Graph showing global-averaged monthly mean atmospheric nitrous oxide (N2O) levels as determined from marine surface sites since 2016. The levels are given as a dry air mole fraction, which is the number of nitrous oxide molecules divided by the total number of molecules in a sample after water vapour has been removed. Nitrous oxide is a powerful greenhouse gas and also depletes the ozone layer. The majority of atmospheric nitrous oxide is produced by microorganisms in the soil and oceans. The red lines and circles are globally averaged monthly mean values centered on the middle of each month. The black line and squares show the long-term trend (similar to a 12-month running mean) where the average seasonal cycle has been removed.