Aviation is a relatively small contributor to climate change. However, with predicted industry growth, that amount is set to slowly rise.

CO₂ emissions are the principal cause of global warming and the United Nation’s Intergovernmental Panel on Climate Change (IPCC), the foremost global authority on the issue, has confirmed that aviation contributes 2% of the world’s CO₂ emissions.

This is small compared to the principal sources of CO₂ emissions, such as power generation and road transport, but this does not mean that the aviation industry is ignoring its commitment to combating climate change proactively.

The IPCC forecasts that aviation’s CO₂ emissions could rise to 3% of the global figure by 2050. Consequently, the air transport industry is undertaking many activities to reduce its contribution to climate change as much as possible, many of which you will find out about in this website.

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Carbon dioxide, CO₂, the most important greenhouse gas – has the same effect on the environment, whatever the source and wherever it is emitted.

However, aircraft engines, like cars, trucks, ships and trains, emit other gases too. Some of these may also affect the climate, and some may have a greater effect at altitude than at ground level. Soot is an example, but soot emissions from jet engines have been largely eliminated in the last 20 years.

Oxides of nitrogen (NO_x) are another example, but they can have both warming and cooling effects. Water vapour in the form of contrails can lead to cloud formation, which is recognised as a challenge for the industry.

Essentially, CO₂ effects are well known and understood, other emissions much less so. There is an additional effect at altitude, but it has not been adequately quantified. However, it is not of a magnitude that justifies diversion of attention away from the main focus, which is CO₂.

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Condensation trails or “contrails” are the visible trails of water vapour sometimes left by aircraft as they fly. Contrails may in turn trigger the formation cirrus clouds.

At present, no-one is entirely certain to what extent contrails and related clouds contribute to global warming. It is thought that contrails, by creating clouds, could trap outgoing radiation emitted by the Earth and atmosphere at a greater rate than they reflect incoming radiation from the sun. This could increase global warming.

However, the effect varies daily and annually, and the overall extent of warming is not well known. Furthermore, it has even been suggested that cirrus clouds can sometimes cause global “cooling” and potentially slow the effects of climate change. Clearly, a better understanding is needed before formulating appropriate responses.

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When you fly you normally take the most direct route between two points, while when you drive or take the train the distance between the same two points is 30 to 40% longer.

However, aircraft are not always allowed to use the shortest distance, as they are often forced to “zigzag” due to restrictions in airspace imposed by governments.

In Europe, for example, the airspace is patched together from old national systems, with segmentation into small, inefficient blocks which use a variety of different air traffic control technologies. The creation of a “Single European Sky”, on which the industry is working together with European regulators, will bring significant environmental benefits, through the reduction of holding (aircraft flying in a fixed pattern waiting for permission to land), more efficient routings thanks to the design of functional airspace blocks (FAB), and enhanced optimal flight profiles.

Shortening routes can indeed significantly reduce CO₂ emissions. In fact, every minute of flying time knocked off a journey saves 62 litres of fuel and 160kg of CO₂ emissions. And everyone arrives sooner!

Therefore, all over the world, airlines and air navigation service providers are looking to shorten routes wherever possible. For example 6 million tonnes of CO₂ were saved in 2006 in various regions as a result of governments playing a role in shortening routes.

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The industry is actively developing and testing potential alternative fuels for aviation. When blending biofuel made of crops or algae with traditional jet fuel, it is possible to substantially reduce CO₂ emissions. One of the problems to be addressed is related to the temperature at which biofuels freeze, since aircraft operate at high altitudes where the outside temperature is very low.

However, industry continues to examine using alternative fuels in the future with major airlines such as South African Airways, Qatar Airways and Virgin all pushing forward alternative fuel projects and trials.

Hydrogen is being explored for application in the very near future in fuel cells for the auxiliary power units (APUs) that provide energy to aircraft standing at the gate. Hydrogen might become an option for aircraft engines from 2050, although significant design and infrastructure changes would be required, in particular regarding the size of the tanks since hydrogen is lighter but far more voluminous than jet fuel.

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Aircraft manufacturers are constantly redesigning and re-engineering aircraft, to incorporate advancements in technologies and designs.

