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In this two photo combination picture, the landmark India Gate is seen lit, top, and then the same location in darkness when the lights are turned out for one hour to mark Earth Hour, in New Delhi, India, Saturday, March 23, 2013. 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 the global climate change. (AP Photo/Altaf Qadri) ( India Earth Hour )

This combo image shows the Parthenon temple standing atop the Acropolis hill before and after turning off lights, to mark the annual Earth Hour in Athens, on Saturday March 23, 2013. In Greece, floodlights in 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. (AP Photo/Kostas Tsironis) ( Greece Earth Hour )

In this two photo combination picture, the Indian Presidential Palace is seen lit, top, and then the same location in darkness when the lights are turned out for one hour to mark Earth Hour, in New Delhi, India, Saturday, March 23, 2013. 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 the global climate change. (AP Photo/Altaf Qadri) ( India Earth Hour )

These combo photos show the Taipei 101 Building before, left, and after, right, turning off its lights to mark the Earth Hour in Taipei, Taiwan, Saturday, March 23, 2013. Organised by the World Wide Fund for Nature, earth hour is observed every year to create awareness about conservation of energy and climate change. Around the world, people and organisations will be turning their lights off from 8:30 to 9:30 pm local time. (AP Photo/Chiang Ying-ying) ( Taiwan Earth Hour )

Senior Vice President of ComEd Fidel Marquez, ComEd customer Kathy Reiser, her children Caitlin and Ramsey, Navy Pier director of External Communications Nick Shields and Ald. Brendan Reilly, 42 Ward, pose for a photo as they turn off the lights of the Ferris Wheel at Navy Pier in observation of Earth Hour in Chicago on Saturday, March 23, 2013. (AP Photo/ComEd, Charles Osgood) ( Earth Hour )

Muslim women light candles during the "EarthHour" in Jakarta, Indonesia, Saturday, March 23, 2013. Hundreds of people gathered in Jakarta Friday to observe the global event that encourages people to turn off their lights for 60 minutes. (AP Photo/Dita Alangkara) ( APTOPIX Indonesia Earth Hour )

A two photo combination showing the 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, Saturday March 23, 2013. 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 the global climate change. (AP Photo/PA, Lewis Whyld) ( Britain Earth Hour )

A combination picture shows the financial Central District of Hong Kong (top) before Earth Hour, and during Earth Hour March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher action to confront climate change. REUTERS/Bobby Yip ( HONGKONG/ )

A combination picture shows the world largest LCD screen at a shopping mall before Earth Hour (top) and during Earth Hour in Beijing March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher action to confront climate change. Picture taken with fisheye lens. REUTERS/Kim Kyung-Hoon ( CHINA/ )

People hold candles during an event attempting to establish a Guinness World of Record for "Blowing out the most number of candles simultaneously" during Earth Hour in Shanghai March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher action to confront climate change. REUTERS/Carlos Barria ( CHINA/ )

People hold candles during an event attempting to establish a Guinness world record for "blowing out the most number of candles simultaneously" during Earth Hour in Shanghai March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher actions to confront climate change. REUTERS/Carlos Barria ( CHINA/ )

Children hold candles while participating in a candlelight vigil to mark Earth Hour in Mumbai March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher actions to confront climate change. REUTERS/Danish Siddiqui ( INDIA/ )

A combination photo shows the Khan Shatyr Shopping and Entertainment Center before (top) and during Earth Hour in Astana March 23, 2013. Earth Hour, when everyone around the world is asked to turn off the lights for an hour from 8.30pm local time, is meant as a show of support for tougher actions to combat climate change. REUTERS/Shamil Zhumatov ( KAZAKHSTAN/ )

A combination picture shows the Turtle tower after (top) and during Earth Hour in Hanoi March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher action to confront climate change. REUTERS/Kham ( VIETNAM )

Students gather around candles during Earth Hour in Hanoi March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher action to confront climate change. REUTERS/Kham ( VIETNAM )

