Fossil fuels and agriculture have driven methane emissions to record highs across the globe claim two new studies. Methane is a colorless gas and comes from natural and human-made sources. The gas is a danger to humans because it traps heat into the atmosphere exacerbating the climate crisis and forms ground-level ozone, which is dangerous to our health.
Methane, the primary component of natural gas, spends twelve years in the atmosphere. That is significantly less than CO2, which lingers for over a century. But per unit, methane is twenty times more potent than CO2.
Between 2000 and 2017, levels of the potent greenhouse gas barreled up toward pathways that climate models suggest will lead to 3-4 degrees Celsius of warming before the end of this century. This is a dangerous temperature threshold at which scientists warn that natural disasters, including wildfires, droughts and floods, and social disruptions such as famines and mass migrations become almost commonplace. The findings are outlined in two papers published July 14 inEarth System Science DataandEnvironmental Research Lettersby researchers with theGlobal Carbon Project, an initiative led by Stanford University scientistRob Jackson.
In 2017, the last year when complete global methane data are available, Earth’s atmosphere absorbed nearly 600 million tons of the colorless, odorless gas that is 28 times more powerful than carbon dioxide at trapping heat over a 100-year span. More than half of all methane emissions now come from human activities. Annual methane emissions are up 9 percent, or 50 million tons per year, from the early 2000s, when methane concentrations in the atmosphere were relatively stable.
In terms of warming potential, adding this much extra methane to the atmosphere since 2000 is akin to putting 350 million more cars on the world’s roads or doubling the total emissions of Germany or France. “We still haven’t turned the corner on methane,” said Jackson, a professor of Earth system science in Stanford’sSchool of Earth, Energy & Environmental Sciences(Stanford Earth).
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Global methane emissions have risen nearly 10% over the past two decades, resulting in record-high atmospheric concentrations of the powerful greenhouse gas.
In 2017, the latest year for which comprehensive data are available, global yearly emissions of the gas reached a record 596 million tonnes, according to scientists with the Global Carbon Project, which tracks changes in greenhouse gases.
Annual emissions have increased by about 50 million tonnes from the 2000–06 average, mainly driven by agriculture and the natural-gas industry, the scientists report in two papers1,2on the global methane budget, released on 14 July. Atmospheric concentrations of the gas — 1,875 parts per billion last year — are now more than 2.5 times above pre-industrial levels (see ‘Record high’).
Roughly one-third of global methane emissions come from bacteria in natural wetlands that produce the gas when decomposing organic material. Agriculture and fossil-fuel sources each account for 20–25% of global methane emissions. The scientists found no evidence that emissions from wetlands or other natural sources had increased substantially from the 2000–06 average. But emissions from agriculture — driven by rising red meat consumption in some parts of the world — rose by almost 12%, to 227 million tonnes in 2017. Fossil fuels — including natural-gas fields and leaking pipelines — contributed 108 million tonnes of methane emissions in 2017, a rise of 17%.
Livestock farming and oil and gas production are clearly two engines powering rising methane emissions, says Robert Jackson, an Earth-systems researcher at Stanford University in California who chairs the Global Carbon Project and is a co-author of both papers. “People may joke, but cows and other ruminants burp as much methane as the oil and gas industry,” he says.
The reports find that emissions have increased in most regions, and most markedly in Africa, the Middle East, China and South Asia. Europe is the only region where methane emissions seem to have dropped in recent years, thanks to declining cattle numbers and policy efforts to reduce emissions such as from landfills and manure.
