Aviation and Global Climate Change in the 21st Century (Invited)

Aviation is a singularly valuable resource in the world community that has grown significantly over the past decades despite world-changing events. Aviation emissions contribute to the radiative forcing (RF) of climate. Of importance are emissions of carbon dioxide (CO2), nitrogen oxides (NOx), aerosols and their precursors (soot and sulphate), and increased cloudiness in the form of persistent linear contrails and induced-cirrus cloudiness. In 2005, aviation operations contributed about 2.5% of anthropogenic CO2 emissions and represented 3-5% of total anthropogenic forcing. Large uncertainties remain in aviation climate forcings, namely the O3 and CH4 changes that occur in response to NOx emissions and aviation induced cirrus cloudiness. The lack of physical process models and adequate observational data for aviation-induced cirrus effects limit confidence in quantifying their RF contribution. Future scenarios of aviation emissions for 2050 that are consistent with IPCC scenarios show an increase in fuel usage by factors of 2.7 to 3.9 over 2000. Simplified calculations of total aviation RF in 2050 show increases by factors of 3.0 to 4.0 over the 2000 value, representing 4%-4.7% of total RF (excluding induced cirrus). An examination of a range of future technological options shows that substantive reductions in aviation fuel usage are possible only with the introduction of radical technologies.