The lights went out at UN Headquarters complex in New York tonight to observe Earth Hour and to join millions of people around the world in a show of support for taking action on climate change.

The act of turning out the lights was symbolic, yet the message delivered by the darkened buildings against the New York City skyline was clear–that the world needs to adopt a path toward a sustainable, low-carbon future..

“Climate change is a people problem,” says UN Secretary-General Ban Ki-moon in a video for Earth Hour. “People cause climate change and people suffer from climate change. People can also solve climate change.”

This year, Earth Hour takes on an even greater meaning for the UN as the world will be coming together to adopt a new sustainable development agenda in September, and a new climate agreement in Paris this December.

Paris, the Secretary-General said, “will be the culmination of a year of action on sustainable development.”

He added that by turning out the lights, “we also highlight that more than a billion people lack access to electricity. Their future well-being requires access to clean, affordable energy.”