A combination picture shows the Brandenburger Tor gate during Earth Hour in Berlin March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher action to confront climate change. REUTERS/Tobias Schwarz ( GERMANY/ )

A combination photo shows the Bosphorus Bridge that links the city's European and Asian sides, with the European side in the background, is seen before (top) and during Earth Hour in Istanbul March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher action to confront climate change. REUTERS/Murad Sezer ( TURKEY/ )

A combination picture shows the National Library of Belarus before (top) and after the lights are turned off during "Earth Hour" in Minsk, March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher action to confront climate change. REUTERS/Vasily Fedosenko ( BELARUS/ )

A combination photo shows a view of St. Basil's Cathedral, Red Square and the Kremlin before (top) and during Earth Hour in Moscow March 23, 2013. Earth Hour, when everyone around the world is asked to turn off the lights for an hour from 8.30pm local time, is meant as a show of support for tougher actions to combat climate change. REUTERS/Mikhail Voskresensky ( RUSSIA/ )

A combination photo shows a view of a Stalin era skyscraper on the Moscow River before (L) and during Earth Hour in Moscow March 23, 2013. Earth Hour, when everyone around the world is asked to turn off the lights for an hour from 8.30pm local time, is meant as a show of support for tougher actions to combat climate change. REUTERS/Mikhail Voskresensky ( RUSSIA/ )

A combination photo shows the monument "Mother Motherland" before (top) and during Earth Hour in Kiev March 23, 2013. Earth Hour, when everyone around the world is asked to turn off the lights for an hour from 8.30pm local time, is meant as a show of support for tougher actions to combat climate change. REUTERS/Sergii Polezhaka ( UKRAINE/ )

People hold candles during Earth Hour after the lights were turned off in central Amman March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher actions to confront climate change. Picture taken with long exposure. REUTERS/Ali Jarekji ( JORDAN/ )

A combination picture shows the city skyline of Frankfurt on the banks of Main river before (top) Earth Hour and during Earth Hour in Frankfurt March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30pm local time, is meant as a show of support for action to confront climate change. REUTERS/Lisi Niesner ( GERMANY/ )

A combination picture shows Hofburg Palace before (top) and during Earth Hour in Vienna March 23, 2013. Earth Hour, when everyone around the world is asked to turn off the lights for an hour from 8.30 pm local time, is meant as a show of support for tougher actions to combat climate change. REUTERS/Heinz-Peter Bader ( AUSTRIA/ )

Emiratis light candles to mark Earth Hour near Burj Khalifa in Dubai, March 23, 2013. Earth Hour, when everyone around the world is asked to turn off the lights for an hour from 8.30pm local time, is meant as a show of support for tougher actions to combat climate change. REUTERS/Jumana El Heloueh ( DUBAI/ )

A combination of pictures shows the medieval Charles Bridge in Prague before (top) and during Earth Hour March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher action to confront climate change. REUTERS/Petr Josek ( CZECH/ )

The Royal Castle in Warsaw is seen during (top) and illuminated minutes before the start of Earth Hour, in this combination picture taken March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher action to confront climate change. REUTERS/Peter Andrews ( EARTH HOUR-POLAND/ )

The UNESCO World Heritage Cologne Cathedral and the Hohenzollern railway bridge along the river Rhine, is seen during (top) and before Earth Hour, in this combination picture taken March 23, 2013. Earth Hour, when everyone around the world is asked to turn off the lights for an hour from 8.30 pm local time, is meant as a show of support for tougher actions to combat climate change. REUTERS/Wolfgang Rattay ( GERMANY/ )

Yasmin Nunes, a student, holds a candle during celebrations of Earth Hour, organized by WWF Brazil, at the Museum of the Republic in Brasilia March 23, 2013. Earth Hour, when everyone around the world is asked to turn off the lights for an hour from 8.30 pm local time, is meant as a show of support for tougher actions to combat climate change. REUTERS/Ueslei Marcelino ( EARTHHOUR/ )

