On March 28 the yearly appointment with the Earth Hour will be back, and citizens from all over the world will be asked to participate by switching off the lights for one hour, from 8.30 to 9.30 pm in their local time.

Earth Hour started in 2007 as a lights-off event to raise awareness about climate change and it has since grown to engage more than 162 countries and territories worldwide, becoming the world's largest open-sourced environmental campaign.

Earth Hour has proved to be a movement able to achieve massive environmental impact, including legislation changes, by harnessing the power of the crowd. In 2014 alone, Earth Hour supporters raised funds to plant millions of trees, promote the use of fuel-efficient stoves and reduce the carbon footprint of thousands of schools.

This year WWF's Earth Hour takes on its biggest challenge ever by strengthening focus on the globe's most stubborn environmental challenge – climate change. As the opportunity for action on climate change peaks in 2015, the world's largest grassroots movement will raise its voice to change climate change.

Please visit the official website for more stories and articles on using the power of the crowd to change climate change.