A CO2 footprint or carbon footprint is the total amount of carbon dioxide emissions produced created as a result of an individuals actions over a set period of time - generally over the time period of a year. Whenever an individual drives a car, heats their home, or buys food and other goods a certain amount of carbon dioxide is produced as a result of the manufacturing, fuel extraction, or transportation. The carbon footprint includes both direct and indirect sources of emissions - direct being emissions attributed directly to an individual and indirect being carbon dioxide created by a country or production process, attributed to a person living in that country. Generally the amount of carbon dioxide is represented in mass units of some kind, such as kg.
In addition to the carbon footprint of an individual, a product has an associated carbon footprint. Larger groups also have a carbon footprint, such as schools, industries, and companies. In 2001, a study was conducted to determine the average carbon footprint of a UK household, accounting for direct and indirect emissions. The study suggested that the average UK household had a carbon footprint of 20.7 tonnes of CO2 in 2001. Numbers in Canada are slightly different, directly every Canadian produces at least five tonnes of carbon dioxide yearly. If Canada's total production of carbon dioxide is averaged over the entire population of Canada, the indirect carbon dioxide production per person is approximately 20 tonnes of carbon dioxide!
For a good summary of what exactly a carbon footprint is, see the video below:
To calculate your personal carbon footprint, a thorough calculation can be done with this calculator.
The major contributors to carbon footprints are: food, consumption, transportation, and household energy. Food is a major contributor to carbon footprints, and meat in particular is an issue. Livestock is responsible for a significant amount of greenhouse gas emissions, and beef is one of the biggest contributors. One kilogram of beef has the same amount of emissions as driving your car about 160 miles. Completely eliminating meat is not necessary, but reducing meat intake helps lower your carbon footprint. Transportation of foods, pesticide use, and purchasing food out of season also contribute to carbon footprints. Processed foods have higher emissions than fresh food as it includes transportation, production in factories, and additional packaging.
Home energy consumption is a major contributor, as energy inefficient homes waste significant amounts of energy through poor insulation, energy inefficient appliances, drafts due to improper sealing, and excessive water use. A main contributor within the home is poor insulation, as heat leaves the house quickly.
Consumption, including clothing, footwear, and household and personal goods all account for a significant amount of an individuals carbon footprint because these items all have associated emissions from gathering materials, production, and transport. As well, many know that transportation significantly contributes to a carbon footprint simply because driving cars is polluting. Group transportation like trains or buses pollute less per person, but still have emissions that are associated with them.