Earth Hour is observed at Berlin's Brandenburg Gate, the Cologne Cathedral and in Frankfurt's city centre (L-R) during (top) and before the lights were switched off, in this combination picture taken March 23, 2013. Earth Hour, when everyone around the world is asked to turn off the lights for an hour from 8.30 pm local time, is meant as a show of support for tougher actions to combat climate change. REUTERS/Tobias Schwarz/Wolfgang Rattay/Lisi Niesner ( GERMANY/ )

People gather with candles during an event of Earth Hour, organized by WWF Brazil, at the Museum of the Republic in Brasilia March 23, 2013. Earth Hour, when everyone around the world is asked to turn off the lights for an hour from 8.30 pm local time, is meant as a show of support for tougher actions to combat climate change. REUTERS/Ueslei Marcelino ( EARTHHOUR/ )

A combination photo shows the "Puente Nuevo" (New Bridge) seen from the terrace of a house with a statue of a cow in the day (top), at night (C) and during Earth Hour in Ronda, near Malaga March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher actions to confront climate change. REUTERS/Jon Nazca ( EARTHHOUR/ )

A combination photo shows the "Puente Nuevo" (New Bridge) in the day (top), at night (C) and during Earth Hour in Ronda, near Malaga March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for tougher actions to confront climate change. REUTERS/Jon Nazca ( EARTHHOUR/ )

The Bandeiras monument is seen during (bottom) and before Earth Hour in Sao Paulo, in this combination picture taken March 23, 2013. Earth Hour, when everyone around the world is asked to turn off the lights for an hour from 8.30 pm local time, is meant as a show of support for tougher actions to combat climate change. REUTERS/Paulo Whitaker ( BRAZIL/ )

The Chicago skyline is seen before (top) and during Earth Hour in Chicago, Illinois, in this combination picture made March 23, 2013. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 p.m. local time, is meant as a show of support for action to confront climate change. REUTERS/Jim Young ( USA-EARTHHOUR )

Empty flag poles frame a dark Taipei 101 building as it observes international "Earth Hour" campaign by switching off its lights for 60 minutes, Saturday, March 23, 2013, in Taipei, Taiwan. (AP Photo/Wally Santana) ( Taiwan Earth Hour )

Combination photos. The 'London Eye' and London skyline can be seen before (left) and after (right) the population of the city observed Earth Hour on Saturday, March 23, 2013. Earth Hour Global is a worldwide event organized by the World Wide Fund for Nature (WWF) encouraging households and businesses to turn off their non-essential lights for one hour to raise awareness about the need to take action on climate change. The event is designed to highlight the impact climate change is having on people and nature. Millions of people in more than 150 countries are expected to take part. Earth Hour 2013 is being held on March 23, 2013 from 8:30 p.m. to 9:30 p.m. during participants' local time. (Richard Stonehouse for WWF/Earth Hour Globa via AP Images) ( WWF/Earth Hour Global Event Observed in London )

In this composite image the Luna Park entrance is seen before on March 21 (top) and after the lights were switched off to recognize Earth Hour on March 23, 2013 in Sydney, Australia. Businesses and households around the world will turn their lights off for on hour at 20:30 local time today, to celebrate Earth Hour, raise awareness about climate change and to show support for the use of renewable energy. Earth hour began in Sydney in 2007 and is now celebrated in over 150 countries around the world. (Photo by Lisa Maree Williams/Getty Images) ( 164369325 )

In this composite image the Sydney Harbour Bridge is seen before on March 21 (top) and after the lights were switched off to recognize Earth Hour on March 23, 2013 in Sydney, Australia. Businesses and households around the world will turn their lights off for one hour at 20:30 local time today, to celebrate Earth Hour, raise awareness about climate change and to show support for the use of renewable energy. Earth hour began in Sydney in 2007 and is now celebrated in over 150 countries around the world. (Photo by Lisa Maree Williams/Getty Images) ( 164369406 )

