Emissions of methane, a powerful greenhouse gas, have increased sharply since 2012, according to a group of researchers. But they struggled to put their finger on why. EURACTIV France reports.
This news is sure to worry the experts at the Intergovernmental Panel on Climate Change (IPCC), which is due to publish its latest research on the state of climate change in 2017.
A greenhouse gas 28 times more powerful than CO2, emissions of methane have skyrocketed in the last four years. But this year’s Global Methane Budget, an annual report that has scrutinised the changing levels of atmospheric methane since 2000, found no clear culprit.
60% of emissions come from human activities such as farming and burning fossil fuels, while the remaining 40% are natural, coming mainly from the earth’s humid zones. This makes methane emissions more difficult to calculate than CO2, which comes largely from industrial activities.
Methane is also something of an oddity as it autodestructs on contact with ozone molecules. This harms the ozone layer, but reduces methane’s longevity in the atmosphere to around ten years.
“This makes methane a good target for regulatory policies,” said Marielle Saunois, a researcher at the French Laboratory for Climate and Environmental Sciences (LSCE), which contributed to the study.
But the increase is more serious than the worst case scenario previously imagined by the IPCC.
Atmospheric methane levels have more than doubled since 1750 and it now accounts for 20% of man-made global warming. This is all the more concerning given the modest amount of research dedicated to the gas, compared to CO2.
As a result, methane, which has only been measured in a serious way since the 1980s, remains surrounded by a certain mystery. The stabilisation of methane levels between 2000 and 2006 has never been adequately explained. And neither has its rebound since 2012.
Emissions are growing faster in some regions than others, particularly South America, South-East Asia and China.
Tropical regions naturally emit more methane due to their humid climates. But the researchers thought it likely that unchecked coal mining in China and gas extraction in Russia, as well as the expansion of rice paddies and landfill waste in South-East Asia, was more to blame for the recent spike in emissions.
Within the fossil fuels industry, oil producers have made efforts to cut their methane emissions, notably by burning off the gas as it comes out of the ground, converting it into less harmful CO2.
Yet emissions from the industry are rising nonetheless. Shale gas exploitation has exploded in recent years, particularly in the United States, but the researchers were unable to isolate a clear “shale effect” on atmospheric methane levels.