FACTBOX: Methane, from Cow Burps to Rice Paddies
Methane is among the most potent greenhouse gases and scientists say controlling emissions from cows and sheep, rice fields and the oil and gas industry is a major step in limiting climate change.
Following are some facts about methane.
WHAT IS IT?
Methane is a major component of natural gas and is 23 times more potent in trapping heat in the atmosphere than carbon dioxide.
The gas lasts about 12 years in the atmosphere before it is oxidized and converted into CO2 and water. Scientists say a fifth of all greenhouse gas-induced global warming has been due to methane since pre-industrial times.
The U.N.'s climate panel says atmospheric concentrations of methane far exceed the natural range of the past 650,000 years, rising about 150 percent since 1750.
WHERE DOES IT COME FROM?
About 60 percent of all methane in the atmosphere is believed to be caused by human activities. Fossil fuels, cattle and sheep, landfills, rice paddies and forest fires are the main human-related sources.
Oceans, wetlands, gas hydrate deposits, permafrost, termites, freshwater bodies, and non-wetland soils are among the natural sources.
ARE EMISSIONS RISING?
Methane concentrations in the air have levelled off in recent years, although scientists are not sure why. One suggestion is that the loss of tropical wetlands, a major methane source, is offsetting a rise in emissions from the oil and gas industry.
But methane levels are expected to resume rising in the future because of increased demand for natural gas and greater demand for rice and meat.
Some scientists also fear a warmer world could release vast amounts of methane trapped in sub-polar permafrost or in methane hydrate deposits under the sea. A rapid release of methane could trigger climate chaos.
HOW ARE EMISSIONS BEING CONTROLLED?
Under the Kyoto Protocol, rich countries can offset their greenhouse gas emissions by investing in projects in poorer nations that capture methane and other heat-trapping gases.
In South America and Asia, scores of projects have been approved that treat manure from large pig and chicken farms to extract methane. This is used to generate electricity or burned to release less harmful carbon dioxide.
Several European nations, including Germany and the Netherlands, have passed policies that make methane capture a money-spinner for farmers. More and more landfills are collecting methane from rotting rubbish to make electricity, while coal mines are also capturing the gas to generate power as well.
Source: U.N. Framework Convention on Climate Change, Intergovernment Panel on Climate Change, NASA, U.S. Department of Energy, Reuters