One Small Step: How to Measure a Carbon Footprint

As a typical American, each year, you’re responsible for approximately 20 tons of carbon dioxide emissions -- otherwise known as your carbon footprint (and a mighty big one compared to those of the citizens of most other countries). Your carbon footprint measures how the things you do every day -- drive a car, turn on your home’s heater -- impact the environment.

Burning fossil fuels for transportation and energy generates carbon dioxide, the most abundant of several greenhouse gases in Earth’s atmosphere. Greenhouse gases trap heat around the planet, creating a greenhouse effect and consequently warming the planet. This phenomenon, for which human activity is largely responsible, is the main factor in climate change.

The good news is that you and your students can do something -- several things, in fact -- to reduce your carbon footprints right now.

First, measure the approximate size of your carbon footprint by using one of the many online personal-emissions calculators. The U.S. Environmental Protection Agency [1]’s Web site has a good one, as does the site for the Oscar-winning documentary An Inconvenient Truth [2]. These calculators, essentially multiple-choice forms with a few blanks for you to type a number into, step you through questions such as “How many people live in your household?” “How many flights do you take every year?” and “What is your average monthly electric bill?”

Once you’ve completed the questionnaire, you simply calculate the size of your footprint with a click of the mouse. The EPA site also includes suggestions for trimming the size of your footprint, such as turning down your thermostat on winter nights (you choose the number of degrees), or replacing 75-watt incandescent lightbulbs (you indicate how many) with 25-watt Energy Star lights. After responding to several such suggestions, use the calculator to determine the pounds per year and the percent by which your total greenhouse gas emissions could be reduced if you follow the site’s advice.

Would you like help exploring this subject with your students? Many free lesson plans are available online:

• The University of Northern Iowa’s Center for Energy & Environmental Education offers Estimating and Reducing Your Carbon Footprint [3], a five-page lesson plan designed for high school students.
• The U.S. Department of Energy’s Atmospheric Radiation Measurement/Climate Research Facility Education and Outreach Program [4] provides global-warming-related lesson plans for middle school students; however, you can modify them to use with your high school or elementary school classes.
• Climate Hot Map’s site, Global Warming: Early Warning Signs [5], offers an image of Earth with clickable annotations to illustrate how our climate is changing. A thirty-page Curriculum Guide [6] produced by the Union of Concerned Scientists complements this site; though the guide is designed for grades 9-12, certain exercises can be adapted to other grade levels.

Finally, we can all take a variety of other steps -- many of them familiar by now, though always worth repeating -- to shrink our carbon footprint:

• Drive less, and when you do drive, use the most fuel-efficient vehicle available. (Twenty-four pounds of carbon dioxide is released into Earth’s atmosphere for each gallon of gas an automobile uses.) If you can carpool to work, do so.
• Replace your incandescent lightbulbs with long-lasting, energy-saving compact fluorescent bulbs [7]. Most hardware stores, and many other stores that sell incandescent bulbs, now carry compact fluorescent bulbs.
• Replace your home’s mechanical thermostat with a digital, programmable one [8] that saves energy by allowing you to preset your heater’s on and off times. Most hardware stores carry these.
• Buy appliances with the Energy Star [9] label -- they use considerably less energy than models without the label. Most appliance stores carry Energy Star-compliant products.
• Recycle, recycle, recycle.

Douglas Cruickshank is the former editor of Edutopia.