AVIATION has long been blamed for its share of anthropogenic global warming. Indeed, some travellers now ask themselves whether their flight is strictly necessary and, if they decide it is, salve their consciences by paying for the planting of trees. These, so they hope, will absorb the equivalent of their sinful emissions. But you, dear reader, are indulging right now in activity that is equally as polluting as air travel: using a computer.

According to a report published by the Climate Group, a think-tank based in London, computers, printers, mobile phones and the widgets that accompany them account for the emission of 830m tonnes of carbon dioxide around the world in 2007. That is about 2% of the estimated total of emissions from human activity. And that is the same as the aviation industry's contribution. According to the report, about a quarter of the emissions in question are generated by the manufacture of computers and so forth. The rest come from their use.

EPA

Down on the server farm

The same report estimates that the spread of computers will increase these associated emissions by about 6% a year until 2020, when one person in three will own a personal computer, half will have a mobile phone and one household in 20 will have a broadband internet connection. Yet computing can also be used to tackle climate change. For example, domestic consumption could be cut by the large-scale employment of smart meters in houses and flats. Households are the biggest users of electricity after manufacturing and transport. In Britain, they accounted for 29% of consumption in 2004, according to a government report.

Small and medium-sized businesses, meanwhile, could save electricity by switching to distributed computing, rather than running their own servers. The delivery of computer services over the internet, from vast warehouses of shared machines, enables firms to hand over the running of their e-mail, customer databases and accounting systems to someone else. Companies that do so use computers more efficiently and thus reduce not only their costs but also their carbon footprints.

Another way to improve the situation is virtualisation—the creation of “virtual” machines (ie, software emulations of separate computers) so that multiple operating systems and applications can run on the same piece of physical kit. Sun Microsystems, a maker of servers, reckons that 70% of the servers in most organisations have only one application running on them. Consolidating these applications onto fewer and fewer machines, courtesy of virtualisation, would be more efficient and thus greener.

Ironically, of course, environmental research itself relies heavily on computers. So, perhaps the best thing the home user can do is donate his inefficiencies to the cause by signing up to climateprediction.net, which uses the idle capacity of home computers to test the accuracy of various computer models of the climate.