WASHINGTON (AP) — The United Nations climate summit in Dubai was wrapping up last month when John Kerry went to a meeting with his Chinese counterpart Xie Zhenhua only to find a surprise waiting for him. Xie’s 8-year-old grandson had brought Kerry a card for his 80th birthday.

The lanky American, who had signed the landmark Paris climate accord with his granddaughter on his knee almost a decade earlier, bent down to thank the boy and praise his grandfather, according to someone who described the private encounter on the condition of anonymity.

Just how overheated a planet those two grandchildren half a world apart will inherit has hinged in part on the unusually warm bond between Kerry and Xie, whose relationship for the past decade and a half helped forge the globe’s stutter-step progress in curbing climate change. Xie, 74, retired in December, and Kerry recently announced that he’s stepping down soon.

It was a partnership that defined one generation’s hopes of saving a future one.

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At a glance, the two men make an odd pairing. Xie is balding and bespectacled, with a face as round as Kerry’s is narrow and angular. Xie got his start in the Chinese countryside during Mao Zedong’s Cultural Revolution before climbing the ranks of the Communist Party in environmental and economic agencies. Kerry is a son of New England privilege and boarding schools who fought in the Vietnam War and later protested against it. He became a politician and a diplomat, marrying into fabulous wealth along the way.

But over the years, Kerry and Xie forged a remarkable level of trust and respect in the world of international climate negotiations. They checked in on each other when they were sick, met each other’s families and spent long hours debating, quarreling and compromising in the fight against global warming.

The result was a series of agreements despite rising tensions between the U.S. and China that have even raised fears of war. Kerry and Xie paved the way for progress at international summits that could have otherwise stagnated. Their passports read like a history of modern climate negotiations — Copenhagen, Lima, Paris, Glasgow, Sunnylands, Beijing, Dubai and many stops in between.

Christiana Figueres, a former United Nations climate chief who oversaw the Paris agreement in 2015, said she struggled to think of any parallel in recent history for the rapport between Kerry and Xie in terms of length and impact.

The two “trusted each other, trusted each other’s sincerity, trusted each other’s attempts, each other’s promises,” she said.

Before the Paris deal, Earth was on a trajectory for about 3.5 degrees Celsius (6.3 degrees Fahrenheit) of warming over pre-industrial levels, scientists projected. Now Climate Action Tracker projects warming of 2.1 degrees (3.8 degrees Fahrenheit) — if world leaders follow through on their promises, that is.

However, even that level of warming may be catastrophic, and the departures of Kerry and Xie are reshuffling climate diplomacy at a moment when scientists warn that the move toward clean energy is still happening too slowly. Xie’s successor has been named, but it’s unclear what will happen with Kerry’s position.

“If the U.S. and China do not get along with each other, then global climate progress will be delayed,” said Li Shuo, an analyst at the Asia Society who previously worked with Greenpeace in Beijing. “It is imperative to kind of align these countries as much as possible if we want to achieve global climate progress.”

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Kerry was settling into a new role as chair of the Senate Foreign Relations Committee when he traveled to Beijing in 2009. It had been five years since he lost the presidential election to George W. Bush, but now he had a fresh opportunity to shape foreign policy during Barack Obama’s administration.

The annual U.N. climate summit was being held in Copenhagen later that year, and Kerry was eager to talk about it with Chinese officials. Xie stood out to Kerry as someone who wanted to lean forward.

There was little progress at first, and the Copenhagen summit was widely viewed as a disappointment. Although China had become the world’s largest emitter of greenhouse gases around this time, it was reluctant to take any steps that could hinder its economic growth.

When Obama was reelected in 2012, he named Kerry secretary of state. Tackling climate change was a priority, and better relations with China was a key part of the strategy. The deadline was 2015, when the U.N. would hold a highly anticipated summit in Paris.

Todd Stern, then the top U.S. negotiator, described climate talks as “a hard Rubik’s Cube,” with every turn of the puzzle creating new challenges to solve. He found Xie to be a tough yet amenable interlocutor.

