The Official Google Blog just published a revealing post breaking down the environmental impact of every search made on the site. The verdict? About 1 kilojoule of energy is used and 0.2 grams of carbon dioxide emitted every time someone enters a query. The company provides a nifty little chart putting these figures in context:

Some of these numbers are surprising — especially considering that 200 million searches pass through the system a day. That means that the company’s data centers release about 45 tons of carbon dioxide a day, the equivalent of a gas-powered car driving 100,000 miles or about 13,000 cheeseburgers.

Then again, it’s not that much relative to how many people depend on Google and use it multiple times a day without giving it a second thought. If everyone who used Google every day even once got in their cars, far more than 100,000 miles would be driven between them. As for energy use, the company says its searches use about 21,000 kilowatt hours every year, about the same amount of energy used by a town of 2,700 people. This also sounds pretty conservative.

These figures are also much lower than estimates made earlier this year by the Times Online that every query emits 7 grams of carbon dioxide. A clarification has been appended to the original article stating that the 7-gram figure is only true of searches that take several minutes and servers to process, and that 0.2 grams is the accepted average. Still, several alarmist blog posts picked up the higher amount, claiming that Google accounts for 289 tons of carbon dioxide every day — an amount that would merit some concern.

While the search engine won’t disclose the locations or precise energy requirements of its data centers, it does say that its facilities are 50 percent more efficient than the industry standard. And it says it’s working to become even more efficient as more people connect to the site via laptops and mobile devices. As part of this effort, it co-founded the Climate Savers Computing Initiative with Intel to reduce the amount of carbon dioxide emitted by computer processes by 54 million tons a year. Other members include Dell, Microsoft and Lenovo.

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