Earth Hour takes place worldwide on the last Saturday of March at 8.30 pm local times, and is a global call to turn off lights for 60 minutes in a bid to highlight the global climate change. Since it began in Sydney in 2007, Earth Hour has grown to become what environmental group WWF says is the world's largest demonstration of support for action on carbon pollution. In Pakistan, the hour was observed in Karachi and Islamabad. – Photos and text by Agencies