In my last post I discussed corporations that are using a vast array of accounting methods to calculate carbon footprints.    An article in the Seattle-Post-Intellegencer discussed variations found in outputs from household on-line carbon footprint calculators.

While US EPA’s forthcoming rule will address measuring emissions of greenhouse gases from large industrial sources, it certainly appears there are more areas needing standardization.  I should not be able to cut in half my personal carbon footprint simply by using a different calculator. 

The article was triggered by a University Washington study of household carbon footprint calculators commonly found and used on the web:

A recent University of Washington study found that when the same values were used with 10 different online calculators, the results varied greatly. In one category, the bottom line for a typical American homeowner varied by more than 32,800 pounds of carbon produced per year.

The variation suggests tallies of carbon emissions have been oversimplified to produce a "one-click" solution to an extremely complicated problem — global warming. Some experts fear calculators suggesting a person plant a few trees to offset driving a gas guzzler may actually discourage needed lifestyle changes that can benefit the planet.

"Everyone assumes that every calculator they use will produce an accurate result, but in reality, there are vast inconsistencies between the calculations being done," said Anne Steinemann, a UW civil and environmental engineering professor who headed the research. "I was really surprised by the magnitude of inconsistency."

The newspaper also did its own research and included a chart showing the dramatic variations.