A group of 195 nations has reached an unprecedented agreement on global climate change.

Delegates from the nations had spent the past two weeks at the COP21 conference in Paris, working to finalize details on a pact aimed at scaling back global greenhouse gas emissions.

On Saturday, they announced they had come to a consensus.

The conference was aimed at preventing average global temperatures from reaching 2 degrees Celsius (3.6 degrees Fahrenheit) above their counterparts during the Industrial Revolution, when greenhouse gas emissions surged. Scientists have publicly warned that eclipsing that long-feared threshold could yield catastrophic results, including massive flooding and droughts.

The nations agreed they would try to do even better and set a goal of keeping temperatures from rising more than 1.5 degrees Celsius (2.7 degrees Fahrenheit), which provides more of a buffer.

“We have entered a new era of global cooperation on one of the most complex issues ever to confront humanity,” U.N. Secretary General Ban Ki-Moon said in a statement. “For the first time, every country in the world has pledged to curb emissions, strengthen resilience and join in common cause to take common climate action. This is a resounding success for multilateralism.”

There’s still some work to be done before the agreement takes effect. It must be individually ratified by 55 countries that produce at least 55 percent of global carbon emissions. And there’s also work to be done before the world feels the effects of the Paris Agreement, as each nation must develop plans to cap its individual emissions as soon as possible and keep reducing them.

U.N. officials said in a news release that 188 countries have already submitted so-called climate action plans toward the Paris Agreement. Now, the countries will be required to submit new plans every five years. Those plans are required to become gradually more proactive over time, with nations working to further reduce emissions to keep temperatures below the feared levels.

But the agreement wasn’t universally hailed. Some climate change activists wanted to see a quicker transition away from fossil fuels and towards clean energy like wind and solar power.

“Every government seems now to recognize that the fossil fuel era must end and soon. But the power of the fossil fuel industry is reflected in the text, which drags out the transition so far that endless climate damage will be done,” Bill McKibben, the co-founder of 350.org, said in a statement. “Since pace is the crucial question now, activists must redouble our efforts to weaken that industry. This didn’t save the planet but it may have saved the chance of saving the planet.”