[VIDEO] Earth Hour 2012: 8:30 p.m. Saturday

Earth Hour, an international effort to raise awareness about climate change, is observed around the globe at 8:30 p.m. local time on the last Saturday of March when households are asked to turn off all non-essential lights for an hour. The island of Samoa was the first location to go dark for this year’s observance.

In Chicago, the Wrigley Field marquee will be one of the local landmarks that will switch off its lights at 8:30 p.m., according to WGN Radio.

The annual event has grown from a one-city initiative to a global movement. Earth Hour, organized by the World Wildlife Fund, was observed in more than 5,200 cities and towns in 135 countries worldwide last year, according to the Earth Hour website.