Greenhouse Gas Calculations – 'Seeing' CO2 from Space – May Improve Monitoring

There are new calculations that may improve our ability to "see" CO2 from space. Scientists have found a way to accurately predict the amount of carbon dioxide in a planet's atmosphere by studying how light of different colors is absorbed by the CO2.

Previous methods for examining CO2 were only accurate to about 5 percent across all wavelengths. These new calculations, though, give an accuracy of .3 percent. That's an improvement that will allow missions to achieve goals which demand an accuracy between .3 and .5 percent.

"Billions of dollars are currently being spent on satellites that monitor what seems to be the inexorable growth of CO2 in our atmosphere," said Jonathan Tennyson, supervising author of the new study, in a news release. "To interpret their results, however, it is necessary to have a very precise answer the question 'How much radiation does one molecule of CO2 absorb?' Up until now, laboratory measures have struggled to answer this question accurately enough to allow climate scientists to interpret their results with the detail their observations require."

In this latest study, the researchers used calculations based on quantum mechanical equations in order to predict the chances of a CO2 molecule absorbing different colors of light, which have defined energies. These predictions, which were made using powerful computers, were then verified using highly precise measurements taken using an extremely sensitive technique called "cavity-ring down spectroscopy."

"We have long known the exact quantum mechanical equations obeyed by a molecule like CO2; however, these equations are much too complicated to solve explicitly. But the combination of modern computers and novel treatments of the problem mean that we can now use quantum theory to calculate how strongly CO2 absorbs light at each wavelength."

The findings are published in the journal Physical Review Letters.

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