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If I make a calculation from the second fast fact in the article "Taking Action on Climate Change" in issue 26 of EnviroZine to know how much greenhouse gas emissions I don't produce by not having a car, I get 100 per cent = five tonnes. Yet, the first fast fact talks about producing on average over five tonnes. That leaves very little greenhouse gases produced as a result of heating and cooling my home, using appliances and other electric equipment, etc. This sounds hard to believe: I'm sure these activities are also significant in the production of greenhouse gases. Could there be a number wrong or missing in either of these paragraphs?
Pierre Tourigny, Toronto, Ontario

While there were no incorrect or missing numbers in the article, the Environment Canada Climate Change Bureau provided some more details to help clarify the 'fast facts' that ran with the article:

Fact 1: On average, each Canadian generates over five tonnes of greenhouse gases per year by driving vehicles, heating and cooling homes, washing and drying clothes and using other appliances.

This calculation is an average of greenhouse gases generated per individual Canadian (about 5.4 tonnes per person). Current estimates indicate that about half of personal greenhouse gas emissions come from transportation (49.9%). The second-largest source of emissions is heating our homes (28.7%). Heating water, using appliances and lighting, and cooling our homes are the other most frequent sources of emissions.

Fact 2: Reducing the use of a car by 10 per cent can reduce greenhouse gas emissions by 0.5 tonnes.

In contrast to the fact above, this fact is calculated per vehicle, rather than per individual Canadian. In many cases, two or more members of one household share the use of one vehicle. Therefore, the 0.5 tonne reduction per vehicle could be split amongst two or more individuals.

It is also important to note that the figure that appeared in the EnviroZine article is based on an average of emissions from various types of vehicles driven in Canada. A typical late-model sport-utility vehicle driven 20,000 km a year produces about six tonnes of carbon dioxide, compared to four tonnes for a recent mid-sized sedan, and just two tonnes for a gasoline-electric hybrid vehicle.

In fact, driving 10 per cent less can reduce greenhouse gas emissions by 0.2 to 0.8 tonnes per year, depending on the vehicle.

The math to arrive at these average figures is quite complex. While it is often necessary to use average figures, whenever possible, care should also be taken to provide facts calculated from a common denominator (in this case, individual Canadians). We have made note of this for future.

For more detailed information, check out the fact sheet A Challenge for Canadians on the Government of Canada Climate Change Web site.

For a more precise calculation of your personal greenhouse gas emissions, try the on-line Climate Change Calculator.

Related Article:

Taking Action on Climate Change