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Aircraft visible in the form of contrails (Carleton

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Aircraft
Emissions and the Future Climate

Brooke
Lewis 

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Embry-Riddle
Aeronautical University Worldwide

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Abstract

Aviation and the
aviation industry will be growing greatly at the rate of 2.7% into the year
2050 and beyond as both airlines expand their fleets, flown routes increase,
and passenger demand continues to rise (Brasseur, 2016). Aircraft have shown to
emit aerosols and ozone’s into the atmosphere such as carbon dioxide (CO2), water vapor, and soot made
visible in the form of contrails (Carleton 2012). The earth’s atmospheric
content has shown a large increase in greenhouse gases, the production is
larger than the earth can absorb and the global temperature is increasing at a
rate higher than normal (Parker, 2010). The study of current emissions is
important to begin the process to reduce emissions for the future. The
increasing of air traffic is showing an increase in contrail production, as a
result contributing to the earth’s increasing amount of greenhouse gasses. Through
the use of data and models it can be shown that improving aircraft engines,
improving technologies, and lowering flight altitudes can all contribute to the
reduction of aviation emissions and reduce the production of contrails.

            Keywords: aircraft emissions,
atmospheric gasses, greenhouse gasses, climate, climate change, aviation,
aviation technology

 

 

 

 

 

Aircraft
Emissions and the Future Climate

Introduction

Aircraft produce
many emissions in the form of gasses, some of those gasses include water vapor,
hydrocarbons, nitrogen and sulfur oxides as well as CO2 into the troposphere as
well as the stratosphere and can be seen in the form of contrails or remain invisible
to the naked eye (Brasseur, 2016). Contrails
are produced when the engines emissions come into contact with ice particles in
the upper troposphere and form a cirrus cloud (Carleton, 2012). As the
contrails are produced, the length of time the contrails exist as well as their
depth can show a significant impact to the environment and the atmospheric
composition in the upper troposphere, atmospheric albedo can be altered as well
as the global climate.  (Carleton, 2012).

Aviation and the
aviation industry will be growing greatly at the rate of 2.7% into the year
2050 and beyond as both airlines expand their fleets, flown routes increase,
and passenger demand continues to rise (Brasseur, 2016). As a result of the
increase in airline traffic, the environmental impact also begins to rise, with
aviation already showing a 2% contribution to the global pollutants (Williams,
2002).

The amount of
emissions an aircraft produces is dependent on the different types of aircraft
as well as their size (Parker, 2010). Global, hemispheric, and regional
emissions can be tested and modeled, however the amount of data is limited when
the area is limited. More data can be available for a global or hemispheric
analysis.

The earth’s
atmospheric content has shown a large increase in greenhouse gases, the
production is larger than the earth can absorb and the global temperature is
increasing at a rate higher than normal (Parker, 2010). The study of current
emissions is important to begin the process to reduce emissions for the future.

The FAA has a standard to reduce aircraft emissions by 2050 (Brasseur, 2016), by
improvements to aircraft engine technology and changing altitudes or
flightpaths. However, the true impacts can only be accomplished by the current
analysis and research of the aviation and aircraft emissions and hypothesizing
how different changes will directly impact the emissions levels.

Literature Review

Contrail
Development and Impacts of the Environment

Aviation has
always been linked to the environment as the aircraft operate within the lower
atmosphere of the earth and contribute to the changes of greenhouse gasses. Aviation
contributed to 4% of total carbon dioxide emissions in 2007 just within the United
States (Moolchandani, 2016). It has been stated by the Intergovernmental Panel
on Climate Change (IPCC) that as aircraft engines emit emissions into the
atmosphere such as carbon dioxide (CO2), water vapor, and soot made visible in the
form of contrails (Carleton 2012). Figure 1 is a visual representation of how
an aircraft engine’s emissions are linked to a change in the global atmospheric
content (Brasseur, 2016).

