You telecommute, while your friends idle in stop-and-go traffic on the way to work. Instead of driving to the mall — and puttering around looking for a parking spot — you do your holiday shopping with a few mouse clicks. But don’t feel so smug. Your virtual carbon footprint may be bigger than you think.


Figuring out the environmental impact of your Internet use, the size of your virtual carbon footprint, should confirm that there is no free lunch. Every human activity, even updating your Facebook status, contributes in some way, to the creation of carbon dioxide (CO2) and other greenhouse gases.


Surfing the Web uses a significant amount of electricity. The world’s data centers — cavernous buildings filled with stacks and stacks of servers filled with webpages, downloadable files, streaming video — suck up a tremendous amount of juice. The data centers around the world use about 30 billion watts of electricity, roughly equivalent to the output of 30 nuclear power plants, according to an article in the New York Times published earlier this year. Data centers in the United States account for one-quarter to one-third of that total.


The PCs, iMacs, laptops, tablets and such used to surf the Web also demand electricity.


All together, Internet use is responsible for about 1 percent of CO2 emissions released from burning fossil fuels, estimates Mike Berners-Lee, author of "How Bad Are Bananas? The Carbon Footprint of Everything."


Engineers at Google, the Internet search giant that has morphed into a verb, crunched the numbers and determined that an average query uses about 1 kilojoule (kJ) of energy and emits about 0.2 grams of carbon dioxide. It takes 10,000 Google searches to equal the CO2 emissions of a five-mile trip in a typical car. While that sounds like a lot, the scale of the Internet is mind-bogglingly massive. A 2010 study calculated that the 62 trillion — that’s right, trillion — spam emails sent each year generate the CO2 emissions equivalent to 1.6 million cars driving around the globe.


So keep that mind before you forward the funny kitten pictures to everyone on your contact list.


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