Author Nicholas Carr has claimed that virtual inhabitants of the online world Second Life are having a real-world impact.

In a recent posting on his Rough Type blog, Carr suggests that the users of each avatar in the virtual word consume as much electricity keeping their online creations functioning as the average citizen of Brazil.

Carr proposed that, on average, there are about 12,500 active avatars on Second Life at any given point of the day. He reasons that the 4,000 data servers and cooling systems used to support the world, combined with the 12,500 PCs that are used to control the avatars amounts to 1,752 kWh of electricity used by each avatar over the course of one year.

"The average citizen of Brazil consumes 1,884 kWh," writes Carr, "which, given the fact that my avatar estimate was rough and conservative, means that your average Second Life avatar consumes about as much electricity as your average Brazilian."

That amount of electricity used by the average citizen varies widely by region, Carr points out.

The average citizen in a developed nation uses 7,702 kWh per year, while the average developing-world citizen uses only 1,015, according to the World Resources Institute.

In a comment left on Carr's blog, David Douglas, vice president of eco-responsibility for Sun Microsystems pointed out that the amount of CO2 that is emitted while producing 1,752 kWh of electricity is 1.17 tons. To produce that much CO2 in an SUV, writes Douglas, a person would have to drive over 2,300 miles (about 3,700 kilometers), roughly the distance from New York to Las Vegas.

"Avatars aren't quite as intangible as they seem," writes, Carr.

"They don't have bodies, but they do leave footprints."