The World’s Most Successful Environmental Treaty Could Tame Nitrous Oxide

Nitrous oxide has lived a strange double life in the politics of the atmosphere. Chemists understood its power to destroy stratospheric ozone before they understood the same about chlorofluorocarbons, and yet the gas has never been seriously regulated by the treaty built to protect the ozone layer. Meanwhile, it sits in the basket of greenhouse gases under the United Nations Framework Convention on Climate Change, but only eleven countries have ever committed to quantifiable reductions. A new perspective published in the journal Ambio argues that this patchwork of neglect is no longer tenable, and that the international community should consider a bold institutional move: bringing nitrous oxide under the Montreal Protocol, the agreement widely regarded as the most successful environmental treaty in history.

The numbers behind the argument are stark. According to the 2024 Global Nitrous Oxide Assessment, a joint effort by the Climate and Clean Air Coalition, the United Nations Environment Programme, the Food and Agriculture Organization and the International Nitrogen Management System, nitrous oxide has a 100-year global warming potential of 273, making it the third most abundantly emitted greenhouse gas. It accounts for roughly five percent of global greenhouse gas emissions in carbon dioxide equivalents and about ten percent of all warming since the Industrial Revolution. Its ozone-depletion-potential-weighted emissions now exceed those of all other ozone-depleting substances combined. Emissions are rising faster than even the most pessimistic scenarios projected, driven by rising demand for food and animal protein and by industrial chemicals such as nitric and adipic acid.

About three-quarters of anthropogenic nitrous oxide comes from agriculture, specifically the over-application of synthetic fertilizer and manure. Microbes transform excess nitrogen into the gas through nitrification and incomplete denitrification in soils, or indirectly after nitrogen is first lost as ammonia or nitrate. The consequences of continued inaction are severe: if current trends persist while climate policy concentrates on carbon dioxide and methane, stratospheric ozone levels could sink below the lowest recorded values of the 1990s, pushing certain skin cancer rates up by as much as ten percent. Limiting warming to 1.5 degrees Celsius, the authors contend, is likely impossible without ambitious nitrous oxide cuts, which could reduce emissions roughly 40 percent below 2020 levels by 2050 and avoid 235 billion tons of carbon dioxide equivalent.

The co-benefits extend well beyond climate and ozone. Because nitrous oxide sits within the intertwined nitrogen cycle, abatement would also curb ammonia and nitrogen oxides, major air pollutants, and nitrate, a key water contaminant. The assessment estimates that ambitious action could avoid up to twenty million premature deaths by 2050 through improved air quality alone. Policy momentum has begun to build around nitrogen more broadly, with United Nations Environment Assembly resolutions, the 2019 Colombo Declaration and the Kunming-Montreal Global Biodiversity Framework all calling for nitrogen losses to be halved by 2030. Yet the authors observe a troubling disconnect: only eleven Nationally Determined Contributions contain quantitative nitrous oxide targets, covering roughly thirteen percent of global emissions, and the Montreal Protocol has never come close to listing the gas despite its inclusion in the Vienna Convention’s Annex I nearly four decades ago.

Why the oversight? The authors trace it to historical contingencies. International climate governance grew out of concern over fossil carbon dioxide, and it took decades for non-CO2 gases to receive serious attention; methane only got its Global Methane Pledge in 2021, and hydrofluorocarbons were shifted to the Montreal Protocol in 2016 under the Kigali Amendment. On the ozone side, the dominant worry about stratospheric nitrogen oxides in the 1970s and 1980s involved high-altitude aircraft fleets that never materialized, while chlorofluorocarbons were rising faster and proved easier to abate than agriculture, a sector long treated as politically exceptional out of deference to food security and farm lobbies.

The legal case for action under the ozone regime is stronger than most policymakers assume. The 1985 Vienna Convention obliges parties to protect human health and the environment against activities that modify the ozone layer, and its negotiators explicitly flagged nitrogenous fertilizers as a concern. Article 2(10) of the Montreal Protocol allows parties to add substances to its annexes, and Decisions IX/24, XI/20 and XIII/5 establish a working procedure for evaluating new substances. Nitrous oxide was formally added to the Ozone Secretariat’s list of reported new substances in May 2012. The authors conclude that the ozone regime already possesses the legal authority and purview to control the gas, and that a special report from the Protocol’s three assessment panels could provide the scientific foundation for a formal proposal.

What makes the Montreal Protocol uniquely suited to this task is its architecture. Its “start and strengthen” approach has allowed the treaty to evolve as science matured, expanding from its original controlled substances to nearly a hundred chemicals phased out by 99 percent across 198 parties. Independent scientific, environmental effects, and technology assessment panels feed policy-relevant expertise into the process, while the Multilateral Fund has disbursed 4.3 billion dollars across 144 developing countries to finance compliance. Crucially, the Protocol regulates production and consumption rather than diffuse emissions, making enforcement tractable. For agriculture, the authors argue, this translates naturally into targets for nitrogen use efficiency or nitrogen surplus, metrics already tracked at national scale and convertible into nitrous oxide estimates through well-validated emission factors.

