeless on this because my data does have a positive implication: most of the methane emissions are anthropogenic, so we have more control.

"If we can reduce our emissions, it's going to have more of an impact."

Methane emissions to the atmosphere have increased by around 150 percent over the past three centuries, according to the researchers.

Determining how much of these heat-trapping emissions originate from human activity has been a challenge for scientists as methane can be emitted naturally, from biological sources such as wetlands or animals.

Prof Hmiel and his colleagues used ice core measurements from Greenland from between 1750 and 2013 and previous data from Antarctica.

Persist

Ice core samples contain air bubbles with small quantities of ancient air trapped inside, which can act like time capsules.

The researchers use a melting chamber to extract the ancient air from the bubbles and then analyse its chemical composition.

They found that almost all of the methane emitted into the atmosphere had been biological until about 1870, around the time when humans started using fossil fuel.

They also found that methane emissions from fossil fuels are underestimated by about 38-58 teragrams per year.

Methane is the second largest contributor to global warming after carbon dioxide, but it has a relatively short shelf-life as it lasts an average of only nine years in the atmosphere, while carbon dioxide can persist for about a century.

Net zero

According to the researchers, this makes methane "an especially suitable target for curbing emission levels in a short time-frame".

Phillip Williamson, honorary reader at the University of East Anglia, who was not involved in the study, said: "These results indicate that human activities are inadvertently responsible for much more of the problem of rising methane.

"Yet that is actually good news, since it should mean that there are now greater incentives to prevent methane leaks from oil and gas extraction.

"Furthermore, the phase-out of these fossil fuels on the pathway to net zero will bring the bonus of reducing atmospheric methane more rapidly than we had expected."

This Author

Nilima Marshall is a PA science reporter. 

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