Most people don't realise that the IT sector has nearly the same carbon footprint as the aviation industry," says Trewin Restorick, chief executive of Global Action Plan, a charity that works to help people from all sectors reduce their impact on the environment.
"If nothing changes," he adds, "computers will overtake aeroplanes in the UK as a source of global warming in the next couple of years."
It is a problem that people are starting to recognise, according Adam Clamp of the Green IT company, who has run seminars on the environmental impact of computers for years.
The good news, he says, is that, unlike aviation, IT is something the average charity can do something about - and often in a way that brings big financial savings at the same time.
"The big problems with computers are energy use and hazardous components," he says. "Computers give off a lot of heat and use a lot of power. They can also contain harmful products such as lead, cadmium and mercury. If not recycled properly, they can do a lot of damage to the environment. And of course, whole communities can be damaged by the mining that is needed to get these products out of the ground in the first place.
"As well as helping the environment, cutting energy will save you money, too. And if the two go hand in hand, great."
The easiest start to a green IT policy, he says, is to buy the right products. With a fairly small outlay, he suggests, this can slice your IT carbon footprint in half - and then maybe in half again.
"If you buy the right equipment," he says, "your computers could use less wattage than a standard lightbulb."
He says laptops use less power and are often more flexible. "Check whether your computers need the capacity you're buying," he suggests. "A lower-spec machine will use less power. Look for power supplies that comply with the US government's Energy Star rating. This can cut the amount of power a machine draws by two-thirds. Ask suppliers what the computer is made of, and think about how you will get rid of something later - make sure that anything you buy is compliant with various regulations for computer disposal."
Of course, many charities are not in the position to buy new computers. Even for these, however, there are plenty of ways to save energy. And growing numbers of people are providing advice on energy- efficient offices.
For small charities in London, Global Action Plan offers five-day eco-audits. And charitable foundations have also offered grants for free green support. "We find a lot of simple things charities can do that make a big difference," said Donnachadh McCarthy, an independent eco-auditor who has worked with the City Bridge Trust, which has a programme designed to help charities reduce their carbon footprints.
He recommends installing timers to turn off photocopiers and printers at night, installing 'night-watchman software' on office computers to make them function as efficiently as possible, and using software to measure energy use.
GAP's Restorick says a lot of energy is wasted in running network servers. "Most servers run at 10 to 15 per cent of their capacity," he says. "And a server in an office of 50 people has the same carbon footprint as a 4x4 vehicle. The trouble is, most IT departments aren't responsible for paying the energy bills, so they have looked only at hardware costs. But that's changing."
Server efficiency can often be increased, he says, through virtualisation - where one computer runs several 'virtual' operating systems, letting it emulate different machines.
He cautions, however, that green changes cannot be pushed through without staff backing. "One thing you can do is appoint an environmental champion to identify ways to save energy and to encourage other workers," he says. "Staff often become committed to the projects. We've had volunteers go round the office during the night to tie red balloons to monitors that were left on and green ones to monitors that were turned off. That was effective at changing behaviour."
But do the experts believe that such behaviour can be widespread in the charity sector? Restorick is confident that it can - if only because it will become necessary. "It's been a slow response from the sector," he says, "but external pressures will begin to take effect. Funding bodies are giving grants for green behaviour. Funders and local authorities are asking more questions about green credentials."
McCarthy agrees that change is coming. "Charities are starting to understand that all their beneficiaries are affected by the environment," he says, "from the elderly who die in heatwaves, to the poor in Asia displaced by rising sea levels. Everyone needs to have an environmental policy."
CASE STUDY - CFDG
One small organisation that has begun to take steps to reduce its carbon footprint is umbrella body the Charity Finance Directors' Group. "We started looking at how charities could report on green issues," says David Membrey, CFDG's deputy chief executive. "We thought we couldn't ask anyone to do what we're not doing ourselves.
"There's technology that can help. We had a fax machine and two printers. We're replacing them with one machine that will do all three jobs at half the cost.
"And we bought remote switches for our plugs for £50, which means we can easily turn computers off at the wall and save energy. But the main thing is a change of habit - making sure computers are turned off. It's no extra work, and it makes a difference."