I'm a reasonably green guy – I recycle, buy mostly organic, a “residential vegetarian” (no meat in my fridge), walk or bike to work more days than not, keep lights and power strips off when not in use, compost…is it enough? Am I doing my part?

Just about everything we do as "civilized" human beings – from driving to running computers to heating our homes to growing our food – releases carbon dioxide, which, what with several billion of us doing it all 24 hours a day, collectively contributes to increasing atmospheric carbon levels, which the overwhelming preponderance of evidence suggests is affecting our climate…for the worse.

So, what's my personal contribution to the coming apocalypse? I have a car, I travel by plane, I obviously use some amount of electricity, I have certain spending habits, eating habits, etc., etc. Am I a responsible inhabitant of the earth or a pain in its ass? How do I rate compared to the average American, to the average human? What's my carbon footprint…and how can I make it smaller?

The Internet is teeming with carbon footprint calculators, each purporting to be a measure of the amount of carbon you are personally releasing into the atmosphere on an annual basis. Many also provide tips for directly reducing your footprint, and financial means for offsetting your footprint.

The most basic carbon calculators measure three basics to all our lives: driving, flying and home electricity/gas use. Just to warm up, I visited three of these basic calculators and did my best to answer questions as accurately as I could, considering I don’t have a carbon emission-ometer attached to my belt: (my answers in parentheses)

1. Yahoo.com (http://green.yahoo.com/calculator/) asks 1) very general questions about your home: size (apartment in "big" apartment building), bedrooms (just one, it's San Francisco, after all) and State (CA), 2) very general questions about your car: what do I drive (small car) and how often (<8,000 miles/year) and 3) very general flying habits – how many & how far (2 "cross-country (4-7 hours)" trips).

Results: I emit 8.1 tons/year vs. the average American (9.44 tons/year)…not TOO bad, and almost half is due to my two flights…now that’s a drag.

2. Sustainable Travel International (https://sustainabletravelinternational.org/documents/op_carboncalcs.html), digs a little bit deeper into the details than Yahoo’s version: 1) Home Energy (“one person in a small living area less than 700 square feet in an apartment with low energy consumption in North America”…whew), 2) Driving (“8000 miles/year, 27 mpg for a 2004 Toyota Matrix, per www.fueleconomy.gov”), 3) air travel…now here’s where the breakdown occurs: I can only enter one flight, but I took 2 economy-class, round trips – one to Costa Rica (from San Francisco) and one to New York City; but using some clever math, I’m able to enter both separately and extract the difference to get the total contribution.

Results: I emit…9.8271 metric tons/year…interesting; my footprint is larger than per Yahoo…something to do with the inability to calculate multiple flights simultaneously? Well, third time's a charm, right?

3. Terrapass (http://www.terrapass.com/carbon-footprint-calculator/) asks 1) specifics on car, 2) slightly more specifics on flights (to be more specific, both my flights had 1 stop), and 3) specifics on gas AND electricity ($34/month in 94118 zip code - vs. $131 for average SF residents…nice!)

Results: I emit 6.8 metric tons/year…good lord, I'm a friggin' rock star! But this site doesn't compare me to the average American…

So, some fairly wide variation here in my first three tries. Seems like the more detail I can add, the better I am doing for the planet. Yahoo and Sustainable Travel International say I'm a little bit greener than the average American, while Terrapass, which gives me the best result of the three, doesn't provide an opportunity to gloat over anyone else.

In the next posting, I look at a calculator that delves considerably deeper into the make-up of our carbon footprint, beyond just driving, flying and electricity, and into our diets, our spending habits, even the clothes we wear!