If the previous two 'Earth Hour' events were successful in calling attention to climate change, then this year's edition can fairly be described as an unprecedented blockbuster. From the remote Chatham Islands in the southern Pacific Ocean to Sydney's Opera House to the Eiffel Tower to the Empire State Building to Seattle's Space Needle, lights dimmed for an hour in a symbolic call to action on the environment front.

It began over the Chatham Islands on 28 March, and from there, time zone by time zone, Earth Hour 2009 marched around the globe, with hundreds of cities and communities and millions of individuals dimming or dousing their lights. In all, nearly 1,000 global landmarks went dark for an hour, including the dome of St. Peters in the Vatican and the Christ the Redeemer statue overlooking Rio de Janeiro.

While Earth Hour sponsor Worldwide Fund for Nature (better known by its old name of World Wildlife Fund) did not have full data yet, it estimated that the participation far exceeded that of 2008, when some 53 million people in 371 cities in 35 countries participated. The 2007 inaugural Earth Hour was limited to Sydney, Australia.

World leaders are scheduled to meet in Copenhagen, Denmark, in December to hammer out more climate change controls. Yvo de Boer, the United Nations' top climate change official, said Earth Hour marked a global momentum to seek climate change mandates in the Kyoto Protocol, including controlling heat emissions.

WWF officials called Earth Hour the first-ever global vote on the future of the planet. "The true power of Earth Hour can be seen in the tremendous opportunity for individuals, communities, businesses and governments around the world to unite for a common purpose, against a common threat which affects us all," said US WWF president and chief executive Carter Roberts.

"As the world witnessed Saturday night, the simple action of turning off lights can inspire people around the world to take action and to make a serious long-term commitment to living more sustainable lives," he added.

Earlier, UN secretary-general Ban Ki-moon had described Earth Hour as the largest demonstration of public concern about climate change ever attempted. "Earth Hour is a way for the citizens of the world to send a clear message they want action on climate change," said Ban.

Demand plummets in Delhi
The demand for power in New Delhi fell by as much as 1,000 mw on Saturday evening, when many city residents and establishments switched off their lights. While state power department officials admitted that the pleasant weather following evening showers, along with breakdowns, contributed significantly to the drop in demand, they said the campaign itself resulted in electricity savings of about 500-550 mw.

A majority of power guzzlers like hotels, monuments, industries and commercial units - many of them closed anyway at that hour - had pledged to be part of the event, but experts said the major contributors were the residents of Delhi, as up to 65 per cent of the power load in the evenings comes from the domestic sector.

''I was monitoring the situation last evening and there was a considerable dip in demand. We have to also take into account the cool weather on Saturday,'' said power secretary Rajendra Kumar. He added that power distribution companies played a big role in spreading awareness about Earth Hour.

Meanwhile, Tamil Nadu says it saved 1.6 crore units of power, during Earth 

Hour, sources in the transmission department of the Tamil Nadu Electricity Board told the Times of India. Hundreds of homes, offices and restaurants switched off power on Saturday and used candles instead, resulting in savings in electricity on a large scale.

Similar figures for the country's financial capital, Mumbai, and other parts of the country were not made available.