Science |Calculating Carbon Footprints

Under the climate treaty approved in Paris this month., almost every nation has agreed to limit its greenhouse gas emissions. In the United States, the average carbon footprint per capita is one of the highest in the world, at about 17 metric tons, according to The World Bank.

Several organizations offer free online calculators that let you figure out your individual or household emissions, but results differs from one to another depending on what each one takes into account. Here are a few notable ones:

• The U.S. Environmental Protection Agency calculator tends to calculate on the low end. It doesn’t include emissions from airplanes and it doesn’t ask about diet, even though eating meat and air travel are carbon-intensive activities.
• The Cool Climate Calculator from the University of California, Berkeley takes into account many more factors, including diet and air travel, and even clothing and furniture purchases. As a result, your carbon footprint will probably be higher. But to use this calculator effectively, you need to know how many miles on the subway you travel each year, and your yearly heating bill (the latter being particularly difficult for apartment dwellers to calculate).
• The Nature Conservancy’s calculator is better tailored to city living, and is easier to use than the Cool Climate Calculator. (It will give you credit for living in a large apartment building, for example.) But your footprint will likely be even higher than under the two other calculators. (The Conservancy says the data is from 2005 and 2006; since then, New York City’s energy grid has become much more friendly to the environment.)

See the article, “6 Ways to Shrink Your Carbon Footprint,” and tweet out how many you already do.