I haven’t always been pleased with the performance of Secretary of State John Kerry. In particular, his efforts to convince Congress to authorize an attack on Syria in response to the 2013 sarin attacks were so inept and risible that it nearly fried my synapses. In the end, the president found a last minute way out of that jam, and I’m aware that Kerry was trying to enact a policy as much as he was trying to create one.

If he got off to an inauspicious start, however, his recent performances have been nothing short of spectacular. The thaw with Cuba and the nuclear deal with Iran involved heavy lifting and cut against the grain of decades of international and domestic suspicion and hostility. And what a difference there is between the outcome of the climate talks in Paris and the 2009 debacle in Copenhagen!

It’s a long way from 2007 in Bali where a delegation led by neoconservative PNAC signatory Paula Dobriansky was “booed and hissed by the representatives of nearly 190 nations” for its bad faith obstructionism.

James Wimberly notes two beneficial side effects of the success of the Paris conference. First, while the death sentence of the oil, coal and natural gas industry has been delayed, it is now in writing. And, second, “the defeat” of the climate science “denialist and delayist ideologues…is on such a total scale that surely the movement will start to unravel.”

There is a lot of credit to go around, especially for French President François Hollande, Foreign Minister Laurent Fabius, and climate change envoy, Laurence Tubiana. But John Kerry needs to get his due.

As the New York Times details, it was the agreement with China that set the stage for Paris, and Kerry was the major force who made the China agreement happen.

China’s views on climate change shifted, as well. The vast expansion of coal-fired power plants that was fueling China’s rapid economic growth was also choking its cities with pollution.

With public anger rising over record levels of toxic smog, Chinese officials began to take steps to curb China’s use of coal.

Paying close attention to that shift was Mr. Kerry, now secretary of state. He saw an opportunity to broker a deal, and to try to pave the way toward a broader agreement in Paris.

Throughout 2014, Mr. Kerry held a series of meetings in Beijing focused on climate change. In October 2014, he invited the top Chinese environment official, Yang Jiechi, to a private lunch at the Legal Seafoods restaurant overlooking Boston Harbor. They spoke for three hours about the changes that had already influenced their pollution politics at home and discussed the possibility of turning that into new policy on the world stage.

The next month, Mr. Obama visited Beijing, where he and President Xi Jinping of China announced that they would move forward jointly on plans to reduce their greenhouse gas pollution.

That announcement broke the deadlock that had stalled climate change negotiations for over 20 years.

The following month in Lima, Peru, negotiators wrote a first draft of what would ultimately become the Paris Agreement. In language modeled on the agreement between the United States and China, the Lima pact required every country to submit its own climate change plan before meeting in Paris.

“The China announcement changed everything,” said Mr. Kerry in an interview. “It changed people’s thinking about this. Without the China announcement, you wouldn’t have 184 nations ready to come to Paris, the homework done, the table set.”

I know that it was a lifelong ambition for John Kerry to serve as Secretary of State. I am happy to see that he knew what to do with the opportunity once he finally got it. In a short time, he’s built a very impressive legacy.