Nitrous oxide fingered as monster ozone slayer

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New calculations indicate that nitrous oxide has risen to become the leading threat to the future integrity of stratospheric ozone, Earth’s protective shield against the sun’s harmful ultraviolet rays.

Most people know nitrous oxide as the laughing gas that dentists reserve for drill-phobic patients. But once it enters the atmosphere, N2O is no laughing matter. New calculations indicate that it has risen to become the leading threat to the future integrity of stratospheric ozone, Earth’s protective shield against the sun’s harmful ultraviolet rays.

Currently, Freon and other chlorofluorocarbons — or CFCs — are the leading source of ozone thinning, especially in the hole that forms annually over Antarctica. The surprise is not that N2O is also ozone-toxic. That’s been known for decades. What’s new is a measure of how its ozone-destroying potency compares to CFCs, specifically to one known as CFC-11.

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Calculations by a trio of scientists from the National Oceanic and Atmospheric Administration in Boulder, Colo., now indicate that each molecule of N2O is almost one-fiftieth as effective at depleting ozone as is CFC-11.

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