The most comprehensive international agreement ever to combat man-made climate change will take effect next month, less than a year after negotiators from more than 190 countries reached a final deal on the issue, the United Nations said Wednesday.

The Paris Agreement commits participating countries to working to reduce their greenhouse gas emissions and transparently reporting those results with the goal of keeping global temperature rise from pre-industrial levels below 2°C (3.6°F) by 2100.

“This is our chance to set us on course towards a safer, more sustainable and more just future for all on a healthy planet,” UN Secretary-General Ban Ki-moon said shortly before the milestone. “Let us seize the moment and be true to the values and aims of our organizations.”

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The news that the agreement will take effect this year diminishes the chances that it can be undone by Donald Trump should he be elected president. Trump has called climate change a “hoax” and promised to scrap the deal. The document locks participants into the deal for at least three years and requires a one-year waiting period once a withdraw is announced.

A slew of countries acted quickly to join the Paris Agreement in recent weeks at least in part because of the Trump threat. The world’s three top emitter countries—China, the United States and India—all joined in September or October. The European Union pushed the accord past the threshold required for it to take effect this week. The agreement required 55 countries representing 55% of the world’s greenhouse gas emissions to join before taking effect.

The news represents a significant achievement for President Obama, who made addressing the issue on the international stage a top priority in his second term. In brief remarks Wednesday from the White House, Obama called the achievement a “turning point for the planet.”

The milestone was celebrated immediately by climate policy makers and advocates, but many pointed out that deal is just a first step in addressing climate change. The Paris agreement provides a framework for countries to develop and share their plans to address climate change, but scientists say the current plans fall short of the Agreement’s target. The framework requires countries to reconsider their pledges every five years, hopefully to improve upon them, but experts say those improvements should start now.

Read More: U.S. Likely to Fall Short of International Climate Change Commitments

“There’s no question we all applaud the Paris Agreement,” says Bob Watson, former chair of the Intergovernmental Panel on Climate Change (IPCC). “If government in the world are serious about slowing down the rate of climate change, they immediately have to reconsider their pledges and strengthen them quite considerably.”

An IPCC report, considered the gold-standard synthesis of the latest climate research, found that the world needs to reduce greenhouse gas emissions by 22% by 2030 to keep temperatures from rising above the 2100 target. Under current proposals, emissions would increase 6%, according to a recent report from Watson and colleagues.

Part of that gap could be closed for by a global agreement to cap aviation emissions, which are currently about equivalent to those from the entire country of Germany and expected to grow rapidly in coming years. Negotiators in Montreal are expected to announce an agreement in that area this week after two weeks of talks.

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Write to Justin Worland at justin.worland@time.com.