SINGAPORE - MARCH 23: (EDITORS NOTE: Image is a digital composite.) The Arts and Science Museum and the Singapore city skyline is seen before (left) and after the lights were switched off to recognize Earth Hour on March 23, 2013 in Singapore, Singapore. Businesses and households around the world switch their lights off for an hour at 20:30 local time on March 23, to celebrate Earth Hour and raise awareness about climate change and renewable energy. Earth hour began in Australia in 2007 and is now celebrated in over 150 countries around the world. (Photo by Suhaimi Abdullah/Getty Images) ( 164371210 )

SINGAPORE - MARCH 23: (EDITORS NOTE: Image is a digital composite.) The Louis Vuitton boutique and the Singapore city skyline is seen before (top) and after the lights were switched off to recognize Earth Hour on March 23, 2013 in Singapore, Singapore. Businesses and households around the world switch their lights off for an hour at 20:30 local time on March 23, to celebrate Earth Hour and raise awareness about climate change and renewable energy. Earth hour began in Australia in 2007 and is now celebrated in over 150 countries around the world. (Photo by Suhaimi Abdullah/Getty Images) ( 164371205 )

SINGAPORE - MARCH 23: (EDITORS NOTE: Image is a digital composite.) The ArtScience Museum and the Marina Bay Sands is seen before (top) and after the lights were switched off to recognize Earth Hour on March 23, 2013 in Singapore, Singapore. Businesses and households around the world switch their lights off for an hour at 20:30 local time on March 23, to celebrate Earth Hour and raise awareness about climate change and renewable energy. Earth hour began in Australia in 2007 and is now celebrated in over 150 countries around the world. (Photo by Suhaimi Abdullah/Getty Images) ( 164371212 )

BEIJING, CHINA - MARCH 23: This composite photograph shows a huge LED sky screen before and during the Earth Hour 2013 power switch off at the Central Business District on March 23, 2013 in Beijing, China. Earth Hour, launched in 2007 in Australia by the World Wide Fund for Nature (WWF), a global conservation group, calls on people, organizations and cities to turn off their non-essential lights for one hour starting at 8:30 p.m. local time. (Photo by Feng Li/Getty Images) ( 164374174 )

BEIJING, CHINA - MARCH 23: This composite photograph shows Sanlitun Village before and during the Earth Hour 2013 power switch off on March 23, 2013 in Beijing, China. Earth Hour, launched in 2007 in Australia by the World Wide Fund for Nature (WWF), a global conservation group, calls on people, organizations and cities to turn off their non-essential lights for one hour starting at 8:30 p.m. local time. (Photo by Feng Li/Getty Images) ( 164376062 )

HONG KONG - MARCH 23: (L-R) The Bank of China Tower, Cheung Kong Centre, The HSBC Building and Standard Charter building are seen before the lights were switched off to recognize Earth Hour on March 23, 2013 in Hong Kong. Businesses and households around the world will turn their lights off for on hour at 20:30 local time today, to celebrate Earth Hour, raise awareness about climate change and to show support for the use of renewable energy. Earth hour began in Australia in 2007 and is now celebrated in over 150 countries around the world. (Photo by Jessica Hromas/Getty Images) ( 164437545 )

HONG KONG - MARCH 23: The HSBC Building (C) and the Standard Charter Bank Building (R) are seen after the lights were switched off to recognize Earth Hour on March 23, 2013 in Hong Kong. Businesses and households around the world will turn their lights off for on hour at 20:30 local time today, to celebrate Earth Hour, raise awareness about climate change and to show support for the use of renewable energy. Earth hour began in Australia in 2007 and is now celebrated in over 150 countries around the world. (Photo by Jessica Hromas/Getty Images) ( 164437556 )

