Trade-off Analysis of Options for Mitigating Climate Effects of Aircraft Induced Clouds

Abstract

It is a little-known fact that not all of anthropogenic (i.e. human made) Global Warming is a result of "greenhouse gases." Whereas 98% of anthropogenic Global Warming is the result of emissions of "greenhouse gases" (e.g. CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and methane), the remaining 2% is the result of Aircraft Induced Clouds (AIC) that are generated by jet engines. These high clouds reflect back to Earth approximately 33% of the outgoing "thermal" radiation.This paper describes the results of a multi-attribute utility analysis to evaluate the potential of alternate technologies and operations to reduce AIC. The analysis identified technologic and operational solutions for each of three processes that result in radiative forcing from AIC: (1) propulsion chemistry that converts aviation fuel to water vapor and soot, (2) clouds physics that converts water vapor and soot into ice-crystals, and (3) radiative forcing physics that absorb the radiation.The highest utility and lowest design and implementation costs are to flight plan trajectories to minimize cruise flight levels in airspace with atmospheric conditions that are conducive to AIC generation. Other alternatives such as reduced-Sulphur kerosene-based jet fuel, drop-in bio and synthetic fuels, require significant investment to scale production. Options such as jet engine designs to reduce soot emissions, alternate energy sources such as liquid natural gas and liquid hydrogen, and engine and aircraft designs to reduce fuel burn, require significant research and turn-over of the existing fleets. Fuel additives to suppress ice crystal formation and/or change the Radiative Forcing (RF)properties of ice-crystals are still nascent research topics. The implications and limitations are discussed.