World leaders from 195 nations and the European Union have agreed on a proposal to try and limit greenhouse gas emissions in order to prevent the worst effects of climate change.
The agreement is a commitment by almost all countries in the world to try and limit greenhouse gas emissions in order to prevent global temperatures from rising 2 degrees Celsius above pre-industrial levels.
"The final draft text recognizes the imperatives of the science community to tackle climate change. The three key elements to do it are there in some form: keep warming well below two degrees, practically move away from fossil fuels, and review each country's contribution every five years so they scale up to the challenge," Dr. Corinne Le Quéré, a professor of climate change science at the University of East Anglia, told the UK's Science Media Centre before the final proposal was approved.
Still, the question remains: will it be enough?
"The emissions cuts promised by countries now are still wholly insufficient," Le Quéré said.
The agreement to limit emissions is not legally binding. That concession was made so that the US could support the plan without needing the Senate to ratify a treaty, according to the New York Times' Coral Davenport.
For now, countries have presented plans that show what they plan to do to limit emissions. Experts say, however, that they'll need to do more to actually hit the below 2 degrees C target.
"[W]hile the text recognizes the importance of keeping global warming below 1.5 degrees C, the current commitments from countries still add up to well over 3 degrees of warming,"May Boeve, the executive director of the climate change action group 350.0rg told The Guardian. "These are red lines we cannot cross."
In order to hit the goals in the agreement, experts say that most nations will have to achieve net zero greenhouse gas emissions within the second half of the 21st century.
The plan also calls for countries to update their commitments to reduce gas emissions in 2020 and every five years after that.
All around the world, observers had been watching as the summit decided whether or not it would adopt the proposal, which UN Secretary General Ban Ki-moon has said there is "no Plan B" alternative to.
In Paris, demonstrators took to the streets.
"By comparison to what it could have been, it's a miracle," writes George Monbiot in The Guardian. "By comparison to what it should have been, it's a disaster."
Others were even more uncertain. Paul Oquist, representing Nicaragua at the summit, noted in a statement afterwards that the agreement fell far short of what was needed to prevent a 3 degree C rise, and said there was a need for developed countries to provide compensation for the loss and damage that climate change had already caused and will continue to cause in parts of the world.
Still, any agreement is better than none in the eyes of many.
The Guardian reports that Al Gore was "visibly moved" in the hallway at the summit as the decision was officially "gavelled in."
"No agreement is perfect, and this one must be strengthened over time, but groups across every sector of society will now begin to reduce dangerous carbon pollution through the framework of this agreement," Gore reportedly said.
It'll be some time before legal experts and scientists have been able to fully evaluate the plan.