Written by Patrick Galley / Science Alert
Emissions of methane – a planet-warming gas several times more potent than carbon dioxide – have risen by nine percent in a decade driven by humanity’s insatiable hunger for energy and food, a major international study concluded Wednesday.
Methane (CH4) has a warming potential 28 times greater than CO2 over a 100-year period and its concentration in the atmosphere has more than doubled since the Industrial Revolution.
Over a 20-year period, it is more than 80 times as potent.
While there are a number of natural methane sources such as wetlands and lakes, the team behind the study concluded that 60 percent of CH4 emissions are now manmade.
These sources fall principally into three categories: extracting and burning fossil fuels for power, agriculture including livestock, and waste management.
The 2015 Paris climate agreement saw nations commit to limit temperature rises to “well below” two degrees Celsius (3.6 Farenheit) above pre-industrial levels.
While emissions are expected to fall somewhat this year due to the pandemic, the levels of atmospheric methane are increasing by around 12 parts per billion each year.
This trajectory is in line with a scenario modelled by the Intergovernmental Panel on Climate Change (IPCC) that sees Earth warming as much as 3 to 4 degrees Celsius by 2100.
“Regular updates of the global methane budget are necessary … because reducing methane emissions would have a rapid positive effect on climate,” said Marielle Saunois, a researcher at France’s Laboratoire des Sciences du Climat et de l’Environment and lead on the study.
“To meet the objectives of the Paris Agreement, not only do CO2 emissions need to be reduced but also methane emissions.”
The Global Carbon Project, a consortium of more than 50 research institutions around the world, has gathered data from more than 100 observation stations.
The world now produces around 50 million additional tonnes of methane every year than it did between 2000-2006.
Around 60 percent of human-made CH4 emissions were estimated to come from agriculture and waste, including as much as 30 percent from the digestive processes of cattle and sheep.
Twenty-two percent comes from the extraction and burning of oil and gas, while 11 percent leaks from the world’s coal mines, the study found.
But recent studies based on new techniques for spotting methane leaks using satellite data suggest that emissions from the oil and gas sector may be significantly higher than those shown in the study, which only included data through 2017.
Short-term threat
While the overall trend is upwards, emissions levels fluctuate between regions.
For instance, Africa, China and Asia each produce 10-15 million tonnes annually. The US churns out around 4-5 million tonnes.
Europe is the only region where methane emissions are falling – between 2-4 million tonnes since 2006, depending on the estimation method.
The United Nations says that to hit the more ambitious Paris target of a 1.5 degrees Celsius warming cap, all greenhouse gas emissions must fall by 7.6 percent annually this decade.
“The 20-year framework (of methane’s warming effect) may be more appropriate given our policy goals,” said Saunois.
