Impact of biofuels on contrail warming

Caiazzo, Fabio; Agarwal, Akshat; Speth, Raymond L.; Barrett, Steven R. H.

doi:10.1088/1748-9326/aa893b

Cited by 39 publications

(55 citation statements)

References 40 publications

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“…Target year The net radiative forcing impacts of contrails have been quantified using both global climate models (Chen and Gettelman, 2013;Ponater et al, 2002) and dedicated modeling approaches such as the Contrail Cirrus Prediction Tool (CoCiP) (Schumann, 2012) and the Contrail Evolution and Radiation Model (CERM) (Caiazzo et al, 2017). These approaches have resulted in estimates of total contrail radiative forcing ranging from +15.2 mW/m 2 (Chen and Gettelman, 2013) to +63.0 mW/m 2 (Schumann et al, 2015) for 2006, as shown in Table 1.…”

Section: Sourcementioning

confidence: 99%

“…According to recent market forecasts, global air traffic is projected to grow by ~4.5% per year over the next 20 years (Airbus 2018, Boeing 2019). The scaling of contrails radiative forcing impacts with the expected traffic growth will depend on multiple aspects, especially (i) potential changes in contrail formation likelihood with changes in engine efficiency and the use of biofuels (Schumann, 2000;Caiazzo et al, 2017); (ii) the emergence of new markets with different prevailing atmospheric conditions (Boeing, 2019); and (iii) increased likelihood of contrail-contrail overlap as existing markets and flight paths become more saturated.…”

Section: Sourcementioning

confidence: 99%

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Effect of contrail overlap on radiative impact attributable to aviation contrails

Sanz-Morère

Eastham

Allroggen

et al. 2020

Preprint

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Abstract. Condensation trails (“contrails”) which form behind aircraft are estimated to cause on the order of 50 % of the total climate impact of aviation, matching the total impact of all accumulated aviation-attributable CO2. The climate impacts of these contrails are highly uncertain, in part due to the poorly-understood effect of overlap between contrails and other cloud layers. With the airline industry projected to grow by approximately 4.5 % each year over the next 20 years, instances of contrail overlap are expected to increase, including any potential mitigating or amplifying effects on contrail-attributable radiative forcing. However, the impacts of cloud-contrail overlaps are not well understood, and the effect of contrail-contrail overlap has never been quantified. In this study we develop and apply a new model of contrail radiative forcing which explicitly accounts for overlap between cloud layers. Cloud-contrail overlap is found to be responsible for 93 % of net radiative forcing attributable to 2015 contrails. We also find significant variation in the sensitivity of contrail radiative forcing to cloud cover with respect to geographic location. Clouds significantly increase warming at high latitudes and over sea, transforming cooling contrails into warming ones in the North-Atlantic corridor. Based on the same data, our results indicate that disregarding overlap between a given pair of contrail layers can result in longwave and shortwave radiative forcing being overestimated by up to 16 % and 25 % respectively, with the highest bias observed at high optical depths (> 0.4) and high solar zenith angles (> 75°). When applied to estimated global contrail coverage data for 2015, contrail-contrail overlap reduces both the longwave and shortwave forcing by ~ 2 % relative to calculations which ignore overlap. The effect is greater for longwave radiation, resulting in a 3 % net reduction in the estimated RF when overlap is correctly accounted for. This suggests that contrail-contrail overlap effects can likely be neglected in estimates of the current-day environmental impacts of aviation. However, the effect of contrail-contrail overlap is likely to increase in the future as the airline industry extends into new regions, intensifies in existing regions, and invests in higher-efficiency engines which are thought to promote contrail formation.

