Anthropogenic climate change: evidence from isotopic ratios

2009-11-18

in Geek stuff, Science, The environment

Back in 2003, Prosenjit Ghosh and Willi Brand described one of the more clever ways in which the link between fossil fuel combustion and the accumulation of carbon dioxide in the atmosphere has been demonstrated. In their article “Stable isotope ratio mass spectrometry in global climate change research” (PDF), they discuss how the ratio of isotopes of carbon in the atmosphere can be used to identify the sources of atmospheric CO2. Their work was published in 2003, in the International Journal of Mass Spectrometry.

By tracking the ratio of carbon-12 to carbon-13 in the atmosphere, the distinctive imprint of fossil fuel combustion can be identified. This is really just confirmation of the inevitable chemical fact that burning coal, oil, and natural gas produces CO2. Nevertheless, it is nice to have an independent line of evidence showing that human activities really are the major cause behind observed increases in the atmospheric concentration of CO2.

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. September 3, 2010 at 12:15 pm

“The use of the refrigerants and aerosol propellants was restricted by a global treaty in 1987, but they have stayed in the air longer than many expected.

A UK-German team has now shown how it is possible to chemically “fingerprint” CFCs to potentially trace their origin.

The group’s work is published in the journal Science.

The researchers from the universities of East Anglia and Frankfurt worked on samples of atmosphere retrieved from high in the stratosphere (up to 35km; 115,000ft) by French space agency balloons.

Using mass spectrometers, they were able to detail the ratios of different types (isotopes) of chlorine atoms present in fantastically small concentrations – just 500 parts per trillion – of chlorofluorocarbon-12.

CFC-12 is one of the dominant man-made ozone-eating gases and was widely used in refrigerators, air conditioning systems, fire extinguishers and spray cans before being phased out under the Montreal Protocol.

The ability to make fine measurements of the type reported in Science opens the door to chemical fingerprinting – of being able to tie a particular sample to a known origin.”

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