Almost 200 governments signed an unprecedented agreement last year to phase out fossil fuels in favour of renewable energy in the second half of the century.
This agreement, signed in the French capital and seen as a turning point for global climate policy, comes into force on Friday.
Al Jazeera explains why the deal matters and what it means for the future.
| What is the Paris Agreement?
In December last year, after years of negotiations, 195 nations made a new commitment to work together to address global climate change.
The Paris Climate Agreement aims to limit global temperature rise to 2 degrees Celsius above pre-industrial levels by 2100.
This level is considered a crucial tipping point, above which there will be serious consequences for global food production and more frequent and dangerous climate events, such as flooding and drought.
To achieve this, global greenhouse gas emissions will need to be cut by an estimated 40-70 percent by 2050, and by 2100 the planet must be carbon-neutral.
Under the Paris accord, each country must submit its own plan to reduce emissions of greenhouse gases and deal with the impact of climate change.
The agreement as a whole is not legally binding and does not penalise nations who fail to meet their commitments. But it does impose an obligation on countries to implement their plans, and includes a review process designed to shame them into compliance, while putting pressure on them to increase the scope of their efforts every five years.
| Why is it coming into force on November 4, 2016?
Before the agreement could enter into force it had to be formally accepted by at least 55 countries, which accounted for 55 percent of global greenhouse gas emissions.
This happened on October 5, 2016, triggering a month-long countdown.
Most of the world's largest emitters of greenhouse gases, including India, China, the United States and the European Union, have ratified the agreement.
Last December, 195 nations made a new climate commitment in Paris [Christophe Petit Tesson/EPA]
Russia and Japan have said they will do so in the coming months.
During the run-up to the Paris meeting, it was widely considered that any agreement made would not enter into force until 2020.
But the fact that so many nations ratified the accord, and that it will come into force in less than a year, demonstrates huge political will to tackle climate change and makes the Paris agreement one of the fastest multilateral deals ever to have entered into force.
| Once in force, what will happen?
As hard as it was to get a global agreement, the real concrete work to address climate change will begin now in earnest.
Few expected the Paris agreement to be in force before the COP22 meeting that starts next week in Morocco. But as it is, the event must now host the first meeting of those who signed up (called CMA1).
This meeting will focus mostly on how to implement the agreement, on establishing procedures and guidelines for how it will work, and setting up the review process and requirements for transparency that nations must meet.
It is possible that this first meeting will be suspended or partly suspended for a year to give nations adequate time to prepare.
| What else will be happening at COP22?
One of the main focus points of COP22 will be how to make the abstract goals outlined in the Paris agreement - to accelerate and intensify the actions and investments needed for a sustainable low carbon future - a concrete reality.
Hundreds of engineers, researchers and scientists will be attending what the UN has described as a "brainstorming session" to look at ways to de-carbonise our lives.
They will consider a wide range of clean energy technologies, including renewables, carbon capture systems, battery technology, and green transport.
| Could Trump derail the Paris agreement?
US presidential candidate Donald Trump has said he would withdraw the United States from the Paris agreement if he becomes president.
But because Washington has already ratified it and it comes into force before the November 8 election, even if Trump wins, the US is bound by the agreement to remain part of it for at least three years. After this, if a country decides to exit the agreement it must wait another year before it can formally leave.
In practical terms, unless Trump were to win a second term, another US president would be in office when any final exit date would take effect.
| What role will carbon trading play?
The Paris agreement does not detail how the private sector or carbon markets can be used in emission-reductions efforts, but does endorse them as a way of reducing carbon emissions.
Many countries already have carbon-trading schemes - which regulate the buying and selling permits to emit carbon dioxide - and some trade carbon credits internationally.
| Few expected the Paris agreement to be in force before the COP22 meeting, which starts next week in Morocco [Etienne Laurent/ EPA]
The UN says these countries must account for the way these schemes affect their total emissions and ensure there is no double counting when traded. But it leaves the future of carbon-trading schemes - both national and international - in the hands of individual nations.
The Paris agreement, however, sends a clear signal to companies around the world that they must look to reduce emissions now, or end up paying a high price later.
| Any additional help for developing countries?
The Paris agreement does not build on a previous commitment by developed countries to jointly raise $100bn per year by 2020 to help developing countries to cope with climate change, but it did raise the public profile of the Green Climate Fund.
The agreement called on developed countries to take the lead to "mobilise" climate finances but failed to create binding requirements on individual nations to do so.
It does not define how the $100bn - if it is raised - should be administered, stating it may come from "bilateral or multilateral, public or private sources, including innovative financing".
The UN's Green Climate Fund aims to support countries in the global south to build clean energy and climate-resilient economies. It currently has more than $10bn pledged to it, well short of early targets.
Some developing countries have expressed disappointment with the Paris agreement for not doing more to detail how developed countries can help them to become greener economies while meeting their development and poverty-reduction goals.
Source: Al Jazeera News