Demonstrations are taking place in at least 50 cities across the world to coincide with UN climate change talks in Bali - including this one on the island itself.
The rallies come midway through a summit which is considering how to cut greenhouse gas emissions after current Kyoto Protocol targets expire in 2012.
Marchers in London are delivering a letter to Prime Minister Gordon Brown calling for a strong UK climate change law.
Hilal Atici was one of hundreds of Turkish environmental campaigners that gathered in Istanbul.
Hundreds of people rallied in the Philippines capital, Manila, to highlight the use of solar power.
In Berlin, an ice sculpture of a polar bear was carved out of 15 tonnes of ice as a memorial to climate protection.
Lebanon was one of six Arab nations taking part in the day of action for the first time. This girl is among the 2,000 people who marched through Beirut. Picture: Wael Hmaidan.