We all think of the Internet as pretty clean technology. No huge plants spewing chemical effluent, no big smoke stacks, no packaging to swell the world’s already-groaning landfills…

But a Harvard University physicist says there’s a significant hidden cost to the environment every time you click on a Web site link.

Researcher Alex Wissner-Gross has calculated that, every time you click the Google Search button, you cause the generation of about 7 g of carbon dioxide. Two searches generates roughly the same amount of greenhouse gas as bringing a kettle to the boil.

How can that be, you ask?

“Google operates huge data centers around the world that consume a great deal of power,” Wissner-Gross told The Sunday Times of London this past weekend. “[Every] Google search has a definite environmental impact.”

That power has to be generated somehow, somewhere — usually via a process that involves buring some sort of fossil fuel or biomass to generate steam to drive turbine generators. And, worldwide, that puts a lot of carbon into the atmosphere.

A Gartner Group study last year showed that the information technology sector contributed about 2 per cent of all global carbon emissions — about the same amount as all the world’s airlines taken together.

Google disputes Weissner-Gross’s claim, saying it is one of the most efficient online services currently operating. In fact, Google is a charter member of the Climate Savers computing initiative, established last spring.