Observed changes in stratospheric circulation: decreasing lifetime of N₂O, 2005–2021

Abstract. Using Aura Microwave Limb Sounder satellite observations of stratospheric nitrous oxide (N2O), ozone, and temperature from 2005 through 2021, we calculate the atmospheric lifetime N2O to be decreasing at a rate −2.1 ± 1.2 %/decade. This decrease is occurring because abundances in middle tropical stratosphere, where photochemically destroyed, are increasing faster than bulk lower atmosphere. The cause appears more vigorous circulation, which models predict result climate change. If observed trends implied emissions continue, then change over 21st century will 27 % less those projected with fixed lifetime, impact on global warming ozone depletion proportionately lessened. Because caused part by N2O, this finding an example negative climate–chemistry feedback.