The Walls Need Watering

Having spent some time looking at emissions relating to aviation and people's perceptions about aviation and climate change, I aim to now investigate what steps are being made to make aviation greener. 

In the video I posted in the second blog post, Willie Walsh talks about the responsibility the aviation industry faces to continually innovate and improve its environmental impact. As a slightly different introduction into this, I am posting a video that commercial aircraft manufacturer, Boeing posted on their YouTube channel a couple of months ago. 

In the video, they show how they are developing cabin interiors made out of the flax plant, commonly used in the production of cloth as a way of minimising their environmental impact, yet not compromising on performance or safety. 

I believe it is a small step in terms of the overall negative impact aircraft emissions have on the atmosphere (I've not even considered anything else but the aircraft flying - the environmental impact of an airport or manufacturing a plane for instance). However it demonstrates well the continuous strive for improvement, and the effort going into the development of more environmentally friendly materials. 

It seems there is much self evaluation on what can be made better as the environment is a word so closely tied with aviation in the minds of many people today. Although as has been stressed in the posts looking at peoples perceptions, technological change alone is not sufficient in making reality the ambitious goals set for aviation related emissions reduction. 

Air Travel, Alleviator Of Poverty

To conclude this series of post I have been doing about peoples perceptions about climate change and aviation, I am going to look at a recent article concerning tourism and its effect on the environment (Peeters and Eijgelaar, 2014). It zooms out of what people are thinking and looks to possible future scenarios and current gaps in research. 

The article questions where to strike the balance between tourism in developing countries  as a tool for development and efforts to reduce and mitigate aviation related climate change. Looking at tourism in developing countries, long haul air travel to such places is involved and these emissions contribute a large proportion to the emissions of tourism. 

The article states that despite the number of guest nights and trips not increasing, there has been an increase of tourism related emissions. This reflects the increasing distances that people travel to go on holiday (to more tropical and developing countries). This has also been confirmed in de Brujin et al. (2012). The paper also backs up what I wrote about in the last post about how technological change alone is not sufficient in being able to reduce aviation related emissions (to below 2005 levels). 

With this in mind, difficulty arises in the possibility of setting limits or increasing costs for long haul travel when having these air travel options available is currently benefiting many developing countries. Curbing the growth of aviation encounters strong opposition from tourism and transport sectors on the grounds of the 'poverty ethics argument' (Peeters and Eijgelaar, 2014). This is as a result of acknowledging air transport in efforts by developing countries to develop sustainably through tourism, impeding upon this is seen as taking a step back. 

Rather than the people themselves justifying why they continue to travel by air despite knowing the impacts it has on the environment as I have looked at in the past couple of posts. Insights from this paper see how people who are benefiting from (long haul) air travel yet who may not have access to it themselves are having their views represented on behalf on them. The UN for instance in its past conferences on climate change have made the case for aviation growth relating to poverty alleviation (Peeters and Eijgelaar, 2014). 

Thus in light of the scientific effects air travel has on the environment and continuous calls for it to be made greener and more efficient and regulated, policy makers it seems (as well as people themselves) continue to see the benefits of air travel. When considering how much it contributes to development as this post has explored, it makes the debate on where and to what extend to curb and restrict aviation that much more difficult considering that as well as responsibilities to the environment and nature, we also must take care of each other, and aviation has made many things possible that were not within just a couple of generations! I'm sure those living near an airport fight path would disagree! 

Wonder if the noise bothers them? (Source: Live Mint)

Please Fill Out The Passenger Feedback Form

In the last post I started to consider peoples attitudes towards flying. I am going to bring the topic of aviation and climate change closer to home in this post and look at the attitudes of British tourists, and how climate change influences their travel decisions. I will be  looking at the findings of Hares et al. (2010) and Gössling and Peeters (2007)  .