Manufacturers have developed lighter materials, more aerodynamic designs, and better engines so that the aircraft they produce are more efficient, reducing fuel burn and therefore emissions.

For example, the new Airbus A380 has the lowest fuel consumption per passenger of any large commercial airliner yet built. It requires less than three litres of fuel per passenger per 100km travelled, making it more fuel-efficient than even the latest family cars. For more information about the A380, please visit the Airbus website.

Also, as much as 50% of the main structure of Boeing’s new B787 Dreamliner - including the fuselage and wing - will be made of composite materials. This will make the aircraft lighter and will, therefore, reduce fuel consumption and CO₂ emissions. For more information about the B787, please visit the Boeing website.

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Yes, aircraft engines are becoming more and more efficient and are helping limit the impact of aviation on climate change. Continuing to improve efficiency is a key consideration for aircraft engine manufacturers.

For example, Rolls-Royce, partnering with the University of Bristol, is researching the engineering and application of composite materials in engine design. These composite materials make engines significantly lighter and, therefore, reduce the amount of CO₂ produced during a flight. Rolls-Royce’s Trent 1000 engine, designed and built for the Boeing B787 Dreamliner, has 15% lower fuel burn than comparable engines of a decade ago, and delivers 40% lower emissions than required by current international legislation.

Engine manufacturers are also cutting emissions of non-CO₂ emissions such as oxides of nitrogen or NO_x. For example, in the 1990s, the engine manufacturer CFM International pioneered the development of an ultra-low NO_x combustor for aircraft, reducing NO_x emissions by up to 40%.

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Aviation transports people across the world, over distances of up to 15,000km.

A high-speed train can be a suitable alternative or complement between large cities, while air transport remains the best, if not the only option for trips above 1,000 km, which represent 80% of air traffic.

Intermodal solutions combining high-speed trains and planes are being developed. This is the case, for example, between Roissy Airport in Paris and Brussels Airport where Air France transports its passengers arriving from North America or Asia via high-speed train. This rail link replaces all flights between these two cities (see www.airfrance.com).

High-speed trains have a large capacity, comparable to that of, for example, the A380, which limits its market to large cities. For regional links between medium-sized cities, air transport is more efficient and cost-effective since it has the flexibility to adapt the aircraft-type to the size of the market (from fewer than 20 seats to a few hundred).

It is important to remember that trains do also produce emissions – directly through diesel engines and indirectly as they run off the electricity grid. Generally, their noise footprint is larger than aircraft and they also have a much greater land use footprint.

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Carbon offsetting is a voluntary way of combating climate change by funding sustainable projects all over the world.

Although it is perhaps not a long-term solution, offsetting means paying a little more for your ticket to compensate for the CO₂ resulting from your flight. The money helps to fund diverse projects around the world; for example, to replace non-renewable fuel, such as coal, with renewable forms of energy such as biomass or solar, or perhaps to support forest restoration, which helps absorb CO₂ from the atmosphere.
More and more airlines are offering passengers to opportunity to offset their carbon emissions. The main ones are British Airways, SAS Group and Cathay Pacific. On top of this many organisations are helping individuals and companies to offset their carbon emissions. Some of the main ones are The CarbonNeutral Company, and The Conservation Fund.

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There are many different techniques used by airports and airlines. In some countries, all waste coming off an aircraft must be destroyed for quarantine reasons and many of these airports are now moving from incinerating this waste to more environmentally-sound techniques such as steam sterilisation.

Recycling bins have been installed in the passenger terminal buildings of many airports and in their administrative facilities. Thus, waste is sorted before being collected in order to reduce the volume of refuse and to maximise recycling. Bottles, cans, sometimes newspapers, batteries and other recyclable items are recovered by designated collectors.

Furthermore, washing aircraft is important in all conditions. One benefit beyond a clean plane is that a clean engine functions more efficiently, saves fuel, and therefore reduces emissions. Also, aircraft can be washed without water. A gel is applied to the fuselage and wings using mops. It is left on for about 15 minutes and then removed, again with mops. The mops are washable and can therefore be re-used, while the gel is biodegradable and harmless to the environment. In addition, the gel leaves a thin, protective film on the aircraft's surface, which helps it to stay clean for longer. According to one airline, this technique enabled it to save around 360,000 litres of water in 2002.

