Global methane emissions have risen nearly 10% over the past two decades, resulting in record-high atmospheric concentrations of the powerful greenhouse gas.
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.
Methane, an odorless gas, comes from several natural and anthropogenic sources. It is an important contributor to global warming because it traps heat in the atmosphere. It is also involved in the ground-level formation of ozone, which is an air pollutant and bad for human health.
Methane’s atmospheric lifetime of around 12 years is much shorter than that of carbon dioxide, which lingers for more than a century.
But methane is, per unit, more than 20 times as potent as CO2 as a greenhouse gas. That means that over a 20-year period, the global-warming potential of one tonne of atmospheric methane is similar to that of around 85 tonnes of CO2.
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.
Livestock farming and oil and gas production are clearly two engines powering rising methane emissions. Emissions from agriculture, driven by rising red meat consumption in some parts of the world, rose by almost 12%.
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.
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