The term "carbon footprint" has been growing in popularity over the past several years, primarily due to the heightened awareness of climate change. A carbon footprint consists of the net greenhouse gases emitted by an entity, individual, organization or nation.

There is more than one interpretation of carbon footprint and it is often incorrectly interchanged with similar terms such as "environmental footprint" and "ecological footprint". Personal carbon calculators define a carbon footprint as the net carbon dioxide attributable to an individual over a one year period. Since there are many different greenhouse gases, the specific gas(es) must be converted to tonnes or kilograms of equivalent carbon dioxide. More information on carbon footprint can be found at Wikipedia.

The concept behind the personal carbon calculator is to allow an individual to calculate his or her own carbon footprint and then buy carbon offsets to "neutralize" their footprint. There are several websites that assist individuals in determining a carbon footprint:

U.S. Environmental Protection Agency

MyCarbonFootprint

Very often, the term carbon footprint is confused with another term called ecological footprint.  Carbon footprint only considers net greenhouse gases emitted, whereas ecological footprint is much more encompassing. The ecological footprint is a calculation of productive land and water required by an individual, both in terms of usage and also to absorb wastes that the individual produces. A carbon footprint is measured in tonnes or kilograms of carbon dioxide equivalent. An ecological footprint is expressed in terms of global hectares.

An ecological footprint is broken into four consumption categories: carbon, goods and services, housing and food. The carbon category includes transportation and home energy use. An ecological footprint can also be broken down by ecosystem types or biomes. These consist of forestland, pasture land, cropland and marine fisheries. In addition to consumption categories, waste must also be considered.

Scientists have calculated the average per capita ecological footprint to be 23.47 global hectares. On a renewable basis there are only 15.71 global hectares available meaning that we are collectively overshooting the Earth's ecological capacity by almost 50%.

There are still issues with the ecological footprint calculation and not everything is accounted for. For instance, unsustainable resource management and pollution are ignored, resulting in an ecological footprint that is generally underestimated. There are online ecological footprint calculators that are similar to the carbon footprint calculators (identified above).  All of the ecological footprint calculators make certain assumptions about lifestyle based upon country of residence and are biased towards that country.

For example, if you were a reclusive monk living in California you would be assigned a large ecological footprint even if you hardly made an impact. Also, individuals are responsible for a portion of a city's infrastructure and the footprint is assessed accordingly. Needless to say the calculators are still evolving.  Here are some ecological footprint calculator websites:

E.P.A. (Australia)

Redefining Progress

There are several ways of reducing an individual’s ecological footprint. One significant but controversial way is to shift from a meat to a vegetarian diet. According to a recent study, it was determined that a vegetarian diet was more environmentally friendly than a meat diet.  It requires approximately 0.18 global hectares per person while a meat diet (high fat) requires almost five times as much, or 0.85 global hectares per person per year. There are many contributing factors for the meat diet, including deforestation and energy required for processing / transportation. And don't forget cow flatulence. Scientists have estimated that the meat consumption life cycle contributes 18% of worldwide greenhouse gas emissions.  More emissions results in larger effect on the climate.

Another method of reducing one's ecological footprint is to buy local fresh food from farmers markets and preferably organically produced. It is important to eliminate transportation and refrigeration costs as much as possible. Organic foods eliminate the environmental impact of pesticides (including transportation and packaging). Farmers markets generally incorporate less packaging materials and food is fresh with no refrigeration or electricity requirements.  More environmentally friendly all around.

When purchasing a new house there are many green initiatives that should be considered. Take advantage on the house orientation towards the sun for heating in the winter and cooling in the summer. Consider rooftop gardens and soil-less turf on outside walls as in the Olympic exhibition hall . Passive solar heating, water efficient fixtures, sustainable building materials and other green design features should be incorporated where possible.

It is estimated that households can reduce their water footprint by 60% just by adopting more conservative water usage. On the carbon front, most people can significantly increase gas mileage by changing their driving habits. And don’t forget to take mass transit whenever possible.