What is a Carbon Footprint?

Graphics/Elín Edda

In recent years, by virtue of climate change and global warming, the term “carbon footprint” has become staggeringly prominent in political and corporate arenas and is now increasingly circulating across the media. Other footprint indicators, like water footprint and land footprint, are less widely recognized by the population at large.

The term “footprint” refers to an effort to quantify human demand on nature. Earth’s natural resources are finite. How much nature is viable, and how much do we consume? The concept of carbon footprint comes from the more general ecological footprint[1], which is a measure of the amount of nature it takes, in terms of land and sea area, to support an economy, a person, or a group of people. More specifically, it’s a comparison between the total resources that people consume and the land or water area that is needed to replenish them.

A common criterion to differentiate the carbon footprint from other ecological indicators is to define it as a measure of the quantity of gas emission germane to climate change and global warming and associated with anthropogenic activities. However, the spectrum of definitions is very wide and ranges from direct carbon dioxide (CO2) emissions to full life-cycle greenhouse gas (GHG) emissions.

Environmental scientists Laurence A. Wright, Simon Kemp, and Ian Williams have suggested defining the carbon footprint as: “A measure of the total amount of carbon dioxide (CO2) and methane (CH4) emissions of a defined population, system or activity, considering all relevant sources, sinks and storage within the spatial and temporal boundary of the population, system or activity of interest. Calculated as carbon dioxide equivalent using the relevant 100-year global warming potential (GWP100)” [2].

Climate change and global warming are mainly caused by GHG emissions, such as methane (CH4), carbon dioxide (CO2), water vapour and nitrous oxide (N2O). Since the impact of each greenhouse gas is different, all GHGs are measured in CO2 equivalents. It’s a quantity that represents the amount of CO2 that would have the same impact on the climate, as the given mixture of GHG emissions over a specified timescale.

Carbon footprint calculations are in strong demand; however, there is no consensus on how to measure a carbon footprint, and the units of measurement are not clear. A plethora of approaches have been proposed, ranging from basic online calculators to a more sophisticated one. However, no footprint calculation is precise. The most popular online calculator can be found at the following website:

 https://www.carbonfootprint.com/calculator.aspx

[1] Rees, William E. (October 1992). "Ecological footprints and appropriated carrying capacity: what urban economics leaves out". Environment & Urbanization. 4 (2): 121–130. doi:10.1177/095624789200400212.

[2] Wright, L.; Kemp, S.; Williams, I. (2011). "'Carbon footprinting': towards a universally accepted definition". Carbon Management. 2 (1): 61–72. doi:10.4155/CMT.10.39.