It took 21 years for nearly 200 countries to reach an agreement in Paris last year to put the brakes on climate change.

Now for the hard part.

At the COP22 summit in Morocco from November 7-18, negotiators will have to decide on the details of how to make sure each country is actually reducing its emissions (and not just saying it is); how to compensate poorer countries for the damage done by hurricanes, floods, droughts and other effects of climate change; and how to shore up financial aid from the developed to the developing world.

“It was a massive leadership challenge to get to Paris. It’s an even bigger leadership challenge to implement Paris,” said Rachel Kyte, head of the U.N.'s Sustainable Energy for All initiative.

The landmark deal agreed upon at the United Nations’ COP21 summit in the French capital last December laid out the ambitious goal of slowing global warming to well below 2 degrees Celsius and eventually to 1.5 degrees by the end of the century. It’s a tough — and some say impossible — ask, given that the planet's temperature reached 1 degree above pre-industrial levels in late 2015.

The Paris agreement requires almost every country in the world to tackle climate change. But it does not spell out how. The 197 members of the U.N. climate change secretariat must now come up with their own plans and targets for cutting greenhouse gas emissions. Some say they’ll put a price on carbon dioxide. Others want to go big on renewable energy. A few are looking at emissions-free nuclear.

Here are five things to help you get primed for Marrakech:

1. Remember Paris

The Paris climate agreement does not require specific cuts to countries' greenhouse gas emissions. It instead creates a system that requires all countries to pitch in with something, then monitors their progress and urges them to continue ramping up efforts.

It also sets an end goal, which is key for buy-in from businesses and investors. That goal is a world where humans emit only as much carbon dioxide as can be naturally absorbed or stored by the middle of the century and a limit on global warming at well below 2 degrees and eventually 1.5 degrees. That reassures investors that there will be demand for technologies to store and use CO2 emissions and generate clean, green energy.

In a huge surprise to most climate negotiators and advocates, countries rushed to ratify the deal as quickly as possible, pushing it past the threshold needed for it to enter into force (with a final shove from the EU) three days before the start of the COP22.

The speedy ratification was a huge symbolic win for the climate change movement, because it tells the world it has to start cutting carbon emissions. But the sum of national plans still falls short of the long-term goal. Promises now on the table mean a temperature rise of at least 3 degrees.

The Paris agreement's goals therefore put even more pressure on governments to boost their efforts in 2018, when they meet for the first time to review their progress, and again at the Paris agreement’s required check-ins every five years after that.

"To have a two-in-three, or 65 percent, chance of holding global warming to 2 degrees by the end of this century, we will need to decarbonize the electricity supply and reduce greenhouse gas emissions by 40 to 70 percent by 2050, relative to 2010, and have net emissions approaching zero by 2100," Hoesung Lee, chair of the U.N.'s Intergovernmental Panel on Climate Change, said in interview. His panel of thousands of climate scientists will publish a report in 2018 on what more it will take to limit global warming to 1.5 degrees.

2. Marrakech battle lines

The broad political agreement reached in Paris isn't enough to erase the deep battle lines drawn over two decades of slow-moving climate negotiations, which are likely to flare up again as the focus shifts to laying down rules.

“We’ve resolved the big political questions,” said Jo Tyndall, the co-chair of the Ad Hoc Working Group on the Paris Agreement, which oversees negotiations following the deal. “But you look at a cooking show and you can give a bunch of contestants a box with exactly the same ingredients, and they will come up with a whole lot of different dishes.”

The biggest difference is between poorer countries that believe the wealthy world should carry the burden of slowing the climate change its industrialization helped cause and developed countries that argue the division should be more nuanced, to take into account big emerging economies able to do more than the smallest and least developed ones.

The most contentious debates will likely center on four issues: how to measure, report and verify emissions; how to ensure those emissions numbers are transparent; how to account for the loss and damage countries have already suffered from climate change; and how to expand the financial aid to help developing countries adapt to climate change and curtail emissions.

It will be tough to convince countries to open themselves up to monitoring, verification and reporting their emissions data. Rules can help ensure they don't fiddle with the stats, but they also expose countries to international scrutiny and risk the shaming that comes with it.

“Monitoring, reporting and verification is where the equity and fairness debate will play out,” said Liz Gallagher, a senior associate at the environmental think tank E3G. “So if you’re Georgia, what kinds of standards of accounting and reporting and verification should you have in comparison to China, and how much support is available for you to improve your data collection and analysis?”

Transparency rules are similarly touchy, but also key to tracking the world's progress on climate change.

