Aviation Impact on Air Quality and Global Warming

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Table of Contents

Introduction
Pollution by the Aviation Industry
The Corrective Action to Reduce the Effect
Effectiveness of the Corrective Actions
Conclusion
Bibliography
Footnotes

Introduction

Carbon dioxide emissions attributed to the aviation industry within the EU have grown rapidly, even in countries where the sector is seen as already mature. The United Kingdom’s aviation sector is the largest, most mature, yet the fastest expanding source of CO₂emissions compared to any other industry in the country. In 2011, over 200 million passengers were received in the United Kingdom’s mainland airports. It is anticipated that the number of passengers going through the UK’s mainland airports will rise to 255 million by 2020, and well over 300 by 2030. Nevertheless, the overall potential impact of the industry on the environment has remained difficult to understand due to the uncertainties surrounding it. For instance, Bows and Anderson note that CO₂emissions by aircraft are well understood and hence easy to compare with various sectors.¹ However, the lack of concrete information and understanding of the atmospheric chemistry behind climate change has resulted in an international reluctance to act on this majorly disturbing problem. This report will elaborate on the various effects of the aviation sector on the environment, particularly, air quality and global warming. The study is founded on the numerous ways by which air travel affects the environment. For instance, besides destroying ecosystems, air pollution has been identified as a contributing factor to global warming.

Pollution by the Aviation Industry

Aviation is an important part of the UK economy. In addition, the aviation industry supports other important activities such as tourism and import/exports. However, the benefits of a robust aviation sector do not come without a cost. Aircraft and airport ground operations such as airport vehicles release tonnes of emissions into the air every day. Such emissions are then absorbed into the air. As a result, the quality of air has degraded substantially over the years. Poor air quality has a damaging effect on the health of living organisms. This effect can range from slight irritations to severe symptoms depending on the level of pollution. People who suffer from respiratory diseases are likely to experience more pronounced health effects compared to everyone else.

To begin with, the pollutants released by aircraft engines include greenhouse gasses such as carbon dioxide (CO₂) and other non-CO₂emissions, for instance, water vapor. These substances have the effect of depleting the ozone layer, the shield responsible for blocking harmful ultraviolet (UV) radiation from the sun from reaching the earth’s atmosphere. Such radiations have the potential of altering the climate of a country, hence threatening the life of all organisms. As Lee, Pitari, and Grewe explain, CO₂in the atmosphere traps radiation from the sun, thus preventing it from escaping back into space.² As a result, the earth’s atmosphere experiences a net effect of warming, commonly referred to as global warming.

CO₂is the most abundant carbon-containing gas released from aircraft. According to the European Environment Agency, the amount of CO₂released by aircraft rose from 88 million to 156 million tonnes between 1990 and 2005, a 77% increase.³ However, recent times have seen improvements in aviation fuels, a situation that has resulted in minimized CO₂production by aircraft. Nevertheless, the amount of CO₂released in aviation-related activities is still alarming, particularly given that the industry continues to expand each year. In addition to CO_2,burning aviation fuel produces carbon monoxide (CO) and some hydrocarbons (HCs).⁴ CO and HCs occur because of incomplete combustion of aviation fuels. The gasses affect the quality of air, particularly near the airports. In addition, while CO is known to be a ‘weak’ greenhouse gas, its presence in the atmosphere can influence the concentration of other greenhouse gasses such as tropospheric ozone, methane, and CO₂. For instance, CO readily combines with the hydroxyl radical (OH) to form CO₂, a much stronger greenhouse gas.

Aviation combustion results in other non-carbon emissions and effects that have a net warming/cooling effect on the atmosphere. Common non-carbon emissions include nitrogen oxides, sulfur oxides, and, water vapor. Just like CO₂, these substances often have a negative effect on the ozone and consequently climate. Besides CO_2,Portmann, Daniel, and Ravishankara reveal that nitrogen oxides are the biggest threat to the ozone layer.⁵ Nitrogen oxides are produced due to the high combustion temperatures present in aviation engines. The high temperatures provide ideal conditions for the formation of nitrogen oxides. As a result, an abundance of nitrogen oxides in the atmosphere is detrimental to nitrogen species, which may have a long-term effect on disrupting ecosystems.

