Climate Matters•November 9, 2022
Solutions Series: Cutting Methane Emissions
Two characteristics make methane a significant greenhouse gas: it has more than 80 times the warming power of CO2 over a 20-year period, but it also breaks down in the atmosphere after about a dozen years (as opposed to multiple centuries for CO2). This means that rapidly cutting methane could have a big payoff this decade.
Estimating methane emissions is complex, but remote-sensing technology–like satellites—is significantly improving the data that inform reduction strategies.
About 60% of methane emissions come from human activity—primarily agriculture, the energy sector, and waste management. There are a number of low-cost strategies available to reduce emissions, particularly in fossil fuel operations.
COP27 marks one year since the launch of the Global Methane Pledge–an agreement through which 125 nations have committed to voluntary actions to reduce global methane emissions at least 30% from 2020 levels across all sectors by 2030.
Reducing methane, a key climate solution
Greenhouse gases have warmed the Earth by 2°F(1.1°C) since pre-industrial times. Of these gases, carbon dioxide is the biggest contributor to climate change. But at least 30% of current warming is due to human-caused emissions of another potent greenhouse gas: methane.
Methane’s significance stems from two key characteristics: how much heat it traps, and how long it lasts in the atmosphere. Methane traps over 80 times more heat than the same amount of CO2 during a 20-year period. But it also breaks down far more quickly, with an atmospheric life of about a dozen years, compared to multiple centuries for CO2.
Because methane has a relatively high heat-trapping potential during its lifetime, cutting emissions can quickly slow warming in the near term. In addition, reducing the methane burden buys time to implement other measures to reduce carbon pollution and slow warming in the long term.
Sources of methane emissions
Human activity is the biggest source of methane emissions across the globe. About 60% of methane emissions come from human activity, with the remaining 40% from natural sources such as wetlands.
Globally, about 40% of human-derived methane comes from agriculture (mainly livestock and rice cultivation), about 35% from the energy sector (especially production of oil, natural gas, and coal), and about 20% from waste management (primarily landfills). The five largest global emitters of methane are China, the U.S., Russia, India, and Brazil.
According to the U.S. Environmental Protection Agency’s national inventory, about 38% of methane emissions in the U.S. come from fossil fuels, 36% from agriculture, 17% from landfills, and the remaining 9% from a variety of smaller sources.
But it is important to note that national inventories may significantly understate energy-related emissions. Notably, the current approach does not effectively account for ultra-emitting events–sporadic releases of large amounts of methane during maintenance operations or equipment failures. The International Energy Agency (IEA) estimates that the energy sector actually contributes 54% of U.S. methane emissions.
In the U.S. the top five states in terms of overall emissions are Texas, California, Pennsylvania, Oklahoma, and West Virginia. A complete list of emissions by sector for all 50 states (plus the District of Columbia and U.S. Territories) is available in the full report.
Cutting methane across the sectors
Many consider the energy sector–specifically oil and gas production–to be the best opportunity for significant, near-term methane cuts. Key solutions include finding and repairing leaks throughout production, as well as capturing and using gas vented during normal operations. Many of the technical solutions can be achieved at zero or low net-cost, because implementation costs are offset by the value of captured gas.
There are efforts underway to similarly capture and use methane from agriculture and waste facilities (known as biogas). There is a growing range of strategies to otherwise reduce methane production from farming and landfills, including alternative feed for cows and composting to reduce waste.
Climate Central’s full report on methane elaborates on sector-specific strategies and key initiatives to reduce methane from these main sources.
How methane is measured
Accurate emissions information is key for setting priorities and tracking progress–or lack thereof–toward reduction goals. But collecting data on an odorless, invisible gas requires specialized technology, so direct measurements of methane emissions are thin.
As a result, most estimates of methane emissions come from a “bottom-up” approach—existing inventories of equipment or activities are assigned standardized emission factors based on sample measurements and standard methodology.
“Top-down” methods, by contrast, look at the concentration of methane actually present in the atmosphere, through aerial measurements. Methane-sensing equipment takes measurements from tall structures, aircrafts, drones, or satellites.
These top-down measurements are starting to provide far more detail on the sources of methane—not only which sectors, but also which specific facilities. Those data can help decision makers prioritize and target reduction strategies.
Limitations of methane emission estimates
On their own, neither bottom-up nor top-down estimates provide a full picture of emission sources. And when compared to one another, striking discrepancies may emerge. For example, a group of researchers who compiled top-down measurements on U.S. gas facilities concluded that methane emissions from those facilities were approximately 60% higher than shown in the EPA inventory estimate.
This problem is not unique to the U.S. The IEA recently concluded that global emissions from the energy sector are about 70% higher than the total reported in national inventories.
Synthesizing results from bottom-up and top-down approaches can produce better estimates. The most comprehensive result to date is the Global Methane Budget, a massive effort in which dozens of scientists examined all available data for 2000-2017.
The International Methane Emissions Observatory, launched in 2021 by the UN Environment Program and others, will collect, gather, and reconcile the various sources of methane data going forward, with an initial focus on fossil fuels.
POTENTIAL LOCAL STORY ANGLES
What are the primary sources of greenhouse gas emissions in your state?
The U.S. Environmental Protection Agency’s Greenhouse Gas Inventory Data Explorer provides state-specific data on greenhouse gas emissions, including methane. In addition, many states publish their own official inventories of greenhouse gas emissions.
What role do satellites play in localized measurements of methane?
A growing array of satellites is gathering methane data. Some provide a global overview, while others map emissions from particular facilities, referred to as point sources. A third category takes a hybrid approach. A hybrid example, MethaneSat, is expected to launch in early 2023 and will eventually provide publicly available data in near-real time. Satellite imagery and aerial remote sensing can be used to detect large emissions from any point source in the landscape, such as oil and gas facilities, landfills, or farming operations.
Why else is methane relevant during COP27?
In 2021, COP26 launched the Global Methane Pledge–an agreement in which 125 nations committed to voluntary actions to reduce global methane emissions at least 30% from 2020 levels across all sectors by 2030. A year later, going into COP27, half of the top emitting countries (including China, Russia, and India) are not yet Pledge participants.
The SciLine service, 500 Women Scientists or the press offices of local universities may be able to connect you with local scientists who have expertise on methane and climate change. The American Association of State Climatologists is a professional scientific organization composed of all state climatologists.
Drew Shindell, PhD
Professor/Chair of Science Advisory Panel
Duke University/Climate and Clean Air Coalition
Related expertise: climate policy, reducing methane emissions, air quality
Gabby Dreyfus, PhD
Institute for Governance and Sustainable Development
Related expertise: Science policy, short-lived climate pollutants, energy efficiency