Its exact purpose is a bit vague, but here is what its web site says:
In 2009, Earth Hour is being taken to the next level, with the goal of 1 billion people switching off their lights as part of a global vote. Unlike any election in history, it is not about what country you’re from, but instead, what planet you’re from. VOTE EARTH is a global call to action for every individual, every business, and every community. A call to stand up and take control over the future of our planet. Over 74 countries and territories have pledged their support to VOTE EARTH during Earth Hour 2009, and this number is growing everyday.
Here is my problem with Earth HourMany people, having switched off the electric lights, will light candles. These give a warm glow to accompany the moral glow of satisfaction in being part of a global eco-happening. These candles will emit many thousands of tonnes of greenhouse gases into the atmosphere. A candle emits the same amount of combustion products as a 60 Watt incandescent lamp running on electricity from a coal-fired power plant. But it gives only one-seventieth as much light.
Most candles are made from fossil hydrocarbons (80%). Some are made from beeswax or plant oils, so at least they are not as large net contributors to greenhouse gas emissions. If you are going to light up (a candle) during Earth Hour use one made from a renewable form of wax, or use an oil lamp.
WWF, the global conservation organization which is promoting the event, says "Earth Hour 2009 aims to reach more than 1 billion people in 1000 cities around the world, inviting communities, business and governments to switch off lights for 1 hour and send a global message that we need to take action on climate change."
I hope those one billion people use the time to write, or at least compose, letters to their political leaders urging real action on climate change. Darkness is cheap. Change is work.