Alex Wissner-Gross decribes his research in detail | Google's response to the story

Clarification added 16th January: A report about online energy consumption (Google and you'll damage the planet, Jan 11) said that "performing two Google searches from a desktop computer can generate about the same amount of carbon dioxide as boiling a kettle" or about 7g of CO2 per search. We are happy to make clear that this does not refer to a one-hit Google search taking less than a second, which Google says produces about 0.2g of CO2, a figure we accept. In the article, we were referring to a Google search that may involve several attempts to find the object being sought and that may last for several minutes. Various experts put forward carbon emission estimates for such a search of 1g-10g depending on the time involved and the equipment used

Performing two Google searches from a desktop computer can generate about the same amount of carbon dioxide as boiling a kettle for a cup of tea, according to new research.

While millions of people tap into Google without considering the environment, a typical search generates about 7g of CO2 Boiling a kettle generates about 15g. “Google operates huge data centres around the world that consume a great deal of power,” said Alex Wissner-Gross, a Harvard University physicist whose research on the environmental impact of computing is due out soon. “A Google search has a definite environmental impact.”

Google is secretive about its energy consumption and carbon footprint. It also refuses to divulge the locations of its data centres. However, with more than 200m internet searches estimated globally daily, the electricity consumption and greenhouse gas emissions caused by computers and the internet is provoking concern. A recent report by Gartner, the industry analysts, said the global IT industry generated as much greenhouse gas as the world’s airlines - about 2% of global CO2 emissions. “Data centres are among the most energy-intensive facilities imaginable,” said Evan Mills, a scientist at the Lawrence Berkeley National Laboratory in California. Banks of servers storing billions of web pages require power.

Though Google says it is in the forefront of green computing, its search engine generates high levels of CO2 because of the way it operates. When you type in a Google search for, say, “energy saving tips”, your request doesn’t go to just one server. It goes to several competing against each other.

It may even be sent to servers thousands of miles apart. Google’s infrastructure sends you data from whichever produces the answer fastest. The system minimises delays but raises energy consumption. Google has servers in the US, Europe, Japan and China.

Wissner-Gross has submitted his research for publication by the US Institute of Electrical and Electronics Engineers and has also set up a website www.CO2stats.com. “Google are very efficient but their primary concern is to make searches fast and that means they have a lot of extra capacity that burns energy,” he said.

Google said: “We are among the most efficient of all internet search providers.”

Wissner-Gross has also calculated the CO2 emissions caused by individual use of the internet. His research indicates that viewing a simple web page generates about 0.02g of CO2 per second. This rises tenfold to about 0.2g of CO2 a second when viewing a website with complex images, animations or videos.

A separate estimate from John Buckley, managing director of carbonfootprint.com, a British environmental consultancy, puts the CO2 emissions of a Google search at between 1g and 10g, depending on whether you have to start your PC or not. Simply running a PC generates between 40g and 80g per hour, he says. of CO2 Chris Goodall, author of Ten Technologies to Save the Planet, estimates the carbon emissions of a Google search at 7g to 10g (assuming 15 minutes’ computer use).

Nicholas Carr, author of The Big Switch, Rewiring the World, has calculated that maintaining a character (known as an avatar) in the Second Life virtual reality game, requires 1,752 kilowatt hours of electricity per year. That is almost as much used by the average Brazilian.

“It’s not an unreasonable comparison,” said Liam Newcombe, an expert on data centres at the British Computer Society. “It tells us how much energy westerners use on entertainment versus the energy poverty in some countries.”

Though energy consumption by computers is growing - and the rate of growth is increasing - Newcombe argues that what matters most is the type of usage.

If your internet use is in place of more energy-intensive activities, such as driving your car to the shops, that’s good. But if it is adding activities and energy consumption that would not otherwise happen, that may pose problems.

Newcombe cites Second Life and Twitter, a rapidly growing website whose 3m users post millions of messages a month. Last week Stephen Fry, the TV presenter, was posting “tweets” from New Zealand, imparting such vital information as “Arrived in Queenstown. Hurrah. Full of bungy jumping and ‘activewear’ shops”, and “Honestly. NZ weather makes UK look stable and clement”.

Jonathan Ross was Twittering even more, with posts such as “Am going to muck out the pigs. It will be cold, but I’m not the type to go on about it” and “Am now back indoors and have put on fleecy tracksuit and two pairs of socks”. Ross also made various “tweets” trying to ascertain whether Jeremy Clarkson was a Twitter user or not. Yesterday the Top Gear presenter cleared up the matter, saying: “I am not a twit. And Jonathan Ross is.”

Such internet phenomena are not simply fun and hot air, Newcombe warns: the boom in such services has a carbon cost.

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