Calculate your carbon footprint by choosing comprehensive calculators
Calculating carbon emissions from activities is a necessary step to design an emission reduction strategy and purchase equivalent carbon offsets.
We focus on energy use from fossil fuels for buildings and transportation because it is the greatest source of anthropogenic CO2 emissions from individual and corporate activities aside from manufacturing. Calculation methods use measurements of electricity consumed for stationary energy production and distance traveled for transport. These simple inputs, however, yield a great variety of results depending on the way the calculations are set out (Figure 1).
Differences in the estimates result from:
1) considering CO2 emissions only versus all greenhouse gases (methane (CH4), nitrous oxide (N2O), hydro fluorocarbons (HFCs), per fluorocarbons (PFCs), and sulphur hexafluoride (SF6)),
2) including or excluding non-gas components that affect the radiative forcing such as surface reflection (albedo) of plane contrails and forest canopies,
3) setting different boundaries for emissions responsibility (considering only the energy used in a particular flight versus adding a proportion of the energy used for airport services).
In the case of air transportation, the additional climate forcing that emissions at high altitudes create (beside the warming potential of the various greenhouse gases) is included by applying a radiative forcing (RF) index between 2 and 3 times the actual emissions (IPCC 1999 see also Environmental Change Institute (2005) for a report on Aviation Emissions and Offsets (pdf 207kb).
For impacts other than transport, calculations factor in the quantity and carbon intensity of energy used. The amount of tonnes of carbon dioxide equivalent (tCO2-e) for an event are estimated using energy use, expressed in kilowatt hours per day, multiplied by an emissions factor for energy generation in that country.
Select an offset provider with calculators that are reliable, accurate and transparent
A carbon offset provider using stringent standards will likely include comprehensive calculators that take into account the full range of radiative forcings, not just greenhouse gas emissions.
IPCC (1999) Aviation and the Global Atmosphere. http://www.grida.no/climate/ipcc/aviation/index
Jardine C. (2005) Calculating the Environmental Impact of Aviation Emissions. Environmental Change Institute. http://climatecare.org/wordpress/wp-content/uploads/2013/07/Calculating-the-Environmental-Impact-of-Aviation-Emissions.pdf