What does carbon footprint refer to?

• A. amount of carbon in the atmosphere
• B. total energy consumption of a building per year
• C. amount of carbon in the soil
• D. carbon dioxide emissions per year

Answer: (A)

The idea being tested is how we define a carbon footprint: it is the total greenhouse gas emissions produced by a person, organization, or activity over a period of time, typically one year, usually expressed as CO2 equivalents. That makes the best fit the description of carbon dioxide emissions per year, because it focuses on the annual flow of emissions rather than a static amount stored somewhere. The amount of carbon in the atmosphere is a stock, not the rate at which emissions occur. The amount of carbon in the soil describes stored carbon in a different reservoir, not the footprint. And while a building’s energy use contributes to emissions, the footprint is about the resulting emissions over time, not energy use alone.