It has been estimated that from an average British holiday that involves air travel, 60-95% of the holiday's contribution to global warming can be attributed to the flight.  (Gössling and Peeters, 2007). With the number of international tourists and number of people flying only predicted to increase, (Hares et al. 2010) look at behavioural changes of tourists flying as a way to potentially reduce aviation related emissions. Behavioural changes comes in a list that also includes technological changes and market based changes. They estimate technological changes will reduce aircraft emissions by approximately 20% by 2050, and mention the unpopularity of market based approaches such as fuel taxes, which have been opposed in the past. 

There is a general consensus that people talk about tourism travel and everyday life as two different entities, talking more responsibility for everyday life (Becken, 2007). When a group of people were interviewed (Hares et al. 2010), general observations included that there were different understandings of what climate change was at the offset, with many people being skeptical about it. As far as going to address their impact on the environment through flying, many participants in the study believed that their individual actions were negligible. When speaking of their consciousness to general environmental concerns, where they did take steps in life to reduce their impacts, these were heavily tied with the financial costs of doing so. Many people for example said they recycled, which is seen as being popular due to its low cost and minimal inconvenience for the individual doing it.

The findings of this paper tie in well with those of (Gössling and Peeters, 2007). They attribute development, low cost air travel and increased leisure time to the transition of travel from the wealthy to hypermobility of many more people throughout Europe, where such movement of people is now considered the norm. Action from society doesn't materialise due to uncertainty in the topic. Many people do not see their individual behaviour to be accountable -  the paper addresses this as "psychology of denial". The paper also addresses how some misinformation about the impact of aviation stems from the aviation industry itself, which use scientific language and enthusiasm about technological change to paint a more positive image than reality. An example used is that the emissions performance of aircraft are often compared to small cars with low occupancy rates, which are themselves not considered environmentally friendly. When comparing cars to aircraft, cars with higher occupancy rates should be considered for a more accurate comparison. 

In comparing the findings from these two papers from the study done in Rocinha, the Brazilian favela, which was covered in the last post, despite the relatively greater understanding of the impact of air travel in Europe and the UK, there does not appear to be a dissimilar response from that of Rocinha. People flying to go on holiday or to see family once to a few times a year do not consider themselves to be the problem. Shaw and Thomas (2006) write of how people in the UK see themselves as having a right to fly and take holidays abroad. 

Should anyone still be reading this! What do you think? Would you fly less in a bid to reduce your own environmental impact, if you go on holiday? Do you see it as your problem? 

We can always just take Bus 24 to Australia anyway?! It runs 24/7 and has Wi-Fi. 

Calling at Pimlico, Paris, Pune and Perth 

First Class Passengers Can Start Boarding

In the last post I talked about the EU-US Open Skies Agreement, which demonstrated how it is necessary to take more than just the environmental impact of the aircraft itself into consideration when looking at the overall impact of aviation. I aim to build further on this today by looking at the types of people who fly and how and why this would affect things. 

I will be looking at an article (Freire-Medeiros and Name, 2013) exploring the attitudes people living in Rio de Janeiro's largest  favela, Rocinha, have towards flying, often for the first time. I will compare it with a report (Collins et al. 2008) about private jets. 

The general consensus that was reached by the people interviewed in Brazil (Freire-Medeiros and Name, 2013) was that a shift from taking a bus to travel, compared to a plane reflected the changing economic status of a person. By being able to fly, the people perceive themselves as leading a better life (along with a trip to Disneyland and a shopping stopover in Miami - a common "strategy" to define middle class!). One family came to the conclusion that even though they lived in the favela, they were not poor because they could afford to fly. 

On the subject of the environment, most of the people interviewed did not dispute it was an important, man made problem, and that steps were needed to reduce global carbon emissions. When quizzed about green taxes on flights however, although they saw themselves as part of the problem, they justified their reasons for continuing to fly because it is something that they do not do often. Instead they believed people who travelled more often (like their boss) should pay an extra green tax. Through talking to the residents of this "middle class poor" in Rocinha, it demonstrated that despite their economic prosperity increasing in that they could now afford to buy plane tickets, the people were still economically very conscious and that despite an increase in economic status, they remain aware about their expenses and environmental impact. 