Another example of waste and recycling concerns “de-icing”. In cold climates, both aircraft and runways have to be de-iced to prevent any risk of accidents. Airports limit the impact of de-icing activities by collecting and reusing the de-icing chemicals. Traditional de-icing fluids are being replaced with products that are less polluting or even fully biodegradable.

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There are a number of reasons why you might have to taxi to or from the runway for a long time in an arriving or departing aircraft at some airports. One reason is that the runway your flight will use may be located some distance from the terminal building (remember that runways are often three or four kilometres long).

However, the most common reason for lengthy taxiing is congestion on the ground. There will be different reasons for this, depending on the airport, but the industry has determined that congestion is a major contributor in some regions, and will continue to be as passenger numbers grow. Traffic delays affect the quantity of emissions released and also inconveniences passengers.

Expansion of airport facilities and more efficient use of air routes will help ease the congestion experienced at some airports.

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The simple answer is because of capacity constraints at airports and in the air over major hubs – when there are large numbers of aircraft trying to use the same runway or airspace, air traffic control will queue the flights and allocate them slots to land in safely.

All sectors of the air transport industry are working together to reduce the amount of time that flights have to circle through more efficient landing approach techniques, flight paths and on-the-ground operational programmes to clear runways more quickly. However, at some of the more constrained airports such as London’s Heathrow, the only option may be to build more runway capacity.

As a result of political and public pressure, it may become increasingly difficult for airports in some regions to be allowed to increase capacity unless the aviation sector can demonstrate that it is addressing its impact on climate change and other environmental issues. Aviation partners understand that proactive work is vital to ensure the ability to meet the capacity challenge.

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Of all the different forms of transport, cars produce by far the most CO₂ emissions.

According to the recently-published Stern Review (The Economics of Climate Change), cars are responsible for 76% of all CO₂ emissions from the transport sector with ships and aircraft 10% and 12% respectively.

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The heavier an aircraft, the more fuel it consumes and a large portion of an aircraft’s weight is due to cargo and baggage carried. A plane saves 34,000 litres of fuel per year for each kilogramme less in weight per seat.

Each individual traveller can, therefore, make a big difference to fuel consumption by packing lightly. The cumulative weight reduction will reduce the total loaded weight of the aircraft and enhance fuel economy, which, in turn, means fewer CO₂ emissions.

Packing tips can be found in many places online. For example, see these packing tips from the American Society of Travel Agents (ASTA).

More generally, you might also wish to look at the travel tips on responsibletravel.com.

There are other ways to limit your climate change impact when flying. How you decide to travel to the airport can affect CO₂ emissions and local air quality. For example, choosing public transport rather than taking a car saves emissions.

More and more passengers are also choosing to offset the emissions of their flight. Please see the answer to question 9 ('How does carbon offsetting work?') for more information on how to offset.

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An emissions trading scheme is a way of reducing CO₂ emissions by setting an overall limit on emissions, then allowing companies to buy and sell emission “allowances” to meet their reduction targets.

Each company participating in the scheme is allocated a permitted level of CO₂ – its allowance. For example, a particular company might be allowed to produce 100,000 tonnes of CO₂ a year. If it produces less than this amount, it can sell the surplus of its allowance to other companies who cannot meet their targets. Because emissions allowances have cash value, those companies that are able to reduce emissions below their targets can make money by selling credits, whereas those that exceed their targets have to buy credits. The intent of such a scheme is to incentivise reductions in industries that can achieve reductions most cost-effectively.

Emissions trading schemes are either mandatory or voluntary. Mandatory schemes can be found in the USA, where emissions trading is used to reduce sulphur dioxide from electric utilities, and in the European Union (EU) where an emissions trading scheme aims to reduce C0₂  emissions from industrial installations. The Chicago Climate Exchange, where companies can trade carbon allowances, is an example of a voluntary scheme.

