Among greenhouse gasses, methane is now the second most important one causing climate change. Its expansion in the last few years can be linked to the larger development of shale gas and shale oil, according to a new study based on chemical fingerprints.
The research, published in the journal Biogeosciences, reports that methane released from the exploitation of shale gas and oil a different carbon-13/carbon-12 ratio than conventional natural gas and other fossil fuels such as coal, which serves as a chemical signature of sorts.
This carbon-13 signature means that since the use of high-volume hydraulic fracturing (also known as fracking) shale gas has greatly contributed to the global release of methane into the atmosphere, according to the paper’s author, Robert Howarth.
The level of methane in the atmosphere had previously risen during the last two decades of the 20th century but tapered in the first decade of the 21st century. Then, they increased dramatically from 2008–14 due to global human-caused methane emissions in the last 11 years.
“This recent increase in methane is massive,” Howarth said. “It’s globally significant. It’s contributed to some of the increase in global warming we’ve seen, and shale gas is a major player.”
While it increased in the atmosphere, the carbon composition of the methane has also changed. Methane from biological sources such as cows and wetlands have low carbon-13 content -- compared to methane from most fossil fuels. Previous studies erroneously concluded that biological sources are the cause of the rising methane, Howarth said.
About two-thirds of all new gas production over the last decade has been shale gas produced in the United States and Canada. Global shale-gas production has exploded 14-fold, from 31 billion cubic meters per year in 2005 to 435 billion cubic meters per year in 2015.
Unlike carbon dioxide, the climate system responds quickly to changes in methane emissions and reducing methane emissions could provide an opportunity to immediately slow the rate of global warming and meet the goal of the Paris Agreement to limit the temperature increase to 2ºC.
“If we can stop pouring methane into the atmosphere, it will dissipate,” Howarth said. “It goes away pretty quickly, compared to carbon dioxide. It’s the low-hanging fruit to slow global warming.”
