Sydney residents embraced their second annual Earth Hour with candlelight dinners and beach bonfires.
"This provides an extraordinary symbol and an indication that we can be part of the solution" to global warming, Australian Environment Minister Peter Garrett told Sky News television, standing across the harbor from the dark silhouette of the Opera House.
Following Asia, the lights will go out in Europe and then North America as dusk descends there too. One of the last major cities to participate will be San Francisco - where the Golden Gate Bridge, the Bay Bridge and office towers throughout the city planned to go dark. Some restaurants plan to turn off exterior lights and offer candlelight dinners. Atlanta, Chicago and Phoenix were also taking part.
Sydney's business district was mostly dark; organizers said 250 of the 350 commercial buildings there had pledged to shut off their lights completely, and 94 of the top 100 companies on the Australian stock exchange were also participating.
Organizers were hoping to beat last year's debut, when 2.2 million people and more than 2,000 businesses shut off lights and appliances, resulting in a 10.2 percent reduction in carbon emissions during that hour.
"I'm putting my neck on the line but my hope is that we top 100 million people," Earth Hour Australia chief executive Greg Bourne said.
This year 26 major world cities and more than 300 other cities and towns have signed up to participate.
New Zealand and Fiji kicked off the event. In Christchurch, New Zealand, more than 100 businesses and thousands of homes were plunged into darkness, computers and televisions were switched off and dinners delayed from 8 to 9 p.m. Suva, Fiji, in the same time zone, also turned off its lights.
Auckland's Langham Hotel switched from electric lights to candles as it joined the effort to reduce the use of electricity, which generates creates greenhouse gases that contribute to global warming.
WWF Thailand said the campaign in Bangkok saved 73.34 megawatts of electricity, which would have produced 45.8 tons of carbon dioxide.
In Manila, the grounds of the seaside Cultural Center of the Philippines went dark after four city mayors ceremonially switched off its lights. Street lamps around Manila were shut off.
Even popular search engine Google put its support behind Earth Hour, with a completely black page and the words: "We've turned the lights out. Now it's your turn."