A post-Kyoto partner: considering the stratospheric ozone regime as a tool to manage nitrous oxide

Abstract

Nitrous oxide (N2O) is the largest known remaining anthropogenic threat to the stratospheric ozone layer. However, it is currently only regulated under the 1997 Kyoto Protocol because of its simultaneous ability to warm the climate. The threat N2O poses to the stratospheric ozone layer, coupled with the uncertain future of the international climate regime, motivates our exploration of issues that could be relevant to the Parties to the ozone regime (the 1985 Vienna Convention and its 1987 Montreal Protocol) should they decide to take measures to manage N2O in the future. There are clear legal avenues to regulate N2O under the ozone regime as well as several ways to share authority with the existing and future international climate treaties. N2O mitigation strategies exist to address the most significant anthropogenic sources, including agriculture, where behavioral practices and new technologies could contribute significantly to reducing emissions. Existing policies managing N2O and other forms of reactive nitrogen could be harnessed and built on by the ozone regime to implement N2O controls. There are several challenges and potential cobenefits to N2O control which we discuss here: food security, equity, and implications of the nitrogen cascade. The possible inclusion of N2O in the ozone regime need not be viewed as a sign of failure of the United Nations Framework Convention on Climate Change to adequately deal with climate change. Rather, it could represent an additional valuable tool in sustainable development diplomacy.

Fig. 1

Illustration of the nitrogen cascade showing the sequential effects that a single atom of N can have in various reservoirs after it has been converted from nonreactive N₂ to a reactive form (yellow arrows) and examples of existing international management policies. Adapted with permission from the GEO Yearbook 2003, United Nations Environment Programme (UNEP), 2004 (8) which was based on Galloway et al., 2003 (7).

Fig. 2

Sector-by-sector contribution to anthropogenic N₂O emissions in 2005. Smaller sources, such as wastewater treatment and aquaculture, are included in the “Other” bar. Error bars represent the range of leading estimates taken from US Environmental Protection Agency (6), Davidson (10), Syakila and Kroeze (11), and Crutzen et al. (12) with the total error bar representing the sum of the individual error bars.