Aviation and global climate change in the 21st century

Abstract

a b s t r a c tAviation emissions contribute to the radiative forcing (RF) of climate. Of importance are emissions of carbon dioxide (CO 2 ), nitrogen oxides (NO x ), aerosols and their precursors (soot and sulphate), and increased cloudiness in the form of persistent linear contrails and induced-cirrus cloudiness. The recent Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) quantified aviation's RF contribution for 2005 based upon 2000 operations data. Aviation has grown strongly over the past years, despite world-changing events in the early 2000s; the average annual passenger traffic growth rate was 5.3% yr À1 between 2000 and 2007, resulting in an increase of passenger traffic of 38%. Presented here are updated values of aviation RF for 2005 based upon new operations data that show an increase in traffic of 22.5%, fuel use of 8.4% and total aviation RF of 14% (excluding induced-cirrus enhancement) over the period 2000-2005. The lack of physical process models and adequate observational data for aviationinduced cirrus effects limit confidence in quantifying their RF contribution. Total aviation RF (excluding induced cirrus) in 2005 was w55 mW m À2 (23-87 mW m À2 , 90% likelihood range), which was 3.5% (range 1.3-10%, 90% likelihood range) of total anthropogenic forcing. Including estimates for aviation-induced cirrus RF increases the total aviation RF in 2005-78 mW m À2 (38-139 mW m À2 , 90% likelihood range), which represents 4.9% of total anthropogenic forcing (2-14%, 90% likelihood range). Future scenarios of aviation emissions for 2050 that are consistent with IPCC SRES A1 and B2 scenario assumptions have been presented that show an increase of fuel usage by factors of 2.7-3.9 over 2000. Simplified calculations of total aviation RF in 2050 indicate increases by factors of 3.0-4.0 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. Incorporation of aviation into an emissions trading system offers the potential for overall (i.e., beyond the aviation sector) CO 2 emissions reductions. Proposals exist for introduction of such a system at a European level, but no agreement has been reached at a global level.

Global Modeling of the Contrail and Contrail Cirrus Climate Impact

“…Current modeling studies are based on an approach that cannot be used to estimate contrail cirrus radiative forcing because the method is not suited to the simulation of long-lived contrail cirrus and because of the lack of contrail cirrus observations (Burkhardt et al 2008a, section 2e). Radiative forcing resulting from AIC has been estimated to range between 0.013 and 0.087 W m −2 (Lee et al 2009), exceeding that of past aircraft CO 2 emissions. The effect of AIC has been estimated from observational data and the level of scientific understanding is judged to be very low.…”

Short/medium-term prediction for the aviation emissions in the en route airspace considering the fluctuation in air traffic demand

“…On the other hand, the effect on climate change of aviation activities, which is most related to the cruise phase at the altitude of 6-12 km, has been rarely addressed. During the cruise phase, most of the emissions are generated in the en route airspace at altitude of 6-12 km, and have increased effect on the modification of the chemical and particle microphysical properties of the atmosphere relevant to the climate change [3] .…”

“…A recent research shows that aviation is responsible for 13% of the transportation-related fossil fuel consumption and 2% of all anthropogenic carbon dioxide emissions [1] . The anticipated annual growth of global air traffic by 5.8% in the next 20 years [2] will result in elevated aviation pollution levels in the airspace: A recent study [3] suggests a greater-than-three-fold increase between 2000 and 2050 without supervision.…”

“…A European emission trading scheme was developed in 2008, where the incorporation of aviation into the emissions trading system was proposed to cut 40% of the emissions in European airspace by 2020 [3] [11] . Motivated by the concepts in this policy, Virgin America airlines began to charge their passengers for aviation-induced environmental impact, planning to cut the aircraft emission to 1990 levels by 2020 [12] [13] .…”

“…Eyer et al and Horton et al predicted the global aviation emissions up to 2025 and 2030, respectively, using the AERO2k database and ICAO's global traffic forecast results [16] [17] . Lee et al adopted a global aviation inventory model, FAST, to predict the aviation emissions CO 2 by the year 2050 under two emission scenarios [3] . Olsthoorn predicted the international aviation emissions CO 2 by year 2050 based on the liner regression relationship between fuel prices, global gross domestic product (GDP) and the aviation fuel consumption [18] .…”