HONG KONG - MARCH 23: (L-R) The Bank of China Tower, Cheung Kong Centre, The HSBC Building and Standard Charter building are seen in the dark after the lights were switched off to recognize Earth Hour on March 23, 2013 in Hong Kong. Businesses and households around the world will turn their lights off for on hour at 20:30 local time today, to celebrate Earth Hour, raise awareness about climate change and to show support for the use of renewable energy. Earth hour began in Australia in 2007 and is now celebrated in over 150 countries around the world. (Photo by Jessica Hromas/Getty Images) ( 164437560 )

HONG KONG - MARCH 23: The HSBC building (red lights) and in the blue lights the Standard Charter Bank Building are seen before the lights were switched off to recognize Earth Hour on March 23, 2013 in Hong Kong. Businesses and households around the world will turn their lights off for on hour at 20:30 local time today, to celebrate Earth Hour, raise awareness about climate change and to show support for the use of renewable energy. Earth hour began in Australia in 2007 and is now celebrated in over 150 countries around the world. (Photo by Jessica Hromas/Getty Images) ( 164437565 )

People light candles as they take part in an event to promote "Earth Hour" in the financial district of Shanghai on 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 including China's commercial hub of Shanghai to raise awareness of climate change.PETER PARKS/AFP/Getty Images ( 518405615 )

This general shot shows buildings from Manila's financial district after the lights were turned off to mark Earth Hour in Manila on March 23, 2013. Millions of people were expected to switch off their lights for Earth Hour on March 23, in a global effort to raise awareness about climate change. Since it began in Sydney in 2007, Earth Hour has grown to become what environmental group WWF says is the world's largest demonstration of support for action on carbon pollution. NOEL CELIS/AFP/Getty Images ( 518406409 )

In this combination photo the China National Stadium, known as the Bird's Nest, with lights on (top) and off, is seen during the Earth Hour in Beijing on March 23,2013. Iconic landmarks and skylines were plunged into darkness on Saturday as the "Earth Hour" switch-off of lights around the world got under way to raise awareness of climate change. WANG ZHAO/AFP/Getty Images ( 518406881 )

This two combo photograph shows the lighted Welcome Monument located in central Indonesia's capital city of Jakarta with lights on in the top photograph and bottom photograph taken during "Earth Hour" event on March 23, 2013 with the monument's lights switched off. Iconic landmarks and skylines were plunged into darkness on Saturday as the "Earth Hour" switch-off of lights around the world got under way to raise awareness of climate change. While more than 150 countries took part in last year's event, the movement has spread even further afield this year, with Palestine, Tunisia, Suriname and Rwanda among a host of newcomers pledging to take part. ROMEO GACAD/AFP/Getty Images ( 518408251 )

This combo of pictures shows the Bulgarian National Theatre with the lights on (L) and with the lights off (R), as part of the Earth Hour in Sofia on March 23, 2013. Millions of people were expected to switch off their lights for Earth Hour on March 23 in a global effort to raise awareness about climate change that was even to be monitored from space. NIKOLAY DOYCHINOV/AFP/Getty Images ( 518410690 )

A fire acrobats performs in front of the Bulgarian National Theatre, with lights turned off as part of the Earth Hour in Sofia on March 23, 2013. Millions of people were expected to switch off their lights for Earth Hour on March 23 in a global effort to raise awareness about climate change that was even to be monitored from space.. NIKOLAY DOYCHINOV/AFP/Getty Images ( 518410633 )

A combination picture shows (from top left to right) the ancient Temple of Parthenon atop the Acropolis hill before and during the Earth Hour in Athens on March 23, 2013. Iconic landmarks and skylines were plunged into darkness on Saturday as the "Earth Hour" switch-off of lights around the world got under way to raise awareness of climate change. ARIS MESSINIS/AFP/Getty Images ( 518410712 )

