On our website, we have used the calculator from the Swiss Non-Profit Organisation MyClimate to determine the CO2 emissions generated by certain flights. The calculation includes CO2 emissions generated by aircraft fuel, but also incorporates the additional environmental impact of aircrafts releasing greenhouse gases such as nitrous oxide and water vapour at high altitude. This is known as “radiative forcing”.
Including the effect of radiative forcing is important because certain gases are much more harmful to the atmosphere when released at high altitude than if they were released at the Earth’s surface (e.g. by driving a car). There is uncertainty in estimating the exact effect of radioactive forcing from airplane emissions, but the UK Department of Business, Energy and Industrial Strategy suggests incorporating a 90% increase in the estimate of CO2 emissions from a flight, in order to account for radiative forcing.[i]
Unlike other online calculators, the International Civil Aviation Organization’s (ICAO) calculator determines CO2 emissions generated by aircraft fuel only. It does not include the effect of radiative forcing. Its purpose is to estimate the carbon emissions generated by fuel, per passenger, so that the information can be used in carbon offsetting programs (e.g. those offered by airlines when you book your flight). As per the ICAO website:
“The scientific community has not yet reached consensus on the use of the radiative forcing index (RFI) or other such multipliers and therefore ICAO will only adopt a multiplier if and when the scientific community reaches a general agreement on this issue. ICAO is working in collaboration with IPCC on this subject and will adapt a multiplier methodology in due course accordingly.” [ii]
[i]https://www.gov.uk/government/publications/greenhouse-gas-reporting-conversion-factors-2019 [ii]https://www.icao.int/environmental-protection/CarbonOffset/Documents/Methodology%20ICAO%20Carbon%20Calculator_v10-2017.pdf
