Global atmospheric levels of methane, a potent but short-lived greenhouse gas, rose by a record amount last year, the National Oceanic and Atmospheric Administration said Thursday, worrying scientists because of the role importance of methane in climate change.
The preliminary level of airborne methane jumped 17 parts per billion, reaching 1895.7 parts per billion last year. This is the second year in a row that methane has increased at a record rate, with a 15.3 ppb increase in 2020 compared to 2019, according to NOAA.
Methane levels are now well over double pre-industrial levels of 720 parts per billion, said Lindsay Lan, an atmospheric scientist at NOAA and the University of Colorado.
The role of methane in climate change
According to the Intergovernmental Panel on Climate Change (IPCC), methane is a major contributor to climate change, causing an increase in temperature of around 0.5°C since the 19th century. Carbon dioxide caused about 50% more warming than methane.
It is the only greenhouse gas whose emission reductions can rapidly cool the climate– Zeke Hausfather, climatologist
“This trend of accelerating methane increases is extremely concerning,” said Robert Howarth, a methane researcher at Cornell University.
Methane is about 25 times more powerful at trapping heat than carbon dioxide. But it only lasts nine years in air instead of thousands of years like carbon dioxide, Lan said.
Because it doesn’t last long in the air, many countries agreed last year to target methane for rapid emissions reductions as a low-hanging fruit in global efforts to limit future warming to 1 .5 or 2 C since pre-industrial times. The world has already warmed by 1.1 to 1.2 C.
“To limit warming to well below 2°C this century, we need to drastically reduce our methane emissions, and today we are clearly moving in the wrong direction,” climate scientist Zeke Hausfather of Stripe and Berkeley Earth said in a statement. E-mail.
“Reducing methane has great immediate benefits for the climate, because it is the only greenhouse gas for which emission reductions can quickly cool the climate (instead of slowing or stopping the rate of warming ).”
NOAA has been monitoring methane levels in the air since 1983.
Lan said early signs point more to natural causes of the methane jump, due to La Nina, the natural, temporary cooling of parts of the Pacific that alters weather around the world, but it’s still early days.
La Nina tends to bring more rain in some tropical regions and the two consecutive years of record increases during La Nina indicate that methane is leaking from wetlands, she said.
Where does methane come from?
Methane is the main component of natural gas, an increasingly used source of energy. Much of the methane comes from livestock and human agriculture, as well as landfills. Scientists also fear the future release of methane trapped under the ocean and in the frozen lands of the Arctic, but there is no evidence of this happening on a large scale.
The key question is whether this upward trend could aggravate climate change concerns or is it a pandemic-related event due to the decrease in methane-destroying nitrogen oxides due to a decrease in automobile and industrial pollution, said Rob Jackson, a climatologist at Stanford University.
“It seems to be something else instead of COVID,” Lan said. It figures high levels in 2020, then even higher levels in 2021, when containment measures were relaxed, far from a pandemic effect.
Fossil fuels and agriculture are both key to the rise in methane, Howarth said. But he said, “my research strongly indicates that fossil fuels are the main cause of the increase since 2008, with increased emissions from shale gas production from hydraulic fracturing in the United States being one. important part”.
In a study last year, Lan looked at chemical isotopes to isolate where the steady increases in methane emissions since 2006 might have come from. The chemical signature has moved away from fossil fuels as the biggest culprit and more towards the emissions from natural wetlands or agriculture, she said.
NOAA also said carbon dioxide levels in the atmosphere last year rose 2.66 parts per million from 2020, one of the highest increases in history, but not a record. The annual average for 2021 for carbon dioxide was 414.7 parts per million. Pre-industrial is about 280 parts per million.
NOAA said carbon dioxide levels are now the highest they’ve been in around 4.3 million years, when sea levels were around 23 meters higher and the average temperature was around 3 .9°C warmer.
“Our data shows that global emissions continue to move in the wrong direction at a rapid pace,” NOAA Chief Rick Spinrad said in a statement.