Emission metrics for quantifying regional climate impacts of aviation

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.

Global Transportation Demand Development with Impacts on the Energy Demand and Greenhouse Gas Emissions in a Climate-Constrained World

“…The consequence may be that as soon as the road mode shifts for newly sold vehicles to BEV or sustainable hydrogen-based FCEV options, the pressure on ship operators and airlines grows fast for ambitious defossilization measures. The pressure for airlines may be more drastic, as recent research indicates that zero GHG emissions for the aviation sector may not be possible with fuel measures alone, since contrail-cirrus formation cannot be reduced to zero [158]. Lund et al [158] conclude that the 100 years of global temperature change impact of contrail-cirrus formations is about 12% of the aviation CO 2 emissions.…”

Marginal climate and air quality costs of aviation emissions

“…RF due to other non-CO 2 aviation emissions, including non-methane volatile organic compounds (NMVOC), carbon monoxide (CO), and organic carbon (OC) have been shown in prior studies to be negligible (Brasseur et al 2016). The indirect radiative impacts of aviation emissions on cloud formation are too uncertain to justify inclusion (Lund et al 2017a uncertain for this emissions regime (Fuglestvedt et al 2010).…”

“…Our climate results exclude the impact of climate-carbon feedbacks, the impact of differing temperature responses due to different climate forcers, and the impact of aerosol-cloud interactions. In particular, aerosol-cloud interactions could have a large impact on results, but the scientific literature has yet to agree on the sign of this impact (Lund et al 2017a). Moreover, the impacts due to BC are likely underestimated in this work, resulting from (i) the exclusion of BC radiative impact on albedo changes (section 2.2), (ii) not accounting for differential toxicity in air quality impacts, and (iii) the use of a large modeling grid (section 2.3).…”

“…Climate impact studies typically estimated the total speciated radiative forcing from one year of aviation emissions (Penner et al 1999, Sausen et al 2005, Lee et al 2009, Brasseur et al 2016, or focused on studying one climate forcer, including specifically contrails (Burkhardt and Kärcher 2011, Chen and Gettelman 2013, Schumann and Graf 2013, Chen and Gettelman 2016, Bock and Burkhardt 2019 and aviation NO x emissions (Wild et al 2001, Stevenson et al 2004, Köhler et al 2008, Hoor et al 2009, Holmes et al 2011, Søvde et al 2014, Skowron et al 2015. In addition, Lund et al (2017a) presented regionalized aviation impact climate metrics. Freeman et al (2018) aimed to identify optimal aviation climate policy considering the tradeoffs between NO x emissions and CO 2 emissions, disregarding the air quality impacts from NO x emissions.…”

Sensitivity of surface temperature to radiative forcing by contrail cirrus in a radiative-mixing model

“…The sensitivity of surface temperature to contrail cirrus changes is relevant with respect to aviation climate impact (D. S. Boucher et al, 2013;Lund et al, 2017). Long-lived contrails of significant optical thickness (> 0.1) are estimated to cover about 0.2-0.5 % of the Earth, with higher values in northern midlatitudes Schumann et al, 2015;Bock and Burkhardt, 2016).…”