Google disputes Harvard fellow’s pollution estimate


The carbon footprint of a search query is nowhere near what a Harvard academic estimated, Google said late Sunday.

British newspaper The Sunday Times published a story on Sunday with results of a study by Alex Wissner-Gross, a physicist who estimates that a Google search produces 7 grams of carbon dioxide (CO2), a little less than half as much CO2 as cooking a kettle for a cup of tea.

Wissner-Gross claims that a Google search has “clear environmental implications”.

However, Google argues that 7 grams is far off and trivial compared to other CO2-emitting activities such as driving.

A search query releases the equivalent of 0.2 grams of CO2, wrote Google’s Senior Vice President of Operations, Urs Hölzle, in a company blog late on Sunday.

It’s hard to see how Wissner-Gross or Google arrive at their conclusions as no technical details are provided.

However, the discrepancy may be because Google and Wissner-Gross measure different things. The Sunday Times article states that the researcher’s study covers a search query from a desktop computer that could include the emissions caused by the operation of that PC. Google’s answer focuses on the data center.

The Wissner-Gross study is due to be published shortly by the US Institute of Electrical and Electronics Engineers, according to the Times.

Google estimates that one search, including a portion of the energy used to build the search engine’s index, uses 0.0003 kWh of energy, or 1 kilojoule. The average human body uses about 8,000 kilojoules of energy daily, and so a search would use the same amount of energy as a human burns in 10 seconds, Hölzle wrote.

Hölzle wrote that the energy consumption of a search query pales in comparison to driving a car. The EU standard for vehicle emissions is around 140 grams of CO2 per kilometer driven, so most cars produce enough CO2 for a thousand Google searches if they only travel one kilometer, Hölzle wrote. Google said in the past people often had to drive to a library to find information.

Google and other big tech companies like Microsoft have sought locations for new data centers near cheap hydroelectric power to reduce their own energy bills. Server manufacturers have also tried to reduce the energy consumption of their products.

“We’ve made great strides in reducing the energy consumption of our data centers, but we still want clean and affordable power sources for the electricity we use,” Hölzle wrote.

In October, Google released internal test results on power consumption in its data centers.

Google uses a metric called Power Usage Effectiveness (PUE) to measure the efficiency of its data center. PUE is the ratio of the total power consumption of a data center to the power consumption of all IT equipment used in the facility. A PUE of 2.0 shows that for every watt that powers IT equipment, one watt is used to cool and distribute power to the equipment.

The US Environmental Protection Agency estimated in 2006 that typical data centers have a PUE of 2.0 or higher, but that number would drop to 1.2 by 2011 due to new cooling techniques. Google said its PUE average is now around 1.13.

That efficiency has been achieved by using more efficient power supplies, efficient voltage regulators on motherboards, and by designing server racks that use as little fan power as possible, Google said.

It is estimated that greenhouse gas emissions from the IT industry account for around 2 percent of total global emissions, which is roughly the same as the aviation industry. However, technology companies are coming under increasing pressure from environmental organizations and consumers to become more aware of emissions and other issues such as device disposal.

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