According to new research, emissions of anthropogenic nitrous oxide (N2O) are now causing more damage to the ozone layer than those of any controlled ozone depleting substance and this is projected to remain the case for the rest of this century. The study suggests that limiting N2O emissions could help both the recovery of the ozone layer and tackle climate change.
Many ozone-depleting substances (ODS) have been phased out as a result of the Montreal Protocol and are regulated by EU legislation. N2O is emitted from natural and anthropogenic sources, the latter including as a byproduct of agricultural fertiliser use and from fossil fuel combustion. Its role in ozone depletion has been known for some years and it is similar to CFCs in that it is stable when it is near the earth’s surface but releases ozone-destroying active chemicals when transported into the stratosphere (between 10 and 50km from the surface). However, N2O is not defined as an ODS under the Montreal Protocol and, although it is a greenhouse gas (GHG) included in the basket of gases under the Kyoto Protocol, its emissions remain unregulated.
The study was the first to calculate the ozone-depleting potential (ODP) of N2O. Current global emissions of anthropogenic N2O are approximately 10 million metric tonnes per year, in comparison with annual emissions of one million metric tonnes of CFCs at the peak of their production in the 1980s.
These emissions of N2O also have a significant impact on the climate. Of all the non-CO2 GHGs included under the Kyoto Protocol, N2O emissions have the second most powerful impact on the climate (after methane). Ozone plays a role in breaking down methane so N2O emissions continue to increase, this will lead to increase levels of methane in the atmosphere as there is less ozone around to break it down.
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