The World Wildlife Fund's (WWF) Earth Hour is an annual global event held on the last Saturday of March, in which participants turn off non-essential electrical appliances for an hour in order to raise awareness on climate change. This picture provided by Commonwealth Edison shows buildings in downtown Chicago darkened during Earth Hour 2009 on Saturday, March 28, 2009. The Wrigley Building is seen at center.
Eric Y. Exit/Commonwealth Edison/AP
WWF activists stood with candles as The Rialto Bridge lights are turned off, in Venice, Italy, Saturday, March 28, 2009. From the Great Pyramids to the Acropolis, the London Eye to the Las Vegas strip, nearly 4,000 cities and towns in 88 countries planned to join in the Earth Hour, a time zone-by-time zone plan to dim nonessential lights between 8:30 p.m. and 9:30 p.m.
People ride pushed bikes fitted with custom-made electric generators in Melbourne, Australia, Saturday, March 28, marking Earth Hour 2009. Called Future Spark, the activity ran from March 23 to the 28, finishing at the completion of Earth Hour, and generated enough power to run a free open-air concert.
A night view of the site of the ancient Giza Pyramids during Earth Hour, in Cairo, Egypt on Saturday, March 28, 2009.
A combination picture shows the landmark St. Stephens tower of the Houses of Parliament in central London during Earth Hour, left, and right, with its lights back on, Saturday, March 28, 2009. The campaign began in Sydney, Australia in 2007.
A man wearing a traditional costume held a candle to support Earth Hour in Jakarta March 28, 2009. The World Wildlife Fund's stated goal for Earth Hour 2009 was for one billion participants.
The Las Vegas Strip is pictured, much darker than usual on a Saturday night, during the one hour call to action for climate change on Saturday, March 28, 2009, in Las Vegas, Nev.
A combination photo shows the Empire State building before (top) and during Earth Hour in New York March 28. 2008 was the first year the Empire State Building, along with many other American architectural icons, was darkened for Earth Hour.
Cars passed in front of the Greek Parliament whose lights have been dimmed during Earth Hour in Athens, on Saturday March 28, 2009. In Greece, floodlights in several monuments and public buildings were switched off for one hour at 8:30 p.m. local time. Thousands of companies and municipalities also dimmed their lights.
A man held a candle during an Earth Hour event in Guatemala City March 28, 2009. Cities around the world saw large dips in electricity use, Saturday, including a decrease of 1000MW in Delhi, a 15.1% decrease in Toronto, and a drop of 140,000 kWh in Vietnam.
This picture shows buildings that have turned off their nonessential lights during Earth Hour at the main roundabout at the main business district in Jakarta, Indonesia, Saturday, March 28, 2009.