In contrast to some of the people of Rocinha, who have just been able to afford to fly, Collins et al. (2008) refer to private jets as "one of the most powerful symbols of extreme inequality". The report makes the point that private jets not only burden taxpayers (the report is from the USA), shareholders and other air travellers, they also degrade the environment, social cohesion and public security. 

To put some of this into perspective, The environmental impact of flying in a private jet for an hour is the equivalent to driving for a whole year. And general aviation, which includes private jets, pays 3% air traffic control costs despite using 16% of the services, whilst commercial aviation pays 95% when it uses 73%. Private jets emit the same types of pollution and emissions as commercial airliners that I have talk about in previous posts, however they do not carry half as many passengers and the report highlights that 40% of private jet flights in the U.S fly empty with no passengers on board.

In a world where such inequality prevails, many people that are just beginning to see the benefits of flying believe that their circumstances mean that they should not have to pay of for the environmental burden of flying. This is in contrast to the minority where the world is not only their oyster but they are most likely having an entrée of oysters in their private jets whilst en route to Oyster Bay!

Window seats for everyone!

Open Skies

It is not only the planes themselves that have an impact on the environment. The ways in which they are regulated also needs to be taken into consideration as this can determine where aircraft can fly, how often, and if they meet a set of standards. I am going to look at the environmental impacts of the EU-US Open Skies Agreement, which was written about by Mayor and Tol (2009). In addressing the environmental concerns, I also hope to make apparent the complexities in co-ordinating global air travel. 

The EU-US Open Skies Agreement was launched in 2007 and came into effect the following year. It had the aim of making aviation a more levelled playing field between Europe and the USA, two of the largest global aviation markets. It was to remove  bilateral agreements in place between the USA and countries of Europe, and replace it with a single aviation agreement. It was hailed from and economic and financial point of view - but its environmental impacts have not been extensively examined - which is where the article  (Mayor and Tol 2009) comes in handy!

The agreement allows European and American carriers to fly to any city in the opposite continent, from any city in their own. This liberalisation allows for greater competition to and from both small airports and larger hubs. Before this for example British Airways and Virgin Atlantic were the only two British carriers entitled to fly from London Heathrow to JFK in New York (Heathrow's most flown route). Such an agreement would undoubtedly result in increased passenger flows and traffic. More details of the agreement can be found in this Guardian article.

The paper hints at greater carbon dioxide emissions that will make climate policy objectives increasingly difficult to achieve, especially considering that only until recently was aviation included into European emission reduction policies. A model to predict future scenarios resulting from increased tourist travel and lower plane fares as a result of the agreement was used. It found that the global emissions will increase will be smaller than the increase in transatlantic travel, due to a reduction in travel to other places, as a result of more transatlantic flights.

Do not unfasten your seat belt to go and book your dream holiday to America just yet though! A single person on a round trip transatlantic flight from New York to Europe will produce 1 to 2 tonnes of carbon dioxide, according to this article from the New York Times. It  discusses aviation emission reduction policies - where it describes the EU emissions trading scheme prohibition act of 2011 as a "somewhat lonely attempt to rein in planet-warming emissions." It is safe to say they weren't on board!

Open Skies:
Mon - Fri 7am - 10pm
Sat 7am - 11pm
Sun 9am - 6pm

I See A Ship Out The Window

Over the posts so far, I have been exploring how aircraft effect the environment in terms of the emissions they release when they fly. I aim to put this into context and compare it with other modes of transport - after all as I mentioned in my very first post (and is talked about in the video in the second post), although planes appear to be absolutely detrimental to the environment from the media attention they receive, they only account for around 2% of annual global CO₂ emissions.