Countries now use a variety of methods to calculate emissions reduction pledges. The EU measures its emissions against the level in 1990, just before the collapse of the Soviet Union’s high-polluting smokestack industry. China aims to peak its emissions in 2030; Japan compares its emissions cuts to the level in 2013, when coal-fired power went up to cover for shuttered nuclear reactors. Others say they will measure reductions against 2015 levels.

Then there's the unresolved issue of money and other forms of support, like the transfer of technology.

The developing world succeeded in getting a section in the Paris agreement that specifically acknowledges the loss and damage suffered from natural disasters — everything from food shortages to destroyed homes. But the agreement is careful not to hold the developed world liable for the climate change caused by its early industrialization. That was a red line for the U.S., EU and others.

In Marrakech, negotiators will have to work out a timeline for providing support in areas such as early warning systems, risk assessment and management, and risk insurance.

They'll also have a preliminary discussion on how to move beyond the developed side's pledge to come up with $100 billion per year of public and private climate finance by 2020, although a firmer agreement isn't expected until the COP23 in 2017.

For now they’re on track to provide just over $90 billion by 2020, of which $67 billion is public, according to a report developed countries released in October. But the amount of money that’s actually needed to tackle climate change is estimated to be in the trillions.

"In Paris they postponed meeting this commitment, and developing countries are now rightly asking to deliver the climate finance promises," said Mohamed Adow, senior climate change adviser at the NGO Christian Aid.

3. Gang of two

China and the United States, the world’s first- and second-largest CO2 emitters, again emerged as the climate change leaders this year.

Presidents Xi Jinping and Barack Obama triggered a race to push the agreement into force in time for the Marrakech summit by joining the Paris deal together in early September.

“The fact that the U.S. and the Chinese could be a G2 was a fundamental spanner in the works of those who wanted to play an old-fashioned bloc negotiating system that would just see everybody circling around common-but-differentiated responsibility,” the U.N.'s Kyte said.

Yet the future of the new U.S.-China climate partnership depends on the outcome of the American presidential elections on the second day of the COP22 and the new leader's willingness to follow through on commitments made in Paris.

An unexpected victory for Republican nominee and climate-skeptic Donald Trump would threaten to break up the couple and knock the U.S. out of its leadership post on the international climate stage.

It would take Trump four years to withdraw the U.S. from the ratified agreement. But that wouldn't stop the new president from disrupting efforts to meet its global warming targets, simply by refusing to pass the laws needed to meet the country's emissions-cutting commitment.

4. Europe still means business

The EU was, and remains, a fundamental alliance-builder on this front.

It led the effort to build the informal “high-ambition coalition” of wealthy and poor countries in Paris, throwing weight behind a demand from island nations to include the 1.5-degree goal, and it brokered a deal among EU member countries in September to quickly ratify the Paris agreement even though only seven national parliaments had done so.

How it translates the Paris goals into climate policies for the years 2020 to 2030 will be key to maintaining that reputation.

The issue has already created divisions within the bloc, with some countries (including Germany, Sweden, the U.K. and France) pushing to amp up the EU's climate efforts to match the new 1.5-degree target and others (including Poland and Italy) still clinging to struggling industries such as coal and steel and arguing the policies should be aimed at limiting global warming to 2 degrees, since that's what EU leaders agreed to in October 2014.

The Commission has said it will wait for the Intergovernmental Panel on Climate Change's report on how to meet the 1.5-degree goal, due by September 2018, before proposing tougher targets. NGOs argue it's waiting too long.

5. What the COP22 won't change, yet

The key achievement from Paris is that the world has committed to slashing CO2 emissions. That doesn't mean fossil fuels are dead — at least not yet.

“There is a point on the horizon — mid-century — that we have to be at, and you work back from that and you make your decisions about risk and opportunity,” Kyte said.

“If you’re Georgia, what kinds of standards of accounting and reporting and verification should you have in comparison to China, and how much support is available for you to improve your data collection and analysis?” — Liz Gallagher, a senior associate at the environmental think tank E3G, on international scrutiny that will come with the sharing of data

That means businesses can start taking tough emissions cuts into account for long-term strategies. Bankers, for instance, are trying to understand how their clients and markets might be exposed to the shift away from fossil fuels, while renewable energy companies are jumping into poor and emerging economies.

Oil and gas producing companies and countries have cautioned that renewables, energy storing batteries and other green technologies are still too young to take over from fossil fuels. Oil remains a crucial fuel for transportation and gas is the sturdy partner for smaller, more intermittent solar and wind sources, they argued.

“Yes indeed, humankind is moving towards green energy,” Russian President Vladimir Putin said in a speech in October. “But at the same time, the world’s oil and gas production continues to increase, although a bit slower than before.”

Kalina Oroschakoff contributed reporting.

This is part of a POLITICO special report, COP22: Acting on climate promises.