A recent NASA study has revealed the reason behind the global rise of atmospheric methane, a prominent greenhouse gas.
The researchers found that the quantity of atmospheric methane has sharply increased from 2006. Burning fossil fuels contributed to 17 teragrams of methane gas emission per year while wetlands or rice farming attributed to 12 telegrams of the gas emission.
However, the research has also revealed a decrease in methane emission from fires by 4 teragrams per year. The research concluded that methane emissions contributed to about 25 teragrams of the total annual emission to earth's atmosphere, which is around 550 teragrams (one teragram weighs 110,000 tons).
Earlier studies on emissions from oil and gas industries and microbial production of methane in wet tropical ecosystems like marshes and rice paddies showed wide disparity from the actual emissions. The sum of these emissions was found to be greater than the actual methane emission per year.
A team of scientists led by John Worden of NASA's Jet Propulsion Laboratory in Pasadena, California, has found that the total area of vegetations burned yearly has decreased to around 12 percent from the early 2000s. NASA's Moderate Resolution Imaging Spectrometer satellite instrument provided data for the study. Worden's team found that decrease in the rate of fires resulted in the decrease of methane emission to almost half as much as the earlier assumptions.
According to the report published in the journal Nature Communications, the research team subtracted this decrease in emission from the sum of all emissions and found that the total methane budget was tallying with the numbers.
The most difficult part of the study was that most of the methane molecules in the atmosphere did not have any identification features to determine their origin. The team measured other gases, chemical analyses, isotopic signatures, and land use patterns to reach a conclusion.
The researchers used carbon isotopes as a clue for their studies. Fires emitted largest percentage of heavy carbon isotopes while microbial emissions were the smallest, whereas, fossil fuels emitted an intermediate quantity of carbon isotopes. Increase in methane in the atmosphere indicated an increase in fossil fuel use. The quantity of carbon monoxide in the atmosphere also proves the point.
Data from the Measurements of Pollutants in the Troposphere instrument on NASA's Terra satellite and the Tropospheric Emission Spectrometer instrument on NASA's Aura had been used to detect the carbon monoxide and methane emission level.
Earlier research has proved that cattle produce a huge volume of methane. Researchers have been putting more efforts to help find ways to decrease the quantity of methane output from livestock. It was found that the entire fermentation procedure in cattle and swine and the management of their manure has a significant effect on the methane quantity in the atmosphere.