BBC has a post on the Carbon Cost of Google Search.

'Carbon cost' of Google revealed

The research found a google search produced 7g of carbon dioxide

Two search requests on the internet website Google produce "as much carbon dioxide as boiling a kettle", according to a Harvard University academic.

US physicist Alex Wissner-Gross claims that a typical Google search on a desktop computer produces about 7g CO2.

However, these figures were disputed by Google, who say a typical search produced only 0.2g of carbon dioxide.

A recent study by American research firm Gartner suggested that IT now causes two percent of global emissions.

Dr Wissner-Gross's study claims that two Google searches on a desktop computer produces 14g of CO2, which is the roughly the equivalent of boiling an electric kettle.

Google’s Urs Hoelzle has a response.

Recently, though, others have used much higher estimates, claiming that a typical search uses "half the energy as boiling a kettle of water" and produces 7 grams of CO2. We thought it would be helpful to explain why this number is *many* times too high. Google is fast — a typical search returns results in less than 0.2 seconds. Queries vary in degree of difficulty, but for the average query, the servers it touches each work on it for just a few thousandths of a second. Together with other work performed before your search even starts (such as building the search index) this amounts to 0.0003 kWh of energy per search, or 1 kJ. For comparison, the average adult needs about 8000 kJ a day of energy from food, so a Google search uses just about the same amount of energy that your body burns in ten seconds.

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 in the U.S.) produces as many greenhouse gases as a thousand Google searches.

We've made great strides to reduce the energy used by our data centers, but we still want clean and affordable sources of electricity for the power that we do use. In 2008 our philanthropic arm, Google.org, invested $45 million in breakthrough clean energy technologies. And last summer, as part of our Renewable Energy Cheaper than Coal initiative (RE<C), we created an internal engineering group dedicated to exploring clean energy.

WSJ discusses the tougher times has Google gearing down.

MOUNTAIN VIEW, Calif. -- Corporate austerity is reaching one of the most extravagant spenders of the boom years. Google Inc. has begun to tighten its belt.

For much of its 10-year history, Google spent money at a pace that was the marvel of Silicon Valley. It hired by the thousands and dished out generous perks, including three free meals a day, free doctors, ski trips and laundry facilities, and subsidized personal trainers. It let engineers spend 20% of their time pursuing pet projects. The company's goal was to develop new products that would reduce its nearly total reliance on selling ads connected to Internet searches.

The Data Center group has been effected as well.

Google used to build with abandon new data centers to house its computer servers. It figured that demand for the company's products would inevitably catch up with capacity. Mr. Pichette has made the company pay more attention to aligning its capacity with its needs, say people familiar with the matter. Google's operating committee recently decided to delay opening a new facility in Oklahoma that was planned during flusher times.

Who is Mr. Pichette?

Google recently hired a new chief financial officer, Patrick Pichette. Trained in "Six Sigma" management practices -- a rigid quality-control system designed to eliminate waste -- Mr. Pichette is looking to reduce inefficiencies and delay spending when possible.

Besides slowing things down, these times are forcing shifts in priorities.  If you are a PUE fanatic, your efficiency projects are getting more attention.  Just wait until energy prices start rising.

This messiness is about to spill into public view on two levels. Globally, diplomats are convening over the next two weeks in Poland for a climate-change conference, where the official purpose is to protect the planet and the subtext is to shift the cost to someone else. In the U.S., the same basic battle soon will heat up as President-elect Barack Obama, who has pledged to push for deep cuts in U.S. emissions of global-warming gases, moves into the White House.

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One lesson from all this is that regulatory sticks aren't likely to be enough. Financial carrots also will be important to try to convince polluters, whether companies or countries, that cleaning up their act is in their economic interest. Here again, however, those interests are being defined in narrowly local terms.