What does a carbon footprint include?

The IPCC (Sixth Assessment Report, Working Group III glossary, 2022) describes a carbon footprint as the total carbon dioxide caused directly and indirectly by an activity, or built up over the life stages of a product. It also defines a household carbon footprint as the emissions from home energy, transport, food and other goods and services that a household buys.

In everyday practice, most calculators and reporting standards go one step further and include all the main greenhouse gases, not only carbon dioxide, converted into one unit called CO2 equivalent. When you read "carbon footprint" in a company report or an app, it almost always means this wider greenhouse gas footprint.

A footprint has two kinds of emissions:

• Direct emissions come from things you burn or release yourself: petrol in your scooter, LPG in your kitchen stove, diesel in a company's generator.
• Indirect emissions happen somewhere else because of what you use: coal burnt at a power plant to make the electricity for your fan, fuel burnt to grow and transport your food, energy used to make your phone or cement for your house.

For most households and most companies, the indirect part is larger than the direct part.