Every action we perform results in the emission of CO₂ or other greenhouse gases, leaving a trace in the atmosphere that is referred to as “carbon footprint”. More precisely, an individual's carbon footprint is the sum of all greenhouse gas emissions produced in daily activities, including emissions from the products they consume.
It is expressed in tonnes of CO₂ equivalent, a unit of measurement which takes into account the different climate-changing potential of each greenhouse gas by relating it to that of carbon dioxide. Average, it is estimated that the annual carbon footprint is 6 tonnes of CO₂ equivalent for each European citizen, 14 tonnes for a US citizen and 8.2 tonnes for a Chinese citizen (IEA 2021 data). An important part is related to energy consumption.