Water vapor for its part amplifies the warming effect caused by other greenhouse gasses such as CO_2.Consequently, a continued increase in water vapor in the atmosphere may alter the composition of the ozone in the polar areas.⁶Another impact of aviation combustion is the formation of aviation-induced clouds. Supersonic aircraft fly through the stratosphere, letting out emissions that form aviation-induced cirrus clouds. These clouds can cause a warming or a cooling effect on the earth’s surface by either trapping or reflecting away infrared (long-wave) radiation from the earth’s surface. Nevertheless, aviation-caused clouds are commonly associated with a warming effect. According to Bows and Anderson, contrails and cirrus clouds cause a sudden warming effect that is believed to be four times what is caused by CO₂ on a short-term basis.⁷

The Corrective Action to Reduce the Effect

Establishment of International Standards

In Europe, various regulations and recommendations have been established with the aim of curbing aviation pollution. For example, attempts such as improving fuel combustion efficiency aim at reducing the release of CO₂into the atmosphere. Recently, the UK government put in place the Airports Commission, which was tasked with evaluating the long-term airport capacity concerns in the country. This decision was in line with the country’s 60% carbon reduction objective. Some of the areas examined by the Airports Commission include the issue of air quality. Lee et al. point out that aircraft engines generally burn fuel efficiently, resulting in limited smoke emissions.⁸ However, surface traffic at airports, as well as ground-level emissions by aircraft, cause the air around the airports to be polluted.

The chief pollutant around airports is nitrogen dioxide (NO₂). One way that the problem of NO₂ is being addressed is by setting international standards on jet emissions. For example, the International Civil Aviation Organisation (ICAO) sets international standards regarding smoke and some pollutant gasses for newly created large jets. The latest ICAO standards were released in 2013 to apply to jets and engine types manufactured after this date. The proposals suggest that technology should be used to improve fuel consumption with the aim of reducing emissions. The aircraft used are already 70 percent more fuel-efficient compared to those made four decades ago. As Bows and Anderson explain, current efforts geared at reducing fuel combustion target to minimize the emission of CO_2,which is understood to be the biggest contributor to global warming.⁹ In addition, there have been recommendations to minimize sulfur content in jet fuel. This move will help in minimizing the release of sulfurous gasses in the atmosphere. Sulfur has an impact on both the quality of air, as well as a depleting effect on the ozone layer.

Carbon Reduction Policy

The 2003 Energy White Paper triggered the UK government to endorse a campaign aimed at reducing CO₂ emissions by 60% before 2050. The 60% figure was informed by a previous analysis conducted by the Royal Commission on Environmental Pollution (RCEP), published a year earlier in 2002. The RCEP paper suggested that a 60-90% reduction in CO₂was crucial in industrialized nations to avoid the treacherous climate transformation.¹⁰ Just like most industrialized nations, the UK recognizes the role that its industries play in releasing tonnes of CO2 into the environment. The determination by the UK government follows the “Contraction and Convergence” framework that is used at the international stage to apportion the budget for contracting CO₂ emissions. In other words, a country’s contribution toward reducing the CO₂ in the atmosphere should be commensurate with the number of emissions caused by its industries.

Effectiveness of the Corrective Actions

The 60 percent carbon-reduction target adopted by the UK was aimed at maintaining global CO₂ concentrations at 550 ppmv, which is the level believed to be safe to prevent dangerous climate change. Although it is commendable, this initiative has been shown to pose dramatic threats to other sectors of the UK economy. It is worth noting at this point that other countries are yet to adopt the UK’s 60% target or a similar initiative. This situation may be problematic in several ways. First, the 60% target means that the government must impose fuel taxes on domestic aviation companies aimed at reducing energy combustion. Because other nations are yet to adopt similar policies, the situation may result in a reduced competitive advantage at the international state.¹¹ Additionally, emissions released during international flights may not be easily attributed to a specific country. This case presents a challenge in attempting to implement the Contraction and Convergence framework.

The recent improvements in jet engines to reduce carbon emissions have brought forth challenges of their own. In the past, combustion in the aircraft engines would occur at much lower temperatures, which caused high carbon emissions. The preferred solution was to raise combustion temperatures for little carbon-containing pollutants to be formed. However, this efficiency in fuel combustion has come at the expense of raising the level of nitrogen oxides produced.¹² In fact, high combustion temperatures create an ideal environment for nitrogen oxides to form in the air. As such, it appears that a trade-off exists between reducing CO₂ and increasing nitrogen-based emissions. Nevertheless, Green has proposed two technology options (drag and weight reductions) that may be adopted to reduce both carbon and nitrogen oxides emissions simultaneously.¹³

