San Francisco and San Diego have the lowest household energy emissions, but very high transportation footprints. Minneapolis, which has the lowest household size also has the largest overall carbon footprint, a bit of a surprise. New York, Boston and Baltimore have relatively high household incomes, and low overall carbon footprints. Changing diet (less red meat and dairy products) saved the most money, about $850 a year. Driving a more fuel-efficient car had the greatest impact on the footprint, even if the gain is only five miles per gallon.
The researchers note that if a person can't afford a new economical car, he or she could achieve a similar result by driving slower and less aggressively. That could also save a life.
Footprint Calculators Viewed as Simplistic by Some
The Berkeley website is the latest in a long line of "footprint calculators," many of which have come under attack by researchers who view them as simplistic -- and often incorrect -- answers to a very complex problem. To really know your footprint, you need to know just about everything that is required to sustain your life: How much damage was done all along the way in building that economy car, or getting that steak to the dinner table, or producing the electricity to power your coffee pot.
That has become a somewhat heated issue in the production of biofuels. A Duke University study found that if you want to reduce greenhouse gas emissions, don't plant corn for ethanol production. Leave the land vacant instead. Growing, harvesting and converting corn can be a messy business. That, in turn, has come under attack by other researchers, including Michigan State University's Bruce Dale, who argues that proper crop management could still make corn-ethanol production a good deal.
It's a very complex issue with many poorly understood variables, as evidenced by the lack of consensus among experts.
Incidentally, carbon footprint may be a relatively new term, but it's not a new phenomenon.
Ohio University scientists stumbled upon evidence that native Americans left a carbon footprint more than 2,000 years ago. Working with scientists at several other institutions, the Ohio team was studying historic drought cycles in North America using carbon isotopes in stalagmites. To their surprise, the carbon record contained evidence of a major change in the local ecosystem at around 100 B.C.
That coincided with archeological evidence found in a nearby cave of a Native American community there 2,000 years ago. The scientists believe the Indians altered the local ecosystem by clearing and burning forests, probably to increase production of nuts and fruits.
So, long before anyone knew that greenhouse gases were altering the global climate, humans were already leaving a carbon footprint.