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Section: Sourcementioning

confidence: 99%

Section: Sourcementioning

confidence: 99%

Effect of contrail overlap on radiative impact attributable to aviation contrails

Sanz-Morère

Eastham

Allroggen

et al. 2020

Preprint

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“…Similarly, we do not consider the reduction of non-CO 2 climate pollutants emitted by the aviation sector in the mitigation scenarios. However, offsetting schemes such as CORSIA do implement the use of biofuels as well as aircraft technology and air traffic management improvements, both of which have the potential to impact future emissions of non-CO 2 climate pollutants and the density of contrail-cirrus (Bock and Burkhardt, 2019;Caiazzo et al, 2017;Burkhardt et al, 2018). While the influence of these changes on the non-CO 2 impact of international aviation is currently not well estimated, their impact should be considered in future analyses as understanding develops.…”

Section: Avoided Warming From Mitigation Measuresmentioning

confidence: 99%

Climate benefits of proposed carbon dioxide mitigation strategies for international shipping and aviation

et al. 2019

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Abstract. While individual countries work to achieve and strengthen their nationally determined contributions (NDCs) to the Paris Agreement, the growing emissions from two economic sectors remain largely outside most countries' NDCs: international shipping and international aviation. Reducing emissions from these sectors is particularly challenging because the adoption of any policies and targets requires the agreement of a large number of countries. However, the International Maritime Organization (IMO) and the International Civil Aviation Organization (ICAO) have recently announced strategies to reduce carbon dioxide (CO2) emissions from their respective sectors. Here we provide information on the climate benefits of these proposed measures, along with related potential measures. Given that the global average temperature has already risen 1 ∘C above preindustrial levels, there is only 1.0 or 0.5 ∘C of additional “allowable warming” left to stabilize below the 2 or 1.5 ∘C thresholds, respectively. We find that if no actions are taken, CO2 emissions from international shipping and aviation may contribute roughly equally to an additional combined 0.12 ∘C to global temperature rise by end of century – which is 12 % and 24 % of the allowable warming we have left to stay below the 2 or 1.5 ∘C thresholds (1.0 and 0.5 ∘C), respectively. However, stringent mitigation measures may avoid over 85 % of this projected future warming from the CO2 emissions from each sector. Quantifying the climate benefits of proposed mitigation pathways is critical as international organizations work to develop and meet long-term targets.

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“…However, these rates will be outpaced by the anticipated global aviation demand growth of around 4.5% per year [10,11]. In contrast to fuel efficiency improvements, low-carbon fuels (e.g., biofuels) could partially decouple CO 2 emissions from aviation growth, although these options face cost and scale limitations and do not significantly help with non-CO 2 impacts [12,13], except for a potential thinning of contrails with an uncertain sign of the effect [14,15]. Similarly, liquid hydrogen [16] and liquified natural gas [17] could greatly reduce direct CO 2 emissions, but these fuels' higher hydrogen content would result in enhanced contrail and cirrus cloud formation.…”

Section: Introductionmentioning

confidence: 99%

Technological, economic and environmental prospects of all-electric aircraft

et al. 2018

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Ever since the Wright Brothers' first powered flight in 1903, commercial aircraft have relied on liquid hydrocarbon fuels. However, the need for greenhouse gas emission reductions along with recent progress in battery technology for automobiles has generated strong interest in electric propulsion in aviation. This work provides a first-order assessment of the energy, economic, and environmental implications of all-electric aircraft. We show that batteries with significantly higher specific energy and lower cost, coupled with further reductions of costs and CO 2 intensity of electricity, are necessary for exploiting the full range of economic and environmental benefits provided by all-electric aircraft. A global fleet of all-electric aircraft serving all flights up to a 400-600 nmi (741-1,111 km) distance would demand an equivalent of 0.6-1.7% of worldwide electricity consumption in 2015. Whereas lifecycle CO 2 emissions of all-electric aircraft depend 2 on the power generation mix, all direct combustion emissions and thus direct air pollutants and direct non-CO 2 warming impacts would be eliminated.

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Impact of biofuels on contrail warming

Cited by 39 publications

References 40 publications

Effect of contrail overlap on radiative impact attributable to aviation contrails

Effect of contrail overlap on radiative impact attributable to aviation contrails

Climate benefits of proposed carbon dioxide mitigation strategies for international shipping and aviation

Technological, economic and environmental prospects of all-electric aircraft

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