Today's worldwide People's Climate March is off to an exciting start as over 100,000 people are expected to flood the streets of New York City, alongside many thousands of others in London, Melbourne, and other cities around the globe.

Marching proudly in the streets of New York City today are recently-nominated Messenger of Peace for the UN, Leonardo Dicaprio, as well as Mark Ruffalo, Sting, Edward Norton, Evangeline Lilly, and more. The march began this morning at around 11:30 a.m. and has since featured a moment of silence followed by a moment of alarm, where participants were encouraged to make as much noise as possible in order to draw attention to climate change.

The march is intended as a forerunner to Tuesday's UN Climate Summit, where world leaders will discuss climate change.

The march in New York began at 86th and Central Park West and is heading downtown toward 34th Street. Groups have been split up according to climate cause and in a rare move for the UN, the Secretary General, Ban Ki-moon, has also joined the march with Al Gore and mayor Bill de Blasio.

In London, Emma Thompson joins the march:

All the action is being livestreamed at the People's Climate March website.

[Image via Twitter]