What Is a Carbon Footprint and Why Does It Matter?
A carbon footprint is the total greenhouse gas (GHG) emissions caused directly and indirectly by an individual, organization, or product over a defined period, typically one year. It is measured in tonnes of CO2e — carbon dioxide equivalent — a unified unit that accounts for all greenhouse gases (CO2, methane, nitrous oxide, and F-gases) weighted by their global warming potential (GWP) over 100 years. Methane, for example, has a GWP of 28–36 over 100 years, meaning one tonne of methane is equivalent to 28–36 tonnes of CO2 in terms of warming impact. The average American's carbon footprint is approximately 16 tonnes of CO2e per year — roughly double the global average of 7 tonnes and nearly four times the 4 tonnes per person target consistent with the Paris Agreement's 1.5°C warming goal. Understanding this gap — between current behavior and sustainable behavior — is the foundation of effective individual climate action. Individual action matters: household decisions collectively account for 60–70% of global GHG emissions through consumption choices. The remaining 30–40% comes from industry and infrastructure, which is also influenced by consumer demand.