A typical search through the online giant's website is thought to generate about 7g of carbon dioxide. Boiling a kettle produces about 15g.
The emissions are caused both by the electricity required to power a user's computer and send their request to servers around the world.
The discovery comes amid increasing warnings about the little-known environmental impact of computer and internet use.
According to Gartner, an American research firm, IT now causes about two per cent of global CO2 emissions and its carbon footprint exceeded that of the world's aviation industry for the first time in 2007.
Dr Alex Wissner-Gross, a physicist from Harvard University who is leading research into the subject, has estimated that browsing a basic website generates about 0.02g of CO2 for every second it is viewed.