Abstract
Abstract. This study examines the impacts of emissions from aviation in six source regions on global and regional temperatures. We consider the NOx-induced impacts on ozone and methane, aerosols and contrail-cirrus formation and calculate the global and regional emission metrics global warming potential (GWP), global temperature change potential (GTP) and absolute regional temperature change potential (ARTP). The GWPs and GTPs vary by a factor of 2–4 between source regions. We find the highest aviation aerosol metric values for South Asian emissions, while contrail-cirrus metrics are higher for Europe and North America, where contrail formation is prevalent, and South America plus Africa, where the optical depth is large once contrails form. The ARTP illustrate important differences in the latitudinal patterns of radiative forcing (RF) and temperature response: the temperature response in a given latitude band can be considerably stronger than suggested by the RF in that band, also emphasizing the importance of large-scale circulation impacts. To place our metrics in context, we quantify temperature change in four broad latitude bands following 1 year of emissions from present-day aviation, including CO2. Aviation over North America and Europe causes the largest net warming impact in all latitude bands, reflecting the higher air traffic activity in these regions. Contrail cirrus gives the largest warming contribution in the short term, but remain important at about 15 % of the CO2 impact in several regions even after 100 years. Our results also illustrate both the short- and long-term impacts of CO2: while CO2 becomes dominant on longer timescales, it also gives a notable warming contribution already 20 years after the emission. Our emission metrics can be further used to estimate regional temperature change under alternative aviation emission scenarios. A first evaluation of the ARTP in the context of aviation suggests that further work to account for vertical sensitivities in the relationship between RF and temperature response would be valuable for further use of the concept.
Highlights
The global aviation sector has historically been one of most rapidly growing economic sectors, and the increase in activity is projected to continue in the foreseeable future
We have examined the impacts of aviation emissions on global and regional temperature, characterizing them using emission metrics
We address the impacts of nitrogen oxides (NOx) on ozone and methane, aerosols and contrail-cirrus formation, and consider six emission regions spanning both hemispheres
Summary
The global aviation sector has historically been one of most rapidly growing economic sectors, and the increase in activity is projected to continue in the foreseeable future. Knowledge about contributions of individual sectors to total climate impact, and the effects of specific measures, is essential for the formulation and assessment of effective mitigation strategies Emission metrics, such as the global warming potential (GWP) and global temperature change potential (GTP), are tools which can serve as a bridge to policy making, and are commonly used for aggregating information and placing different emissions on a common scale. The set of regional climate sensitivities that form the basis for the ARTP, by expressing the inter-regional relationship between radiative forcings and temperature response, have so far only been derived by one climate model and for four broad latitude bands (Shindell and Faluvegi, 2009) Establishing such sensitivities requires a large number of multi-decadal simulations and is very costly in terms of computer resources. Taking our analysis one step further, we compare the regional temperature response to aviation ozone and black carbon aerosols estimated using these regional climate sensitivities with results from simulations with three other climate models, performing a first evaluation of the application of the ARTP in the context of selected aviation forcing mechanisms
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