As stated earlier,
contrails develop from the emissions of the engines, producing ice particles which
form a cloud (Williams, 2002). There have been some studies that focus on the
contrails thickness and diurnal period affecting the atmospheric albedo for the
short term (Carleton, 2012). When the earth’s albedo is affected, the amount of
sunlight that reaches the surface is inhibited. This can lead to a decrease in solar
radiation reaching the earth’s surface.  It
is hypothesized that the longer the contrail is present, the higher impact it
has on the atmosphere as the presence of more cloud cover can contribute to a
change in the local weather patterns and eventually impact the global climate
and weather (Carleton, 2012). Current research is still focusing on the expanded
knowledge of how contrails creation of cirrus clouds and aviation soot aerosols
have an impact on the atmospheric composition as well as the possible addition
to the atmospheres ability to refract (Brasseur, 2016). Figure 2 is a
representation of the fraction percentage of contrail development taken from global
flight paths. The contrails might only last a short time the amount of time,
the aerosols and ozone emitted can impact the atmosphere for decades (Brasseur,
2016).

European airspace
is also analyzed and modeled to produce simulations of different scenarios such
as CO2 emission comparison at different altitudes (Williams, 2002). By 2050,
the largest contributor to aircraft emissions affecting the environments will
be the creation of contrails. Since the creation of contrails contributes highly
to the changes in climate, changing the altitudes of the flights can be a possible
way to reduce contrails. Figures 3 and 4 are a representation of how changing
the altitude of an aircraft can change the probability of contrails being created
(Williams, 2002).  Figure 3 shows flights
at flight level 33,000ft. The production of contrails are present throughout
the whole year with the highest numbers in winter and fall months (Williams,
2002). Figure 4 shows that by reducing flight levels the production of
contrails are eliminated in the summer months with levels lower in the spring,
however higher in the winter (Williams, 2002). By reducing contrails,
environmental impacts can be reduced and by lowering the flights altitude,
contrail production can be reduced (Williams, 2002).

 

Improvements of Aircraft and Technology to Reduce Emissions

The FAA’s Aviation Climate Change
Research Initiative (ACCRI) studies the climate impact commercial aviation
emissions for the present (2006) up until 2050 (Brasseur, 2016). The current
research conducted by the FAA’s ACCRI states that there needs to be an increase
in aircrafts fuel efficiency, alternate or advanced operational procedures,
alternate fuels, and advanced aircraft technologies are needed to reduce the
emissions by aircraft by 2050 (Brasseur, 2016). Increased flight’s miles,
increased flights, and increased passenger loads have all contributed to the
current environmental impacts (Carleton, 2012).

National Aeronautics and Space Administration
(NASA) is contributing to the reduction of aircraft emissions as well. NASA’s
Subsonic Fixed Wing (SWF) project has set emissions standards and goals for all
fixed wing aircraft and works with the International Air Transport Association
(IATA) which has set a goal that all carbon dioxide emissions be reduced by 50%
by 2050 (Tetzloff, 2014). In order for airlines to reduce emissions the IATA
has set up a four-pillar strategy: 1.) advance new aircraft technology, 2.)
improve operational practices, 3.) improve airspace infrastructures, and 4.)
provide economic incentives for reaching emissions goals (Tetzloff, 2014). The
calculation of new-fleet additions to an already existing fleet is analyzed, as
well as the four-pillars strategies and how airlines can benefit (Tetzloff,
2014).

The Federal Aviation
Administration (FAA) along with EUROCONTROL Single European Sky ATM Research
(SESAR) projects are working together to develop more efficient and
environmentally compliant programs for aviation and the future operations as
seen in figure 6 (Marais, 2012). The FAA and EUROCONTROL are both working on
operational upgrades that reduce emissions and improvement to the air traffic
system (Marais, 2012). The areas of the operation that are assessed for change
are on the surface, departure, cruise, approach, and miscellaneous (Marais,
2012). Each area was evaluated for their environmental impacts, fuel burn
reduction, climate impact, air quality, and noise (Marais, 2012).

