Using rare oxygen molecules trapped in old ice and snow, US and French scientists have answered a long-standing question: How much have ‘bad’ ozone levels increased since the start of the Industrial Revolution?

«We’ve been able to track how much ozone there was in the ancient atmosphere,» said Rice University geochemist Laurence Yeung, the lead author of a study published online today in Nature. «This hasn’t been done before, and it’s remarkable that we can do it at all.»

Researchers used the new data in combination with state-of-the-art atmospheric chemistry models to establish that ozone levels in the lower atmosphere, or troposphere, have increased by an upper limit of 40% since 1850.

«These results show that today’s best models simulate ancient tropospheric ozone levels well,» said Yeung. «That bolsters our confidence in their ability to predict how tropospheric ozone levels will change in the future.»

The Rice-led research team includes investigators from the University of Rochester in New York, the French National Center for Scientific Research’s (CNRS) Institute of Environmental Geosciences at Universite Grenoble Alpes (UGA), CNRS’s Grenoble Images Speech Signal and Control Laboratory at UGA and the French Climate and Environmental Sciences Laboratory of both CNRS and the French Alternative Energies and Atomic Energy Commission (CEA) at the Universite Versailles-St Quentin.

«These measurements constrain the amount of warming caused by anthropogenic ozone,» Yeung said. For example, he said the most recent report from the Intergovernmental Panel on Climate Change (IPCC) estimated that ozone in Earth’s lower atmosphere today is contributing 0.4 watts per square meter of radiative forcing to the planet’s climate, but the margin of error for that prediction was 50%, or 0.2 watts per square meter.

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Materials provided by Rice University. Original written by Jade Boyd. Note: Content may be edited for style and length.