Combination photo shows The Eiffel Tower submerging into darkness at 8:30 pm (local time) as part of the Earth Hour switch-off on March 23, 2013 in Paris. Organisers expect hundreds of millions of people across more than 150 countries to turn off their lights for 60 minutes on Saturday night -- at 8:30 pm local time -- in a symbolic show of support for the planet. While more than 150 countries joined in last year's event, the movement has spread even further afield this year, with Palestine, Tunisia, Suriname and Rwanda among a host of newcomers pledging to take part. BERTRAND LANGLOIS/AFP/Getty Images ( 518411390 )

The Eiffel tower is seen while submerging into darkness at 8:30 pm (local time) as part of the Earth Hour switch-off on March 23, 2013 in Paris. Organisers expect hundreds of millions of people across more than 150 countries to turn off their lights for 60 minutes on Saturday night -- at 8:30 pm local time -- in a symbolic show of support for the planet. While more than 150 countries joined in last year's event, the movement has spread even further afield this year, with Palestine, Tunisia, Suriname and Rwanda among a host of newcomers pledging to take part. AFP PHOTO BERTRAND LANGLOIS ( 518411395 )

This combo of pictures shows Vienna's Rathaus (Townhall) with lights on before (top) with lights turned on and during (below) the Earth Hour with the lights turned off in Vienna on March 23, 2013. Millions of people were expected to switch off their lights for Earth Hour in a global effort to raise awareness about climate change. Since it began in Sydney in 2007, Earth Hour has grown to become what environmental group WWF says is the world's largest demonstration of support for action on carbon pollution. ALEXANDER KLEIN/AFP/Getty Images ( 518412128 )

This combo of two photos shows the hostel ship Af Chapman (R) before and during Earth Hour in Stockholm, Sweden on March 23, 2013. Millions of people were expected to switch off their lights for Earth Hour in a global effort to raise awareness about climate change. Since it began in Sydney in 2007, Earth Hour has grown to become what environmental group WWF says is the world's largest demonstration of support for action on carbon pollution. AFP PHOTO / SCANPIX SWEDEN / JOHAN NILSSON ( 518412811 )

This combination picture shows Vienna's Rathaus (Townhall) before and after submerging into darkness as part of the Earth Hour switch-off in Vienna on March 23, 2013. Organisers expect hundreds of millions of people across more than 150 countries to turn off their lights for 60 minutes on Saturday night -- at 8:30 pm local time -- in a symbolic show of support for the planet. While more than 150 countries joined in last year's event, the movement has spread even further afield this year, with Palestine, Tunisia, Suriname and Rwanda among a host of newcomers pledging to take part. ALEXANDER KLEIN/AFP/Getty Images ( 518412659 )

This combination of two photos shows the National Congress in Brasilia before (top) and during Earth Hour on March 23, 2013. Millions of people were expected to switch off their lights for Earth Hour in a global effort to raise awareness about climate change. Since it began in Sydney in 2007, Earth Hour has grown to become what environmental group WWF says is the world's largest demonstration of support for action on carbon pollution. VARISTO SA/AFP/Getty Images ( 518416542 )

This picture shows a woman lighting candles arranged to read "Tunisia" in the Habib Bourguiba avenue after submerging into darkness as part of the Earth Hour switch-off in Tunis on March 23, 2013. Organisers expect hundreds of millions of people across more than 150 countries to turn off their lights for 60 minutes on Saturday night -- at 8:30 pm local time -- in a symbolic show of support for the planet. While more than 150 countries joined in last year's event, the movement has spread even further afield this year, with Palestine, Tunisia, Suriname and Rwanda among a host of newcomers pledging to take part. Isafa laamiri/AFP/Getty Images ( 518413844 )

Large electronic billboards supporting the New Year's ball stand dark on Times Square as their lights were turned off too 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. EMMANUEL DUNAND/AFP/Getty Images ( 518417285 )

Large electronic billboards stand dark on Times Square as their lights were turned off too 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. EMMANUEL DUNAND/AFP/Getty Images ( 518417577 )

