IN COMPUTING, buzzwords are in most cases just that. But the latest, “cloud computing”, stands for a real trend: computing is increasingly being supplied as a service over the internet (depicted as a “cloud” in many charts). Still, there is something wrong with the term.

It implies that by moving into the ether, computing is becoming weightless, with no connection to the resource-constrained real world. In fact the opposite is true. The corollary of more computing in the sky is more and bigger data centres on earth. These are warehouses packed with humming electronic gear, and in particular thousands of servers, the powerful computers that crunch and dish up data. The biggest facilities are the size of half a dozen football pitches and house as many as 80,000 servers (see article). They are huge energy hogs: in America alone, according to the country's Environmental Protection Agency (EPA), data centres already account for 1.5% of electricity consumption.

And this figure is growing. Data centres consumed 0.6% of the world's electricity in 2000, and 1% in 2005. Globally, they are already responsible for more carbon-dioxide emissions per year than Argentina or the Netherlands, according to a recent study by McKinsey, a consultancy, and the Uptime Institute, a think-tank. If today's trends hold, these emissions will have grown four-fold by 2020, reaching 670m tonnes. By some estimates, the carbon footprint of cloud computing will then be larger than that of aviation.

Yet the industry's attitude towards its growing environmental impact is rather unusual: computer-makers actually seem to enjoy drawing attention to it. Not for them the defensive approach favoured by the airlines, which is to emphasise the economic benefits of flying, note what a small share of overall emissions it releases and promise that some wondrous technology will lead to reductions in the distant future. Instead, computer-makers prefer to emphasise the scale of the problem—since that leads naturally to a sales pitch for the various technologies they have devised to mitigate it.

The firms that run data centres are less forthcoming. A research programme set up by the EPA to establish best practice for data centres has signed up only 54 volunteers, the EPA said this week, which suggests that many companies would rather not reveal how inefficient they are. On average, McKinsey and the Uptime Institute found, a third of servers run idle. In most data centres, administrators do not even know which programs run on which servers. “Let's pull the plug and see who calls” is not just a joke. This has prompted industry chatter that data centres risk having regulations imposed upon them if they do not pull their socks up. That would be just fine for vendors, since it would spur sales.

Technologies including multi-core processor chips, more efficient power supplies and smart cooling systems are already available. So too is software that allocates computing resources more efficiently. Where they once boasted about performance, computer-makers now talk about performance-per-watt, and emphasise their energy-saving credentials. “Slash energy consumption up to 45%,” screams an advertisement for Dell, in green type. “Virtualise servers to help maximise performance and reduce energy usage. Implement best practices to enhance efficiency and lower cooling costs.” (It makes a change from talk of gigahertz and terabytes.) Deploying the latest kit could cut the power consumption of data centres in half, according to the EPA.

Doing well by doing good

It is easy to be cynical about all this. However energy-efficient computers become, the bigger task will be to generate electricity using technologies that do not emit carbon dioxide. Yet this is one case when market forces and environmentalism align. A cap-and-trade system or a carbon tax, of course, would make such alignments more commonplace. But even without putting a price on carbon, there are already plenty of examples, as in computing, where adopting more efficient technology would both save money and help the environment.

Greenery does not have to be motivated by altruism; and it is far more likely to be effective when it is not. If it helps to reduce carbon-emissions, self-serving greenery is as good as any other kind. The planet cannot tell the difference.