One of the main causes of climate change, methane emissions, has not been reduced globally. Under a worldwide methane promise, more than 150 countries have committed to reducing methane emissions by 30% this decade; yet, recent data indicates that methane emissions have increased more quickly than ever before during the last five years.
The trend “cannot continue if we are to maintain a habitable climate,” the researchers write in a perspective article in Environmental Research Letters published alongside data in Earth System Science Data. Both papers are the work of the Global Carbon Project, an initiative chaired by Stanford University scientist Rob Jackson that tracks greenhouse gas emissions worldwide.
Methane concentrations in the atmosphere are at their highest point in at least 800,000 years, more than 2.6 times higher than they were before the industrial revolution. The most extreme trajectory utilized in emission scenarios by the world’s top climate scientists continues to see an increase in methane emission rates.
By the end of this century, global warming will have risen past 3 degrees Celsius, or 5 degrees Fahrenheit, on the current trajectory. Jackson, the lead author of the Environmental Research Letters research and the Michelle and Kevin Douglas Provostial Professor at the Stanford Doerr School of Sustainability, stated, “At this point in time, the objectives of the Global Methane Pledge appear as far away as a desert oasis.” “We all hope they aren’t a mirage.”
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
More methane from fossil fuels, agriculture, and waste
A short-lived but extremely powerful greenhouse gas, methane originates from both natural (such as wetlands) and man-made (or “anthropogenic”) sources, including landfills, fossil fuels, and agriculture. Methane is a major target for containing global warming in the near future since it heats the atmosphere about 90 times quicker than carbon dioxide does in the first 20 years after release.
However, the latest estimates show that over the past 20 years, total yearly methane emissions have risen by 61 million tons, or 20%, despite greater policy focus on methane. Emissions from coal mining, oil and gas production and consumption, cattle and sheep ranching, and the decomposition of food and organic waste in landfills are the main causes of the increases.
“Only the European Union and possibly Australia appear to have decreased methane emissions from human activities over the past two decades,” said Marielle Saunois of the Université Paris-Saclay in France and lead author of the Earth System Science Data paper. “The largest regional increases have come from China and southeast Asia.”
In 2020, the most recent year for which complete data are available, nearly 400 million tons or 65% of global methane emissions came directly from human activities, with agriculture and waste contributing about two tons of methane for every ton from the fossil fuel industry. According to the researchers, human-caused emissions continued to increase through at least 2023.
Assessing pandemic impacts
Our atmosphere accumulated nearly 42 million tons of methane in 2020 — twice the amount added on average each year during the 2010s, and more than six times the increase seen during the first decade of the 2000s.
Pandemic lockdowns in 2020 reduced transport-related emissions of nitrogen oxides (NOx), which typically worsen local air quality but prevent some methane from accumulating in the atmosphere. The temporary decline in NOx pollution accounts for about half of the increase in atmospheric methane concentrations that year — illustrating the complex entanglements of air quality and climate change.
“We’re still trying to understand the full effects of COVID lockdowns on the global methane budget,” said Jackson. “COVID changed nearly everything — from fossil fuel use to emissions of other gases that alter the lifetime of methane in the atmosphere.”
Quantifying humans’ influence on methane from wetlands and waterways
In their most recent estimate of worldwide methane sources and “sinks,” such as forests and soils that absorb and retain methane from the atmosphere, the scientists of the worldwide Carbon Project have made a significant adjustment.
All methane from lakes, ponds, rivers, and wetlands was classified as natural in earlier evaluations. However, the new methane budget attempts to estimate the increasing amount of emissions from these kinds of sources due to human activities and impacts.
For instance, reservoirs built by people lead to an estimated 30 million tons of methane emitted per year, because newly submerged organic matter releases methane as it decomposes. “Emissions from reservoirs behind dams are as much a direct human source as methane emissions from a cow or an oil and gas field,” said Jackson, who published a new book about methane and climate solutions titled Into the Clear Blue Sky: The Path to Restoring Our Atmosphere (Scribner) in July.
According to the experts, human-caused variables such as reservoirs and emissions boosted by fertilizer runoff, wastewater, land use, and rising temperatures are responsible for around one-third of wetland and freshwater methane emissions in recent years.
The scientists write, “The world has reached the threshold of 1.5C increases in global average surface temperature, and is only beginning to experience the full consequences,” following a summer in which heat waves and severe weather have provided a preview of the extremes anticipated in our changing climate.