In December 2006, the European Commission (EC) proposed to expand its current emissions trading scheme to cover CO₂ emissions from the aviation industry. Flights inside the EU would be included from 2011 and all flights to and from the EU from 2012.

If this scheme is approved by the European Parliament and Council, this will place a cap on CO₂ emissions from aircraft flights, while allowing airlines with sufficient financial means to grow by purchasing allowances from other industries as well as from a number of emissions reducing projects in the developing world. Since the scheme sets an overall limit on emissions, the overall environmental benefit is guaranteed.

A number of governments outside Europe have already informed the EC of their opposition to the inclusion of non-EU airlines in the European scheme. The aviation industry has stressed that the unilateral inclusion of flights to and from third countries should be avoided.

You can find more information about emissions trading from Emissions trading section of this site, International Air Transport Association (IATA) and the Association of European Airlines (AEA).

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The amount of CO₂ that a company can emit under an emissions trading scheme can be allocated in different ways. Simply put, allowances are distributed to companies either by “auctioning” or by distributing them free-of-charge. When distributed free-of-charge, allowances can be determined by past emissions of the company (‘‘grandfathering’’) or by basing the allocation on their emissions’ efficiency when compared with a sector average (‘‘benchmarking’’).

With regards to aviation, the “auctioning” of allowances could have a very substantial cost impact, as competing airlines will drive up the price. Allowance distribution based on past emissions (grandfathering) would penalise airlines that took early action to modernise their fleets and reduce CO₂, while a “benchmarking” approach, if designed properly, would reward more efficient operations.

You can find more information about emissions trading from the Emissions trading section of this site, International Air Transport Association (IATA) and the Association of European Airlines (AEA).

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The aviation industry believes that climate change is a global issue that requires a global solution through the International Civil Aviation Organization (ICAO) – the UN body dealing with aviation at the worldwide level. This is the best way to minimise competitive distortions and to maximise environmental benefit.
 
A well-designed emissions trading scheme should be based on the consent of those states whose airlines are involved in the scheme, on the understanding that the unilateral inclusion of foreign airlines or flights to and from states outside the scheme should be avoided.
 
European airlines believe emissions trading is a useful tool to manage the industry’s greenhouse gas emissions, while strongly opposing fuel taxes and emission charges that do nothing for the environment. (The Association of European Airlines (AEA) provides additional information).
 
Emissions trading should only be considered as a complement to other more efficient and permanent measures such as technological, operational and infrastructure developments, which can deliver direct environmental benefits.
 
An emissions trading scheme is only one of the tools available to limit air transport CO₂ emissions. To be fully effective, emissions trading must also go hand-in-hand with the industry’s other efforts to combat climate change. You can find out more about these by viewing the ‘Flying Experience’ (coming soon).
 
You can find more information about emissions trading from the Emissions trading section of this site, the International Air Transport Association (IATA) and the Association of European Airlines (AEA).
 

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No. If anything, green taxes harm the industry’s ability to limit its climate change contribution.

This is due to a number of reasons. Taxes drain the aviation sector of financial resources needed for investments into research and development.

Green taxes are explicitly aimed at changing demand for air transport – which simply means pricing passengers out of the market. This is made worse by the fact that, in many instances, travellers have no reasonable alternative to air transport.

Green taxes on aviation deliver additional revenue for governments with no guarantee that this revenue will be used for environmental objectives, neither for the passenger nor the airline. They provide no incentive whatsoever for airlines to invest in more efficient aircraft, or more efficient fuels: both major factors in reducing CO₂ emissions that should be encouraged not discouraged.

Green taxes are not a viable solution to address aviation’s contribution to climate change.

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We do not need to fly less, but we do need to adopt a responsible approach to limiting aviation’s impact and that is exactly what the commercial aviation industry is doing.

Flying meets the need for global connections, and without it the global economy would suffer. In many cases, flying simply cannot be replaced by other modes of transport. In many parts of the world, road and rail infrastructure is grossly inadequate. Traffic demand is growing worldwide, not diminishing, including developing nations that are in great need of affordable passenger and cargo traffic to build their economies.

