In terms of greenhouse gases, one Google search is equivalent to about 0.2 grams of CO2. The current EU standard for tailpipe emissions calls for 140 grams of CO2 per kilometer driven, but most cars don't reach that level yet. Thus, the average car driven for one kilometer (0.6 miles for those of in the U.S.) produces as many greenhouse gases as a thousand Google searches.
Official Google Blog: Powering a Google search
Google search in terms of greenhouse gases
