ACTING cool will help save the planet, according to top stars, who are setting out to convince the world. They have launched a 10-year campaign to try to make environmentally friendly living fashionable, putting pressure on world leaders to act. The multimillion-pound campaign aims to persuade a billion people worldwide to take simple steps to reduce their emissions of carbon dioxide, the main cause of global warming, by one ton per year.

The stars plan to lead by example, showing how they have already done this - and more - through measures ranging from switching off their televisions at the wall to installing solar panels and driving hybrid cars.

The campaign, called Global Cool, will use pop concerts, webcasts and mass texting to get the message across. The organisers stress that they want to make people feel good by reducing their carbon footprints, rather than guilty about the amount of pollution they produce.

The Scottish singer KT Tunstall will front the campaign; she has personally saved more than four tons of CO2 a year by deciding not to have a car, installing energy-efficient lightbulbs, showering instead of having baths (except when "really tired") and unplugging all her electrical equipment when she is not using it. On top of that, she runs her American tour bus on biodiesel and makes her CDs carbon neutral.

The actors Orlando Bloom, Jude Law and Josh Hartnett have also joined the campaign. And a battery of other stars - including Brad Pitt, Jake Gyllenhaal, 11Cameron Diaz, Leonardo DiCaprio, Julia Roberts and George Clooney - have reduced their footprints through the work of another organisation, the Environmental Media Association, which is forming a partnership with Global Cool.

In the world of music, Pink, the Scissor Sisters, the Killers, Sugababes, Maroon 5 and Razorlight are all supporting the drive.

"So many people are getting involved that it is becoming really quite uncool not to be involved, " says Tunstall.

"It's really shocking when someone tells you how much carbon dioxide is emitted by keeping your phone charger plugged in.

"The music industry has always been trend-led and the culture we live in is so obsessed with celebrity and fashion that they have great power to raise the profile of the issue."

Global Cool is the brainchild of a former music broker and advertising executive, Dan Morrell, who was one of the first to develop the idea of carbon offsetting, reducing the impact of flights and other polluting activities by planting trees and investing in energy-saving programmes.

Ten years ago, he founded Future Forests, now known as the CarbonNeutral Company, using a phrase he coined. But he came to realise that, by itself, this only scratched the surface of the problem. He decided the answer was to persuade people to cut back their emissions by making this "an aspirational lifestyle". He enlisted Hollywood stars, raised finance in the city and, with the help of environmentalists and business people, put together an unusually well-planned campaign.

The idea is that anyone can easily save well over one ton of CO2 a year. Unplugging phone chargers, TVs, DVD players and microwaves when not in use will save 0.9 tons. Turning the central heating thermostat down will save another 0.6, and replacing lightbulbs with energy efficient ones up to 0.4.

For pollution that cannot be reduced, a sophisticated offset scheme has been devised, which aims to help drive up the price of carbon on the market, encouraging businesses to economise. By creating a mass movement, Global Cool's organisers hope to force politicians to take action.

GREEN STARS Kate Bosworth - 1 ton The actress, best known for her role as Lois Lane in Superman Returns, turns off equipment at the wall when she is not using it, making a saving of 0.9 tons a year. Further, the US star buys only local food, making savings of an extra 0.1 tons.

Orlando Bloom 1.3 tons Bloom, who starred as Legolas in the Lord of the Rings trilogy, is in the process of installing solar power at his home, which will save 0.4 tons of CO2 annually. Not leaving appliances in standby mode boosts the Pirates of the Caribbean actor's savings by a further 0.9 tons.

Jake Gyllenhaal - 1.4 tons Gyllenhaal, best known for his role in Brokeback Mountain, saves a ton of CO2 every year by driving a Toyota Prius around LA. The star of Donnie Darko uses compact fluorescent light bulbs, more commonly known as energy-saving light bulbs, saving another 0.4 tons of CO2.

Josh Hartnett 1.6 tons Actor Hartnett ensures he unplugs his phone charger when it is not in use, saving 0.2 tons of CO2, while low-energy bulbs increase his savings by 0.4 tons. But his biggest contribution is the Toyota Prius he has driven for several years, accounting for one ton each year.

Leonardo DiCaprio - 2 tons The Oscar-nominated actor drives a Toyota Prius, which saves one ton of carbon dioxide. He cuts down on elecricity usage with long-life, low-energy light bulbs, which add another 0.4 tons to his savings. DiCaprio also makes another major contribution by recycling his landfill waste, which contributes an extra 0.6 tons.