The right choice is not to fly less, but to continue to make sure that the air transport sector proactively and progressively addresses emissions, noise, and a range of community concerns in order to balance environmental commitment and growing capacity needs.

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International air services are exempt from fuel taxes under the Chicago Convention. The Chicago Convention establishes the rules of airspace, aircraft registration and safety, and details the rights and obligations of countries around the world in relation to international air travel.

Fuel tax exemption is not an “unfair subsidy” for aviation. The Chicago Convention is based on the international legal principle of “reciprocity” where States agree to mutual tax exemption in order to avoid unilateral imposition of fiscal measures. However, this does not restrict States from imposing fuel taxes on domestic air services, which some do, or indeed other taxes on the ticket, passenger, customs, immigration, etc. – taxes which are quite universal.

Generally speaking, it is a falsehood to say that aviation is “under taxed”. In fact, the opposite is true: in many places aviation is as heavily taxed as alcohol and tobacco. Far from enjoying tax privileges, air transport finances its entire infrastructure costs through specific user charges such as landing, en-route and passenger fees, as well as taxes paid to national treasuries. By paying for the building, maintenance and use of its infrastructures, air transport gives more back to public funds than it receives.

In Germany, for example, aviation charges and taxes generate a net surplus of €10 per 1,000km, while rail infrastructure costs result in a public subsidy of €54 per 1,000km – to be borne by the taxpayer.

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The commercial aviation industry has a responsibility to meet the challenge of climate change. It is taking many steps to limit its impact on the environment.
 
The industry has taken a multitude of fuel conservation measures on its own. It is investing in the latest and most efficient aircraft and engine technology; airlines are reducing aircraft weight and saving fuel, and are introducing carbon offsetting schemes. Those in Europe are constructively moving towards emissions trading in the European Union’s emissions trading scheme (ETS).
 
The airlines are also urging their governments to take the steps necessary to modernise air traffic systems in every region. This means reducing delays and congestion and inefficient routings that cause airlines to use fuel unnecessarily. The Intergovernmental Panel on Climate Change (IPCC) has estimated that these measures – which can only be taken by governmental authorities – can reduce fuel use by 8 to 18%.
 
These are just a handful of the many initiatives that are being taken across the whole industry, across the globe.
 
If you want to see what steps the industry is taking to limit its emissions at each stage of a typical journey have a look at our Flight Path Section.
 

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Europe’s major airlines typically renew their fleets when the aircraft are between 11 and 13 years old.

Fleet renewal is one of the principal ways that airlines are improving their environmental performance - every new aircraft is more environmentally efficient than the one it replaces. The rate at which airlines renew their fleet is naturally dependent on many factors, and has significant commercial implications for individual airlines.

However, as part of the established Emissions Containment Policy (developed by the Association of European Airlines and other aviation stakeholders), European airlines are undertaking to factor in environmental impact as well as purely economic considerations into their fleet renewal decisions.

More and more airlines across the world are investing in the latest and most efficient aircraft, such as the Airbus A380 and the Boeing B787 Dreamliner. 1,375 aircraft are currently on order from European airlines (equivalent to 25% of the existing fleet). A large proportion of these new aircraft will be replacements for older less fuel-efficient aircraft.

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Different flight “phases” (such as landing, cruising, and take-off) require different engine power settings for the aeroplane. Both the amount of fuel consumed per second and the amount of emissions per unit of fuel can differ for each power setting.

So it is true to say that a plane creates more greenhouse gases when it takes off than when it is flying on its normal cruising altitude when comparing a given unit of time in each phase (i.e. a second or a minute for example).

For example, because an aircraft uses a higher power setting at take-off and climb (typically 85-95% of full power) it will use more fuel and emit more CO₂ (which is proportional to fuel burn). This will be more, per second, than during cruise when engines normally run anywhere between 45-70%.

Similarly, during descent and landing aircraft engines will run at less than 30% so fuel burn and emissions per second will be much lower than during cruise or take-off and climb.

However, a comparison between the total emissions at each flight “phase” is largely determined by the amount of time the aircraft spends in each phase. For most flights, cruise emissions will dominate the total flight emissions simply because the aircraft spends most of its time cruising. However, on very short flights (say less than 30 minutes) it is possible that emissions during take-off and climb will constitute the largest part of total flight emissions.