Airlines can also contribute to
the research on how to reduce emissions. NASA’s has created a model called the
Fleet-Level Environmental Evaluation Tool (FLEET) model. FLEET will simulate
the impact new aircraft and technologies have on the environments emission and
noise levels and produce models for airlines to use for future efficiency for
fleet and route planning (Moolchandani, 2016). The emissions and noise of
aircraft are controlled through NASA and International Air Transport
Association to help reduce the carbon footprint left by aircraft since the
emissions are produced at high altitudes. Due to the high altitudes, the impact
of the emissions is still being studied (Moolchandani, 2016). NASA’s plans for
the future show a lower emission standard, meaning aircraft manufactures will
need to produce more efficient engines and incorporate the use of cleaner
fuels, or alternative fuels, for the future (Moolchandani, 2016).

Hypothesis

Contrail
production and aircraft emissions have contributed to global climate change and
increase in atmospheric greenhouse gasses. In order for aviation and aircraft
to reduce emissions by the year 2050 there will be many areas for improvement
and advancement.

Hypothesis:
Improving aircraft engines, improving technologies, and lowering flight
altitudes can all contribute to the reduction of aviation emissions and reduce
the production of contrails.

Null
Hypothesis: Aviation emissions and contrail production are not reduced.

 

Research Methods

The data
collection will be an ex post facto approach as conditions are already existing
and have been occurring for quite some time in regard to the changing
atmospheric composition and previous data collection of emission levels (Leedy,
2016, p. 369). Majority of the data will be referenced from previous projects
and utilized for the future planning and analysis. It is difficult when working
with data that has been collected over the years as different scenarios and
possible errors could have occurred. It is important during the analysis
process to assume there could be room for error. Since the analysis could
include statistical testing, there will need to be a test in place to prevent
the occurrence of type 1 or type 2 errors so that either the hypothesis or null
hypothesis are proven correct (Leedy, 2016, p. 238). The data sets will be
larger so that should contribute to the prevention of error.

The type of
research that will be used will be quantitative analysis of the models results.

 Since there are many parameters and
models to use different models will be run to show multiple outcomes. One model
will show how possible changes different aircraft and atmospheric conditions
contribute to the emissions and changes it can make to the reduction of emissions.

Another model will use a specific aircraft and show the emissions with current
equipment and then predict emissions with upgraded equipment. Another model
will show how different flight levels can produce different emission levels and
the production of contrails.

There is also a
possible qualitative data analysis of the specific aircraft part upgrades and
how they are projected to change the emissions of the aircraft. Since there are
many different types of aircrafts and parts, it will be best to use a specific
aircraft type, possibly a more popular design, and apply different types of
upgrades. It is possible that by using one or two popular aircraft types that
the changes seen can be applied to other aircraft as well.

The design method
of research that will likely be used for analysis of the data will be an Embedded
Design (Leedy, 2016, p. 313) due to the use of both the quantitative data and
the qualitative data. The quantitative data will be used as the primary means
of proving the hypothesis using graphs and images of model output to quantify
the changes in emission output as well as atmospheric composition. The
qualitative data will be used as secondary data for proving the hypothesis proving
that changes in technology and equipment can change an aircraft emission level.

Summary

 Aviation and the aviation industry will be growing
greatly into the year 2050 and beyond as both airlines expand their fleets,
flown routes increase, and passenger demand continues to rise (Brasseur, 2016).

Aviation has contributed 4% of total carbon dioxide emissions in 2007 just
within the United States alone (Moolchandani, 2016). As a result of the
increase in airline traffic, the environmental impact also begins to rise, with
aviation already showing a 2% contribution to the global pollutants (Williams,
2002).

Aircraft produce
many emissions in the form of gasses, some of those gasses include water vapor,
hydrocarbons, nitrogen and sulfur oxides as well as CO2 visual in the form of
contrails or remain invisible to the naked eye (Brasseur, 2016). Contrails are produced when
the engines emissions come into contact with ice particles in the upper
troposphere and form a cirrus cloud (Carleton, 2012). As the contrails are
produced, the length of time the contrails exist as well as their depth can
show a significant impact to the environment and the atmospheric composition
(Carleton, 2012).

Improving aircraft
engines, improving technologies, and lowering flight altitudes can all
contribute to the reduction of aviation emissions and reduce the production of
contrails. With the increase of contrails in the upper troposphere, atmospheric
albedo can be altered as well as the global climate.

