A new study has revealed a relentless rise in nitrous oxide (N2O) emissions, a potent greenhouse gas, over the past four decades. Published in the Earth System Science Data journal, the “Global Nitrous Oxide Budget (1980-2020)” report represents the most thorough analysis of N2O emissions from human activities and natural sources.
The study, led by researchers from Boston College in collaboration with the Global Carbon Project, was conducted by a team of 58 scientists from 55 organizations in 15 countries. It highlights a 40% increase in nitrous oxide emissions due to human activities, amounting to an additional 3,306,930 tons of N2O annually. This surge has resulted in the highest atmospheric growth rates recorded since 1980.
Nitrous oxide, like carbon dioxide (CO2), is a long-lived greenhouse gas contributing significantly to climate change. It also plays a vital role in the depletion of the stratospheric ozone layer, which protects Earth from harmful ultraviolet radiation.
The report identifies agricultural production as the predominant source of N2O emissions from human activities. Key contributors include the extensive use of commercial nitrogen fertilizers and animal waste on croplands. This practice not only elevates N2O emissions but also leads to increased nitrogen runoff, polluting inland waters and coastal ecosystems.
In 2020, agricultural nitrous oxide emissions reached 8,818,480 tons, accounting for 74% of total N2O emissions from human activities in the last decade. The study advocates for better agricultural practices, such as more efficient use of nitrogen fertilizers and improved animal manure management, to mitigate N2O emissions and reduce water pollution.
Lead author Hanqin Tian, Schiller Institute Professor of Global Sustainability at Boston College, emphasized reducing N2O emissions to meet the Paris Agreement’s goal of limiting the global temperature increase. “Reducing N2O emissions is the only viable solution since we currently lack technologies to remove N2O from the atmosphere,” Tian asserted.
The study’s conclusions are derived from millions of N2O measurements taken over four decades and detailed models of the global nitrogen cycle across terrestrial, marine, and atmospheric systems.
While some regions have significantly reduced N2O emissions, the global picture remains troubling. China and Europe have shown reductions in emissions due to successful policies and practices. However, in the United States, agricultural emissions continue to rise slightly, offsetting industrial emissions reductions and resulting in stagnant emission levels.
Prof Parv Suntharalingam from the University of East Anglia, a key contributor to the ocean model component of the report, highlighted the dominant role of human activities in the observed increase in atmospheric N2O. "Natural sources such as oceans and soils have remained stable, underscoring the need for effective strategies to curb human-induced emissions," Suntharalingam explained.
Atmospheric concentrations of N2O reached 336 parts per billion in 2022, a 25% increase over pre-industrial levels, exceeding even the most pessimistic scenarios projected by the Intergovernmental Panel on Climate Change (IPCC).
Josep Canadell, Executive Director of the Global Carbon Project and a scientist at CSIRO, Australia’s national science agency, emphasized the necessity for more frequent assessments to identify and target high-emission regions and economic activities. “To achieve the objectives of the Paris Agreement, we need an improved inventory of N2O sources and sinks,” Canadell remarked.