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On average, an aircraft will burn about 0.03kg of fuel for each kilogramme carried per hour. This number will be slightly higher for shorter flights and for older aircraft and slightly lower for longer flights and newer aircraft.

Based on that average, and given that the total commercial fleet combined flies about 57 million hours per year, saving one kilogramme on each flight could save roughly 1,700 tonnes of fuel and 5,400 tonnes of CO₂ per year.

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Aviation plays a vital role in bringing fresh produce to stores and enabling consumers to have the best choice of goods; it transports goods that otherwise would not be offered in European supermarkets; it supports the economies of developing nations that would otherwise be unable to sell their produce; and it is not as damaging to the environment as many in the environmental movement would have you believe (see question 1 - What is aviation’s contribution to climate change?).

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Transport is just one part of the food production/distribution chain – the whole chain takes us from the seed to delivery to the consumer. If you want to identify the carbon footprint of a product, other transport modes must be included in the assessment. But don’t stop there – the impact of the entire supply chain must be included, not just transport emissions. Different agricultural practices and resource requirements often mean that food produced overseas can have a much lower carbon footprint overall, even when transport is taken into account.

For example, a Lincoln University study found that lamb raised on New Zealand’s pastures and shipped to Britain produces 1,520 pounds of CO2 emissions per tonne while British lamb produces 6,280 pounds of CO2 per tonne, in part because poorer British pastures force farmers to use feed. In other words, it is four times more energy-efficient for British consumers to purchase lamb imported from New Zealand, even taking into account it being transported 19,000 kilometres by ship. In another case, a report commissioned by Sainsbury’s and World Flowers and carried out by Cranfield University showed carbon emissions from Kenyan roses, including air transport, were 5.8 times lower than for Dutch roses.

Therefore, the concept of ‘food miles’ is flawed because it is too simplistic and does not provide a meaningful measure of all the factors of production that contribute to a product’s environmental footprint. Indeed, it could actually mislead consumers who are trying to adopt more sustainable lifestyles.

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Quite aside from consumer choice and the ability for people to widen their food experiences, many types of produce flown to supermarkets in Europe come from developing nations. The exports of exotic fruits and vegetables are vital to the economies of many of these countries, providing income and employment in areas that do not have other industries to fall back on. For example, over one million livelihoods in Africa are supported by UK consumption of imported fresh fruit and vegetables [James Mac Gregor and Bill Vorley (2006) - Fair Miles? The concept of “food miles” through a sustainable development lens].

In Kenya, for example, the flower industry is the nation’s second largest export activity, making up 65% of all exports and employing over 50,000 people. Without air transport, these flowers could not be delivered to the markets of Europe. As discussed in question 26, Kenyan flowers result in 5.8 times less carbon emissions than those imported from The Netherlands, including the transport.

Recently, the Geneva-based UN agency, the International Trade Centre, revealed that 83% of air freighted organic produce sold in the UK is imported from “least developed or lower-middle income developing countries”… The major exporters of air-freighted organic products, representing 70% of the market, are from the Dominican Republic, Kenya, Ghana and Egypt.

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Carbon offset programmes are a relatively new development in the airline industry. So far, these programmes have been developed by individual airlines in response to demand from their customers. They are still largely offered to passengers as a voluntary option because not all passengers want to offset their flights.

Right now, therefore, most airlines believe that it is not appropriate to mandate carbon offsets although they promote them extensively and in some cases even offer the passenger the option to use their frequent flyer miles to purchase offsets.

It should also be noted that the current carbon offset programmes are considered part of the "Voluntary Emissions Reduction" or "VER" category of offsets and are not fully recognised under many existing or proposed emissions trading schemes, therefore giving no carbon credit to the airlines involved. Carbon offsets have to be considered therefore as complementary to a worldwide emissions trading scheme for aviation, which is under active consideration by the International Civil Aviation Organization (ICAO), with the active support of the whole air transport industry.

Carbon offsetting is an area of great interest, and IATA has published a set of best practice guidelines to help the industry in developing these programmes.

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