A new UN Global Nitrous Oxide Assessment warns that nitrous oxide (N₂O), a potent greenhouse gas, is rapidly accelerating climate change and damaging the ozone layer. Launched at the 2024 UN Climate Change Conference (COP29) in Baku, Azerbaijan, the assessment signals that emissions are rising faster than expected and that immediate action is required to curb the environmental and health impacts of this super pollutant.  

What is nitrous oxide?

N₂O is approximately 270 times more potent than carbon dioxide in terms of warming the planet and is currently responsible for approximately 10% of net global warming since the Industrial Revolution. Primarily emitted from agricultural practices such as the use of synthetic fertilizers and manure, N₂O is the third most significant greenhouse gas and the top ozone-depleting substance still being released into the atmosphere.   

The assessment’s findings are clear: urgent action on N₂O is critical to achieving climate goals, and without a serious reduction in emissions, there is no viable path to limiting warming to 1.5°C in the context of sustainable development, as outlined in the Paris Agreement.   

“N₂O is very much the forgotten pollutant; without concerted action on it concurrently with carbon dioxide and methane, there is no sustainable pathway to limiting global warming to 1.5°C, and progress on protecting the ozone layer could be reversed,” said SEI’s Kevin Hicks, a coordinator and author of the Assessment. 

The Global Nitrous Oxide Assessment

This Assessment identifies practical, cross-sectoral decreasing strategies that could cut N₂O emissions by more than 40% from current levels. By transforming food production systems and rethinking societal approaches to nitrogen management, even deeper reductions could be achieved, offering a critical opportunity to move the world closer to its climate, environmental, and health goals.  

It also shows that N₂O emissions from the chemical industry can be quickly and cost-effectively reduced; agricultural and industrial practices impact the natural nitrogen cycle, leading to increased N₂O emissions. 

“A sustainable nitrogen management approach not only reduces nitrous oxide emissions but also prevents the release of other harmful nitrogen compounds,” said A.R. Ravishankara, Chemist and atmospheric scientist at Colorado State University and Co-Chair of the Assessment. “This could improve air and water quality, protect ecosystems, and safeguard human health, all while maintaining food security.” 

Nitrous oxide is currently the most significant ozone-layer-depleting substance emitted into the atmosphere. The Assessment shows that proactively tackling N₂O would also support the continued recovery of the ozone layer, helping to avoid a future where much of the global population is exposed to harmful UV levels.  

“The ozone layer is crucial for all life on Earth. For decades, parties to the Montreal Protocol have worked hard to safeguard it. This Assessment highlights the need for continued vigilance, commitment and action for the ozone layer to recover as soon as possible to its pre-1980 levels,” said Megumi Seki, Executive Secretary of the Montreal Protocol Ozone Secretariat, United Nations Environment Programme.

“This Assessment sounds the alarm on a relatively forgotten super pollutant that contributes greatly to climate change and air pollution,” said Martina Otto, Head of the Secretariat of the UNEP-convened Climate and Clean Air Coalition. “By using the abatement tools highlighted in the Assessment that are already available to us, we can yield multiple benefits across climate, clean air, and health”, she added.   

Reducing nitrogen oxide emissions and ammonia simultaneously would also significantly improve air quality, potentially avoiding up to 20 million premature deaths globally by 2050. Abatement measures would also enhance water quality, improve soil health, and protect ecosystems from the impacts of nitrogen runoff. 

The Assessment underscores the need for immediate and ambitious action to reduce N₂O emissions as part of a broader strategy to tackle super pollutants, which, alongside efforts to achieve net-zero carbon dioxide emissions, can put the world on track to meet long-term climate, food security and health goals.