The Internet produces 300 million tonnes of carbon dioxide a year, equivalent to everyone in the UK flying to America and back, twice over.
According to an article published today by UK newspaper The Guardian, data centres account for around half a per cent of all global carbon emissions, with the total estimated output for all Internet-related activity amounting to around one per cent of global man-made CO2.
That's equivalent to all of the fossil fuels burned in Poland or Turkey in a year, or half those burned in the UK.
The estimate of the environmental cost of cyberspace comes from a recent book, How Bad Are Bananas?, by environmental consultant Mike Berners-Lee, brother of world-wide web pioneer Tim.
The news isn't all bad, though: Berners-Lee notes that Internet-based services such as videoconferencing could go some way to reducing the need for other more environmentally damaging activities such as long-haul air travel.
Recent figures suggest the UK's carbon emissions have dipped 8.6 per cent over the last year, chiefly due to a decline in manufacturing output, as we've shifted all that to China.