1 What is a carbon footprint, and why is it important?

A carbon footprint is the annual amount of greenhouse gas emissions, mainly carbon dioxide, that result from the activities of an individual or a group of people, especially from their use of energy and transport and consumption of food, goods and services. It’s measured in kilograms or tonnes per year, either of carbon dioxide (CO₂) emissions alone, or of CO₂ plus the mass of other greenhouse gas (GHG) emissions converted into their carbon dioxide equivalent (CO₂e).

GHG emissions associated with human activities are responsible for the enhanced greenhouse effect. More heat is being ‘trapped’ in the atmosphere than it otherwise would be, known as global warming, which is in turn resulting in our climate changing.

A carbon footprint can also be calculated for an event such as a music festival, or for making and distributing a product such as a car or computer.

The carbon footprint is an environmental indicator – a way of measuring impacts on the environment, in this case mainly climate change. This means that a carbon footprint doesn’t measure other impacts, except sometimes indirectly. For example, driving a petrol or diesel car, as well as emitting CO₂, results in local air pollution from nitrogen oxides (NO_X), especially the irritant gas nitrogen dioxide (NO₂) and other engine emissions; so the larger your carbon footprint from driving, the more local air pollution you are creating.