In this combo photo large electronic billboards stand dark (R) on Times Square as their lights were turned off to mark 'Earth Hour' in New York, March 23, 2013. More than 150 countries across the world, switched off their lights for an hour at 20:30 local time to support action to create a sustainable future for the planet.

This combination photo shows the Eiffel Tower submerging into darkness at 8:30 p.m. local time as part of the Earth Hour switch-off March 23, 2013, in Paris.

Earth Hour was marked worldwide at 8.30 p.m. local time and is a global call to turn off lights for 60 minutes in a bid to highlight global climate change.

A photo combination shows Elizabeth Tower, which houses Big Ben at the Houses of Parliament in London, illuminated, left, and then in darkness as the lights were turned off to mark Earth Hour 2013 March 23, 2013.

The London Eye and London skyline can be seen before, left, and after the population of the city observed Earth Hour March 23, 2013.

In this photo combination, the Belarusian National Library is seen before and after the lights are turned off during the worldwide Earth Hour, a global campaign to highlight the threat of climate change, in Minsk, Belarus, March 23, 2013.

This combination picture shows the Serbian National Assembly building in Belgrade before and after submerging into darkness as part of the Earth Hour switch-off March 23, 2013.

The Parthenon temple stands atop the Acropolis before and during the annual Earth Hour in Athens, Greece, March 23, 2013. In Greece, floodlights on several monuments and public buildings were switched off for one hour at 8:30 p.m. local time; thousands of businesses and municipalities also dimmed their lights.

In this composite image, Hong Kong buildings, with the HSBC building in the middle, are seen before and after the lights were switched off to recognize Earth Hour March 23, 2013.

Photos show the Taipei 101 Building before and after turning off its lights to mark Earth Hour in Taipei, Taiwan, March 23, 2013. Organized by the World Wide Fund for Nature, Earth Hour is observed every year to create awareness about conserving energy and climate change.

Empty flagpoles frame a darkened Taipei 101 building during Earth Hour, Saturday, March 23, 2013, in Taipei, Taiwan.

The Singapore city skyline is seen before and after the lights were switched off to recognize Earth Hour March 23, 2013. Businesses and households around the world switched their lights off for an hour at 8:30 p.m. local time to celebrate Earth Hour and to raise awareness about climate change and renewable energy.

Earth Hour began in Australia in 2007, and is now celebrated in more than 150 countries around the world.

People participate in Dance 2 Power Earth Hour at the Marina Floating Platform March 23, 2013, in Singapore. Kinetic energy generated from footsteps are converted to electricity, which is stored and used for the outdoor film screening.

This combination of pictures of Moscow shows the Kremlin, left, GUM (State Universal Shop) and St. Basil's Cathedral, right, with lights on and off, during Earth Hour March 23, 2013. Iconic landmarks and skylines were plunged into darkness as the Earth Hour switch-off of lights around the world got under way to raise awareness of climate change.

In this combination photo, the Indian Presidential Palace in New Delhi is seen lit and then in darkness when the lights were turned off to mark Earth Hour March 23, 2013.

Lanterns are displayed during Earth Hour at a hotel in Nusa dua on the resort island of Bali March 23, 2013. Bali is participating in the global campaign for Earth Hour.

A tourist looks at the moon through a telescope during an Earth Hour event at a hotel in Nusa dua on the resort island of Bali March 23, 2013.

This combination photograph shows the lighted Welcome Monument, located in central Indonesia's capital city of Jakarta, before and during Earth Hour March 23, 2013. Iconic landmarks and skylines were plunged into darkness as the annual switch-off of lights to raise awareness of climate change got under way around the world.

With more than 150 countries taking part in last year's event, the movement has spread even further this year, with the Palestinian Territories, Tunisia, Suriname and Rwanda joining the global commemoration.

An Indonesian girl holds a candle during Earth Hour in Jakarta, Indonesia, March 23, 2013. Hundreds gathered in Jakarta to observe the global event that encourages people to turn off their lights for 60 minutes.