A combination picture shows St. Basil's Cathedral before (L) and during Earth Hour in Moscow March 28, 2015. 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/Sergei Karpukhin TPX IMAGES OF THE DAY

A combination picture shows Big Ben and the Houses of Parliament before (top) and during Earth Hour in central London March 28, 2015. REUTERS/Stefan Wermuth 

Combination picture shows the Hungarian parliament building before (top) and during Earth Hour in Budapest, March 28, 2015. 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/Bernadett Szabo

A combination picture shows the city hall before (top) and during Earth Hour in Vienna March 28, 2015. 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/Heinz-Peter Bader 

A combination picture shows the Brandenburger Tor gate before (top) and during the Earth Hour in Berlin March 28, 2015. 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/Hannibal Hanschke

A combination photo shows the Serbian Parliament building before (L) and during the Earth Hour in Belgrade March 28, 2015. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 pm local time, is meant as a show of support for tougher action to confront climate change. REUTERS/Marko Djurica TPX IMAGES OF THE DAY

A combination picture shows the Stadthalle, where the Eurovision Song Contest will be held in May, before (top) and during the Earth Hour in Vienna March 28, 2015. Lights around the world are switched off to mark Earth Hour to raise awareness about energy consumption. REUTERS/Leonhard Foeger

A combination photo shows St. Sava church before (L) and during the Earth Hour in Belgrade March 28, 2015. Earth Hour, when everyone around the world is asked to turn off lights for an hour from 8.30 pm local time, is meant as a show of support for tougher action to confront climate change. REUTERS/Marko Djurica 

A combination picture shows the Chhatrapati Shivaji terminus railway station, also known as Victoria terminus, during (top) and before Earth Hour in Mumbai March 28, 2015. 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/Shailesh Andrade 

A combination picture shows the Acropolis hill before (top) and during (bottom) Earth Hour in Athens March 28, 2015. Lights go off around the world at 8.30 p.m. local time in a show of support for renewable energy during Earth Hour, an event organised since 2007 to promote a sustainable future for the planet. REUTERS/Kostas Tsironis 

A combination picture shows the Old Bridge before (top) and during the Earth Hour in Mostar March 28, 2015. Lights go off around the world at 8.30pm local time in a show of support for renewable energy during Earth Hour, an event organised since 2007 to promote a sustainable future for the planet. The 16th-century bridge was destroyed during the war in Bosnia between 1992-1995, rebuilt and opened again in 2004. REUTERS/Dado Ruvic 

A combination picture shows the "Puente Nuevo" (New Bridge) in the day (top), illuminated by artistic lights (C), both before the Earth Hour, and during the Earth Hour (bottom) in Ronda, southern Spain, March 28, 2015. 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. The Puente Nuevo is 120 metres (390 feet) high and the gorge of the river divides the city of Ronda. REUTERS/Jon Nazca 

A combination picture shows the Taipei 101 building before (top) and during Earth Hour in Taipei March 28, 2015. 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/Pichi Chuang

A combination picture shows Madrid's Royal Palace before (top) and during (bottom) the Earth Hour in Madrid March 28, 2015. Lights go off around the world at 8.30 p.m. local time in a show of support for renewable energy during Earth Hour, an event organised since 2007 to promote a sustainable future for the planet. REUTERS/Susana Vera 

Combination picture shows Yintai Centre buildings before (top) and during Earth Hour, when they turn off the red lights on the tops, in Beijing's central business district, March 28, 2015. Lights around the world are switched off to mark Earth Hour to raise awareness about energy consumption. REUTERS/Kim Kyung-Hoon

A combination picture shows London Eye before (top) and during the Earth Hour in central London March 28, 2015. Lights go off around the world at 8.30 p.m. local time in a show of support for renewable energy during Earth Hour, an event organised since 2007 to promote a sustainable future for the planet. REUTERS/Stefan Wermuth

This combination picture shows Yintai Centre buildings before (top) and during Earth Hour, when the red lights on top of the buildings have been switched off, in Beijing's central business district, March 28, 2015. Lights around the world are switched off during Earth Hour to raise awareness about energy consumption. Picture taken with fish-eye lens.
REUTERS/Kim Kyung-Hoon

A combination picture shows Hong Kong's central financial district's (from L to R) Bank of China Tower, Cheung Kong Centre, HSBC headquarters, Standard Chartered Bank before (top) and during Earth Hour March 28, 2015. Lights go off around the world at 8.30pm local time in a show of support for renewable energy during Earth Hour, an event organised since 2007 to promote a sustainable future for the planet. REUTERS/Tyrone Siu 

Leifeng Pagoda is seen behind the West Lake before Earth Hour in Hangzhou, Zhejiang province, March 28, 2015. 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/Chance Chan 

Leifeng Pagoda is seen behind the West Lake during Earth Hour in Hangzhou, Zhejiang province, March 28, 2015. 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/Chance Chan 

People sit near candles during Earth Hour, after lights were turned off in the city of Cali March 28, 2015. 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/Jaime Saldarriaga 

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People hold balloons with lights inside as they wait for the start of the Earth Hour outside Madrid's Royal Palace March 28, 2015. Lights go off around the world at 8.30 p.m. local time in a show of support for renewable energy during Earth Hour, an event organised since 2007 to promote a sustainable future for the planet. REUTERS/Susana Vera