The Guardian hazards a guess at how much CO2 is emitted by our use of the Internet. While the findings don't account for emissions offset by our use of the Web (shopping online, for example, saves a trip to the mall), they are still surprisingly low: "as much as all the coal, oil and gas burned in Turkey or Poland in one year, or more than half of those burned in the UK." And if the Koomey Corollary to Moore's Law holds up, that might be even further reduced over time.
By Gartner's figures, the world's PCs and monitors are even more power hungry, accounting for around 40% of the total ICT energy demand and 0.8% of global CO2 emissions. If we decided (somewhat arbitrarily) that half of the emissions from all these laptop and desktop machines were down to internet-based activity, and then add on the emissions from the data centres that make all this online activity possible, then the internet would clock in at around 1% of all the CO2 emissions released from burning fossil fuels. Put another way, the internet releases around 300m tonnes of CO2.
Read the full story at The Guardian.