A volunteer during Earth Hour in Bangkok. (AFP)

March 29: People switched off lights for an hour across the world on Saturday night, dimming buildings, hotels and iconic landmarks in a symbolic expression of concern for a planet threatened by global warming.

Up to 30 million people were expected to switch off their lights for 60 minutes by the time Earth Hour — which started at 8pm local time in Suva, Fiji, and Christchurch, New Zealand — completed its cycle westward. People from more than 370 towns and cities scattered across 35 countries have signed up for the campaign.

“Earth Hour shows everyday people are prepared to pull together to find a solution to climate change. It can be done,” said James Leape of the World Wide Fund for Nature, which is running the campaign. “But we need to harness some of the co-operative spirit we’ve seen with Earth Hour to find a global solution,” he said.

Lights at Sydney’s Opera House and Harbour Bridge were put off and Australians had candle-lit beach parties.

In Bangkok, some business districts, shopping malls and billboards went dark. One big hotel invited guests to dine by candlelight and reported brisk business.

There’s no formal Earth Hour initiative in India, but volunteers in seven cities in an energy-hungry country plagued by power cuts had pledged to turn off their lights at 8pm, said Moses Pereira, a spokesman with WWF India.

“India is energy deficient, we still have people with no electricity at all, and with power cuts, some of our cities have Earth Hours daily,” Pereira said. “It’s a purely voluntary action by individuals and businesses.”

Earth Hour organisers said volunteers in Ahmedabad, Bangalore, Mumbai, Chandigarh, Chennai, Delhi and Pune agreed to support the movement. But in parts of Delhi, at least, malls and large building complexes continued to shine during Earth Hour.

The organisers of Earth Hour said while switching off a light for an hour would have little impact on carbon emissions, the fact that so many people were taking part showed the concern over the climate crisis.

In the age of the Internet, the UK arm of search engine Google, too, turned its home page black ahead of time with the message: “We’ve turned the lights out. Now it’s your turn.”