N?O Emissions is Key to Meeting 1.5°C Climate Target and Protecting Human Health and Biodiversity (GS Paper 3, Environment)
Overview
- A recent report from the United Nations highlights the urgent need to address nitrous oxide (N₂O) emissions if the world is to limit global warming to 1.5°C above pre-industrial levels.
- Without significant reductions in N₂O emissions, it is unlikely that global warming can be kept under the critical threshold.
- In fact, if left unchecked, N₂O is expected to contribute an additional 0.2°C of warming by 2100.
- However, the report also suggests that implementing available mitigation solutions could help reduce this warming by up to 0.1°C by the end of the century.
The Importance of Tackling N₂O
- N₂O, commonly known as laughing gas, is the third most important greenhouse gas after carbon dioxide (CO₂) and methane (CH₄), and it has a much higher global warming potential.
- One tonne of N₂O has 270 times the warming effect of a tonne of CO₂.
- Moreover, it is the primary substance responsible for ozone depletion, contributing significantly to the thinning of the stratospheric ozone layer.
- Despite its importance in both climate change and ozone layer degradation, N₂O is not currently regulated under the Montreal Protocol, which aims to phase out ozone-depleting substances.
- The report, presented at COP29, draws attention to the fact that agricultural activities are responsible for around 75% of global N₂O emissions.
- The remaining 25% come from a variety of sources including industrial processes, fossil fuel combustion, wastewater treatment, aquaculture, and biomass burning.
- Since the industrial revolution, human activities have led to a 20% increase in N₂O emissions, contributing to 0.1°C of global warming so far.
Health and Biodiversity Impacts
- The report underscores that reducing N₂O emissions is not only crucial for mitigating climate change, but also for protecting human health and biodiversity.
- One of the primary benefits of curbing N₂O emissions is the potential to reduce ozone depletion.
- The ozone layer protects life on Earth from harmful ultraviolet (UV) radiation, and its degradation can increase incidences of skin cancer, cataracts, and other health issues.
- According to the report, if N₂O emissions are not significantly reduced, the resulting ozone depletion could lead to a 0.2–0.8% increase in cataract cases and a 2-10% increase in skin cancers by the 2080s, particularly in regions closer to the equator.
Pathways to Reduction
The good news is that significant reductions in N₂O emissions are possible using existing technologies. Current measures could reduce emissions by more than 40% below current levels. Some of the most effective strategies include:
- Controlled-Release Fertilisers: These fertilisers release nitrogen more slowly, preventing excess nitrogen from being converted into N₂O.
- Manure Management: Better management of livestock manure can significantly reduce the amount of N₂O released into the atmosphere.
- Changes in Dietary Habits: Reducing animal protein consumption in certain populations could also lower agricultural N₂O emissions, as livestock farming is a major contributor.
- Industrial Abatement: Industries can adopt low-cost, existing abatement measures that could eliminate N₂O emissions. These measures could cost between $1,600 and $6,000 per tonne of N₂O reduced.
The report warns that while industrial sources currently represent only about 5% of anthropogenic N₂O emissions, this figure could rise in the future if the use of ammonia as a fuel for marine shipping and biofuels from fertilised crops increases. These technologies, which are seen as potential solutions for reducing carbon dioxide emissions, may inadvertently increase N₂O emissions and offset some of their climate benefits.
Multiple Benefits Across Sectors
- Experts believe that addressing N₂O emissions can yield multiple benefits.
- Martina Otto, head of the UNEP-convened Climate and Clean Air Coalition, emphasized that reducing N₂O emissions would not only mitigate climate change but also improve air quality and public health.
- “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 said.
- The report concludes that N₂O is a "relatively forgotten super pollutant" that has been overshadowed by the focus on CO₂ and methane.
- However, tackling N₂O emissions is a key element in achieving climate goals, protecting public health, and preserving biodiversity.
The Way Forward
- While significant reductions in N₂O emissions are achievable, the report stresses the need for continued research to better understand the trade-offs in abatement efforts across gases such as CO₂, methane, and N₂O.
- This research will be crucial for identifying the most effective strategies for each sector and ensuring that efforts to mitigate one pollutant do not inadvertently exacerbate another.
- Ultimately, addressing N₂O emissions could be one of the most cost-effective ways to slow global warming, protect human health, and safeguard the ozone layer.
- However, to do so, coordinated efforts across industries, agriculture, and global governance will be essential.
- By acting now to tackle this overlooked greenhouse gas, the world can reduce warming and protect future generations from the harmful impacts of climate change and ozone depletion.