Fugletvedt et al. (2008) wrote about how although contributing significantly to global emissions, the contribution of different modes of transport has not been quantified. They  predict that whereas today (or in 2008!) transport in general accounted for 20-25% of total annual CO₂ emissions, by 2050 this is estimated to rise to 30-50%. 

The paper describes four main mechanisms through which all transport related emissions can effect the climate. These are:

1. The direct emission of greenhouse gases, notably CO_2.

2.  The emission of indirect greenhouse gases, for example gases like nitrogen oxides, and carbon monoxide that affect the oxidising capacity of the atmosphere.

3. The direct emission of aerosols or aerosol precursors such as black and organic carbon and sulphur compounds. 

4. The indirect emission of aerosols that trigger alterations in the distribution and properties of clouds. 

Note that many of these effects has already been discussed in relation to aviation in previous posts. 

Attributing these effects to certain modes of transport is difficult because multiple chemical and physical mechanisms can occur when these emissions are released. The paper highlights further difficulty in calculating the climatic costs of transport due to the differing time scales involved. The effects of  transport emissions on ozone, sulphates and black carbon may last months and days, where as more well mixed greenhouse gases (methane, CO₂, and NO_x) have an adjustment period of decades and centuries. Based on these timescales, it is estimated that current emissions from transport will be responsible for 16% of the integrated net forcing over the next 100 years for all man made emissions. The paper  places road transport as being responsible for the most warming and shipping for producing the greatest cooling effect. 

Complementing the above mentioned paper is Berntsen and Fuglestvedt (2008). They have expanded on how depending on time scale, different modes of transport, have differing effects on the climate (not surprising seeing as the same author worked on the aforementioned paper). They reiterate that different effects and emissions from transport can result in either a warming or cooling effect. Looking at the year 2000, road transport is seen to have the largest effect on global mean temperature. Road travel comes before aviation, which despite having strong but short-lived effects, they can resonate up to a decade after emission. In contrast shipping results in a cooling effect  (through the release of sulphur dioxide and NO_x) which can last up to 4 years after emission but on a longer timescale, shipping too leads to a warming effect. 

More work on the matter was done a couple years later by Borken-Kleefeld et al. (2010)  - also featuring Fuglestvedt as a co-author (I would have been more surprised not to have seen his name!). Anyway, they again emphasise looking at the timescales of modes of transport in relation to the type of radiative forcing caused. They mention that air travel results in a lower temperature change per passenger-kilometre than the car... in the long run. And that per passenger-hour travelled, aviation's impact is higher than for cars, which doesn't really come as a surprise!

By looking into the effects of different modes of transport, it has become apparent that there is no one way at looking and comparing them. There are many variables to consider: the time scales involved with the emissions, frequency of use, size of the emissions released, passenger-kilometre, passenger-hour.. maybe if you stop for food a the service station? I agree with Berntsen and Fuglestvedt (2008) in the difficulty of accounting for different modes of transport on creating policy for the improvement and reductions of this sector... when for example would you set a time scale when at first the effects of shipping emissions are cooling but then revert to warming? And that air travel is worse on a short scale but road travel is worse overall in the long run. 

Future temperature change (in K) from different modes of transport based on constant emissions for the year 2000. Taken from Berntsen and Fuglestvedt (2008)

Oxygen Masks Will Drop From Above

Following on from the ways in which nitrogen oxides, released from aircraft alter the chemistry of the atmosphere, as was discussed in the previous post, I am going to focus on a paper I found (Barrett et al. 2010), that discuses the human health implications of these and other aviation related emissions. 

Passengers in planes aren't the only people who need oxygen masks!

The study finds that there are around 8000 annual premature mortalities attributable to emissions released by aviation, and which alter air quality. Such emissions can effect widespread areas of the world despite originating in isolated regions and corridors. A lot of this is due to global atmospheric circulation - which conveniently helps to funnel down the harmful and polluting chemicals into the lower troposphere so we can all benefit from them too.

