Turning the world on to switching off
It is rare that Sydney has an opportunity to take the high moral ground.
Founded as a dumping ground for British felons, the harbour city has always had a shady reputation - historians say its first crime, a stabbing, was committed 24 hours after the First Fleet dropped anchor in Port Jackson.
No wonder, then, that Sydney's normally jaded citizens are cock-a-hoop about Earth Hour - an event which encourages householders, government agencies and private businesses to turn off their electricity for 60 minutes.
Launched in March last year as a Sydney-only initiative, Earth Hour was designed to show how ordinary citizens could make a small but important impact on global warming by reducing their energy consumption.
Such was the success of the inaugural event - an estimated 2 million Sydneysiders and 2,200 businesses turned off their power last year - that Earth Hour has now gone global: on Saturday, people in 24 cities around the world, including Toronto, Chicago, Copenhagen, Melbourne, Dublin and Tel Aviv, will flick the power switch.
The phenomenal growth of Earth Hour over the past 12 months has taken everyone by surprise, even the organising committee. This year, the number of people participating is expected to reach 25 million. 'We initially set a target of having 10 cities involved, if possible,' Earth Hour executive Andy Ridley says. 'So we were more than delighted when they kept on signing up.'
Mr Ridley believes part of the appeal of Earth Hour - which nicely dovetails with growing concern about global warming, sustainable living and other environmental issues - is its simplicity. 'You can participate in Earth Hour if you are in a village or a city,' he says.
Companies like McDonald's, Lend Lease, Coca-Cola and Westfield have signed up to turn off their lights on Saturday; even the city zoo, Victoria Barracks and the Sydney Opera House will be plunged into darkness.
But Sydney's environmental campaigners are not quite as enthusiastic about Earth Hour, pointing out that the city has a poor record on recycling and waste management and relies almost entirely on electricity generated in outdated and highly polluting coal-fired power stations. The city's global footprint is about to become even larger with the opening of a massive desalination plant in 2010.
'Sydney has a bad record for resources management and energy renewal,' says Jane Castle of the Total Environment Centre. 'There's no mandate on recycling, so the situation is spiralling out of control. For example, waste paper from offices accounts for 10 per cent of all waste going into landfill. That's just ridiculous.'
While praising Earth Hour as a worthwhile public awareness campaign, Ms Castle believes the people of Sydney should not be lulled into a false sense of environmental smugness.
Some people believe Sydney should get its own energy-sapping house in order before it starts preaching to the rest of the world.
'Exactly one year ago my wife and I were in Sydney on vacation and noticed that certain stores on Pitt Street Mall had their air conditioning blowing on high while the doors and windows were wide open,' writes Ted Smit from Canada.