Another major challenge regarding the control of aviation pollution relates to the projected enormous growth of the industry in the future. As observed earlier, traffic through the UK’s airports will have reached well over 300 million passengers per year in 2030. As Lee and colleagues argue, this huge growth of the industry will outmatch efforts aimed at reducing fuel combustion and hence emission per passenger for each kilometer.¹⁴ Recent moves such as the introduction of new aircraft, improved fuel combustion efficiency, and operational efficiency have caused the average fuel use per passenger to reduce by up to 19%. While this trend is impressive, recent findings indicate that the current engine technology is mature and that no considerable improvements in terms of efficiency are expected for the next 30 to 50 years.¹⁵ At the same time, aviation traffic continues to grow. Growth implies more emissions. Therefore, aviation emissions will continue to expand, despite efforts geared toward fuel efficiency. Figure 1 demonstrates how CO₂ emissions are likely to experience an upward trend in the days to come after remaining stable for several years (2005-2014).

*After remaining stable between 2005 and 2014.*

Conclusion

Despite its immense benefits to the economy of the world, aviation is responsible for a huge proportion of carbon emissions in the world. Coupled with other emissions (nitrogen oxides, sulfur oxides, and water vapor), and aviation affects (contrails and cirrus clouds), carbon emissions make aircraft a significant contributor to global warming. The continued growth of the industry’s traffic then means that more emissions will be released into the environment, thus contributing to the risk of dangerous climate change. While various measures such as the UK’s 60 % carbon-reduction, the use of improved jet engines, and increased operational efficiency have been put in place, they do not seem capable of outmatching the steady growth in aviation traffic going forward. In addition, increased fuel combustion to reduce carbon emissions has been counterproductive in the sense that it has facilitated the amplification of nitrogen oxides emissions. The available engine technology is regarded as mature, meaning that any further fuel efficiency may not be easily achieved any time before 2050. On a positive note, the upward trend in the emission of nitrogen oxides can be tamed through the adoption of advanced combustor technologies.

Bibliography

Bows, Alice, and Kevin Anderson. “Policy Clash: Can Projected Aviation Growth be Reconciled with the UK Government’s 60% Carbon-Reduction Target?” Transport Policy 14, no. 2 (2007): 103-110.

European Environment Agency. “European Aviation Environmental Report 2016.” Publications Office. Web.

Green, Edward. “Civil Aviation and the Environmental Challenge.” Aeronautical Journal 107, no. 1072 (2006), 281-299.

Lee, David, Gibson Pitari, and Vivien Grewe. “Transport Impacts on Atmosphere and Climate: Aviation.” Atmospheric Environment 44, no. 37 (2010): 4678-4734.

Portmann, Raymond, Jim Daniel, and Ambrose Ravishankara. “Stratospheric Ozone Depletion due to Nitrous Oxide: Influences of other Gasses.” Philosophical Transactions 367, no. 1593 (2012): 1256-1264.

RCEP. “The Environmental Effects of Civil Aircraft in Flight: Special Report of the Royal Commission on Environmental Pollution, Pollution.” Aviation Report. Web.

Footnotes

Alice Bows, and Kevin Anderson, “Policy Clash: Can Projected Aviation Growth be Reconciled with the UK Government’s 60% Carbon-Reduction Target?” Transport Policy 14, no. 2 (2007): 103.
David Lee, Gibson Pitari, and Vivien Grewe, “Transport Impacts on Atmosphere and Climate: Aviation,” Atmospheric Environment 44, no. 37 (2010): 4679.
European Environment Agency, “European Aviation Environmental Report 2016,” Publications Office, Web.
Lee, Pitari, and Grewe, 4705.
Raymond Portmann, Jim Daniel, and Ambrose Ravishankara, “Stratospheric Ozone Depletion due to Nitrous Oxide: Influences of other Gasses,” Philosophical Transactions 367, no. 1593 (2012): 1257.
Lee, Pitari, and Grewe, 4700.
Bows and Anderson, 103.
Lee, Pitari, and Grewe, 4720.
Bows and Anderson, 107.
RCEP, “The Environmental Effects of Civil Aircraft in Flight: Special Report of the Royal Commission on Environmental Pollution, Pollution,” Aviation Report, Web.
Lee, Pitari, and Grewe, 4705.
Lee, Pitari, and Grewe, 4700.
Edward Green, “Civil Aviation and the Environmental Challenge,” Aeronautical Journal 107, no. 1072 (2006), 284.
Lee, Pitari, and Grewe, 4690.
Bows and Anderson, 104.
European Environment Agency, 21.

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