The figure below taken from the paper describes how aircraft emissions in the upper troposphere in the Northern Hemisphere interact with existing circulation patterns. Peak aircraft emissions occur in the Ferrel atmospheric circulation cell. Air mixed with pollutants released from aircraft in this cell experiences subsidence at 30ºN latitude - as is shown by the brownish line in the Figure. 

(Barrett et al. 2010)

The truly global nature of the way aircraft emissions are spread around the world are explored in the paper. Impacts specifically to humans are linked by pointing aircraft attributable aerosols as responsible for around 3500 premature deaths in India and China despite their relatively low contribution to aircraft emissions. Their geographic location (at around 30ºN latitude) in relation to this atmospheric circulation is believed to be a large determining factor of this.  India for example experiences 7 times more deaths in relation to its aircraft emissions compared to the United States which experiences 7 times fewer deaths. It must be noted however that the number of premature deaths generated for India and China also takes into consideration background ammonia and the high population density in this region.

The paper quotes some quite alarming numbers of premature mortality aircraft cause, which admittedly isn't my top go to cloud gazing topic to think about when I do get the chance to fly (and a window seat), the paper does not really go beyond quoting numbers, and I imagine it is difficult to pin point premature mortality on aircraft emissions, given that their effects probably get manifested in various medical conditions? There is not much to compare such a study too either. Despite this, the study confirms that it is not only take off and landing emissions, close to ground level that are able to have an impact, and that emissions emitted at cruising altitudes are also able to exacerbate the balance of toxic chemicals lower down in the atmosphere. 

In case you haven't had the pleasure of studying Weather and Climate  - the following diagram simplifies global atmospheric circulation, the Ferrel cell that was referred to earlier is marked on. (Taken from the Met Office).

Don't Get On The Wrong Side of An Oxide

Despite contrails being the most visible indication of the impact aircraft are having on the environment, they are certainly not the only form of pollution. In my first post, I touched upon the impacts of CO₂ being released however, they are not the only emissions of environmental significance. The potent nitrogen oxides (NO_x) and sulphur oxides (SO_x) are also released, albeit in smaller quantities as CO₂ but with potentially more damaging consequences. I must mention that these pollutants contribute to the formation of contrails and the modification of natural cirrus clouds too, for the sake of being able to mention contrails again!

Today, I am going to be looking at the well documented effects of nitrogen oxides. NO_x emitted from aircraft today are 5 times more efficient at affecting the global ozone burden than emissions originating from ground transportation such as road vehicles (Hauglustaine and Koffi 2012). In spite of its higher potency as pollutant than CO₂, the radiative forcing of NO_x is relatively small as described in Fuglestvedt et al. (2009), Myhre et al. (2011), and Holmes et al. (2011). This is as a result of the opposing effects it has on ozone and methane in the atmosphere. 

NO_x from aircraft promotes the formation of ozone (O₃) in the troposphere and lower stratosphere. Ozone has a positive radiative forcing (i.e a warming effect). This enhancement of ozone is offset by the chemical alterations NO_x has on the oxidising capacity of the atmosphere. NO_x cause an enhancement of the oxidising capacity, which reduces the lifetime of atmospheric methane (CH₄). This reduction in  methane leads to a negative forcing (i.e a cooling effect). Less methane also means less ozone is produced. This renders nitrogen oxides a forcing agent that is able to affect the chemistry of the atmosphere. 

Although the effects of NO_x released by aircraft may not seem that bad, Köhler et al. (2008) investigated the disturbances to methane and ozone in the atmosphere as a result of nitrogen oxide input from aircraft. They concluded impacts varied depending on the altitude of the aircraft for example, a plane flying at 11 km would lead to an ozone increase of 200% and a reduction in methane lifetime per emitted mass of  NO_x, 40% as strong as a plane flying 5 km altitude. 

