Injured by wars, fragmented by incompetent leadership, divided by income inequality, the world needed to hear some good news. A different climate!

On a murky, late-autumn day, after two decades of scepticism, rivalries, cunning politics and pervasive special interests, humanity has decided to give itself the gift of hope. Yesterday in Paris, almost 200 nations “have signalled an end to the fossil fuel era, committing for the first time to a universal agreement to cut greenhouse gas emissions and to avoid the most dangerous effects of climate change at crunch UN talks in Paris,” reporters wrote in yesterday’s issue of the Guardian, the British paper that has become a known for good reporting on climate change.

What happened yesterday in Paris was written in Copenhagen six years ago, when a similar document was proposed, only to be rejected by big polluters like China and India during a last-minute secret meeting. The U.S. was forced to join the meeting, which ended in a separate agreement that was signed by America, Brazil, India, South Africa and China. The document, which replaced a global agreement negotiated during the week-long Copenhagen Conference, was a short, last-ditch sketch of a non-binding emissions deal that was also aimed at aiding those most vulnerable to warming. During the Conference, Copenhagen was named “Hopenhagen,” a city of hope, but after the secret deal, it was immediately dubbed “Flopenhagen” and even “Brokenhagen.”

But on that December night in 2009, the failure of the Conference was not the only broken hope. It was also the end of the trust that the international community had previously bestowed upon the freshly elected, young and promising American president.

Obama did not have direct responsibility for the flop of the Copenhagen Agreement. The Chinese foiled the Summit’s plans. But since Obama signed a separate deal with the plotters, did not inform his other partners, and then literally fled into the night like the thief, he lost all the trust and sympathies of the international community. It was unbelievable. It happened in a split second, in a packed Bella Center, where 15,000 delegates were expecting a press conference. As I reported for a Slovenian paper, on that Hamlet-like night in Copenhagen, people were ready to stone Obama when they heard that he had fled with a secret deal in his pocket.

If Obama lost the hardly-earned trust of Europeans that night, the plotters – the Chinese premier Wen Jiabao in particular – lost the trust of Americans, while the world was deprived of hope for any change. While these were extraordinary stories for us journalists to report, that cold Copenhagen night was depressing for humanity.

It took another six years, more delusions, further destruction and some changes in leadership to regain the political agreement on climate change that was signed by 184 countries yesterday in Paris. In the hours before the agreement, I was trying to figure out what was going on and capture the atmosphere in Paris as I sat in New York. In my efforts, I found a nice report in the Paris Review. But while nice, it – as with several other reports – did not tell me what was going on behind the scenes.

So when the news from Paris arrived and the whole world began to celebrate, I first started to look for the reactions of various environmental movements and NGOs that monitor climate change data and normally predict the world’s upcoming catastrophes. On the other hand, there are special interests of the corporations and individual countries that measure and report the climate change in accordance with those interests. For many years, China, for instance, pretended to stand on the front lines to combat climate change, but in reality, Beijing only recently started to report more objective pollution data – statistics that the Chinese population has experienced firsthand for years.

However, the Guardian prepared a nice infographic that shows how various countries contribute to climate change. This information helps explain why Paris 2015 is important.

But how were the countries in Paris able to reach such an important deal?The answers come from Fred Pierce, a contributor to Environment 360, a Yale University website:  

Scientists insist that the best way to achieve a low-carbon world is by setting a temperature target the policy makers said that “top-down” science-based approach failed in Copenhagen six years ago.  

The Paris approach has instead assembled voluntary targets from individual nations, in the hope that these commitments will unlock investments that ratchet up ambition on reducing emissions and eventually achieve the low-carbon world that all sides want.  

Caution is required here. The national pledges made in Paris are not binding in international law. And, even if fully implemented, they will not deliver two degrees, let alone 1.5. To rectify that, campaigners here in Paris pushed hard for the inclusion of a regular review process every five years that would oblige nations to improve their pledges, beginning before the agreement enters full force in 2020. But the real game, many believe, is to unleash the forces of capitalism in the name of fighting climate change and achieving a low-carbon economy. It could eventually make national targets and policing them almost irrelevant. Many here believe the agreement has done that. “It sends a very powerful signal to the world’s markets,” said Michael Jacobs, of the New Climate Economy, a think tank.

This model is similar what the “cap and trade” proposed in Copenhagen. It never really evolved worldwide because some of the polluters, like the U.S., never put it into motion. But this time around, the proposed business model is backed by political agreement. Or at least, this is what Fred Pierce hopes.

What mattered was to create the political certainty behind a move to a low-carbon future that would “unlock trillions of dollars” from private investors, said Edward Cameron, of Business for Sustainable Development. ‘We want to be able to go back and tell companies that the world has changed, that we are creating a whole new global economy.’  

How has this moment of apparent triumph for the long campaign to secure a strong global deal on climate change been achieved?  

This deal arose out of the chaos of Copenhagen in 2009, where the last efforts at a top-down scientifically based deal on limiting emissions failed. The following year, at the next climate conference in Cancun, Brazil, Mexico, South Africa, and others showed up with unilateral promises on emissions. This trickle became a flood in Paris when 184 nations delivered their voluntary pledges, which form the heart of the new agreement.  

Arguably the moment that sealed success here came in Washington 13 months ago when President Obama and Chinese President Xi Jinping signed their own joint emissions pledges. The world’s two largest emitters, whose deadlock poisoned the atmosphere in Copenhagen, became climate collaborators.  

But in the end, a deal has to be negotiated. The French turned out to be good at the task – much better, Fabius even felt able to boast at the end, than his counterparts in Copenhagen six years before. In the final hours here, the deal came down to three things: transparency, differentiation, and finance.

It sounds like a brilliant explanation. Almost too good to be true in this world deprived of any political vision. But time will tell, and if this agreement holds, the time will come to forgive Obama for what he did that night in Copenhagen.