UNITED NATIONS (AP) — The Paris Agreement to combat climate change became international law on Friday — a landmark deal about tackling global warming amid growing fears that the world is becoming hotter even faster than scientists expected.

So far, 96 countries, accounting for just over two-thirds of the world’s greenhouse gas emissions, have formally joined the accord, which seeks to limit global warming to 2 degrees Celsius (3.6 degrees Fahrenheit). More countries are expected to come aboard in the coming weeks and months.

Secretary General Ban-Ki moon commemorated the event, talking with civil society groups at U.N. headquarters in New York to hear their concerns and visions for the future.

“Today we make history in humankind’s efforts to combat climate change,” Ban said before opening the meeting.

He praised the civil groups for mobilizing hundreds of millions of people to back fighting climate change, but warned the outcome remained uncertain.