Air Travel FAQs

How does my flight contribute to climate change?
Aeroplanes burn kerosene; a non-renewable fossil fuel. This releases carbon dioxide (CO2) and other greenhouse gases into the atmosphere, which contribute to global warming and climate change.

If my flight is longer, does that mean that the impact on the environment is greater?
It’s not that simple. On a per-passenger kilometre basis, long haul flights are more fuel-efficient than short haul flights. This is because take-off and landing require more fuel than cruising. On a short-haul flight, the landing and take-off cycle accounts for a greater proportion of the total flight than on a long-haul flight. However, the additional miles flown on a long-haul flight yield a greater overall greenhouse gas impact.

What is carbon offset?
The impact of greenhouse gas emissions can be counteracted or ‘offset’ by Emission Reduction projects which remove an equivalent amount of CO2 from the atmosphere, or preventing greenhouse gas emissions elsewhere. 

The CarbonNeutral company can calculate the CO2 emissions created by your air travel, and find projects to ‘offset’ the emissions. These projects might be renewable energy, energy efficiency,  methane capture or forestry.   In paying to make your flight CarbonNeutral , you contribute to these projects.

Does that mean that it’s OK to travel by air provided that I offset my emissions?
Carbon offset is not a substitute for reducing emissions at source but is the ‘next best’ solution for mitigating remaining emissions from travel. It is also consistent with the policy of many governments and policy makers.  The UK government, for example, offset all their emissions from air travel. 

How does The CarbonNeutral company’s flights calculator work?
Our flights calculator uses the official DEFRA (Department for Environment, Food and Rural Affairs) emissions factors to calculate the CO2 that your flight creates. We work this out for long and short-haul flights according to the average number of passengers per flight and the distance between the origin and destination airports.

Try using our Flight Calculator

Why do different company websites give different emissions calculations?
Different calculators use different methods to calculate aircraft emissions.
The different gases that aircraft emit have different effects, so emissions are usually calculated as ‘carbon dioxide equivalents’. To do this the ‘global warming potential’ of non-CO2 gases relative to CO2 needs to be known, but unfortunately, reliable figures are not yet available for non-Kyoto greenhouse gas emissions.

Some calculators attempt to account for all the various effects of aircraft emissions at altitude, but this involves using emission factors with a high degree of associated uncertainty. Our calculation method is consistent with current DEFRA guidelines on reporting greenhouse gas emissions.

Why do different companies give different prices to offset emissions from the same flight?
In addition to the different calculation methods mentioned above, there are variations in the price of offset credits. Contributions to this cost come from the different types and size of project supported, plus transaction or service fees paid to the project partner.

What are the other effects of aircraft emissions at altitude?
Burning kerosene produces mostly carbon dioxide and water. Other exhaust products are methane, nitrous oxide, soot particles, sulphate aerosols and nitrogen oxides.

Because of its relatively high atmospheric concentration and longevity, CO2 is an important greenhouse gas. CO2, methane and nitrous oxide are the only aircraft emissions currently covered by the Kyoto Protocol, but these contribute only part of the total global warming effect caused by aircraft emissions.

Water vapour can act as a greenhouse gas just like carbon dioxide. It also forms clouds that insulate the earth and contribute to global warming. The white trails behind aircraft are caused by hot water vapour condensing in cold air onto soot particles and sulphate aerosols. These condensation trails, or ‘contrails’ can persist as cirrus clouds. Their contribution to global warming is difficult to measure, but it could be very significant to the total impact of aircraft emissions.

Nitrogen oxides have an indirect effect on global warming through chemical reactions in the atmosphere. When released at cruising altitude (about 10km) they react with oxygen to produce ozone. The ozone layer (about 10-15km higher) absorbs harmful UV radiation, but at 10km ozone acts as a greenhouse gas. Nitrogen oxides are also involved in the breakdown of methane, another greenhouse gas, but warming through ozone production is thought to outweigh this effect.

The total impact of aircraft emissions at altitude is the result of a complex relationship between many different gases and processes. While it is likely that this results in aircraft emissions having a larger climate change impact than direct CO2 emissions alone, the gaps in our current knowledge of these processes make accurate quantification impossible.