Many carbon calculators were developed by companies selling carbon offsets - particularly for plane flights, which have a very high environmental impact. Carbon calculators demonstrate how regular eco-efforts (composting, recycling, efficiency measures, investing in renewable energy) are negated by just one return flight.
One flight is responsible for roughly 0.17 kilograms (kg) of carbon dioxide (CO2) per passenger-kilometre. These emissions should be multiplied by a factor of 2.5 due to the increased warming effect of upper atmosphere emissions (some carbon calculators don't include this factor). A return flight from London to Malaga (2,300 km) would emit almost 1 tonne of CO2 equivalent.
Carbon offsetting companies calculate your share of the emissions created during your journey and then sell you a method of neutralising the impact of those emissions, such as planting trees or investing in renewable energy. We do not see this as a viable solution for the following reasons:
- Firstly, most offsets do not include the warming effect of greenhouse gases in the upper atmosphere, where planes fly.
- Secondly, when a tree rots or is burned, any carbon absorbed is released again. So trees only take carbon out of the atmosphere temporarily. There is also a long time delay between the planting of the tree sapling and the absorption of carbon by the fully grown tree, so it takes a very long time for a tree to absorb the CO2 emitted by the plane. There is no guarantee that these trees will make it to this stage. Poorly sited tree plantations can have negative effects on habitats, water supplies and local people. Young trees use lots of water, so if many are planted they can reduce the water available to farmers downstream.
- Finally, there is the danger that carbon offsetting schemes leave people feeling that it is fine to fly as they can just buy their way out of the consequences. It is far better to reduce your emissions at source by travelling by train rather than plane and taking holidays closer to home. If you have to fly, you could always give your money to an environmental charity rather than a carbon offset company.