How Can we Separate Man Made Greenhouse Gases from Those Naturally Occurring?

A research team has developed a new monitoring system to analyze and compare emissions from man-made fossil fuels and trace gases in the atmosphere, a technique that likely could be used to monitor the effectiveness of measures regulating greenhouse gases.

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The University of Colorado Boulder-led team looked at atmospheric gas measurements taken every two weeks from aircraft over a six-year period over the northeast United States to collect samples of CO₂ and other environmentally important gases.

Their method allowed them to separate CO₂ derived from fossil fuels from CO₂ being emitted by biological sources like plant respiration, said CU-Boulder Senior Research Associate Scott Lehman, who led the study with CU-Boulder Research Associate John Miller.

The separation was made possible by the fact that CO₂ released from the burning of fossil fuels like coal, oil and gas has no carbon-14, since the half-life of that carbon radio isotope is about 5,700 years - far less than the age of fossil fuels, which are millions of years old.

In contrast, CO₂ emitted from biological sources on Earth like plants is relatively rich in carbon-14 and the difference can be pinpointed by atmospheric scientists, said Lehman of CU's Institute of Arctic and Alpine Research.

The team also measured concentrations of 22 other atmospheric gases tied to human activities as part of the study, said Miller of the CU-headquartered Cooperative Institute for Research in Environmental Sciences. The diverse set of gases impact climate change, air quality and the recovery of the ozone layer, but their emissions are poorly understood. The authors used the ratio between the concentration level of each gas in the atmosphere and that of fossil fuel-derived CO₂ to estimate the emission rates of the individual gases, said Miller.

GreenHouse Gases via Shutterstock.

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