A simple framework for assessing the trade-off between the climate impact of aviation carbon dioxide emissions and contrails for a single flight

Abstract

Persistent contrails are an important climate impact of aviation which could potentially be reduced by re-routing aircraft to avoid contrailing; however this generally increases both the flight length and its corresponding CO 2 emissions. Here, we provide a simple framework to assess the trade-off between the climate impact of CO 2 emissions and contrails for a single flight, in terms of the absolute global warming potential and absolute global temperature potential metrics for time horizons of 20, 50 and 100 years. We use the framework to illustrate the maximum extra distance (with no altitude changes) that can be added to a flight and still reduce its overall climate impact. Small aircraft can fly up to four times further to avoid contrailing than large aircraft. The results have a strong dependence on the applied metric and time horizon. Applying a conservative estimate of the uncertainty in the contrail radiative forcing and climate efficacy leads to a factor of 20 difference in the maximum extra distance that could be flown to avoid a contrail.

Ice supersaturation and the potential for contrail formation in a changing climate

“…Because they make a potentially large contribution to the climate impact of aviation (e.g. Lee et al, 2009), many studies have considered possible strategies to reduce contrail formation in the future, for example by developments to engine technology Haglind, 2008) or by changing aircraft altitude (Williams et al, 2002;Fichter et al, 2005;Mannstein et al, 2005;Rädel and Shine, 2008;Schumann et al, 2011;Deuber et al, 2013) or route (Sridhar et al, 2013;Irvine et al, 2014b;Soler et al, 2014;Zou et al, 2015) to avoid flying through ISS regions. In addition, it is likely that contrail formation will become more frequent due to increased air traffic, and the introduction of newer, more efficient engines, which consume less fuel but allow contrail formation to occur at higher temperatures and thus over a wider range of cruise altitudes than at present (Schumann, 2000;Schumann et al, 2000;Marquart et al, 2003).…”

Varying percentages of full uniform shading of a PV module in a controlled environment yields linear power reduction

“…Persistent contrails are an important climate impact of aviation that could potentially be reduced by re-routing aircraft. This, however, generally increases both the flight length and its corresponding CO emissions [25]. Contrails are visible for several minutes, or even longer when the relative humidity is slightly below saturation, in particular at low temperatures [26].…”

Assessment of Aircraft Contrail Avoidance Strategies

“…(2), the environmental costs are limited to CO 2 emissions (proportional to m f ) and contrail severity C. The previous analysis indicates that this is by itself an oversimplification, because one could add other pollutants to Eq. (2). The parameter C is difficult to evaluate: it would need to be specified by a combination of contrail length, width, optical depth, and duration (contrail severity) and decide on partial or total avoidance, also in consideration of the geographical position, season of the year, and time of the day.…”

“…Diurnal and cloud-correction estimates are given, for example, by Minnis et al [31]; such corrections would have to be integrated into Eq. (2).…”

“…In a recent paper published by Irvine et al [2], it was contended that an eastbound transatlantic flight can be diverted by up to 2°latitude north or south at a marginal cost of a few extra kilometers. These authors proposed an equation to quantify the additional distance that can be flown so that the contrail avoidance would not offset the additional emissions of carbon dioxide in the atmosphere, due to the extended flight.…”