Carbon Footprint - The Definition
The carbon footprint is a measure of the exclusive global amount of carbon dioxide (CO2) and other greenhouse gases emitted by a human activity or accumulated over the full life cycle of a product or service (see Wiedmann and Minx, 2008).
The life cycle concept of the carbon footprint means that it is all-encompassing and includes all possible causes that give rise to carbon emissions. In other words, all direct (on-site, internal) and indirect emissions (off-site, external, embodied, upstream, downstream) need to be taken into account.
Normally, a carbon footprint is expressed as a CO2 equivalent (usually in kilograms or tonnes), which accounts for the same global warming effects of different greenhouse gases (UK Parliamentary Office of Science and Technology POST, 2006). Carbon footprints can be calculated using a Life Cycle Assessment (LCA) method, or can be restricted to the immediately attributable emissions from energy use of fossil fuels.
An alternative definition of the carbon footprint is the total amount of carbon dioxide attributable to the actions of an individual (mainly through their energy use) over a period of one year. This definition underlies the personal carbon calculators. The term owes its origins to the idea that a footprint is what has been left behind as a result of the individual’s activities. Carbon footprints can either consider only direct emissions (typically from energy used in the home and in transport, including travel by cars, airplanes, rail and other public transport), or can also include indirect emissions (including CO2 emissions as a result of goods and services consumed). Bottom-up calculations sum attributable CO2 emissions from individual actions; top-down calculations take total emissions from a country (or other high-level entity) and divide these emissions among the residents (or other participants in that entity).
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1 comment May 5, 2008
