The deal spells trouble for old-school fossil fuels | KENZO TRIBOUILLARD/AFP/Getty 5 takeaways on the Paris climate deal New alliances came together, while old ones cracked.

LE BOURGET, France — The deal’s done, the negotiators are heading home, and the world got a new roadmap for tackling climate change in the coming decades.

It took tens of thousands of delegates and ministers from 196 governments two weeks of nonstop negotiations to get to the Paris agreement — the first universal, legally binding deal on climate change.

It's the culmination of a negotiating process that began decades ago, leading through the underwhelming Kyoto Accord in 1997, then to the flop at the 2009 Copenhagen summit. All the while increasingly dire temperature statistics, shrinking ice caps, violent storms and growing atmospheric carbon dioxide levels, made clear that the world faced a real threat from global warming.

In Paris, the sense the world had to act was decisive in pushing through an agreement. As the summit wraps up, here are five things you need to know on the COP21 climate summit:

1. What the agreement says and does

The Paris deal doesn’t make national emissions reduction targets legally binding, so its success will largely depend on the effectiveness of a new system to revisit each country’s progress and raise targets every five years.

However, the agreement's goal of limiting global warming to "well below" 2 degrees Celsius, and eventually to 1.5 degrees, should give business the long-term signal that it has to shift investment in the direction of low-carbon technologies — solar power, electric cars or nuclear energy. That spells trouble for old-school fossil fuels, most of which will have to stay in the ground unburned.

“Every country in the world will now bear down on its emissions,” said Michael Jacobs, senior advisor to the New Climate Economy. “And that means, because we’re doing it globally, that the global markets will follow.”

How fast the change happens, however, depends on whether countries start implementing new rules before the Paris agreement actually takes effect in 2020. It “invites” countries to start making the green shift and raise targets again 2018, but can’t require them.

Even if all the greenhouse gas cut pledges made by countries ahead of Paris are carried out, the result would be a world that warms by about 3 degrees. And, by omitting any mention of two of the biggest-polluting sectors — international shipping and aviation — the emissions reduction targets are even more out of whack.

That means it's crucial that countries to ramp up their climate pledges over time. That, plus new technologies, might allow the world to hit the Paris pact's end-of-century goals.

2. How the deal came together

New alliances came together, while old ones cracked.

The big move was a split among developing countries led by the formation of the new “high ambition coalition.” Announced four days before the end of the summit, it built a coalition between poor and wealthy countries eventually including the EU, U.S., Japan, Canada, Brazil, Mexico, Colombia and a long list of vulnerable states from Africa, the Caribbean, and the Pacific.

It wasn’t a formal alliance, but took financial and political overtures to secure.

The developed side lent its support to the vulnerable side’s decade-long struggle to keep global warming at less than 1.5 degrees, rather than 2 degrees. Rich countries also had to put more money on the table.

In return, the grouping shored up the moral and political weight needed to go up against more hardline emerging economies, like India, China and Saudi Arabia. Those countries tried to push back on committing to tough emissions cuts, establishing international reporting rules and periodically reviewing their progress, and sought to keep the more traditional divisions between developed and developing countries intact.

Meanwhile behind closed doors, older alliances like the G77 and China group of 134 developing countries and the BASICs (Brazil, South Africa, India and China) fell apart because of differing priorities. But it also took some last-minute wheeling and dealing among heavyweights like the U.S., China and India to finesse a compromise.

3. The way the power players operated

One thing was abundantly clear during the talks: When the United States draws a red line, it rarely erases it.

The United States gave no ground on its position that key portions of the deal — the domestic climate targets and certain aspects of finance — can’t be legally binding because that would trigger an obligation to submit the deal to the U.S. Senate, which would promptly kill it. It also refused to compromise on its opposition to providing compensation or admitting liability for the losses and damage possibly caused by greenhouse gas emissions.

But it’s not just the U.S. that holds outsized power at the talks. Despite the weakening of the G77, China and India still gave many in the developed world heartburn. The two countries threw their weight around at closed-door meetings throughout the talks, objecting to stringent language on everything from the long-term temperature goal to the way the domestic climate plans should be reviewed.

In the end though, China and India made some concessions in part because there is a growing recognition of the threat of climate change in both countries.

Small islands with populations in the tens of thousands may not have seemed like a big threat. But in the end, the United Nations-style setting, which gives every nation large and small a voice, allowed the Marshall Islands, Tuvalu, Kiribati and others to rise to prominence. They used their exposure to rising sea levels and severe storms to leverage their case for a 1.5-degree goal and a plan for addressing loss and damage, and became instrumental in bridging the wealthy-poor divide.

The European Union was the other key player in building this new cross-cutting alliance. The bloc may not have secured the binding emissions reduction targets it wanted, but it got the second-best option — mandatory five-year reviews of country progress — and made sure not to be locked out the way it was when the U.S. and China brokered a disappointing deal in Copenhagen in 2009.

4. The movers and shakers

— Laurent Fabius: France’s foreign minister and the COP21 president, won broad accolades for his transparent diplomatic maneuvering. “We have no hidden agenda and no secret plan and no text in our pockets,” Fabius told ministers at the beginning of the conference. The fact that he stuck it out night after night, until the early hours, also earned him respect.

— John Kerry: The climate talks were almost certainly a defining moment of the U.S. secretary of state's career — and he was intent on making sure they didn’t end in failure. Kerry has been advocating for measures to tackle climate change for more than two decades and he has made appearances at nearly every major global warming summit. From the moment he arrived in Le Bourget, Kerry immersed himself in the technical details of the text, while delivering standing-room only speeches about the need for a strong deal and holding near-constant bilateral meetings with China, India and island nations.

—Tony de Brum: The Marshall Islands’ foreign minister isn’t one to shy away from emotional speeches on the imminent threat climate change poses to island nations. “I am speaking for a very vulnerable country, an atoll nation that lies out in the middle of the vast blue expanse of the Pacific Ocean,” he repeatedly said. Winning wording in the deal that pushes countries to limit global warming to 1.5 degrees makes it possible for him “to go home and tell my people that our chance for survival is not lost.”

— Miguel Arias Cañete: He was the alliance builder. The EU’s climate and energy commissioner spent the year on taking short- and long-haul flights to solidify support for a deal that makes sure the European Union isn’t left alone with tough climate targets while other economies take. Asked how many hours he'd slept in the last week, he said 11. "Not bad for a COP."

5. What comes next

Negotiators will meet again in Morocco on November 7, 2016, at a COP summit in Marrakesh focused on innovation in adapting to the effects of climate change and curbing emissions.

That feeds in to the big question after this year’s summit: How do countries meet these lofty targets they have now set and promised to periodically hike?

“The big struggle could be in the next years, the struggle for rules,” said Alexey Kokorin, head of the climate and energy program at WWF Russia and a former climate negotiator.

Countries agreed to review their pledged targets in 2018, but how this will pan out is an unknown.

The Paris agreement attempts to lay down new rules to make sure all countries calculate and publicly report their emissions reductions in the same way after 2020, making it possible to keep track of global progress. But developing countries are still new to international reporting on climate policies, and the United Nations still has some work to do to make sure the right information is tracked.

Another unknown is how countries, especially developing ones, will respond to the Paris agreement’s invitation to review their pledged targets in 2018, and possibly lift them further.

“There are many things that we have to deliver in COP22, in Marrakesh and other COPs, but here is the architecture and the design to build a house,” Arias Cañete told reporters.

This article has been corrected to note that Fabius spoke at the beginning of the conference, not in the second week.