Humans responsible for much higher methane emissions than estimated

Rodiano Bonacci
Febbraio 20, 2020

Tiny bubbles of ancient air trapped in ice cores from Greenland suggest we've been seriously overestimating the natural cycle of methane, while vastly undervaluing our own awful impact.

The oil and gasoline business has had a far worse influence on the local weather than beforehand believed, in accordance with a study indicating that human emissions of fossil methane have been underestimated by as much as 40%.

"Our results imply that anthropogenic methane emissions now account for about 30 percent of the global methane source and for almost half of [all] anthropogenic emissions..." the authors write.

The findings are particularly worrying as although methane naturally breaks down quickly in the atmosphere (relative to CO2), it's also a very powerful greenhouse gas, with a global warming potential (GWP) 104 times greater than Carbon dioxide over a 20-year time frame.

"As a scientific community we've been struggling to understand exactly how much methane we as humans are emitting into the atmosphere", says Vasilii Petrenko, a geochemist from the University of Rochester.

More specifically, the researchers detected and counted the carbon-14 isotope in the samples, which is absent from natural sources of methane such as geological seepage, and could therefore be used to distinguish between these sources and the methane generated by human activity.

By drilling and collecting ice cores in Greenland, Petrenko and his colleagues were able to use this isotope as a sort of time capsule for past atmospheres, ranging from roughly 1750 to 2013.

Until about 1870, the findings suggest very low levels of methane were emitted into the atmosphere and nearly all of it was biological in nature. Things started to change after about 1870, when the fossil component began rising rapidly; they explain that this coincides with a sharp increase in fossil fuels at the time. If we're responsible for more of the methane in the atmosphere today, efforts to reduce our emissions would have an even better impact on the climate.

Methane has a greenhouse impact that's about 80 occasions stronger than carbon dioxide over a 20-year interval and is chargeable for at least 25% of worldwide heating, in response to the UN Environment Programme. An earlier study revealed methane emissions from U.S. oil and fuel vegetation have been 60% greater than reported to the Environmental Protection Agency.

"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", Hmiel concludes.

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