Impact of biofuels on contrail warming
Name
Caiazzo_2017_Environ._Res._Lett._12_114013.pdf
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1.23 MB
Format
Adobe PDF
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36e875d50ceeae72e2883f633701ce4a
Author(s)
Caiazzo, Fabio
Agarwal, Akshat
Speth, Raymond L
Barrett, Steven R. H.
Date Issued
November 2017
Journal
Environmental Research Letters
Publisher
IOP Publishing
Citation
Caiazzo, Fabio, Akshat Agarwal, Raymond L Speth, and Steven R H Barrett. “Impact of Biofuels on Contrail Warming.” Environmental Research Letters 12, no. 11 (November 1, 2017): 114013.
Version
Final published version
Abstract
Contrails and contrail-cirrus may be the largest source of radiative forcing (RF) attributable to aviation. Biomass-derived alternative jet fuels are a potentially major way to mitigate the climate impacts of aviation by reducing lifecycle CO2 emissions. Given the up to 90% reduction in soot emissions from paraffinic biofuels, the potential for a significant impact on contrail RF due to the reduction in contrail-forming ice nuclei (IN) remains an open question. We simulate contrail formation and evolution to quantify RF over the United States under different emissions scenarios. Replacing conventional jet fuels with paraffinic biofuels generates two competing effects. First, the higher water emissions index results in an increase in contrail occurrence (~ +8%). On the other hand, these contrails are composed of larger diameter crystals (~ +58%) at lower number concentrations (~ −75%), reducing both contrail optical depth (~ −29%) and albedo (~ −32%). The net changes in contrail RF induced by switching to biofuels range from −4% to +18% among a range of assumed ice crystal habits (shapes). In comparison, cleaner burning engines (with no increase in water emissions index) result in changes to net contrail RF ranging between −13% and +5% depending on habit. Thus, we find that even 67% to 75% reductions in aircraft soot emissions are insufficient to substantially reduce warming from contrails, and that the use of biofuels may either increase or decrease contrail warming—contrary to previous expectations of a significant decrease in warming.
MIT Department
Massachusetts Institute of Technology. Department of Aeronautics and Astronautics
Terms of Use
Attribution 3.0 Unported (CC BY 3.0)
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DOI of Published Version
https://doi.org/10.1088/1748-9326/aa893b
