Although more than 150 countries around the world have pledged to reduce methane emissions by 30% this decade, new research shows that global methane levels are rising at an unprecedented rate, reaching their highest levels in 800,000 years and matching the most extreme emissions scenarios predicted by climate scientists. Methane is a potent greenhouse gas to which human activities such as agriculture, fossil fuel extraction and waste management contribute significantly. It contributes to global warming, with current trends indicating that global temperatures may rise by more than 3°C by the end of the century, casting doubt on the feasibility of meeting global commitments to reduce methane emissions.
Global methane emissions are surging, undermining efforts to curb climate change. Human activity continues to drive emissions from fossil fuels, agriculture and wetlands, warming the climate beyond safe limits.
Methane emissions are a major contributor to climate change and their growth rate continues unabated. Although more than 150 countries around the world have pledged to reduce methane emissions by 30% this decade, new research shows that global methane emissions have surged at an unprecedented rate over the past five years.
"This trend cannot continue if we are to maintain a habitable climate," the researchers wrote in a perspective article published on September 10 in Environmental Research Letters, which was published simultaneously with the data in Earth System Science Data. Both papers are the result of the Global Carbon Project, which is run by Stanford University scientist Rob Jackson and aims to track global greenhouse gas emissions.
At present, the concentration of methane in the atmosphere is more than 2.6 times that before industrialization, and is the highest value in at least 800,000 years. Methane emission rates continue to rise along the most extreme trajectory used by the world's top climate scientists in emissions scenarios.
On current trends, global warming will exceed 3 degrees Celsius or 5 degrees Fahrenheit by the end of the century. "The goals of global methane commitments now seem as distant as an oases in the desert," said Jackson, the Michelle and Kevin Douglas Provost Professor at Stanford's Dole School of Sustainability and lead author of the Environmental Research Letters paper. "We all hope they are not a mirage."
Methane is a short-lived but potent greenhouse gas that comes from natural sources such as wetlands and human or "anthropogenic" sources such as agriculture, fossil fuels and landfills. In the first 20 years after its release, methane heats the atmosphere nearly 90 times faster than carbon dioxide, making it a key target in limiting global warming in the near term.
Despite increased policy emphasis on methane, total annual methane emissions have increased by 61 million tons over the past two decades, a 20% increase, according to new estimates. The increase is primarily driven by growing emissions from coal mining, oil and gas production and use, cattle and sheep grazing, and the decomposition of food and organic waste in landfills.
"Over the past two decades, only the European Union and Australia have likely reduced methane emissions from human activities. The largest regional increases have come from China and Southeast Asia," said Marielle Saunois of the Université Paris-Saclay in France and lead author of the "Earth System Science Data" paper.
In 2020, the most recent year for which complete data are available, nearly 400 million tons (65% of global methane emissions) came directly from human activities, with methane emissions from agriculture and waste accounting for about 2 tons of methane emissions from the fossil fuel industry. According to researchers, methane emissions from human activities will continue to increase until at least 2023.
By 2020, nearly 42 million tons of methane will have accumulated in our atmosphere, double the average annual increase in the 2010s and more than six times the increase in the first decade of the 2000s.
The pandemic lockdowns of 2020 reduced transport-related nitrogen oxide (NOx) emissions, which typically worsen local air quality, but prevented some methane from accumulating in the atmosphere. The temporary reduction in nitrogen oxide pollution accounted for about half of the increase in methane concentrations in the atmosphere that year - illustrating the complex entanglement between air quality and climate change.
"We're still trying to understand the full impact of COVID-19 lockdowns on the global methane budget," Jackson said. "COVID has changed just about everything - from fossil fuel use to emissions of other gases that change methane's lifetime in the atmosphere."
Scientists at the Global Carbon Project have made an important change in their latest accounting of the world's methane sources and "sinks," including forests and soils that remove and store methane from the atmosphere.
In previous assessments, they classified all methane from wetlands, lakes, ponds and rivers as natural methane. But the new methane budget is the first attempt to estimate the growing amount of methane being emitted from these sources due to human impacts and activities.
For example, human-built reservoirs emit an estimated 30 million tons of methane every year because newly submerged organic matter releases methane as it decomposes. "Methane emissions from reservoirs behind dams are as direct a source of human emissions as methane emissions from cows or oil and gas fields," said Jackson, who published a new book on methane and climate solutions in July called "Into Clear Blue Skies: The Road to Restoring the Atmosphere" (Scribner's).
Scientists estimate that about one-third of wetland and freshwater methane emissions in recent years have been affected by anthropogenic factors, including reservoirs and increased emissions from fertilizer runoff, wastewater, land use and rising temperatures.
In a summer of severe weather and heatwaves that have brought to light the predicted extremes of our changing climate, the authors write: "Global average surface temperatures have already reached a tipping point of 1.5C of warming and are only now beginning to experience the full consequences."
Compiled from /ScitechDaily