Data centres emit 0.3% of world’s carbon dioxide emissions…

… which is about half the amount the airline industry currently emits per year, according to a recent report by McKinsey, entitled Revolutionizing Data Centre Efficiency.
They isolate the primary drivers of poor inefficiency as:

• Poor demand and capacity planning within and across functions (business, IT, facilities)
• Significant failings in asset management (6% average server utilization, 56% facility utilization)
• Boards, CEOs, and CFOs are not holding CIOs accountable for critical data center facilities CapEx and data center operational efficiency

Their recomendations to improve the efficiency of data centres include transferring financial accountability of data center assets from Corporate Real Estate to the CIO and the appointment of an Energy Czar (presumably in the US).

In true McKinsey style there is a Power Point presentation (8mb) and an mp3 (22mb) that can be downloaded for those who would like further details.

UPDATE, 22/06/2009: For anyone interested in understanding the architecture and carbon footprint of data centres, this New York Times article is well worth reading.