The study of
aircraft emissions is important to reduce the amount of emissions for the
future. The FAA standard to reduce aircraft emissions by 2050 can only be
accomplished by the current analysis and research of the aviation and aircraft
emissions (Brasseur, 2016). The earth’s atmospheric content has shown a large
increase in greenhouse gases, the production is larger than the earth can
absorb and the global temperature is increasing at a rate higher than normal
(Parker, 2010). Be reducing the amount of aircraft emissions, improving
aircraft engine technologies and equipment, and improving the air traffic
control operational system can the reduction into 2050 be truly attainable.

 

                                                                                                                    

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

References

 

Brasseur, G. P., Gupta, M., Anderson, B. E., Balasubramanian, S.,
Barrett, S., Duda, D., Zhou, C. (2016, May 14). Impact of aviation on climate:
FAA’s aviation climate change research initiative (ACCRI) phase II. Bulletin
of the American Meteorological Society, 97(4), 561-583. Retrieved from
http://journals.ametsoc.org/doi/10.1175/BAMS-D-13-00089.1

Carleton, A. M., & Travis, D. J. (2012, July 18). Aviation-contrail
impacts on climate and climate change: A ready-to-wear research mantle for
geographers. Professional Geographer,
65(3), 421-432. Retrieved from http://www.tandfonline.com.ezproxy.libproxy.db.erau.edu/doi/abs/10.1080/00330124.2020.697795

Leedy,P.,& Ormrod,J. (2016). Practical
research: planning and design (11th ed.). Upper Saddle River,
NJ:Pearson.

Marais,
K., Reynolds, T., Uday, P., Muller, D., Lovegren, J., Dumont, J., Hansman, R.

(2012, July 25). Evaluation of potential near-term operational changes to
mitigate environmental impacts of aviation. Journal
of Aerospace Engineering, 227(8), 1277-1299. Retrieved from
https://doi-org.ezproxy.libproxy.db.erau.edu/10.1177/0954410012454095

Moolchandani,
K., Govindaraju, P., Roy, S., Crossley, W. & DeLaurentis, D. (2016,
December 28). Assessing effects of aircraft and fuel technology advancement on
select aviation environmental impacts. Journal
of Aircraft, 54(3), 857-869. Retrieved from

https://doi-org.ezproxy.libproxy.db.erau.edu/10.2514/1.C033861

Parker, R., & Lathoud, M. (2010). Green aero-engines: Technology to
mitigate aviation impact on environment. Journal
of Mechanical Engineering Science, 224(3), 529-538. Retrieved from
https://search-proquest-com.ezproxy.libproxy.db.erau.edu/docview/366317013?pq-origsite=summon

Tetzloff, I. & Crossley, W. (2014, July 17).  Measuring systemwide impacts of new aircraft
on the environment. Journal of Aircraft,
51(5), 1483-1489. Retrieved from

https://doi-org.ezproxy.libproxy.db.erau.edu/10.2514/1.C032359

Williams, V., Noland, R. B., & Toumi, R. (2002, November). Reducing
the climate change impacts of aviation by restricting cruise altitudes. Transport and Environment, 7(6),
451-464. Retrieved from
http://www.sciencedirect.com.ezproxy.libproxy.db.erau.edu/science/article/pii/S1361136192090200

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Appendix
A

Figure 1. Visual representation
of how aircraft emissions contribute to atmospheric composition changes and can
lead to climate change. Retrieved from Brasseur, 2016

Figure 2. Contrail creation coverage
fraction percentage of mean flight paths. Retrieved from Brasseur, 2016.

 

Figure
3. Potential for contrail development and cover at flight level 33,000.

Retrieved from Williams, 2002.

Figure
4. Potential for contrail development and cover at flight level 26,000-29,000.

Retrieved from Williams, 2002.

 

Figure
5. NASA projection of carbon emissions by aircraft 2005- 2050. Retrieved
from Moolchandani, 2016.

Figure 6. Example of a more efficient
operational procedure to reduce aircraft emissions. Retrieved from Marais,
2012.

 

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