With global warming dominating so many headlines today, it’s no surprise that many of us are looking to reduce the amount of carbon dioxide and other greenhouse gases our activities produce.

By assessing how much pollution each of your individual actions generates—be it setting your thermostat, shopping for groceries, commuting to work or flying somewhere for vacation—you can begin to see how changing a few habits here and there can significantly reduce your overall carbon footprint. Luckily for those of us who want to see how we measure up, there are a number of free online carbon footprint calculators to help figure out just where to start changing.

One of the best is the University of California at Berkeley’s Cool Climate Calculator. The free web-based tool takes into account daily driving mileage and grocery and electricity expenses, among other factors, to assign a carbon score, which users can compare to similar households across the 28 largest urban areas in the U.S. Some of the results are surprising. For example, residents of eco-aware San Francisco tend to have bigger carbon footprints than those in more conservative Tampa, Florida. The reason: San Francisco has a higher cost of living and colder, wetter winters (requiring more fossil-fuel derived heat).

Another great carbon footprint calculator is available at EarthLab.com, an online “climate crisis community” that has partnered with Al Gore’s Alliance for Climate Protection and other high-profile groups, companies and celebrities to spread the word that individual actions can make a difference in the fight against global warming. Users just take a three-minute survey and get back a carbon footprint score, which they can save and update as they work to reduce their impact. The site provides some 150 lifestyle change suggestions that will cut carbon emissions—from hanging your clothes to dry to sending postcards instead of letters to taking the bike instead of the car to work a few days a week.

 “Our calculator is an important first step in educating people about where they are, then raising their awareness about what they can do to make easy, simple changes that will lower their score and positively impact the planet,” says Anna Rising, EarthLab’s executive director. “Our goal isn’t about convincing you to buy a hybrid or retrofit your house with solar panels; our goal is to introduce you to easy, simple ways that you as an individual can reduce your carbon footprint.”

Other websites, green groups and corporations, including CarbonFootprint.com, CarbonCounter.org, Conservation International, The Nature Conservancy and British Oil Giant BP, among others, also offer carbon calculators on their websites. And CarbonFund.org even allows you to assess your carbon footprint—and then offers you the ability to offset such emissions by investing in clean energy initiatives.

CONTACTS: Cool Climate Calculator, www.berkeley.edu/calculator.html; EarthLab, www.earthlab.com; CarbonFootprint.com, www.carbonfootprint.com; CarbonCounter.org, www.carboncounter.org; Conservation International, www.conservation.org; The Nature Conservancy, www.nature.org; BP, www.bp.com.

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