The average U.S. household pumps 49 metric tons of carbon into the atmosphere each year, according to the CoolClimate Network, a University of California, Berkeley consortium that has developed carbon footprint calculators for homes and businesses. What are you doing to create all that carbon? We ran the numbers on some everyday activities.
Note: Your actual carbon footprint depends heavily on your location, said Mia Yamaguchi, the CoolClimate outreach coordinator at UC Berkeley's Renewable and Appropriate Energy Laboratory. In California, for example, electricity generation is relatively climate-friendly, so focusing on vehicular emissions has a greater impact. Visit http://coolclimate.berkeley.edu for personalized estimates.
Driving to work
Let's say you commute 30 miles round-trip to work, which was about average in 2003, according to the U.S. Department of Transportation. That's about 7,800 commuting miles each year. And if you drive a car that gets 22 miles to the gallon every weekday, your annual carbon footprint from commuting is 4.3 metric tons.
If you want to shrink that estimate, try carpooling three times a week. You'll save 0.85 tons of carbon — and $323 dollars in fuel and vehicle depreciation costs — per year.
Chowing down on steak
If you're eating 444 calories a day of red meat (the equivalent of about one 8-ounce steak sirloin), your annual meat-related carbon footprint is 0.8 metric tons of carbon dioxide. Try switching things up with poultry, eggs, or even better, vegetables. Your carbon footprint will barely register.
Going on a shopping spree
Splurging on $100 of clothes each month will set you back 0.5 metric tons of carbon dioxide per year. Throw in a $1,000 furniture purchase once a year and you're up to almost a ton. You sure you need that new sofa?
Flying to grandma's house
You live in California, but you've got to spend Christmas at Grandma's back in Boston. That’s about a 5,000-mile round trip, making your carbon footprint from this airplane trip alone 2.23 tons of CO2.
We're not suggesting you deprive Nana of your company, but taking your trips close to home can give you big carbon savings: Every 1,000 miles you don't fly saves 0.45 tons of CO2.
Throwing clothes in the dryer
Drying one load of laundry a week puts 0.1 metric tons of CO2 into the atmosphere. Hang 'em outside and save yourself $11 in electricity costs while you're at it.
Gym rats, beware: Running on a treadmill for 30 minutes three times a week will boost your carbon footprint by 0.07 metric tons per year. Take it outside and watch that number plummet to zero.
Getting a divorce
A 2005 analysis showed that divorced households used an extra 73 billion kilowatt-hours of electricity compared with married households. The boost in carbon output had to do with the additional homes needed to house the now-separated couples. There were about 16 million divorced households in 2000, which comes to 4,562.5 extra kilowatt-hours of electricity per household. Break that down into carbon emissions and you get an extra 2.8 metric tons per year per household.
Getting busy can be very green. Say you spend a total of two hours per week between the sheets. If you turn off the bedroom lights, you could be saving 0.9 metric tons of carbon dioxide annually. But be careful in there: A 2009 study published in the journal Global Environmental Change found that having a baby will set you back 9,441 metric tons of CO2 over your lifetime.