This combo of views shows the Sydney Opera House with the lights on and the lights off during "Earth Hour," March 28, 2009. The waters of Sydney Harbour plunged into darkness with the iconic Opera House and Harbour Bridge killing their lights for an hour in a global call for swift action on climate change.[Xinhua/AFP]

In the darkness of the night, the happiest person in the world might be a middle-aged man called Andy Ridley.

On the coming Saturday, hundred of millions of people around the globe will turn off their lights for one hour to voice their concern about climate change.

Exactly Four years, thousands of Sydney residents took a positive response initiated by Ridley and turned off their lights for an hour, plunging half of the city to the darkness.

Then what prompted Ridly to make such a campaign? He recalled that in 2007, in the belief that people cared about climate change, "we were inspired by the idea of executing a campaign to provide everyday people and businesses with a platform to voice their concern on climate change by switching off their lights simultaneously."

However, to his surprise, in just a few years, Earth Hour has grown from a one city initiative to a global action that has swept the world with passion and enthusiasm.

"I dreamed that Earth Hour would be embraced by the world but I never expected it on this scale," Ridley, the Earth Hour Co- Founder and Executive Director, told Xinhua on Friday in an exclusive interview.

When asked why the movement could spread into such a large scale, Ridley explained that the speed at which Earth Hour has grown from a one city, one country event to thousands of cities in more than 120 countries has only been possible because of the open- source nature of the campaign and the power of individuals in the age of social media.

"Today's personal communication has unprecedented reach and influence, enabling citizens to take ownership of Earth Hour and spread it's message of hope and action to great effect without any limitation," he said.

In addition to this, the biggest driving forces for Earth Hour apart from World Wildlife Fund are cities and companies. "Support from mayors and city councils has always been strong and our corporate supporters play a large role in spreading the Earth Hour message among their employee's and customer base," he added.