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

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. CO2 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.

[1]  Gunnar Myhre,et al.  On the tradeoff of the solar and thermal infrared radiative impact of contrails , 2001 .

[2]  R. Hendricks,et al.  Alternative Fuels and Their Potential Impact on Aviation , 2006 .

[3]  B. Mayer,et al.  A Parametric Radiative Forcing Model for Contrail Cirrus , 2012 .

[4]  C. Bretherton,et al.  Clouds and Aerosols , 2013 .

[5]  U. Schumann,et al.  On the Life Cycle of Individual Contrails and Contrail Cirrus , 2017 .

[6]  K. Shariff,et al.  Contrail Modeling and Simulation , 2016 .

[7]  L. Sherry,et al.  Reducing global warming by airline contrail avoidance: A case study of annual benefits for the contiguous United States , 2019, Transportation Research Interdisciplinary Perspectives.

[8]  Banavar Sridhar,et al.  Benefits Analysis of Wind-Optimal Operations For Trans-Atlantic Flights , 2014 .

[9]  W. Meier,et al.  Soot Formation and Flame Characterization of an Aero-Engine Model Combustor Burning Ethylene at Elevated Pressure , 2013 .

[10]  Hang Gao,et al.  Aircraft Cruise Phase Altitude Optimization Considering Contrail Avoidance , 2014 .

[11]  Arturo de Risi,et al.  Optimization of the Combustion Chamber of Direct Injection Diesel Engines , 2003 .

[12]  B. Kärcher.  Formation and radiative forcing of contrail cirrus , 2018, Nature Communications.

[13]  Klaus Gierens,et al.  A distribution law for relative humidity in the upper troposphere and lower stratosphere derived from three years of MOZAIC measurements , 1999 .

[14]  K. Trenberth,et al.  Earth's Global Energy Budget , 2009 .

[15]  Anthony P. Brown,et al.  Biofuel blending reduces particle emissions from aircraft engines at cruise conditions , 2017, Nature.

[16]  Aaas News,et al.  Book Reviews , 1893, Buffalo Medical and Surgical Journal.

[17]  S. Solomon.  The Physical Science Basis : Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change , 2007 .

[18]  B. Kärcher,et al.  Global radiative forcing from contrail cirrus , 2011 .

[19]  D. Fahey,et al.  Aviation-Produced Aerosols and Cloudiness , 1999 .

[20]  Bernd Kärcher,et al.  Susceptibility of contrail ice crystal numbers to aircraft soot particle emissions , 2017 .

[21]  Marina Braun-Unkhoff,et al.  Alternative fuels in aviation , 2014, CEAS Aeronautical Journal.

[22]  A. Evans,et al.  Trade-off between Contrail Reduction and Emissions under Future US Air Traffic Scenarios , 2012 .

[23]  Feijia Yin,et al.  A hybrid engine concept for multi-fuel blended wing body , 2014 .

[24]  Robert Sausen,et al.  Potential of the cryoplane technology to reduce aircraft climate impact: A state-of-the-art assessment , 2006 .

[25]  Lukas H. Meyer,et al.  Summary for Policymakers , 2022, The Ocean and Cryosphere in a Changing Climate.

[26]  M. Petters,et al.  Cloud condensation nuclei and ice nucleation activity of hydrophobic and hydrophilic soot particles. , 2009, Physical chemistry chemical physics : PCCP.

[27]  U. Schumann.  On conditions for contrail formation from aircraft exhausts , 1996 .

[28]  Klaus Gierens.  Are fuel additives a viable contrail mitigation option , 2007 .