The largest climate change demonstration in history took place on Sunday. According to organizers of thePeople’s Climate March, an estimated 400,000 people participated in the protest in New York. For comparison, the size of the march was comparable to the scale of the February 15 anti-war demonstration in 2003. The demonstration at the Copenhagen Summit in 2009 mobilized about 100,000 people, but US demonstrations at that time generally mobilized fewer than 1,000 people.