Some large electronic billboards stand dark on Times Square as their lights were turned off too 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. EMMANUEL DUNAND/AFP/Getty Images ( 518417410 )

In this combo photo large electronic billboards stand dark (R) on Times Square as their lights were turned off too 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. EMMANUEL DUNAND/AFP/Getty Images ( 518418390 )

In this combo photo large electronic billboards stand dark (bottom) on Times Square as their lights were turned off too 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. EMMANUEL DUNAND/AFP/Getty Images ( 518417624 )

In this combo photo large electronic billboards stand dark (bottom) on Times Square as their lights were turned off too 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. EMMANUEL DUNAND/AFP/Getty Images ( 518417628 )

In this combo photo large electronic billboards stand dark (R) on Times Square as their lights were turned off too 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. EMMANUEL DUNAND/AFP/Getty Images ( 518418451 )

This combination picture shows the monument "As Bandeiras" before (top) and after lights were turned off during Earth Hour in Sao Paulo, Brazil, on March 23, 2013. Millions of people were expected to switch off their lights for Earth Hour in a global effort to raise awareness about climate change. Since it began in Sydney in 2007, Earth Hour has grown to become what environmental group WWF says is the world's largest demonstration of support for action on carbon pollution. YASUYOSHI CHIBA/AFP/Getty Images ( 518418669 )

These combo photos show the Taipei 101 Building before, up, and after, down, turning off its lights to mark the Earth Hour in Taipei, Taiwan, Saturday, March 23, 2013. Organised by the World Wide Fund for Nature, earth hour is observed every year to create awareness about conservation of energy and climate change. Around the world, people and organisations will be turning their lights off from 8:30 to 9:30 pm local time.(AP Photo/Chiang Ying-ying) ( Taiwan Earth Hour )

In this combo photo The Empire State Buidling stands dark (Bottom) as its lights were turned off too 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. EMMANUEL DUNAND/AFP/Getty Images ( 518418702 )

In this combo photo The Empire State Buidling stands dark (R) as its lights were turned off too 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. EMMANUEL DUNAND/AFP/Getty Images ( 518418721 )

Combination photos. The downtown Singapore skyline can be seen before (top) and after (below) the population of the city state observed Earth Hour on Saturday, March 23, 2013. Earth Hour Global is a worldwide event organized by the World Wide Fund for Nature (WWF) encouraging households and businesses to turn off their non-essential lights for one hour to raise awareness about the need to take action on climate change. The event is designed to highlight the impact climate change is having on people and nature. Millions of people in more than 150 countries are expected to take part. Earth Hour 2013 is being held on March 23, 2013 from 8:30 p.m. to 9:30 p.m. during participants' local time. (AP Images for WWF/Earth Hour Global) ( WWF/Earth Hour Global Event Observed in SIngapore )

Members of SPLASH, the Etobicoke School of the Arts' show choir sing before a WWF-Canada lantern walk in Roncesvalles Village Toronto, celebrating Earth Hour, Saturday, March 23, 2013. (AP Photo/The Canadian Press, Galit Rodan) ( Earth Hour )

Children turn on their LED lights moments before Taipei 101 building turns its lights off to observe international "Earth Hour" campaign, Saturday, March 23, 2013, in Taipei, Taiwan. Around 100 people gathered outside the skyscraper Saturday, using energy saving LED lights to observe the global event that encourages people to turn off their lights for 60 minutes. (AP Photo/Wally Santana) ( Taiwan Earth Hour )

In this combo of two photos the illuminated "New railroad bridge" over Sava river, top, and a picture of the bridge with most of its lights turned off, are seen in Belgrade, Serbia, Saturday, March 23, 2013. Organised by the World Wide Fund for Nature, earth hour is observed every year to create awareness about conservation of energy and climate change. Around the world, people and organisations will be turning their lights off from 8:30 to 9:30 pm local time. (AP Photo/Darko Vojinovic) ( Serbia Earth Hour )