Atmospheric science: Stealth ozone destroyer

Science 326, 123–125 (2009)

Thanks to the Montreal Protocol, emissions of chlorofluorocarbons (CFCs) have dropped, resulting in early signs of recovery of the ozone layer. However, the battle is not yet won. Researchers report that nitrous oxide (N₂O) — a gas that behaves similarly to CFCs in triggering global ozone destruction, but is not regulated by the protocol — is now the most significant ozone-depleter being emitted.

A. R. Ravishankara and his colleagues at the National Oceanic and Atmospheric Administration in Boulder, Colorado, calculated the 'ozone depletion potential' of N₂O and used it to weight the current emissions level. They found that the 2008 weighted emissions level for N₂O was around double that of the next most important ozone-depleting gas.

They also noted that nitrous oxide's global-warming potential is second only to methane among non-carbon dioxide gases in terms of its contribution to warming.