Global Nitrous Oxide (N₂O) Assessment Report

GS Paper III Environment

The Global Nitrous Oxide Assessment has recently been published by the United Nations Environment Programme & the Food and Agriculture Organization.

It is the first international report focused solely on N2O in more than a decade.

Crucial Insights on the Global Nitrous Oxide (N₂O) Assessment Report

Global Warming Impact:
- N₂O currently contributes 0.1°C to global warming.
- Its continued increase in emissions makes it impossible to limit warming to 1.5°C.
Anthropogenic Emissions:
- Increased by 40% since 1980, with 75% originating from agriculture (synthetic fertilizers and manure).
Ozone Depletion and Health Risks:

The Gothenburg Protocol:

The Gothenburg Protocol (was adopted in 1999) was established to address pollutants that cause acidification and ground-level ozone.
It sets limits on air pollutants including sulfur dioxide, nitrogen oxide, ammonia and volatile organic compounds that are hazardous to human health and the environment

- N₂O is the leading ozone-depleting substance, increasing harmful UV exposure.
- Raises risks of cataracts (0.2–0.8%) and skin cancer (2–10%).
Abatement measures: The report highlighted that currently, available abatement measures could reduce N2O emissions by more than 40 per cent below current levels.
Emissions Sources:
- Agriculture: It is currently the source of 75% of those emissions, of which approximately 90% comes from the use of synthetic fertilisers and manure on agricultural soils and 10% from manure management.
- Industry: Industrial sources account for approximately 5% of emissions, and the remaining 20% come from fossil fuel combustion, wastewater treatment, aquaculture, biomass burning, and other sources.
Rise in Emissions: Atmospheric abundance of the gas has risen by over 20% since pre-industrial era; its mean annual growth rate over the past five years (2017–2021) was 1.2 parts per billion a year and was nearly twice that of the early 2000s (2000–2004).

Agriculture: Use of enhanced-efficiency fertilisers, nitrification inhibitors, & slow-release formulations can reduce emissions.
Industry: Industries can eliminate N2O emissions by adopting existing and relatively low-cost abatement measures that could cost $1,600-6,000 per tonne of nitrous oxide.
Fossil Fuel Reduction: Transition to renewable resources in transportation & energy production.
Manure Management: Balance nutrient inputs in animal feed, reduce grazing intensity, & apply anaerobic digestion of manure.
Multilateral Options: Adopting targets like the Gothenburg Protocol on ammonia & nitrogen oxides under the Convention on Long Range Transboundary Air Pollution.
Transformations in food production: Transformations in food production and societal systems could lead to even deeper reductions in Nitrous Oxide emissions.

It is a Greenhouse gas (GHG) 300 times more potent than carbon dioxide (CO2).
It has the third-highest concentration, after CO2 and methane (CH4), in Earth’s atmosphere among GHGs responsible for global warming.
It can live in the atmosphere for up to 120-125 years and is approximately 270 times more powerful than carbon dioxide per tonne of emission at warming the Earth.

Soils: Microbial processes in soils can consume and reduce N₂O emissions.
- Denitrifying bacteria convert N₂O to nitrogen gas (N₂) under anaerobic conditions.
Oceans: Deeper and subsurface oceans absorb N₂O from the atmosphere through dissolution at the air-sea interface.
- Marine phytoplankton play a role in consuming dissolved N₂O
Stratosphere: N₂O reacts with ozone (O₃) which leads to the formation of nitrogen oxides (NOx) and ultimately nitrogen gas (N₂).

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