Methane Emissions Have Been Surging, And No One Is Quite Sure Why

Rice paddies are a source of methane. Witthaya Khampanant/Shutterstock

Much has gone into studying the impacts that the rising level of carbon dioxide is having on the climate. But going somewhat unnoticed has been the creeping rise of the global methane concentrations.

Most of the talk has focused on what will happen when the permafrost melts, and rightly so, but it turns out that while CO2 emissions have been stabilizing over the last decade, methane emissions have already been rocketing. The speed at which they have been increasing has been quantified, and the results have shocked those in the scientific community.

The researchers warn that while most of the effort is currently focussed on reducing the amount of carbon dioxide being pumped into the atmosphere, this could be undermined if the rapidly increasing emissions of methane are not tackled simultaneously. Writing in an editorial for the journal Environmental Research Letters, the international team of scientists behind this latest news implores other researchers to fill in the gap in knowledge surrounding methane emissions.

The current data shows how since 2007 CH4 emissions have been rising, and while at the beginning of the century the yearly increase of methane in the atmosphere was around 0.5 parts per billion (ppb), in 2014 and 2015 this figure had surged to 10 ppb per year, with the total now standing at 1,830 ppb. This is of grave concern, as while there is more carbon dioxide in the atmosphere, methane is actually about 20 times more potent a greenhouse gas.

“The leveling off we've seen in the last three years for carbon dioxide emissions is strikingly different from the recent rapid increase in methane,” explained the University of Stanford’s Robert Jackson, co-author of the 2016 Global Methane Budget. The difficulty comes, says Jackson, in keeping track of the methane. While power plants and the burning of fossil fuels is a clear source of carbon dioxide, there are many different sources for methane. 

To make things harder, many of these are natural. Wetlands and marshes produce a lot of gas, while the melting permafrost is expected to increase this further. But Jackson points out that despite this, over half of all methane emissions are still due to human activities, mainly through agriculture. Cows and pigs produce a lot of the stuff, while the conditions created through the cultivation of rice paddies are ideal for microbes that also release methane.

But what has really puzzled the scientists has been the sudden uptick in emissions.

“Why this change happened is still not well understood,” said Marielle Saunois, lead author of the new paper. “For the last two years especially, the growth rate has been faster than for the years before. It's really intriguing.”

One thing is for certain, however, if methane emissions are not addressed, then the 2°C (3.6°F) warming limit is even more unachievable than before.

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