The Protocol also has direct experience with a dangerous agricultural input. It eliminated methyl bromide, a soil fumigant, through Multilateral Fund projects that trained tens and even hundreds of thousands of farmers in countries from Argentina to Malawi. The phase-out was painful and drawn out, weakened by industry pressure and generous critical-use exemptions, but it established a template for transitioning away from inputs once considered essential. Nitrous oxide presents harder problems: it is emitted from virtually every agricultural sub-sector, nitrogen inputs cannot simply be banned, and enforcement is more diffuse. Even so, abatement practices such as enhanced-efficiency fertilizers, nitrification inhibitors, precision irrigation and the 4R nutrient stewardship framework can cut agricultural emissions by up to half without sacrificing yields. The authors propose minimum efficiency standards informed by a dedicated task force, alongside a “shared responsibility” model that spreads accountability across fertilizer producers, insurers, financiers and food retailers rather than dumping the regulatory burden on farmers alone.

The fastest wins, however, lie in industry. Nitric and adipic acid production contributes only about five percent of global emissions, but roughly six hundred facilities worldwide can deploy catalytic decomposition or thermal destruction technologies that eliminate over 99 percent of by-product nitrous oxide, often at breakeven prices between zero and twenty dollars per ton of carbon dioxide equivalent. The Kigali Amendment already created a precedent for controlling by-product emissions through its treatment of HFC-23, and the Multilateral Fund has financed destruction obligations in China, Argentina and Mexico. A comparable requirement for industrial nitrous oxide could avoid 2.5 billion tons of carbon dioxide equivalent by 2050 and generate ozone benefits equivalent to some 160,000 tons of CFC-11, building momentum for the harder agricultural phase. Food security concerns can be managed, the authors note, by exempting countries with low nitrogen consumption, an approach modeled on the Protocol’s Article 5 thresholds, which would leave nearly all of sub-Saharan Africa free to increase fertilizer use. Genuine obstacles remain, including pollution swapping within the reactive nitrogen cascade, overlapping mandates across conventions, and a volatile geopolitical landscape that sent fertilizer prices up more than 100 percent after 2021 and over 50 percent in 2026. But the authors insist that instability does not preclude opportunity: roadmap-building, panel reports and demonstration projects now could position a coalition of willing parties to act decisively when the political moment arrives, turning the ozone treaty’s proven machinery against a threat the world can no longer afford to ignore.

The governance gap the authors describe is best understood as a sequencing problem in international environmental law. Each successive wave of atmospheric regulation has targeted the gases whose science was mature and whose abatement was cheapest, leaving the politically awkward remainder for later. Methane followed this pattern, moving from vague coverage under the climate convention to dedicated pledges and reporting frameworks only once satellite-based detection made large emission sources visible and attributable. Nitrous oxide now stands at a comparable inflection point, with growing measurement capacity from atmospheric monitoring networks and emerging satellite instruments offering new possibilities for verifying whether national actions actually reduce concentrations.

The stratospheric stakes deserve particular emphasis. Unlike carbon dioxide, which persists for centuries but does not interact directly with ozone chemistry, nitrous oxide is converted in the stratosphere into nitrogen oxides that catalytically destroy ozone, and this chemistry operates regardless of where the emissions originate. Because the gas has an atmospheric lifetime of roughly a century, every ton emitted today commits the ozone layer to decades of additional depletion. This long memory means that delayed action locks in damage that no future agreement can quickly reverse, in contrast to short-lived pollutants where rapid cuts yield near-term benefits.

The equity dimensions of the proposal also merit attention. Developing countries have historically contributed little to cumulative nitrous oxide emissions, yet many face rising fertilizer demand as they expand food production. Any credible regime would therefore need to mirror the principle of common but differentiated responsibility, combining grace periods, financial support and technology transfer. The authors’ suggestion of exemptions for low-consumption countries reflects this logic, and the Multilateral Fund’s track record suggests that financing mechanisms, once established, can build the technical capacity that ambitious targets presuppose.

Subject of Research: Governance of nitrous oxide emissions under the Montreal Protocol as a pathway to protect both climate and stratospheric ozone

Article Title: Nitrous oxide under the international ozone regime: A new governance pathway for a growing threat

Article References: Kanter, D. R., Ferris, T., Nickson, T., & Reinikainen, T. (2026). Nitrous oxide under the international ozone regime: A new governance pathway for a growing threat. Ambio. https://doi.org/10.1007/s13280-026-02477-w

Image Credits: AI Generated

DOI: 10.1007/s13280-026-02477-w

Keywords: nitrous oxide, Montreal Protocol, ozone depletion, climate change, greenhouse gases, nitrogen pollution, agriculture, fertilizer, environmental governance, Vienna Convention, Kigali Amendment, nitrogen use efficiency