Protesters have taken to the streets across the world to demand action on the environment.

Protesters have taken to the streets across the world to demand action on the environment. In about 850 events across 90 countries, hundreds of thousands people are protesting climate change. The event's organizer said climate change is the defining issue of our time. Some groups organized flash mobs while others locked themselves to mining machinery. One astrobiologist in Antarctica even shared a picture of himself holding up a banner in support.