Methane levels in Earth’s atmosphere have surged at an unprecedented rate over the last five years. Currently, at least two-thirds of the annual methane emissions originate from human activities, which include the use of fossil fuels, agriculture, landfills, and waste.
The global response to methane emissions, a significant contributor to climate change, has not been sufficient. Despite commitments from more than 150 nations to reduce these emissions by 30% by the end of this decade under a worldwide methane pledge, recent studies reveal that methane emissions have risen at an alarming pace in the last five years.
The researchers assert in a September 10 perspective piece in Environmental Research Letters, which accompanies data from Earth System Science Data, that this upward trend “cannot persist if we wish to preserve a livable climate.” These studies originate from the Global Carbon Project, an initiative spearheaded by Stanford scientist Rob Jackson, dedicated to monitoring greenhouse gas emissions globally.
Methane levels in the atmosphere are currently more than 2.6 times the levels found in pre-industrial eras, representing the highest concentration in at least 800,000 years. Emission rates of methane are continuing to rise along the most extreme forecast scenarios used by leading climate scientists worldwide.
This trajectory suggests that we could see global warming exceeding 3 degrees Celsius (5 degrees Fahrenheit) by the century’s end. “Presently, the objectives of the Global Methane Pledge seem as unreachable as a mirage in the desert,” stated Jackson, who holds the title of Michelle and Kevin Douglas Provostial Professor at the Stanford Doerr School of Sustainability and is the main author of the article in Environmental Research Letters. “We can only hope they are not an illusion.”
Increased emissions from fossil fuels, agriculture, and waste
Methane is a potent greenhouse gas that, while short-lived, comes from both natural sources like wetlands and human activities, such as agriculture, fossil fuel extraction, and waste management. In the initial 20 years after being released, methane warms the atmosphere almost 90 times more effectively than carbon dioxide, making it a critical target for efforts to reduce global warming in the near future.
However, despite an increasing focus on methane from a policy standpoint, overall annual methane emissions have risen by 61 million tons or 20% over the past 20 years, based on new estimates. This increase is largely fueled by rising emissions from coal mining, oil and gas extraction and consumption, livestock farming, and decaying food and organic material in landfills.
“Only the European Union and possibly Australia seem to have cut back on methane emissions from human activities in the past twenty years,” remarked Marielle Saunois from the Université Paris-Saclay in France, who is the lead author of the study in Earth System Science Data. “China and Southeast Asia have shown the most significant regional increases.”
In 2020, the latest year for which full data is available, nearly 400 million tons, or 65%, of global methane emissions arose directly from human activities, with agriculture and waste accounting for roughly two tons of methane for every ton emitted by the fossil fuel sector. Human-induced emissions appear to have continued to grow through at least 2023.
Understanding the impacts of the pandemic
In 2020, our atmosphere absorbed almost 42 million tons of methane — which is double the typical annual increase during the 2010s and more than six times the rise observed in the first decade of the 2000s.
The lockdowns due to the pandemic in 2020 led to a reduction in transport-related nitrogen oxide (NOx) emissions that typically worsen local air quality but can also impede the accumulation of methane in the atmosphere. The temporary decrease in NOx pollution accounted for about half of the rise in atmospheric methane concentrations that year, highlighting the intricate connections between air quality and climate change.
“We’re still in the process of comprehending the complete effects of COVID lockdowns on the global methane budget,” Jackson noted. “COVID has altered nearly every aspect — from the use of fossil fuels to the emissions of other gases that affect methane’s longevity in the atmosphere.”
Evaluating human influences on methane from wetlands and aquatic ecosystems
The scientists at the Global Carbon Project have made a significant update in their assessment of global methane sources and “sinks,” which are natural systems like forests and soils that absorb and store methane from the atmosphere.
Previously, they classified all methane emissions from wetlands, lakes, ponds, and rivers as natural. However, the new methane inventory attempts to estimate the increasing contributions from these water bodies due to human activities.
For instance, human-made reservoirs are estimated to emit approximately 30 million tons of methane annually, as submerged organic material breaks down and releases methane. “Emissions from reservoirs behind dams should be considered a direct human source, just like methane from livestock or fossil fuel fields,” Jackson stated, adding that he recently released a book titled Into the Clear Blue Sky: The Path to Restoring Our Atmosphere (Scribner) in July, focusing on methane and climate solutions.
The scientists estimate that around a third of methane emissions from wetlands and freshwater sources in recent years have been influenced by human-caused factors such as reservoirs and fertilizer runoff, misguided land use, and rising temperatures.
Following a summer marked by extreme weather events and heatwaves that have foreshadowed the anticipated extremes from our changing climate, the authors conclude, “The world has reached a tipping point with 1.5C increases in global average surface temperature and is only starting to feel the full impact.”
