Measuring and Modeling the Lifetime of Nitrous Oxide Including its Variability

TitleMeasuring and Modeling the Lifetime of Nitrous Oxide Including its Variability
Publication TypeJournal Article
Year of Publication2015
JournalJ. Geophys. Res. Atmos
Volume120
Pages13pp
Date Published05/2015
Abstract / Summary

The lifetime of nitrous oxide, the third-most-important human-emitted greenhouse gas, is based to date primarily on model studies or scaling to other gases. This work calculates a semiempirical lifetime based on Microwave Limb Sounder satellite measurements of stratospheric profiles of nitrous oxide, ozone, and temperature; laboratory cross-section data for ozone and molecular oxygen plus kinetics for O(1D); the observed solar spectrum; and a simple radiative transfer model. The result is 116 ± 9 years. The observed monthly-to-biennial variations in lifetime and tropical abundance are well matched by four independent chemistry-transportmodels driven by reanalysismeteorological fields for the period of observation (2005–2010), but all thesemodels overestimate the lifetime due to lower abundances in the critical loss region near 32 kmin the tropics. These models plus a chemistry-climate model agree on the nitrous oxide feedback factor on its ownlifetime of 0.94 ± 0.01, giving N2O perturbations an effective residence time of 109 years. Combining this new empirical lifetime with model estimates of residence time and preindustrial lifetime (123 years) adjusts our best estimates of the human-natural balance of emissions today and improves the accuracy of projected nitrous oxide increases over this century.

DOI10.1002/2015JD023267
Journal: J. Geophys. Res. Atmos
Year of Publication: 2015
Volume: 120
Pages: 13pp
Date Published: 05/2015

The lifetime of nitrous oxide, the third-most-important human-emitted greenhouse gas, is based to date primarily on model studies or scaling to other gases. This work calculates a semiempirical lifetime based on Microwave Limb Sounder satellite measurements of stratospheric profiles of nitrous oxide, ozone, and temperature; laboratory cross-section data for ozone and molecular oxygen plus kinetics for O(1D); the observed solar spectrum; and a simple radiative transfer model. The result is 116 ± 9 years. The observed monthly-to-biennial variations in lifetime and tropical abundance are well matched by four independent chemistry-transportmodels driven by reanalysismeteorological fields for the period of observation (2005–2010), but all thesemodels overestimate the lifetime due to lower abundances in the critical loss region near 32 kmin the tropics. These models plus a chemistry-climate model agree on the nitrous oxide feedback factor on its ownlifetime of 0.94 ± 0.01, giving N2O perturbations an effective residence time of 109 years. Combining this new empirical lifetime with model estimates of residence time and preindustrial lifetime (123 years) adjusts our best estimates of the human-natural balance of emissions today and improves the accuracy of projected nitrous oxide increases over this century.

DOI: 10.1002/2015JD023267
Citation:
Prather, MJ, J Hsu, NM DeLuca, CH Jackman, LD Oman, AR Douglass, EL Fleming, et al.  2015.  "Measuring and Modeling the Lifetime of Nitrous Oxide Including its Variability."  J. Geophys. Res. Atmos 120: 13.  https://doi.org/10.1002/2015JD023267.