The study also found that much like how the effect of ground based NO_x emissions affect atmospheric ozone and methane differently depending on their geographic location, the same applies to aviation. The geographic distribution of NO_x emissions has consequences for flight route planning, and it is predicted that growing aviation in Asia could lead to significant impacts regarding methane and ozone within the troposphere, even if emissions were to remain constant. 

This raises important questions as to what impact future increases in air travel will have as new flight routes open and increase in frequency, especially considering the planning currently involved in reducing the effects of emissions on the atmosphere. Also how strategies accounting for these harmful types of pollution will continue to be managed. 

How to plan for more planes?

Chemtrails

During my search for information on contrails for the previous two posts, one word kept on coming up which didn't seem to want to go away: chemtrails. 

It is not very scientific of me to be doing a post on them, as you will see! but it was so persistent a word (try searching chemtrails for yourself!), that I thought I would do some digging...

Chemtrails are part of a conspiracy theory. It is the belief that governments are using  aircraft to spray chemical or biological agents for numerous top secret reasons. It is thought they are unlike contrails because they are longer lasting. Just in case all sorts of questions are racing through your mind at this point, rest assured that we in the UK are safe. Earlier this year, UK government via the Department of Energy and Climate Change stated that the "UK population is not being sprayed" after a freedom for information request. 

We all need an education  

Surprisingly, I could not find many scientific articles or journals on the matter. I managed to find an article in Australian Science, in an article entitled 'Chemtrails - Conspiracy theory?'. In it the contents of an hour long video entitled 'What in the World are they Spraying?' made by political activist Michael Murphy are addressed - especially the release of aluminium and its consequential health effects.

It is unlikely we will find evidence for the nanobots being deployed into the atmosphere via aircraft to modify the weather as the link below the picture above describes. Saying that, I found news articles from the BBC and Guardian reporting on how previously classified documents have suggested that experimental cloud seeding conducted by the RAF that was occurring at the beginning of the 1950s were partly responsible of the 1952 floods at Lynmouth, in which 35 people were killed. It remains an allegation that has not been proved. Early scientific studies such as Cooper and Jolly, 1970 have suggested that the sustained use of silver iodide in cloud seeding could have detrimental effects on some ecosystems, and that there was a responsibility to monitor the environmental impacts of such technology. 

I'll let your thoughts simmer whilst you watch this video... 

Contrail Effects

A radiative forcing is something that disturbs the balance between incoming and outgoing radiation in the atmosphere. A positive forcing warms the surface, and a negative one cools it. Contrails, and the clouds which result from them (see the BBC link, mentioned in the previous post) are the largest radiative forcing associated with aviation. Despite their similar appearances, especially when longer lasting contrails begin spread out and resemble clouds, the radiative forcing for contrails is 9 times larger then for similar shaped, naturally formed cirrus clouds (Burkhardt and Kärcher 2011).

Contrails can be expected to have the same effects as cirrus clouds i.e to reflect incoming short wave radiation and to retain long wave outgoing radiation from the surface - this is due to the small ice crystals that contrails are made up of. Small differences in the properties between contrails and cirrus clouds for example the size of ice crystals however, creates some ambiguity and differences in the forcing effects of contrails. Contrails have a smaller vertical depth and are formed at cooler temperatures meaning that contrail induced cirrus clouds can form and persist high in the troposphere even when there are no natural cirrus clouds.

Ascertaining the global coverage of contrails is difficult as only young contrails, which still exhibit the classic line formation (see background picture to this blog) can be distinguished from natural cirrus cloud. It is impossible to tell from satellite imagery whether cirrus clouds have been induced by aircraft or are natural. It is also thought that global atmospheric circulation maintains a higher level of cirrus cloud over Europe in comparison to the USA, where there is more air traffic (Burkhardt and Kärcher 2011).

