Recent increase in N2O growth rate (2013–2023) mainly due to increase of nitrogen-fertiliser and manure use in the Northern Tropics and Southern Landmass

Abstract: Nitrous oxide (N₂O) is a strong greenhouse gas that contributes significantly to global warming and causes depletion of ozone in the stratosphere. Recent observational records show an unprecedented acceleration in atmospheric N₂O growth, reaching 1.15 ppb yr^− 1 in 2019–2023, a significant increase compared to 0.68 ppb yr^− 1 in 2001–2005. This surge in growth rate is particularly pronounced over tropical regions, and has been measured most prominently at the southern-most island of Japan (Hateruma). In this study, we use N₂O observations from globally distributed multi-institutional networks and the MIROC4-ACTM inversion framework to quantify N₂O emissions and identify key regions that are driving the recent acceleration. 

Our results suggest that the major Asian countries, Brazil, Central and Northern Africa, and the Contiguous United States have increased emission sources in the recent 2.5 decades (1998–2023). Further, there has been an increase in land N₂O emissions, at a rate of 106 GgN yr^− 1 per year during 1998–2002 to 2019–2023 (1Gg = 10⁹g). The inversion inferred trends are consistent with increased fertiliser use and manure production to support extensive agriculture, and terrestrial ecosystem model results. The emissions from oceanic regions did not show significant increases in N₂O (rate: 7 ± 2 GgN yr^− 1 per year) in our inverse model setup. 

Our results underscore the importance for improved climate mitigation strategies and emissions reduction policies by increasing nitrogen-fertiliser use efficiency in agricultural land.