Environmental Engineering — Contrails
Contrails are an exhaust manifestation of chemical waste products emitted from jet engines (Fast, 2002). The impact of contrails has been highly debated and often mired in misinformation. Additionally, the environmental impact of contrails emitted from craft is often overlooked and not investigated in a context relevant to the sustainability of environmental quality and standards associated with such environmental protection standards including the Kyoto Protocol. Among the most notable environmental impact attributed to contrails, include the following: (Fast, 2002; Bearn, 2005; Bollier, 2007; Harris, Kuper, Lebel, 2010)
Rise in local air temperature
UV Ray blockage
Sunlight Reduction to Earth surface
Increase in biological extinction rate
Change in migrating patterns of species
The ranking in terms of environmental impact is rather alarming when considering the overall potential in the environmental change capacity over the long run. The most pressing is the increase in the biological extinction rate. Contrail activity linked to increases in core air temperature can lead to an increase in the extinction rate of biological creatures currently inhabiting earth. The bee extinction rate has increased and has not yet been linked to any concrete changes in the earth. However, contrail activity and the increase in air temperature during the critical spring weeks just after winter when pollination is at a critical point.
Potential environmental impact from Contrails emitted by Passenger Airlines
Passenger airlines travel throughout the world on a number of constant routes each day. Contrails emitted from these passenger airplanes are somewhat cloud like in formation, consistency, and appearance. Whether exhaust fumes are the actual contrail emission and that contrails are ostensibly a chemical residual from fuel combustion are linked to environmental deviation is of concern in this case study.
The environmental impact of contrails as observed over the 3 day period after the September 11th attack on the World Trade Centers in New York City was measured as the ability to measure was considered better due to the FDA’s grounding of commercial aircraft and a rare measure on the changes to the environment from jet contrails (Fast, 2002). According to Fast (2002), “Contrails alter temperature the same way that natural high clouds do. Without contrails, then, the daytime temperature would be slightly higher and the nighttime temperature would be slightly lower.” (Fast, 2002)
The environmental impact of contrails according to Fast is a decrease in air temperature or a type of global cooling effect at the sub-orbital level. Contrails have been further described as being a vapor trail (Bearn, 2005), “trapping warmth in the atmosphere and exacerbating global warming, according to the U.K. Engineering and Physical Sciences Research Council (EPSRC) (Bearn, 2005). Climate change is implicated as a function of the increase of contrail activity across the globe.
How do contrails form? According to Bearn (2005), “Contrails form when hot, humid air created in a jet engine mixes with low-pressure, cold air. Generally, the higher the altitude, the colder the air and more likely contrail formation becomes.” (Bearn, 2005) Thus, contrails planes that fly lower in the atmosphere are less likely to produce a contrail. An aircraft emitting a distinct contrail is likely to be flying higher in the atmosphere than an aircraft that is flying lower.
Bollier (2007) suggests many contrails are emitted in the upper troposphere, “from water vapor to carbon dioxide to particulates to unburned hydrocarbons.” (Bollier, 2007) the contrails then form cirrus clouds (Bollier, 2007), which act to trap ultraviolet rays whilst reducing the amount of sunlight to reach below the atmosphere and onto earth. Additionally, Bollier further states the contrail emissions to cause warmer weather.
The duration of contrails in the atmosphere can last for days, according to (Harris, Kuper, Lebel, 2010). Trails may last for days and spread over hundreds of miles. According to Patrick Minnis, senior research scientist at NASA’s Langley Research Center in Virginia, “It helped us get a very good handle on the relationship between natural cirrus clouds and contrails, and separate the two effects. We estimate that contrails have an overall warming effect which is at least the same as aircraft CO2 exhaust, if not more.” (Harris, Kuper, Lebel, 2010)
The white streaks (Murray, 2006), which characterize the contrail left by a flying aircraft is suggested by Murray to be removed as a contaminant by lowering the altitude of the aircraft during flight. Additionally, “because contrails are released at high altitudes, have a more potent effect on the environment than emissions that are released on the ground.” (Murray, 2006) the environmental impact from contrails is attributed to being a similar threat to that of the CO2 emissions speculation that is considered to be a trigger to Global Warming.
Contrails are one of many contributors to the supposed Global Warming problem (Special Report, 2006). Industrial manufacturing activity on the ground contributes pollutants directly into the atmosphere, known to also deplete the ozone layer when chloroflourocarbons and other ozone depleting gases are present. According to Special Report (2005), “Aviation is a relatively small source of the emissions blamed for global warming, but its share is growing the fastest. The evidence is strong that emissions from jet engines, including the streaks of cloud (called contrails) they leave behind in the sky, could be especially damaging. As a result, aviation is increasingly attracting the attention of environmentalists and politicians.” (Special Report, 2006)
The evidence suggests that contrails do alter the environment and create an environmental impact at various levels. The environment in terms of habitat is known to affect the breathing quality of the air for biological entities and all species. The water supply is also indicated to be adversely affected. Such changes to the environment will cause considerable shifts to the ecology and the biology that will arise from the ecological environment.
Contrails are ostensibly chemical particulates and other forms of matter released into the atmosphere in a cloud of condensed gas emission. The ability for this emission to spread across vast distances and settle into streams, lakes, river beds, and onto crops and lawns/playgrounds is of concern to all whom do not know what contrails are. These chemicals are on all environmentally exposed matter that are subject to atmospheric release. The specific results from the environmental impact of the contrail remains remain largely unknown. However, the expectation of Global Warming and contamination of water supply is to suggest an adverse environmental impact.
Fast, E. 2002, “Can contrails alter climate?,” Environment, vol. 44, no. 8, pp. 7.
Beam, S. 2005, “The Trouble with Contrails,” Environment, vol. 47, no. 3, pp. 4.
Bollier, S. 2007, “High Flyers and the Grounding of Equality,” Multinational Monitor, vol. 28, no. 5, pp. 31.
Harris, P., Kuper, S. & Lebel, C. 2010, Sandals Optional: Stories – Environment – Insight; Not all heroes of the green revolution fit the left-liberal activist stereotype.., the Financial Times Limited.
Murray, S. 2006, “FT.com site: Carbon footprints: Reduce, renew, offset and pool – priceless jargon of a modern age,” FT.com,, pp. 1.
Special Report: The sky’s the limit – Aircraft emissions; Aircraft emissions 2006,, the Economist Intelligence Unit.