A comprehensive quantification of global nitrous oxide sources and sinks

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Climate Science

Background:

• Nitrous oxide (N₂O) is a potent greenhouse gas contributing to ozone depletion and climate change.
• Current N₂O inventories are incomplete, lacking natural sources and precise anthropogenic attribution.
• Atmospheric N₂O concentrations are increasing at approximately 2% per decade.

Purpose of the Study:

• To present a comprehensive global N₂O inventory incorporating natural and anthropogenic sources.
• To quantify N₂O sources and sinks from 1980 to 2016 using multiple methodologies.
• To analyze the drivers of increasing N₂O emissions and identify emerging trends.

Main Methods:

• Integrated bottom-up approaches: inventory, flux measurements, land/ocean modeling.
• Top-down approach: atmospheric inversion modeling.
• Analysis of 21 natural and human sectors for N₂O emissions and sinks.

Main Results:

• Global N₂O emissions estimated at 17.0 Tg N yr^-1 (bottom-up) and 16.9 Tg N yr^-1 (top-down) between 2007-2016.
• Human-induced N₂O emissions increased 30% over four decades, primarily from croplands, reaching 7.3 Tg N yr^-1.
• Significant N₂O emission growth observed in emerging economies (Brazil, China, India).

Conclusions:

• Increasing N₂O emissions are primarily driven by human activities, especially agricultural nitrogen additions.
• An emerging N₂O-climate feedback loop is identified, driven by nitrogen additions and climate change.
• The rapid rise in N₂O emissions exceeds projections, highlighting the critical need for mitigation strategies.