What about the times of the year, when you do NOT want to heat your rooms and buildings, when you actually need air conditioning? Unless the campus is somewhere high up in the swiss alps...

This is pretty much what water cooling geeks have been doing with desktops for ages. Circulate water and cool it through a radiator. Companies like Koolance http://www.koolance.com and FrozenCPU http://www.frozencpu.com have been offering kits for ages and there are whole forums dedicated to this (http://hardforum.com/forumdisplay.php?f=91 or http://www.overclockers.com/forums/forumdisplay.php?f=71)

Implausible??. 2% of *global* electricity? Only the datacenters?? The USA alone made around 4000 billion kWh in 2006. Datacenters charge by the amp - usually 1 amp for a regular server, 2 amps for a grunty megaserver - that\'s between 110 and 220 Wh, or somewhere between 1000 and 2000 kWh per year.
Power going into computers turns almost directly into heat, airconditioners are \"heat pumps\" (eg: heat is moved from inside the center to outside, which takes a lot less energy than the amount of heat moved). If we conservatively guesstimate 50% less (and I\'m probably overstimating by an order of magnitude) then...
For that 2% number to be true, there would have had to be more than 40 million servers in datacenters in the USA alone in 2006 - that\'s more than 1 server for every 7 people in the USA.
I\'m sure there\'s a lot of servers in the USA, but 40 million? *all* in datacenters??
I doubt.

As much as I love this idea, and I would like to see watercooling on all machines, how do they expect to handle the volume of hot water needed by buildings near by or a community\'s? THose are tiny tiny tubes comming out of that server. :)

One place to start is using green roofs in combination with PV cells on data center roofs. (http://cleanerairforcities.blogspot.com/2008/07/data-centers-need-green-roofs.html) Not only would the HVAC bill be reduced by 20-30 %, but the PV cells would work more efficiently with a cooler roof. (http://cleanerairforcities.blogspot.com/2009/06/combining-solar-and-green-roofs.html).

@Skipjack: Presumably the same water used for cooling airconditioning would still be cool enough to cool the CPUs.

what about the building up of impurities, they would need something to remove them before the water gets into the computers as, building such a system and having to clean is would be a huge task.

The whole point is to get rid of heat without using energy. If you use water that has been chilled - it would take energy to do it. They merely found a larger radiator - homes that use heat. The real challenge is to convert heat to cold without using energy. Think of the market - no AC, cooling cars and industry. The planet earth is the best example. It absorbs heat which rises then cools to form rain and in return cools the planet. No other celestial object does this. Our tools are electricity, magnetism and water and yet we can not copy the design of our planet.

To christopher
They did say global 2%, that includes China, Europe, Japan, North America ......
China\'s usage on data centres would a lot more given they have a limited numbers of middle class and want to develop a lot more rapid and don\'t care about the cost or whether they are built to be energy efficient.

The CO2 stuff is just trendy distraction. It's the old principle: a heat pump moves energy from unwanted to wanted areas efficiently. That's all that needed to be said.
CO2 is beneficial, but all mankind's output is trivial noise in the ocean-controlled flux in the atmosphere.