Representatives from 196 nations made a historic pact Saturday, agreeing to adopt green energy sources, cut down on climate change emissions and limit the rise of global temperatures — while also cooperating to cope with the impact of unavoidable climate change.
The deal still needs to be adopted by individual governments — but the acceptance by the diplomats gathered in Paris has been hailed as "transformative."
The agreement acknowledges that the threat of climate change is "urgent and potentially irreversible," and can only be addressed through "the widest possible cooperation by all countries" and "deep reductions in global emissions."
But how deep will those reductions be — and how soon, and who's paying for it?
Here are some key figures from the final agreement.
The central goal of the agreement is laid out in one phrase:
"Holding the increase in global average temperature to well below 2 degrees C above pre-industrial levels ..."
Limiting the rise in temperature to 2 degrees (3.6 degrees Fahrenheit) has been discussed as a global goal for several years now. That amount of warming will still have a substantial impact, scientists say, but will be less devastating than allowing temperatures to rise unchecked.
The global average temperature has already risen about 1 degree Celsius, relative to pre-industrial levels.
And even if every signatory country meets its current pledge for reducing greenhouse gas emissions, the world is still expected to pass 2 degrees of warming, as the agreement itself notes with concern. (That section is literally labeled "Notes with concern.")
The current emission targets are just a first step, in short, and the Paris signatories hope the world can figure out how to get closer to the 2-degree goal as time goes on.
... Or 1.5 Degrees
But wait! There's more!
That same sentence in the deal continues: "... and to pursue efforts to limit the temperature increase to 1.5 degrees C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change."
That's right. The big, ambitious goal is immediately followed ... by a bigger, more ambitious goal.
Small island nations, in particular, fought hard to have this number appear in the agreement, noting that even if the temperature increase was held at 2 degrees, the resulting rise in sea levels would be devastating for them.
Island representatives adopted the oft-repeated motto, "1.5 to stay alive," as NPR's Ari Shapiro reported earlier this week.
And while those vulnerable nations didn't manage to establish 1.5 degrees C (2.7 degrees F) as the legally binding target, it is worked in as an aspiration. But it's a goal that would be even harder to achieve than 2 degrees — which, again, is a target the world hasn't yet figured out how to meet.
"To help developing countries switch from fossil fuels to greener sources of energy and adapt to the effects of climate change, the developed world will provide $100 billion a year," NPR's Chris Joyce, who has been covering the climate conference, reports.
But that amount is identified as a "floor," not a ceiling.
"Developed countries won inclusion of language that would up the ante in subsequent years," Chris explains, "so that financial aid will keep ramping up over time."
'As Soon As Possible'
This one isn't exactly a number ... but it's the target time for "global peaking" of climate change emissions.
It's an acknowledgement that in the near future, total emissions of carbon dioxide and other greenhouse gases won't fall — in fact, they'll rise, as developing economies consume more energy.
But the plan assumes that greener technology, conservation efforts and processes to remove greenhouse gases from the atmosphere will eventually allow emissions to decline instead of rise — and at that point, the "peak" will be achieved.
Nations aren't expected to ratchet their emissions back immediately.
"Each country came to Paris with a voluntary pledge to reduce emissions," Chris says. "The agreement now codifies that and sets a framework for those reductions to begin in 2020."
That year is also the deadline for countries to submit a more long-term plan — not an immediate pledge, like their current goals, but one looking decades into the future.
After the 2020 reductions kick in, it's not over: The deal is designed to evolve as the years pass. Every five years, specifically, each nation's targets will be reevaluated to move the world closer to the 2-degree target.
This element of the deal is one strongly supported by President Obama, and it's highlighted in a White House fact sheet:
"Targets must be submitted 9-12 months before they are finalized, creating time for other countries and civil society to seek clarity about the targets submitted," the administration writes.
"Each target should reflect progress from the prior one, reflecting the highest possible ambition that each country can achieve. This durable, long term framework will drive greater climate ambition as technologies improve and circumstances change."
This target date isn't actually precise: The deal describes it as "mid-century."
But that's when the world is supposed to meet another goal, which is much more concrete:
Zero, as in net zero emissions of greenhouse gases.
No one expects that over the next 40 years, the world would entirely stop using every form of technology that releases greenhouse gases. Instead, as Chris Joyce explains, the mid-century target would be met by balancing inputs and outputs:
"Any greenhouse gases emitted would be balanced or zeroed out by removing an equivalent amount from the atmosphere. In the case of carbon dioxide, that would presumably be accomplished by growing forests, which absorb carbon dioxide."
Diplomacy isn't always quantifiable. Many sections of the deal, of course, don't nail down any numbers at all.
For instance, nations around the world "should strengthen their cooperation on enhancing action on adaptation" to the effects of climate change, the agreement states.
"All Parties should cooperate to enhance the capacity of develop country Parties to implement this agreement," it says elsewhere. And "Parties shall cooperate in taking measures, as appropriate, to enhance climate change education, training, public awareness, public participation and public access to information."
55 Countries, 55 Percent
The agreement still needs to be approved by the individual governments of the countries involved.
But the U.N. won't be waiting for all 196 nations to give the green light. Countries have from April 22, 2016, to April 21, 2017, to officially sign on to the agreement.
Once at least 55 nations — representing, between them, at least 55 percent of the world's total greenhouse gas emissions — have signed on, the pact can go into effect.
It will kick in 30 days after that requirement is met.