Two quick searches on Google produce as much carbon dioxide as boiling a kettle, according to research from a Harvard University academic.
The environmental harm of "googling" is part of a study by physicists worried about the impact of information technology.
One recent study estimated the global IT sector generated as much greenhouse gas as all the world's airlines.
Harvard physicist Alex Wissner-Gross found that a typical Google search on a desktop computer produces about 7g (0.25oz) of carbon dioxide.
Mr Wissner-Gross said that Google was able to retrieve fast search results because it uses several data banks at the same time, producing more carbon dioxide than some of its competitors on the net.
Google said that it takes "seriously" the impact its technology has on the environment. It said it had designed and built "the most energy efficient data centres in the world".
"In fact, in the time it takes to do a Google search, your own personal computer will use more energy than we will use to answer your query," the company said in a statement.
Google is currently investing in renewable energy sources as outlined in an initiative called RE< C. The web giant says it's committed to procuring clean energy from sources such as solar thermal and wind power.
In 2007 an energy-saving search engine called Blackle was launched. It uses Google's custom search engine, but employs a black screen because, according to its creators, tests revealed that black screens consume less energy than white screens.
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