Earth Hour's social media response was overwhelming, said Earth Hour Co-Founder and Executive Director Andy Ridley on the Earth Hour Web site.
"People from over 150 countries across the globe are harnessing the power of online platforms to physically care for the future of the planet," Ridley said.
Earth Hour estimated about 15 million people across Russia observed, in solidarity with more than 6,494 towns and cities worldwide, more than 230 monuments and the more than 100,000 individuals who pledged via YouTube and Facebook to adopt sustainable practices.
In front of India Gate in Delhi, about 200 cadets from the National Cadet Corps formed the "60+" Earth Hour Logo, the Deccan Herald Reported.
For the fourth year in a row, the twinkling lights of Fremont Street -- from Caesar's Palace to Planet Hollywood -- were to be switched off in observance of the environmental effort, the Las Vegas Sun reported.
Earth Hour, which began in 2007 in Sydney, called on people worldwide to shut off their lights for an hour to take a stand against global warming. That first year in Sydney alone, 2.2 million people turned off their lights in solidarity.
Millions of people across 135 countries turned off the lights last year in accordance with Earth Hour.