Radiative forcing due to aviation water vapour emissions

• Published in: Atmospheric environment (1994) Vol. 63; pp. 1 - 13
• Main Authors: Wilcox, L.J., Shine, K.P., Hoskins, B.J.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.12.2012; Elsevier
• Subjects: Air transportation and traffic; aircraft; Applied sciences; atmospheric chemistry; Aviation; Climate; Climatology. Bioclimatology. Climate change; Earth, ocean, space; emissions; Exact sciences and technology; External geophysics; Ground, air and sea transportation, marine construction; Inventories; Lagrangian trajectory; linear models; Mathematical models; Meteorology; Radiative forcing; Stockpiling; stratosphere; Trajectories; tropopause; Upper bounds; Vapour emission; water vapor; Climate; Aviation; Radiative forcing; Lagrangian trajectory; Emission inventory; water vapor; radiative transfer; Air transportation; Effect on climate; Forcing; stratosphere; greenhouse gas
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2012.08.072

Three emissions inventories have been used with a fully Lagrangian trajectory model to calculate the stratospheric accumulation of water vapour emissions from aircraft, and the resulting radiative forcing. The annual and global-mean radiative forcing due to present-day aviation water vapour emissions has been found to be 0.9 [0.3–1.4] mW m−2. This is around a factor of three smaller than the value given in recent assessments, and the upper bound is much lower than a recently suggested 20 mW m−2 upper bound. This forcing is sensitive to the vertical distribution of emissions, and, to a lesser extent, interannual variability in meteorology. Large differences in the vertical distribution of emissions within the inventories have been identified, which result in the choice of inventory being the largest source of differences in the calculation of the radiative forcing due to the emissions. Analysis of Northern Hemisphere trajectories demonstrates that the assumption of an e-folding time is not always appropriate for stratospheric emissions. A linear model is more representative for emissions that enter the stratosphere far above the tropopause. ► Radiative forcing due to aviation water vapour emissions was 0.9 [0.3–1.4] mW m−2 in 2006. ► This new value is around a factor of three smaller than recent assessments. ► The upper bound from recent assessments is likely much too high. ► The stratospheric accumulation of emissions is modelled with Lagrangian trajectories. ► The vertical distribution of emissions is key to the estimate of radiative forcing.