By Olivia Rosane and Cristen Hemingway Jaynes
Methane, an invisible and odorless gas found in wetlands, livestock, and household furnaces, has emerged as a critical front in the global effort to combat climate change. As the second most important contributor to the climate crisis after carbon dioxide, methane is a powerful greenhouse gas that accounts for approximately one-third of current global heating. While carbon dioxide remains the dominant long-term driver of atmospheric warming, methane plays an unusually potent role over a much shorter timescale. Because it traps heat far more intensely than carbon dioxide and persists in the atmosphere for only about a dozen years, rapid action to curb methane emissions represents one of the most effective strategies available to stabilize global temperatures over the next two decades.
The gas is a hydrocarbon composed of four hydrogen atoms bonded to a carbon atom. It is abundant in nature, formed through both geological and biological processes. Geologically, methane is created when heat and pressure act on decomposing organic matter over millions of years, forming the primary component of natural gas, which currently generates roughly a quarter of the world’s electricity. Biologically, it is generated through methanogenesis, a process in which underwater microorganisms known as archaea produce methane in oxygen-free environments. This biological pathway accounts for natural emissions in wetlands and the digestive tracts of animals such as termites and cows.
Measuring methane accurately remains a central challenge for scientists and policymakers. Emissions are typically assessed using two main frameworks: bottom-up and top-down approaches. Bottom-up assessments start at the localized source and expand outward, calculating emissions through direct measurements at specific facilities or by multiplying standard emission factors—such as the average leak rate of a piece of equipment or the typical enteric output of a single cow—by the total population of sources. Top-down approaches, by contrast, measure atmospheric concentrations directly from the sky using aircraft, high-altitude platforms, and increasingly sophisticated satellite technology.
As satellite imaging improves, it has revealed discrepancies in traditional inventories, most notably by exposing extraordinary "super-emitting" leaks that bottom-up estimates consistently miss. Studies indicate that a small fraction of major leaks—often the largest five percent—can account for more than half of all gas-industry leak volumes. Furthermore, direct measurements of U.S. oil and gas operations have shown emissions running significantly higher than official government inventory estimates, underscoring the urgent need for enhanced monitoring to understand and control atmospheric levels.
The concentration of methane in the atmosphere has soared by 265 percent compared with pre-industrial levels, reaching 1,934 parts per billion by 2023. Human activities, particularly the burning of fossil fuels, intensive agriculture, and waste management, drive approximately 60 percent of these emissions, while natural sources account for the remaining 40 percent. Although natural sinks—such as soil and the troposphere, where methane is broken down into carbon dioxide and water vapor—naturally counteract background emissions, human-generated volumes have outpaced the capacity of these sinks to absorb them.
The Intergovernmental Panel on Climate Change has calculated that global methane emissions must fall by roughly 34 percent by 2030 compared with 2019 levels if the international community is to successfully limit global heating to 1.5 degrees Celsius above pre-industrial levels. Because methane possesses a relatively short atmospheric lifespan combined with an immense heat-trapping capacity—absorbing up to 86 times more heat per unit of mass than carbon dioxide over a 20-year period—targeted reductions deliver immediate climate benefits. The Global Methane Assessment has concluded that curbing methane is very likely the single most effective strategy for decreasing warming over the next twenty years.
More than 90 percent of current human-caused methane emissions stem from three primary sectors: agriculture, fossil fuels, and waste storage. Agriculture accounts for about 40 percent of anthropogenic emissions, driven largely by livestock. Ruminant animals like cows, sheep, and goats produce methane as a byproduct of enteric fermentation, a digestive process where microbes break down nutrients. Livestock raised for meat and milk alone generate approximately 32 percent of human-caused methane emissions, while manure storage systems contribute additional volumes. Rice cultivation represents another significant agricultural source, accounting for eight percent of human-caused emissions due to the flooded paddy environments that foster methane-producing microbes.
Fossil fuel operations are responsible for roughly 35 percent of human-caused methane emissions. The extraction, transport, and use of oil and gas account for 23 percent, driven by intentional venting during extraction and accidental leaks across supply infrastructure. Coal mining contributes another 12 percent, as methane trapped along coal seams escapes through ventilation and drainage systems during excavation. Fossil fuel projects are frequently implicated in massive super-emitter events, with satellite observations documenting hundreds of high-volume leaks and venting incidents at oil and gas fields and coal mines globally.
Landfills and waste management systems generate approximately 20 percent of human-caused methane emissions. Microbes in wastewater treatment facilities and landfills release methane as they decompose organic material. With rapid population growth and development, emissions from waste are projected to grow faster than any other human-caused methane source, with global solid waste volumes expected to rise significantly in the coming decades.
Natural sources, led by wetlands, account for the remaining 40 percent of atmospheric methane. Wetlands cover a small fraction of the Earth’s land area, but their water-saturated, oxygen-poor soils provide ideal conditions for archaea to produce methane. Climate-driven changes in temperature and rainfall have amplified these natural emissions through positive feedback loops, particularly in tropical and Arctic permafrost regions where thawing soils and expanding wetlands accelerate microbial activity. Oceans also contribute natural emissions through geological marine seepage and the potential destabilization of seafloor methane hydrates, while wildfires add further pulses of the gas into the atmosphere.
The expansion of natural gas infrastructure, including liquefied natural gas exports, has further complicated efforts to rein in emissions. Proponents often frame natural gas as a bridge fuel away from coal because burning gas emits less carbon dioxide per kilowatt-hour. However, this argument frequently overlooks the methane that leaks throughout the extraction, liquefaction, and transport supply chain. Studies indicate that even minor leakage rates can eliminate the climate advantage of natural gas over coal, and major proposed gas field developments risk locking in emissions that undermine global climate targets.
Beyond its role in climate change, methane contributes directly to the formation of ground-level ozone, a dangerous pollutant that damages human lung tissue and agricultural crops. Methane-driven ozone causes hundreds of thousands of premature deaths annually, alongside substantial agricultural losses. Consequently, emission reductions yield immediate public health and food security dividends alongside climate stabilization.
Addressing the crisis requires a combination of systemic transformations and technical fixes across energy, agriculture, and waste systems. In agriculture, solutions range from dietary shifts and food waste reduction to the use of feed additives like seaweed and chemical inhibitors that reduce enteric fermentation in ruminants. For fossil fuels, phasing out production remains the ultimate goal, but immediate operational improvements—such as rigorous leak detection and repair, equipment upgrades, and the deployment of capture technologies—can achieve deep short-term cuts. In the waste sector, expanding composting, upgrading wastewater treatment plants, and capturing biogas from landfills are vital strategies to curtail emissions.
International momentum has grown through initiatives like the Global Methane Pledge, launched at the 2021 UN climate conference, which commits participating nations to cutting global methane emissions by 30 percent below 2020 levels by 2030. Yet, despite these pledges, global emissions continue to rise, highlighting a persistent gap between political commitments and real-world implementation. As scientists and policymakers emphasize, closing that gap through aggressive monitoring and enforcement remains essential to halting the acceleration of global heating.
