This is the average amount of nitrous oxide (N2O) that is in the atmosphere in a given year. The yearly average highlights the long-term trends and hides the seasonal variation.
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.Wikipedia: Nitrous oxide Atmospheric occurrence
The primary unit here is parts per billion (ppb), which describes the average concentration of atmospheric methane per year. The secondary unit here is megatonnes, which describes the average weight of atmospheric nitrous oxide per year. We show this to be able to relate to emissions, which are commonly expressed in megatonnes.Wikipedia: Parts-per notation
There has been a consistent rise in atmospheric nitrous oxide in the last 50 years, from just under 300 ppb to 335 ppb in 2022. The largest driver of this rise is the human emissions from agricultural processes and fossil fuel burning. To realize how high these concentrations are compared to pre-industrial values, we compare them to long-term historical concentrations from ice core studies.
When we look at the last 1,000 years, we can clearly see that the nitrous oxide concentration started rising at the end of the 18th century, coinciding with the industrial revolution.
The 10,000 years before the industrial revolution had steady atmospheric nitrous oxide levels. The last glacial period, roughly 100,000 to 12,000 ago, had much more drastic variations. It was also a drastic period! Ice sheets reached the northern parts of the US, the UK, Germany and Northeast Siberia. There were sea-level changes up to 120 meters.
The last 800,000 years offer some perspective on the nitrous oxide levels during the recurring glacial periods and the unusually high nitrous oxide level of our time. The current level of over 335 ppb was unheard of in the past, which saw values between 200 ppb and 300 ppb.Wikipedia: Methane in Earth's Atmosphere
The data is from two subgroups of NOAA, the Global Monitoring Laboratory for recent data and the National Centers for Environmental Information for paleoclimatology data.
The Global Monitoring Laboratory provides annual and monthly atmospheric nitrous oxide averages. We use the monthly trend data to calculate the average for the current year.
The National Centers for Environmental Information provides atmospheric nitrous oxide levels from several ice core studies.
Globally averaged marine surface annual mean growth ratesCredits: 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 dataCredits: 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 FileCredits: 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 DataCredits: 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
EPICA Dronning Maud Land, EPICA Dome C - 140KYr N2O Data, 800KYr N2O DataCredits: Schilt, A., M. Baumgartner, T. Blunier, J. Schwander, R. Spahni, H. Fischer, T.F. Stocker. 2010. Glacial-Interglacial and Millennial Scale Variations in the Atmospheric Nitrous Oxide Concentration during the last 800,000 Years. Quaternary Science Reviews, 29, 182-192.