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Surge in methane emissions risks efforts to slow climate change

Global concentrations of methane are growing faster in the atmosphere than at any time in the last two decades according to a paper from the journal Environmental Research Letters.

13 DEC 2016 | CHRIS SEEKINGS
Methane reduction the 'best opportunity to slow climate change quickly' ©iStock
Methane reduction the 'best opportunity to slow climate change quickly' ©iStock


It explains how between 2014 and 2015, concentrations shot up by ten or more parts per billion (ppb) annually, following an initial surge around 2007.

This is in stark contrast from the early 2000s when methane went up by 0.5ppb on average each year, with the increase thought to be largely as a result of emissions from agricultural sources such as rice paddies and cattle pastures.

Paper co-author, professor Robert Jackson, said: “The levelling off we've seen in the last three years for carbon dioxide (CO2) emissions is strikingly different from the recent rapid increase in methane.

“The results for methane are worrisome, but provide an immediate opportunity for mitigation that compliments efforts for CO2.”

Methane is much less prevalent in the atmosphere than CO2, but a more potent greenhouse gas, trapping 28 times more heat, making it responsible for 20% of global warming produced by all well-mixed greenhouse gases.

The lifespan for methane is also much shorter than CO2, and therefore getting it under control has the potential to rapidly address climate change according to the research.

“Methane presents the best opportunity to slow climate change quickly, CO2 has a longer reach, but methane strikes faster,” Jackson continued.

“The fossil fuel industry has received most of the attention in recent years but agricultural emissions need similar scrutiny.

“We still need to cut CO2 emissions, but cutting methane provides complementary benefits for climate, economies and human health.”

It is estimated that 60% of methane emissions are due to human activity, with approximately a third of this coming from fossil fuel exploration, where it can leak from oil and gas wells during drilling, but the largest human contributor to emissions is thought to be is agriculture.

However it is still unclear what caused the sudden spike in methane concentrations seen since 2007 or what is driving the increase.

The paper’s lead author, Marielle Saunois, said: "Why this change happened is still not well understood.

“For the last two years especially, the growth rate has been faster than for the years before. It's really intriguing."

Although there are uncertainties, practices that could help reduce methane in the atmosphere could also be beneficial to crop production, as well human health according to the paper.

Such practices include:

•    Modifying ruminants’ diet (such as cattle)
•    Developing farm bio-digesters
•    Modification of rice agriculture practices
•    Venting and flaring of methane in coal mines
•    Detecting and removing natural gas leaks
•    Covering landfills to produce biogas for energy.

“If we want to stay below a two degrees temperature increase, we need to make a rapid turn-around and should do more about methane emissions,” Saunois added.