Reviewed by Danielle Ellis, B.Sc.Sep 11 2024
According to a new study published in Environmental Research Letters, Stanford researchers found that worldwide methane emissions increased faster than ever in the last five years.
Methane concentrations in the Earth’s atmosphere have risen at a record rate during the last five years. Human activities currently account for at least two-thirds of yearly methane emissions, which include the use of fossil fuels, agriculture, landfills, and other waste.
The world has not slowed methane emissions, which are a major contributor to climate change. As part of a global methane pledge, more than 150 countries have committed to reducing methane emissions by 30% this decade.
The trend “cannot continue if we are to maintain a habitable climate,” according to the researchers. They published the findings and the data in Earth System Science Data. Both studies are the result of the Global Carbon Project, which is led by Stanford University scientist Rob Jackson and records greenhouse gas emissions across the world.
Methane concentrations in the atmosphere are currently more than 2.6 times greater than they were before industrialization, the highest level in at least 800,000 years. Methane emissions continue to climb along the most severe trajectory utilized in emission scenarios developed by the world's best climate scientists.
If current trends continue, global warming will exceed 3 degrees Celsius (5 degrees Fahrenheit) by the end of the century.
Right now, the goals of the Global Methane Pledge seem as distant as a desert oasis. We all hope they aren’t a mirage.
Rob Jackson, Study Lead Author and Michelle and Kevin Douglas Provostial Professor, Doerr School of Sustainability, Stanford University
More Methane from Fossil Fuels, Agriculture, and Waste
Methane is a short-lived but very potent greenhouse gas produced by both natural and "anthropogenic" sources, including agriculture, fossil fuels, and landfills. During the first 20 years after emission, methane warms the atmosphere almost 90 times faster than carbon dioxide, making it a critical target for reducing global warming in the near future.
Despite an increasing policy focus on methane, total annual methane emissions have climbed by 61 million tons, or 20%, over the last two decades, according to new data. Increases are largely driven by increases in emissions from coal mining, oil and gas production and consumption, cattle and sheep grazing, and landfill decomposition of food and organic waste.
Only the European Union and possibly Australia appear to have decreased methane emissions from human activities over the past two decades. The largest regional increases have come from China and southeast Asia.
Marielle Saunois, Study Lead Author and Professor, Université Paris-Saclay
In 2020, the most recent year for which comprehensive data is available, about 400 million tons, or 65% of worldwide methane emissions, were caused directly by human activities. Agriculture and waste contributed around two tons of methane for every ton produced by the fossil fuel sector. The researchers estimate that human-caused emissions will continue to rise until at least 2023.
Assessing Pandemic Impacts
In 2020, the atmosphere absorbed approximately 42 million tons of methane, which was double the average quantity added each year throughout the 2010s and more than six times the growth witnessed during the first decade of the 2000s.
Pandemic lockdowns in 2020 lowered transport-related nitrogen oxide (NOx) emissions, which normally affect local air quality while preventing methane accumulation in the atmosphere. The short decrease in NOx pollution accounted for over half of the increase in atmospheric methane concentrations that year, demonstrating the complicated interplay between air quality and climate change.
“We’re still trying to understand the full effects of COVID lockdowns on the global methane budget. COVID changed nearly everything – from fossil fuel use to emissions of other gases that alter the lifetime of methane in the atmosphere,” stated Jackson
Quantifying Humans’ Influence on Methane from Wetlands and Waterways
The Global Carbon Project scientists have made a significant revision to their most recent estimate of global methane sources and "sinks," which include forests and soils that capture and store methane from the atmosphere.
Previous evaluations classified all methane from wetlands, lakes, ponds, and rivers as natural. However, the new methane budget is the first attempt to predict the increasing quantity of emissions from these sources, which are caused by human effects and activities.
For example, human-built reservoirs generate an estimated 30 million tons of methane every year when newly buried organic matter decomposes, releasing methane.
Jackson noted, “Emissions from reservoirs behind dams are as much a direct human source as methane emissions from a cow or an oil and gas field.”
In July, Jackson released Into the Clear Blue Sky: The Path to Restoring Our Atmosphere, a book about methane and climate solutions published by Scribner.
According to scientists, nearly a third of wetland and freshwater methane emissions in recent years have been impacted by human-caused variables such as reservoirs and emissions enhanced by fertilizer runoff, wastewater, land use, and warming temperatures.
After a summer of severe weather and heat waves that gave a taste of the extremes projected in the changing climate, the authors stated, “The world has reached the threshold of 1.5C increases in global average surface temperature, and is only beginning to experience the full consequences.”
Gordon and Betty Moore Foundation, UNEP’s International Methane Emissions Observatory (IMEO), the Australian Government’s National Environmental Science Programme’s Earth Systems and Climate Change Hub, and Future Earth supported the study.
Journal Reference:
Jackson, B, R., et al. (2024) Human activities now fuel two-thirds of global methane emissions. Environmental Research Letters. doi.org/10.1088/1748-9326/ad6463