Nitrous Oxide levels endangering Paris goals: UN report
Nitrous oxide has a lifetime of 120 years and is approximately 270 times more powerful than carbon dioxide per tonne of emission at warming the Earth
New Delhi: Without urgent action on rising N2O emissions, there are “no viable pathways” to limit global warming to 1.5°C, a new report launched at the UN Conference of Parties currently underway in Baku has warned.
The United Nations Global Nitrous Oxide Assessment signals that emissions of what it identifies as the third most important greenhouse gas are rising faster than expected and calls for immediate action to curb environmental, and, more significantly, health impacts.
“This assessment sounds the alarm on a relatively forgotten super pollutant that contributes greatly to climate change and air pollution,” Martina Otto, head of secretariat of the UNEP-convened Climate and Clean Air Coalition, said in a press release along with the launch of the report.
Nitrous oxide has a lifetime of 120 years and is approximately 270 times more powerful than carbon dioxide per tonne of emission at warming the Earth. Its anthropogenic emissions are responsible for approximately 10% (around 0.1°C) of net global warming to date since the industrial revolution, with a direct, and likely the most severe, impact on ozone layer.
And its human-induced emissions, primarily originating from the agricultural use of synthetic fertilisers and manure “are increasing faster than previously projected”, the report said.
Among key messages, the report flagged that 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); and the increase is primarily driven by emissions from agriculture.
“Between 1980 and 2022, atmospheric concentrations increased from 301 to 336 parts per billion. Agriculture 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,” the assessment found.
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.
“Abating N2O emissions could avoid up to 235 billion tonnes of CO2-equivalent emissions by 2100,” said David Kanter, Associate Professor of Environmental Studies at NYU and Co-Chair of the Assessment. “This is equivalent to six years’ worth of current global carbon dioxide emissions from fossil fuels.”
The assessment identified abatement strategies that could cut N2O emissions by more than 40% from current levels.
It suggested transformations in food production and societal systems like controlled-release fertilisers or formulations that inhibit nitrogen losses, improved manure management and behavioural changes, such as lowering the consumption of animal protein in some populations.
It also recommended that 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. “It is a low-hanging fruit for near-term abatement and even though it currently represents approximately 5% of anthropogenic emissions, this could increase in the future,” the report warned.
“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,” Otto added.
Nitrous oxide is currently the most significant ozone-layer depleting substance being emitted to the atmosphere. The destructive capacity of today’s nitrous oxide emissions approximately equals the sum of all other current ozone-depleting substance emissions.
Abatement could avoid a 0.2-0.8% increase in cataract cases and a 2-10% increase in skin cancers by 2080-2090, the report said.
Noting the urgency of the report, Megumi Seki, Executive Secretary of the Montreal Protocol Ozone Secretariat, United Nations Environment Programme, said, “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.”