The aftermath of 9/11 presented a unique research opportunity in that there were no commercial flights in the 3 days that followed. Travis et al. (2002) compare the diurnal temperature range for the 11th - 14th September 2001 with that from 1971- 2000. They found there was an anomalous increase in diurnal temperature (1.1°C), which they partially attribute to the lack of contrails in this 3 day period. It has also been suggested that the presence of contrails, which ties up water vapour in the atmosphere, means that this vapour can not be used to expand natural cirrus clouds - and so can prevent their expansion and counter their own climatic impact (Burkhardt and Kärcher 2011). 

These examples show the difficulty presented in pinpointing the effects contrails have on radiative forcing and the difficulty of assessing their impacts due to their close correlation with naturally occurring cirrus clouds. 

Contrails as seen from the International Space Station. Credits ESA/NASA

Contrail Formation

Over the next few posts I aim to explore the effects aircraft are having on the environment. I'm going to start with contrails as these are perhaps the most telling signs that a plane is flying overhead, or if a plane has flown by, or if you're really struggling to find one out the window at this point they can be seen in the background picture to this blog! They represent a direct anthropogenic input into the atmosphere. There is extensive literature on them, with some of it being quite contrailversial. Today I am going to look at their formation. 

Contrails are linear ice clouds that form behind both propellor and jet aircraft flying in sufficiently cold air (-40 °C), typically found at high altitudes, i.e at the top of the troposphere. They have similar properties and structure to cirrus clouds, which also form at these altitudes. The length of time a contrail lasts for depends on the humidity of the atmosphere the aircraft is flying through. For instance they will be short lived and evaporate quickly (perhaps seconds) when formed in dry air, however more persistent with the possibility of developing into a cirrus cloud layer in air with relative humidity above ice saturation (Schumann et al. 1999).

Cirrus Clouds

The conditions needed to form a contrail can be described using thermodynamics though the Schmidt-Appleman criterion, which is a function of atmospheric temperature, pressure, aircraft fuel energy content, water vapour exhausted, and the aircraft’s overall propulsion efficiency. The 1999 IPCC report on aviation, which I spoke about in my last post, confirmed the reliability of the Schmidt-Appleman equation to predict the conditions of contrail formation. 

In accordance with the Schmidt-Appleman criterion, a contrail is formed when an increase in relative humidity occurs in an engine plume where warm, moist exhaust is expelled from the engine and mixes with surrounding sufficiently cold atmospheric air that enables humidity to reach liquid saturation in the plume (Schumann 2005). The water vapour attaches itself onto condensation nuclei, and in the process freezes into ice crystals almost instantaneously. 

Along with the expulsion of mostly water vapour and CO2 from the aircraft engine, nitrogen oxides, carbon monoxide, hydrocarbons, sulphuric oxides, organic material, chemi-ions, soot, and small metal particles from the mechanical erosion of the aircraft are also released, however in much smaller amounts. Some of these provide condensation nuclei which aid in the formation of contrails or increase the affinity of water vapour to them, for example chemo-ions which support the coagulation of small initial ice particles. Even if they are not released however, contrails will still form due to the condensation nuclei already present in the upper troposphere estimated to be around 10² - 10⁴ cm^-3 (Schumann 2005). 

Despite much research on the formation of contrails, there is comparatively less information on the way that aircraft affect already existing cirrus clouds, and the way in which contrails turn into cirrus clouds when the conditions allow for it. This is due to the microphysical properties of the ice crystals of cirrus clouds being difficult to investigate at  high altitudes. Where it was once thought that soot from ageing aircraft were more likely to result in contrails increasing in size to clouds (Schröder et al. 2000),  a more recent study concluded that reducing or even eliminating soot in the upper troposphere would still lead to contrail formation (Kärcher and Yu 2009). 

The following link is taken from the BBC and shows a series of images of aircraft contrails progressively turning into cloud over the UK. 

Finally, the following video shows a contrail coming out of an a380 (the worlds largest passenger airliner!) really well - although difficult to picture, it shows that not all of the contrail is coming out of the aircraft but that the water vapour created in the exhaust plume is also interacting with condensation nuclei already in the atmosphere. The video further emphasises the atmospheric conditions needed for contrail formation, it appears to have been following the aircraft for some time - and that tells us something about relative humidity of the atmosphere. 

