This picture taken on March 19, 2016 shows the Sydney Opera House with the lights turned off during the Earth Hour campaign in Sydney. (Photo: WILLIAM WEST/AFP/Getty Images)
Cities Mark 10th Annual Earth Hour
This photo shows Yokohama city's Cosmo Tower ferris wheel with the lights turned off during the Earth Hour campiagn in Yokohama on March 19, 2016.
(Photo: TOSHIFUMI KITAMURA/AFP/Getty Images)
Cities Mark 10th Annual Earth Hour
The ancient Temple of Parthenon atop the Acropolis hill goes dark for the Earth Hour environmental campaign in Athens on March 19, 2016. (Photo: PANAGIOTIS TZAMAROS/AFP/Getty Images)
Cities Mark 10th Annual Earth Hour
Picture taken on March 19, 2016 shows the oldest Hungarian bridge, the 'Chain Bridge' with the Buda Castle on top of the Castle Hill of Budapest downtown after the city lights were switched off to mark the annual Earth Hour event. (Photo: ATTILA KISBENEDEK/AFP/Getty Images)
Cities Mark 10th Annual Earth Hour
People attend a candle light vigil at the Vilnius Cathedral as it stands unlit during Earth Hour in Vilnius on March 19, 2016.
(Photo: PETRAS MALUKAS/AFP/Getty Images)
Cities Mark 10th Annual Earth Hour
A picture shows St Peter's basilica at night with the lights turned off during the WWF "Earth Hour" campaign for global climate change awareness on March 16, 2016 in Rome.
(Photo: VINCENZO PINTO/AFP/Getty Images)
Cities Mark 10th Annual Earth Hour
A picture taken on March 19, 2016, in central London, shows Britain's Houses of Parliament after being submerged into darkness for the Earth Hour environmental campaign.
(Photo: NIKLAS HALLE'N/AFP/Getty Images)
Cities Mark 10th Annual Earth Hour
A picture shows the Eiffel Tower in Paris after it went dark for the Earth Hour environmental campaign on March 19, 2016. (Photo credit: MARIN/AFP/Getty Images)
Cities Mark 10th Annual Earth Hour
A picture taken on March 19, 2016, in central London, shows The London Eye (L) after being submerged into darkness for the Earth Hour environmental campaign.
(Photo: NIKLAS HALLE'N/AFP/Getty Images)
Cities Mark 10th Annual Earth Hour
A combination of two pictures shows the Hyllie water tower lit (L) and with the lights turned off during the WWF Earth Hour campaign for global climate change awareness on March 16, 2016 in Malmo.
(Photo: JOHAN NILSSON/TT/AFP/Getty Images)
Cities Mark 10th Annual Earth Hour
View of the Monumento a la Revolucion with the lights off during the Earth Hour in Mexico City on March 19, 2016. (Photo: ALFREDO ESTRELLA/AFP/Getty Images)
