Scientists discover mysterious increasing concentrations of the most potent greenhouse gas
Increasing quantities of a rare greenhouse gas have been found, which is 18,000 times more effective at trapping heat than carbon dioxide, and comes from an unknown origin.
Concentrations of the gas, trifluoromethyl sulfur pentafluoride, (SF5CF3), are extremely rare at about 0.12 parts per trillion in air, but are increasing by about 6% annually. The increase is of additional concern because the source of SF5CF3 remains unknown, although it is believed to derive from human activity, and probably takes more than 1,000 years to break down, says the report, A Potent Greenhouse Gas Identified in the Atmosphere: SF5CF3 , appearing in Science Magazine on 28 July.
The report states that molecule for molecule, SF5CF3, is 18,000 times more effective at trapping heat in the atmosphere than carbon dioxide, and, researchers say, is extremely long-lived, with molecules probably persisting for 1,000 years or more once they are lofted in the air.
“So far, there is far too small a quantity to be of concern,” said William T. Sturges, an atmospheric chemist at the University of East Anglia in Norwich, England, and the study’s principal author. “But I wouldn’t want to see it enormously increased.”
“We estimate that about 4,000 tons have been released so far into the atmosphere so far, and because the proportion is increasing annually, it would imply that the gas is being continually produced as a by-product,” Doctor C. Brenninkmeijer of the Max Planck Institute for Chemistry, one of the report’s authors told Edieon 1 August.
There are currently two theories as to the origin of the gas; The first is that it has been used secretly in the manufacture of military equipment, such as radar, as is a similar gas, sulfur hexafluoride, or SF6. “This is not very likely because it would not explain why concentrations are increasing now, when the equipment that produces this kind of material is not generally in use now,” Brenninkmeijer said. “It is more likely that the gas is an unintentional by-product of some manufacturing process which uses fluorine, such as the production of wax or cleaners.”
The gas was found in samples taken by instrument-laden balloons 21 miles up in the stratosphere and in air trapped under layers of Antarctic snow. The samples were then taken for analysis to the University of East Anglia, where the world’s only equipment capable of analysing such low gas concentrations, is situated. Researchers say that there was no evidence of the presence of SF5CF3 in the air before the 1950’s, with only a scattering of molecules appearing in the 1960’s, before concentrations started to rise steadily to the current total of about 270 tonnes annually.
Because of the potency of the gas, which has the largest radioactive forcing on a per molecule basis of any gas found in the atmosphere to date, researchers hope that the finding will serve as a call to industry and governments to find its source and hope to conduct further tests this year.
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