Using Google to conduct two web searches produces the same amount of carbon emissions as boiling a kettle, according to a US physicist.

Research by Alex Wissner-Gross, who is also a Harvard University academic, revealed that using a PC to conduct one Google search generates 7g of carbon dioxide. Therefore running two searches is equal to the 14g of carbon dioxide produced when boiling a kettle with enough water for one cup of tea. With 2 million internet searches taking place every day, the carbon emissions are beginning to mount up.

Gross said the carbon emissions are a by product of the electricity used by the PC and from the several Google data banks across the globe that provide the answers to a search query. Gross adds that because Google uses several data banks for each query, it's generating more carbon dioxide than other search engines.

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However, Google has rubbished the claims. The search engine says it has "the most energy efficient data centres in the world" and the carbon dixoide figure is "many times" too high.

"Queries vary in degree of difficulty, but for the average query, the servers it touches each work on it for just a few thousandths of a second. Together with other work performed before your search even starts (such as building the search index) this amounts to 0.0003 kWh of energy per search or 1 kJ," the company claimed in a blog.

"In terms of greenhouse gases, one Google search is equivalent to about 0.2 grams of CO2."

See also: Can Google Apps beat Microsoft Office?