Humans responsible for 25-40% more methane emissions from fossil fuels than previously thought: Study

Placing stricter methane emission regulations on the fossil fuel industry will have the potential to reduce future global warming to a larger extent, says an expert

                            Humans responsible for 25-40% more methane emissions from fossil fuels than previously thought: Study
(Getty Images)

We have been releasing 25-40% more methane from fossil fuels than previously thought, finds a new study. These findings suggest that we have grossly underestimated our contributions to the "hidden methane problem".

But by regulating methane emissions from the fossil fuel industry, we could potentially reduce future global warming to a larger extent, says Dr Benjamin Hmiel, a postdoctoral associate from the University of Rochester, and the lead author of the study.

Methane, which is a heat-trapping gas, is roughly 30 times more potent than the notorious carbon dioxide. But it lingers in the atmosphere for a shorter period — it lasts an average of only nine years — making it an attractive target for curbing emission levels, says the study. Carbon dioxide, on the other hand, can circulate for about a century. 

What is worse, methane emissions to the atmosphere have increased by approximately 150% over the past three centuries. The greenhouse gas's source can be traced back to human activities — fossil fuels, landfills, rice fields, and livestock — and other natural sources such as wetlands.

But a lot about methane emissions remain unknown: scientists have not been able to completely tease apart individual emissions from each of these sources. In this new study,  scientists turned their attention to a type of methane emission that accounts for fossil fuel: fossil methane

Fossil methane 

In addition to fossil fuels, fossil methane also comes from natural sources — for instance, methane seeps, which is located within the Earth's crust, hordes methane gas. 

Methane emitted into the atmosphere can be sorted into two categories, based on its signature of carbon-14, a rare radioactive isotope (University of Rochester illustration / Michael Osadciw)

"One of these uncertainties is the exact amount of fossil methane that we emit to the atmosphere through our activities," Dr Vasilii Petrenko, a professor at the University of Rochester and the co-author of the study tells MEA WorldWide (MEAWW).

So the team of scientists set out to track methane emissions before and after the dawn of the industrial revolution. To do so, the team studied ice cores from Greenland, which keep a record of the past. In them, scientists examined air bubbles, which trap small quantities of ancient air.  By examining the ancient air from the bubbles, the team could measure the amounts of methane in them.

"What we have done is use ice cores to go back in time to the preindustrial ear (before the year 1750). At that time there was no fossil fuel use or associated emissions," explains Petrenko. 

Their analysis showed a spike in methane post-1870s — an era that coincides with the industrial revolution. The methane was not from biological sources, meaning it did not come from agriculture, wetlands or livestock.

This narrowed down the hunt to fossil methane. Natural fossil methane changes slowly: on very long time scales and is not expected to have changed over the last 250 years, suggesting the role of fossil fuels.

Their calculations revealed that the natural portion of the released fossil methane was very small, accounting for no more than 1% of the total methane source today — 10 times smaller than previously thought.

"This means that almost all fossil methane in the atmosphere today is from our emissions. We are emitting 25 – 40% more fossil methane than we previously thought," adds Petrenko.

Though the situation appears stark, it can be controlled. "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 [against global warming]," explains Hmiel.

The study has been published in Nature.

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