Mitigating the Climate Forcing of Aircraft Contrails by Small-Scale Diversions and Technology Adoption

Abstract

The climate forcing of contrails and induced-cirrus cloudiness is thought to be comparable to the cumulative impacts of aviation CO2 emissions. This paper estimates the impact of aviation contrails on climate forcing for flight track data in Japanese airspace and propagates uncertainties arising from meteorology and aircraft black carbon (BC) particle number emissions. Uncertainties in contrail age, coverage, optical properties, radiative forcing and energy forcing (EF) from 2 individual flights can be two orders of magnitude larger than the fleet-average values. Only 2.2% [2.0%, 2.5%] of flights contribute to 80% of the contrail EF in this region. A small-scale strategy of selectively diverting 1.7% of the fleet could reduce the contrail EF by up to 59.3% [52.4%, 65.6%], with only a 0.014% [0.010%, 0.017%] increase in total fuel consumption and CO2 emissions. A low-risk strategy of diverting flights only if there is no fuel penalty, thereby avoiding additional long-lived CO2 emissions, would reduce contrail EF by 20.0% [17.4%, 23.0%]. In the longer term, widespread use of new engine combustor technology, which reduces BC particle emissions, could achieve a 68.8% [45.2%, 82.1%] reduction in the contrail EF. A combination of both interventions could reduce the contrail EF by 91.8% [88.6%, 95.8%].

Climate-Optimized Trajectories and Robust Mitigation Potential: Flying ATM4E

“…Teoh et al [7] assessed the possibility of reduction of climate impact (only considering forcing from CO 2 and contrails, rather than the wider set of non-CO 2 forcings considered here). They adopt a different philosophy to ours, whereby they measure climate gain relative to actual flight trajectories in Japanese airspace.…”

“…By contrast, we measure the climate gain relative to the fuel-optimal route; we believe this is preferable the approach, as it clearly distinguishes gains that can be made from climate-sensitive routing from gains that are possible because of inefficiencies in air traffic management. Another recent study [7] adopted a metric called "energy forcing" to measure the climate impact of contrails. This metric is equivalent to the Absolute Global Warming Potential (AGWP) and, when they compare it to the CO 2 AGWP 20 and AGWP 100 , it becomes equivalent to using the GWP20 and GWP 100 , as shown in the Supplementary Information of an earlier study [2].…”

“…A more recent study focused on the mitigation of contrail effects when considering trade-offs in CO 2 [6]. The climate impact of aviation is caused by CO 2 and non-CO 2 effects; hence, for climate-optimization, individual effects have to be simultaneously taken into account, in order to assess and minimize the total climate impact [7]. The impacts of non-CO 2 effects depend on the location and time of emission, e.g., contrail formation and photochemical ozone production and depend significantly on the prevailing weather conditions and synoptic situation at the time the flight occurs.…”

“…A methodology for performing a multi-criteria environmental and climate impact assessment of aircraft trajectories has been developed [5] within the SESAR (Single European Sky ATM Research project) Exploratory Project ATM4E (Air Traffic Management for Environment). It relies on a concept of climate change function (CCF) or environmental change function (ECF) [7] while using mathematical algorithms to derive them from weather forecast data, which in principal can also include metrics to measure noise and air quality impacts [5]. A methodology relying on precalculated CCFs was applied to North Atlantic Air Traffic [3,8], in order to provide a quantitative measure of climate impact of an emission at a specific location and time.…”

Beyond Contrail Avoidance: Efficacy of Flight Altitude Changes to Minimise Contrail Climate Forcing

“…Five strategies are considered, where the trajectories of all flights are selected to minimise the: (i) contrail length; (ii) mean contrail RF'; (iii) EF contrail ; (iv) EF contrail with an additional constraint that flights are only diverted if they do not incur a fuel penalty; and (v) EF total (including the EF of both contrails and CO 2 ). In our previous study [28], the diversion of flights was constrained to only those with the largest EF contrail , while the present study allows for any number of flights to be diverted and for flights to form cooling contrails (with a negative contrail RF' and/or EF).…”