A paper in Science that crowns ‘nitrous oxide’ as the king of ozone depleting substance (ODSs) caught my attention this week. A. R. Ravishankara and colleagues from the Earth System Research Laboratory of the National Oceanic and Atmospheric Administration in Colorado, USA, contend that N2O accounts for the the single most important ODS emission currently and would remain so throughout the 21st century. [Nature News story]
There’s nothing in the Montreal Protocol to regulate N2O. If N2O emissions are contained, it would be something to rejoice for scientists predicting that the depleted ozone layer might be able to heal itself faster. On a happy flip-side, it would also reduce humankind’s contribution to climate change — something the authors of the paper aptly describe as a ‘win-win’ for both ozone and climate.
Takes me back to 2006, when scientists from the small Bengal town of Serampore had challenged the Montreal and Kyoto Protocols. The low profile scientists had published their findings way back in 2000 in the Indian Journal of Physics claiming, in essence, the same thing as the Science paper — that chlorofluorocarbon (CFC) is not the biggest demon, nitrous oxide is.The IPCC mentioned N2O only in the list of greenhouse gases relevant to radiative forcing and not in the list of ozone-depleting gases.
The lead author S. K. Midya of the department of physics at Serampore College in Hooghly district of West Bengal sent me a copy of the paper by post (the journal wasn’t online then and even now doesn’t seem to have online archives prior to 2001). He and his colleagues had analysed data from the Antarctic Survey Station Mc Murdo to show that 61.67 per cent to the depletion of the ozone layer was due to N2O, 27% due to carbon dioxide and 7% due to CFCs. The findings were questioned by several environment scientists at the time. Their contention was that scientists from Mc Murdo would have certainly reported these figures in a paper if this was the case.
The point of this post is: the questions being asked are the same all these years. But the answers remain as elusive as ever. Hope the Copenhagen meet in December takes some policy stand on this alongside all the other landmark discussions it is expected to witness.