The simple use of current technology could have a dramatic impact on global warming, if only we would adopt it. The low-energy light bulb and other efficient lighting systems could prevent a cumulative total of 16 billion tons of carbon from being added to the world's atmosphere over the next 25 years, according to a report by the International Energy Agency.
The agency said it would not need any technology that is not already widely available and - far from costing money - it would save more than £1,300bn. The light used for homes and offices is a major cause of climate change and also creates "light pollution", which means that city children grow up never seeing the stars.
The UK Government alone has 50,000 buildings, with a combined annual energy bill of almost £200m, emitting 0.75 tons of carbon a year. Most of these buildings are using inefficient lighting systems. Two years ago, all government departments were given instructions to improve energy efficiency - but the 12-page framework document setting out their targets makes no specific mention of energy-efficient lighting systems.
Tony Blair did, however, make a symbolic gesture towards efficient lighting when he had a low-energy bulb installed in the lamp that hangs outside the door of 10 Downing Street.
Environmental campaigners argue politicians must give a lead on forcing the use of this technology. Writing in The Independent, Stephen Tindale, the executive director of Greenpeace UK, said: "We do not have the luxury of time to allow individuals to save the world ... Governments must act to ensure that we see a peak and then a decline in global emissions of carbon within the next 10 years. Otherwise we run a severe risk of the global climate spiralling out of control."
Artificial light accounts for almost one-fifth of the world's electricity consumption, substantially more than the output of all the nuclear power stations in the world. It generates around 1.9 billion tons worth of carbon a year, equivalent to nearly three quarters of the carbon coming from the exhaust of all the cars and light vehicles in the world.
That is only the start of the problem. Within 25 years, the global demand for artificial light is projected to be almost twice today's level as the developing world moves towards Western living standards. The average American family uses 10 times more artificial light than a Chinese home and more than 30 times as much as an Indian home. And there are 1.6 billion people in the world with no access to electricity at all.
The IEA says the amount of carbon coming from standard light bulbs could rise to three billion tons a year. "Without rapid action, the amount of energy used for lighting will be 80 per cent higher in 2030 than today," Claude Mandil, the executive director of the IEA, said. "However, if we simply make better use of today's efficient lighting technologies and techniques, global lighting energy demand need be no greater at that time."
Light's Labour's Lost, its report, adds to the debate launched a year ago at the G8 summit of the world richest nations in Gleneagles. The report claims: "When the operating costs are considered, they save far more money in avoided energy bills than they cost."
Britain's Lighting Industry Federation says "a substantial proportion, if not a majority" of lighting installations in the UK use inefficient systems, and efficient bulbs and control could reduce the average bill by 30 per cent without any reduction in the amount of light provided.
Adopting the IEA's proposals would put an end to the standard incandescent light bulb, which has been in use since the 1880s. Bulbs like these give off almost 20 times as much heat as light, and, the report warns, might require additional air-conditioning energy for heat removal.
Efficient lighting is such an obviously good idea that the report's authors say it is hard to explain why common sense and market forces have not combined to bring it about. But they point out that efficient lighting can cost more in the short term. The best systems have installation costs and the people who install lighting systems are not the same as the users who will pay the bills.
The IEA report says it is for governments to take the lead through better regulation of the market and by including lighting systems in the building code. China has recently developed a code which, if implemented in every new Chinese building, would "offset the need for a new Three Gorges Dam project every eight years".
Energy-saving vs incandescent
ENERGY-SAVING BULBS (compact fluorescent lights - CFLs)
* An 11-Watt CFL bulb (equivalent to an ordinary 60W bulb) costs £2.41 to run per year.
* Energy-saving bulbs last on average 12 times longer than ordinary light bulbs, with a life span of around six years.
* They cost about £3.50.
* Each bulb can reduce your electricity bill by up to £10 a year.
* They generate up to 70 per cent less heat.
ORDINARY (incandescent) LIGHT BULBS
* An ordinary 60W bulb costs up to £13.14 in electricity bills per year.
* The average life span is between 750 and 1000 hours, which gives round five months of use.
* An ordinary bulb costs around 50p.
* In most houses lighting accounts for approximately 15 per cent of the electricity bill.
* If every American home switched their five most-used light fittings to energy-saving bulbs, they would save $6bn (£3.2bn) and reduce greenhouse gases by nearly half a million tons.
* 90 per cent of the energy goes into generating heat.