This Sunday, upwards of 100,000 people are expected to take to the streets of New York City in a worldwide climate protest that organizers say will be the largest and most diverse in history.

If these numbers prove correct, then the “People’s Climate March” will likely mark the moment when global warming transitions from being a science and policy issue into a full-fledged social movement. Perhaps it will become as large as the gay rights and civil rights movements. But even if it doesn’t, it could play a crucial part in changing the political environment on this seemingly intractable issue.

Sunday’s Climate Protest Could Be a Turning Point on Global Warming