Air Pollution: How Much Methane Is Contributed by Humans?

The amount of methane that has been emitted into our atmosphere through the combustion of fossil fuels could have been grossly underestimated, according to a new study. The research, published in the scientific journal Nature and led by Benjamin Hmiel from the University of Rochester in New York, analysed the ice bubbles trapped in ice cores in Greenland and Antarctica to reach its results.

By examining samples that have been in situ since before the Industrial Revolution (and in the case of the Antarctica samples, even prior to that) and cross-referencing their findings against recent estimates of methane emissions, the team ascertained that the amount of methane naturally emitted is approximately 10 times lower than previously anticipated, meaning that anthropogenic emissions (mostly caused by the fossil fuel industry) are far higher than we thought.

Natural vs manmade

It’s no surprise that concerns over methane have been growing of late – the gas is the second biggest contributor to global warming behind carbon dioxide. But while methane persists in the atmosphere for far shorter a time period than CO2, it is much more effective at absorbing heat. This is what makes is such a dangerous element, since it can be as much as 84 times more potent as a greenhouse gas (GhG) than CO2.

There are plenty of natural sources of methane across the world, such as wetlands, oceans and termites. However, these emissions are entirely offset by methane sinks, which have kept methane levels relatively steady across the millennia. However, the intervention of the human race – particularly since the beginning of the Industrial Revolution in the mid-18^th century – has seen emissions skyrocket. This latest study reveals that the hike may be even more steep than previously imagined.

Way off the mark

Previous estimates of manmade methane emissions based their assessments on an inventory of known natural sources of methane, but the research from Hmiel and his team was novel in its analysis of actual measurements taken directly from the ice. Their results showed that emissions from natural sources over several centuries were far lower than previously believed, meaning that anthropogenic emissions must account for a much higher percentage.

Specifically, the team found that natural emissions between 1750 and 2013 were roughly 10 times fewer than other research papers had indicated. This means that the methane emitted via anthropogenic means (such as fossil fuel combustion, livestock rearing and landfills) must be far higher. Fossil fuel emissions alone are believed to be between 25% and 40% greater than previous estimates led us to believe.

In our own hands

While the research may appear to show discouraging results, the good news is that methane’s relatively short shelf life means that any action we do take now will have rapid consequences. “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,” explained Hmiel. “If we can reduce our emissions, it's going to have more of an impact.”

With fossil fuel combustion accounting for around a third of all manmade methane emissions, more conferences showcasing new and innovative solutions to the problem could be the answer. “Placing stricter methane emission regulations on the fossil fuel industry will have the potential to reduce future global warming to a larger extent than previously thought,” continued Hmiel.