This past weekend, the world at long last agreed to take global action on climate change. Nearly 200 countries signed up to the Paris Agreement. Like most successes, there were many parents to this achievement, and many people can rightfully claim a piece of the credit.

For me, it was a particularly satisfying moment. My career working on environmental issues started seven years ago, in 2008, just before President Barack Obama’s first election when the expectation and enthusiasm levels for climate action were high. Of course, we all know what happened. The U.S. climate legislation that many believed was imminent stalled out and the global climate deal in Copenhagen fell short.

Over the past five years, even as international climate action slipped down on the public radar, a determined and persistent group, including my colleagues at WRI, continued to push forward. Each year since then, governments have come together for an annual Conference of the Parties (or COP) to UNFCCC and generally agreed to do just enough to keep the process moving.

That persistence paid off, as trust in the system was slowly rebuilt. This year the window of opportunity opened again and the world united around an agreement. The media have hailed it as “landmark” and “historic.” While the true impact will play out over time, there’s no doubt that this is an important moment and a springboard for greater action ahead.

Why Did Paris Succeed?

I would offer three reasons:

  1. The science of climate change has become clearer and the old arguments against action have fallen away. Each year, we learn more about climate change and see more of its impacts. Whereas five or 10 years ago, many people questioned – or openly doubted – if human activity was really altering our climate, today it’s overwhelmingly clear that it is. The crippling drought in the U.S. West, water shortages in Sao Paolo, super-typhoons in the Pacific and massive flooding in India are just a few examples that paint a picture of a changing climate. People are simply no longer willing to have their governments stand by without action. This is true in big countries, like the United States and China, and smaller nations, including those for whom climate is an existential threat, and many in between. Similarly, the old argument that it is going to be too costly has been chipped away, thanks in no small part to the New Climate Economy, which has found conclusively that action is affordable and in many cases even economically beneficial. This is why an overwhelming majority of people worldwide – 78 percent according to a Pew survey – support a global agreement.

  2. This agreement was built from the ground up. Unlike earlier attempts to forge a climate deal, this agreement called for countries commit to action well before they reached Paris, which they did in their national climate plans. Even before COP21, 185 countries had submitted plans, including goals for reducing greenhouse gas emissions, increasing renewable energy, climate adaptation and more. At least 187 countries have now submitted their plans. These plans, voluntarily submitted to the UNFCCC, paved the way for international cooperation. With their commitments on the table, it was easier for countries to get on board with a global agreement.

  3. There truly is broad momentum for climate action. Looking back, one of the big turning points was the joint announcement by U.S. and China in November 2014, when the United States committed to reduce emissions by 26 to 28 percent by 2025 below 2005 levels and China committed to peak its emissions by 2030 or sooner. With these two major countries in the lead, many more were willing to come forward. In addition to increased action by national governments, a growing number of leaders in cities, business, the investment community, and landscape restoration are moving forward with commitments. These are reflected in the 400 cities in the Compact of Mayors, the 114 companies that joined have Science-Based Targets, the large investors in the Breakthrough Energy Coalition, and the countries that have committed to landscape restoration. Together, these commitments provide the political space for countries to act. They create the atmosphere – or the “mood music,” as WRI President Andrew Steer likes to say. With the mood right, world leaders were better able to deliver.

Despite these factors, reaching an agreement never felt fully locked in. It took a deft touch by the French, and hard work by leaders in many countries, including in the U.S., China, India and the European Union. The role of many small countries, including those in the Climate Vulnerable Forum, helped push larger countries to reach further. The result was an agreement that exceeded expectations.

Of course, the hard work is not over. In the coming months, it will be up to national leaders, as well as representatives from businesses, cities, civil society and more, to follow through on their commitments and deliver action on the ground.

The day after the agreement was adopted, as I wandered hazily through the streets of Paris, I had a warm feeling that years of work and determination by my colleagues and peers had truly paid off. This is a rare emotion for many of us who work day-in and day-out on environmental issues, where progress is often incremental and frustration often reigns. This time, the outcome was big and deeply satisfying. As President Obama declared, “We’ve shown that the world has both the will and the ability to take on this challenge.”

We cannot rest, but at least we can enjoy the moment. The Paris Agreement was built on the backs of many people. It’s an agreement that will benefit people and the planet for years to come.