A Long Flight Ahead

Through the course of this blog I aim to travel through the history of commercial aviation, the environmental impacts of air travel, how environmental concerns associated with it are perceived today, and how the aviation industry is responding to such concerns - this is a very loose structure and I'm sure other things will pop up (there may be some unexpected turbulence for instance).

I thought a fitting way into it all would be to share this video published by British Airways on their YouTube channel last week, where Willie Walsh, CEO of the International Airlines Group (AIG), the parent company of British Airways, discuses the  current challenges the aviation industry faces with respect to climate change.

He consolidates the point I made in my previous post on how despite only accounting for around 2% of CO₂ emissions  - aviation has become a "whipping boy" to current climate issues as it is recognised its contribution will only increase. He calls on governments to work together in developing a global scheme covering aviation which can be adhered to by all airlines, and that assistance (read funding?!) should be provided much like it is in developing sustainable fuels for cars, to the airline industry where for the foreseeable future, there will be a reliance on a liquid based, carbon fuel.  

Concerns on the impact air travel was having on the environment were only extensively addressed in the 1999 Intergovernmental Panel on Climate Change (IPCC) report on 'Aviation and the Global Atmosphere'. This was despite calls being made in the late 60s and 70s on the potential impact of contrails relating to aviation, however this was only on the effect supersonic aircraft had on stratospheric ozone (Lee et al. 2009) (which doesn't really help us!). 

In a short space of time our knowledge of the environmental impacts of aviation have increased greatly to become one of the more hotly debated environmental issues of the 21st century. 10 years on from the IPCC aviation report, airlines were to pledge to cut CO₂ emissions to half the 2005 level by 2050 - this was championed by none other than Willie Walsh with the hopes that if it was approved, it would be added to the agenda at the 2009 Copenhagen Summit, marking concrete efforts to address aviation and climate change. 

Introduction: Prepare doors for takeoff

As part of a university module I am taking called Global Environmental Change (which coincidentally has the same code as this flight of discovery I am about to embark on, GEOG3057), I aim to explore the issues surrounding air travel and the impacts it has on the environment. To me, commercial aviation is one of our greatest achievements as a humankind. It involves people from all over the world coming, working, talking, arguing, collaborating, engineering and building things together. It also involves flying through the sky, which is quite neat. 

Currently the aviation sector is responsible for 2% of global annual CO₂ emissions. This may seem insignificant in relation to the  2.2 billion people that gain from flying and the 32 million jobs the aviation industry provides, but it's actually quite a lot of  CO₂. In 2010 for example, aviation produced 760 million tonnes of it (and I feel guilty about having to work in the library, with the lights on when there's plenty of sunlight coming through the windows!).

Global air travel is showing no signs of slowing down despite increasing concern for the impact it is having on the environment, in particular on the atmosphere. Our reliance on air travel in the world today as a means of transporting goods and people for business or leisure in a timely fashion means that wherever possible, infrastructure will always be built to accommodate its growth. No better is this demonstrated than in China, where 82 new airports are being planned to be built by 2015 as outlined in the country's most recent 5 year plan.  

It is estimated that passenger air travel will grow at an annual rate of 5% from 1990 to 2015 with associated annual CO2 emission increases of 2-3%, and this is despite strict regulation and more environmentally friendly aircraft. And that is just looking at CO₂! Most of the growth in aviation will come from outside the US and EU considering that together they are currently responsible for 48% of CO₂ emissions from flights originating within them. 

Its a shame we can't all take the swanky AGV train to Australia

Over the next few months, I hope to address the environmental concerns associated with  aviation. I’m interested in what I will discover in light of the predicted growth of the aviation sector and what this may equate to, perhaps in my lifetime concerning the future of air travel.