“He laughs, he finds things funny, he jokes back at you,” Stern said. “He also gets mad and indignant and all of that.”

China was facing environmental problems that were creating political headaches, such as thick smog that choked cities. It was the opening that the U.S. needed to push for progress, and negotiations advanced behind closed doors.

In 2014, Obama traveled to Beijing to announce a surprise bilateral agreement with President Xi Jinping. The U.S. set a more ambitious target for reducing emissions by 2025, while China promised to peak emissions by 2030.

Stern said the deal “ricocheted around the climate world” and convinced countries that “we can actually get this done.”

The importance of the deal became evident one month later. International negotiators were in Lima, Peru, to lay the groundwork for Paris, but they kept getting stuck. Figueres said Xie came to her office at 3 a.m. and asked, “Can we talk?”

Xie urged Figueres to use the earlier agreement between the U.S. and China to help break the gridlock. She spent the next two hours shuttling between the two countries’ delegations until a deal was reached.

The next year, the Paris summit produced a milestone agreement by obligating all countries to reduce greenhouse gas emissions, creating the foundation for every subsequent negotiation over climate change.

It was the relationship with China, Kerry said afterward, that helped “change the paradigm.”

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The warm feelings were short-lived. Donald Trump was elected president in 2016, and he promptly withdrew the U.S. from the Paris agreement after taking office. Kerry and Xie stepped away from government service.

The hiatus lasted four years. When Joe Biden defeated Trump in 2020, he asked Kerry to serve as special envoy for climate negotiations.

Xi responded by calling Xie out of retirement, seen as a clear signal that Beijing was ready to work together again.

“If your president hadn’t wanted you to come back, I wouldn’t have come back either,” Xie told Kerry, according to a person who requested anonymity to discuss a private conversation. “I’ll be here roughly as long as you’re here.”

Despite Kerry and Xie’s rapport, it was slow going. The coronavirus pandemic made it difficult to travel. And even with Trump gone, tensions remained. Biden described China as a top foreign policy challenge, and disputes piled up over intellectual property, maritime access in the South China Sea and the future of Taiwan.

“These kind of things complicate the conversation,” said Jonathan Pershing, who worked for Kerry then and is now the environment program director at the William and Flora Hewlett Foundation. (The foundation also supports The Associated Press’ coverage of climate change.)

Kerry and Xie stayed in touch informally even after Beijing cut off communications with the U.S. after then-House Speaker Nancy Pelosi visited Taiwan in 2022. Although the island governs itself as a democracy, China views it as part of its territory.

More hurdles were around the corner. First Kerry was waylaid by COVID-19 during the U.N. summit in Egypt. Xie checked in, asking Kerry’s staff “how is my brother John doing,” according to a person briefed on the conversations.

Then Xie suffered his own health problems, believed to be a stroke, and Kerry returned the favor by calling and sending written messages.

“They obviously didn’t agree a lot of the time,” said John Podesta, a climate policy veteran who works in the White House. “You could only take a personal relationship so far.”

However, Podesta said, “having that level of trust and dialogue was important.”

Their work culminated in November, when Kerry and Xie met at the Sunnylands resort in California. China agreed to include methane, a particularly potent greenhouse gas, as part of its emissions target.

The next month was their final U.N. summit in Dubai, which ended with a global agreement to transition away from fossil fuels. It was a better outcome than expected for a summit hosted by the oil-producing United Arab Emirates, but not the aggressive move that some wanted at a time of record temperatures.

When the negotiations were over, Kerry and Xie held a joint press conference.

Kerry described his counterpart as “a partner in this climate fight with many people for these years.” Xie said that “I feel so lucky that I can make such a good friend like Secretary Kerry.” Mentioning his grandson, Xie said he hoped “this cause will be carried forward, generation after generation.”

There was no hug, but they shook hands warmly. Kerry leaned toward the microphone one more time, cracking his widest smile, to say how impressive the young boy had been — “unbelievable, he’s great.”

It was the last public moment for the two grandfathers together.

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Read more of AP’s climate coverage at http://www.apnews.com/climate-and-environment

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