How we work out the figures
Our online calculations for Air Travel, Ground Travel and energy use are based on the following:
Each time you fly the emissions from your trip will vary depending on numerous factors (for example: wind direction and speed, weight of the plane, luggage and passengers). As it would not be practical to ask the pilot how much fuel your share of the flight has used each time you fly, certain assumptions have to be made in order to produce a model for calculating emissions.
We explain the logic behind the assumptions we make in the report produced by Oxford University's Environmental Change Institute which is available here: “Aviation Emissions and Offsets”.
Some of the assumptions made in the report, which may differ from other methodologies, are summarised below:
The emissions from our air travel calculator are based on a curve rather than a ‘per passenger km’ (which produces a straight line), so that a really short flight will have higher emissions per km than a longer one, because the landing and takeoff will represent a higher proportion of the flight and the plane burns more fuel in landing and take-off.
Even though the plane works more efficiently at altitude and burns less fuel per km, there are additional impacts from burning that fuel in the upper atmosphere. These additional impacts (e.g. from the formation of cirrus clouds and vapour trails) are accounted for by applying a multiplier (often referred to as RFI). We take the gas emitted from burning the fuel during the cruise, climb and descent elements of the flight and multiply that by two (as per UK government guidelines).
The weight of people/luggage carried on the plane will have a big impact on the fuel burn, however selecting a ‘load factor’ for the flight (i.e. the percentage of the flight that is filled), is almost impossible as this varies widely according to routes, time of the day and airline. So with ClimateCare you pay for your seat’s share of the emissions from the flight.
Other Travel and Energy Use
All other emissions are calculated using UK Government published conversion factors which are updated annually.
For people who work in managed offices, getting data from energy use can prove difficult. We provide figures per m2 floor space to help those customers get an indication of what their emissions might be based on the type of office they work in using four types of office building mentioned from "Energy Use in Offices" published by the Energy Efficiency Best Practice Programme last Revised March 2003. The emissions from the energy used are updated annually with the UK government’s figures.