- Burning fossil fuels emits 38-58 billion kilograms per year more methane than previously thought.
- This is an extra 25 to 40 per cent of methane emissions.
- Scientists believe this means that restrictions on methane emissions would have a greater impact on climate change than expected.
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 per cent to 40 per cent 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”.
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 per cent 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.
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Prof Hmiel and his colleagues used ice core measurements from Greenland from between 1750 and 2013 and previous data from Antarctica. 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 billion kilograms 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. According to the researchers, this makes methane “an especially suitable target for curbing emission levels in a short time-frame”.
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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.”
Do we really know what climate change will do to our planet?
Asked by: Jennifer Cowsill, via email
There is no doubt that greenhouse gas emissions caused by humans are changing our climate, resulting in a progressive rise in global average temperatures. The scientific consensus on this is comparable to the scientific consensus that smoking causes lung cancer.
Our climate is a hugely intricate system of interlinking processes, so forecasting exactly how this temperature increase will play out across the globe is a complex task. Scientists base their predictions on powerful computer models that combine our understanding of climatic processes with past climate data.
Many large-scale trends can now be calculated with a high degree of certainty: for instance, warmer temperatures will cause seawater to expand and glaciers to melt, resulting in higher sea levels and flooding. More localised predictions are often subject to greater uncertainty.