The scene would be unthinkable elsewhere these days — US and Chinese envoys, smiling and embracing, hailing their friendship as leading the world together in the right direction.

But the spirit of cooperation was on full display in Dubai, where a UN climate summit on Wednesday sealed a historic if watered-down agreement to begin to transition away from oil, gas and coal, the main culprits in the planetary crisis.

Hailing the summit as a success, US climate envoy John Kerry — the former secretary of state, senator and presidential contender — was joined by a beaming Xie Zhenhua, his retiring Chinese counterpart whom he has known for years.

Kerry had welcomed Xie a month earlier for a long weekend at the Sunnylands resort in the California desert, where the two countries — together responsible for 41 percent of global greenhouse gas emissions — agreed on outlines of climate action that partly served as a basis for the nearly 200-nation Dubai deal.

Xie recalled their work together on another major climate accord, in Paris eight years ago, and said he brought his grandson — himself eight years old — to Dubai to meet Kerry, who turned 80 on Monday during the negotiations.

His grandson wanted to say "happy birthday to my good friend Mr. Kerry," Xie said.

Stepping up to embrace the silver-haired American, Xie said, "I would like to invite you to join me to wish my good old friend good health and a happy life."

It was a far cry from the "wolf warrior" diplomacy for which China has recently become known, with shrill, loaded pronouncements attacking the United States and its influence in the world.

While tensions have eased, with Presidents Joe Biden and Xi Jinping meeting last month in San Francisco, the two powers remain at loggerheads on a wide range of issues.

At the height of the round-the-clock negotiations in Dubai, when Xie and Kerry said they were working together, the State Department was issuing a statement denouncing what it saw as aggressive moves by Beijing against the Philippines in the South China Sea.

Climate change should be seen as a "universally accepted humanitarian issue" and "not a bilateral, strategic question in terms of the South China Sea or other kinds of things," Kerry said.

The Biden administration agreed with China to "try to separate other issues and focus on something that is not bilateral but is global," he said.

Seeking to influence others

Climate has not always been insulated, with China cutting off talks last year in fury over a visit by then US House speaker Nancy Pelosi to Taiwan, the self-ruling democracy claimed by Beijing.

The friendly tone is also highly unlikely to continue if Donald Trump returns as president, as he is an avowed skeptic on climate change who rails against China as an arch-enemy.

The Biden administration has also identified China as the biggest challenger to US primacy. But on climate, Kerry said dynamics have shifted in recent years with China emerging as the biggest producer of renewables, even as it remains the biggest emitter.

Kerry said he agreed with China to keep consultations on long-term climate plans and that the two powers wanted to "generate more effort in other countries" to bring a global solution.

The Dubai declaration speaks of ramping up renewables to replace fossil fuels, in line with the joint US-China statement in Sunnylands.

But Li Shuo, an expert on Chinese climate policy at the Asia Society Policy Institute, said the Dubai agreement showed less of the US-China fingerprint than the Paris accord, which looked more like "copy and paste" from the two countries' own understandings.

China, on track to peak emissions, has essentially "graduated" from representing the developing world on climate, he said.

Li said it was also impossible completely to isolate climate from the broader US-China rivalry.

"There are increasing limitations on their ability to lead the rest of war, partly because the contentious relationship between the two countries," he said.