What is the Yearly Atmospheric N₂O Increase?

This is the difference in the atmospheric nitrous oxide (N₂O) of a given year compared to the previous year. We call this an ‘increase’ because in recent history, most years have had more nitrous oxide in the atmosphere than the previous year; in the case of a negative value, this means there was a decrease.

Nitrous oxide has a large warming effect, with a Global Warming Potential (GWP) that is 273 times greater than CO₂. Like CO₂, but unlike methane, it stays in the atmosphere for a long time, on average 116 years. Besides its warming potential, nitrous oxide is also important because it depletes the ozone layer, which protects us from the Sun’s ultraviolet rays.

The yearly nitrous oxide increase depends on the processes that emit nitrous oxide into the atmosphere and on the nitrous oxide sinks, which mostly comprise photochemical atmospheric breakdown in the stratosphere.

Units and measures

The primary unit here is parts per billion (ppb), which describes the increase in the concentration of atmospheric nitrous oxide per year. The secondary unit here is a megatonne, which describes the weight of the increase of atmospheric nitrous oxide per year. We show this to be able to relate to emissions, which are commonly expressed in megatonnes.

Insights from this chart

In recent decades there has been a consistent increase in atmospheric nitrous oxide driven by human emissions. There are three time periods with significant differences in the magnitude of fluctuations. These differences are due to the underlying sources and are explained in the next section.

About the data

The data is from several sources linked to the National Oceanic and Atmospheric Administration (NOAA). National Centers for Environmental Information has data from ice core studies, whereby we average the extrapolated yearly increases of the individual studies. This is used for the time period prior to 1978 and highlights the long-term trend, but it does not show the actual yearly fluctuations.

The Global Monitoring Laboratory provides the annual nitrous oxide mole fraction increase (ppb) from Jan 1 through Dec 31. For the current year, we compare the available months to those a year earlier. Since 1978, N₂O measurement programs have increased the number of measurements, but there were high fluctuations in global N₂O levels due to uncertainty from measurement equipment, which improved over time. Since the late 1990s, a globally distributed network of air sampling sites has greatly increased confidence in the measurements.

Data sources

Globally averaged marine surface annual mean growth rates ESRL's Global Monitoring Laboratory of the National Oceanic and Atmospheric Administration
Credits: Lan, X., K.W. Thoning, and E.J. Dlugokencky (2022): Trends in globally-averaged CH4, N2O, and SF6 determined from NOAA Global Monitoring Laboratory measurements. Version 2022-10, https://doi.org/10.15138/P8XG-AA10Update cycle: monthlyDelay: ~ 3 months

Globally averaged marine surface monthly mean data ESRL's Global Monitoring Laboratory of the National Oceanic and Atmospheric Administration
Credits: Lan, X., K.W. Thoning, and E.J. Dlugokencky (2022): Trends in globally-averaged CH4, N2O, and SF6 determined from NOAA Global Monitoring Laboratory measurements. Version 2022-10, https://doi.org/10.15138/P8XG-AA10Update cycle: monthlyDelay: ~ 3 months

Combined GML N2O Data File ESRL's Global Monitoring Laboratory of the National Oceanic and Atmospheric Administration
Credits: Dutton, G.S., B.D. Hall, E.J. Dlugokencky, X. Lan, J.D. Nance, M. Madronich (2022), Combined Atmospheric Nitrous Oxide Dry Air Mole Fractions from the NOAA GML Halocarbons Sampling Network, 1977-2022, Version: 2022-10-07, https://doi.org/10.15138/GMZ7-2Q16Update cycle: monthlyDelay: ~ 1 month

Law Dome Ice Core 2000-Year CO2, CH4, and N2O Data NOAA National Centers for Environmental Information
Credits: MacFarling Meure, C., D. Etheridge, C. Trudinger, P. Steele, R. Langenfelds, T. van Ommen, A. Smith, and J. Elkins. 2006. Law Dome CO2, CH4 and N2O Ice Core Records Extended to 2000 years BP. Geophysical Research Letters, 33(14), L14810. doi: 10.1029/2006GL026152