Methane is the second-largest contributor to global warming, second only to carbon dioxide. Despite the pandemic's reduction in human activity, methane emissions have continued to rise in recent years. New research has found that global warming not only increases methane emissions but also slows the rate at which methane is removed from the atmosphere. Overall, the impact of global warming on accelerating methane emissions is four times greater than previously estimated.
The findings help explain the rapid growth of methane emissions and suggest that, if left unchecked, methane-related warming will escalate in the coming decades.
Rising temperatures and wildfires boost methane levels
While atmospheric methane concentrations are not as high as carbon dioxide, its global warming potential is significant. Its 20-year global warming potential is 86 times greater than that of carbon dioxide. In recent years, the world has begun to prioritize methane removal as a key component of climate change mitigation efforts.
Approximately 40% of methane emissions come from natural sources such as wetlands, while 60% comes from human activities such as cattle ranching, fossil fuel extraction, and landfills. According to the National Oceanic and Atmospheric Administration (NOAA), atmospheric methane concentrations exceeded 1,900 parts per billion (ppb) last year (2021), nearly triple pre-industrial levels.
"With the global COVID-19 pandemic raging, human-induced methane emissions should have decreased. However, puzzlingly, methane emissions have actually grown at a faster rate over the past two years," said Simon Redfern, an earth scientist at Nanyang Technological University in Singapore.
He analyzed that possible factors for the increase in methane concentrations include increased oil and gas exploration, emissions from agriculture and landfills, warming of tropical wetlands and melting of Arctic tundra. Another possibility is that the chemical reactions that remove methane in nature have slowed down.
Redfern explained that hydroxyl radicals (-OH) can break down methane in the atmosphere, reducing it. However, they also react with carbon monoxide. The increasing frequency of wildfires in recent years has led to an increase in carbon monoxide, which accelerates the consumption of hydroxyl radicals. Consequently, the rate of methane removal slows.
Redfern and his colleague Chin-Hsien Cheng analyzed methane measurements, climate change, and fluctuations in the amount of hydroxyl to understand its sources. Their findings were published in the journal Nature Communications.
The study shows that rising temperatures not only produce more methane (including by accelerating microbial activity in wetlands), but also slow its removal from the atmosphere (as the number of wildfires increases, leading to a decrease in hydroxyl in the upper atmosphere). Altogether, the impact of global warming on accelerating methane emissions is four times greater than previously estimated.
Redfern said this was a very shocking result, suggesting the impacts of climate change could be more extreme and dangerous than we imagined.
To control global warming, help industries and developing countries reduce methane emissions
"This is really worrying," said Euan Nisbet, project director of the UK-based Global Methane Budget. "The rate at which methane concentrations rise is probably the biggest factor in whether we can achieve the Paris Agreement goals."
Nisbon said that most methane emissions come from recently industrialized or developing countries, and they need help. We need to convince China and India, two of the largest emitters, to join global methane reduction commitments and address emissions from mines, agricultural waste burning, and landfills. We also need to focus on Africa, where methane emissions are likely to grow rapidly due to population growth, burning of agricultural waste, landfills, and warming of natural wetlands.
Reducing and preventing forest fires and biomass burning is another key focus. Redfern said that climate change will accelerate the risk of wildfires, and wildfires will increase the concentration of methane in the atmosphere, which will cause climate change. This vicious cycle is really worrying.
Source: Environmental Information Center (https://e-info.org.tw/node/234559)
