GLASGOW (BLOOMBERG) - It was Day 13 of the COP26 summit, and even the trees inside the Glasgow venue were beginning to wilt.

With the meeting running almost 24 hours over its scheduled time and the final outcome hanging in the balance, US climate envoy John Kerry and his Chinese counterpart, Mr Xie Zhenhua, huddled together deep in conversation. At one point Mr Kerry grasped Mr Xie's shoulder, while China's lead negotiator nodded and smiled as he enumerated points on his fingers.

It was a candid moment between two longtime climate diplomats that belied the global rivalry, hinting at the possibility for collaboration ahead of Monday's (Nov 15) virtual meeting between Joe Biden and Xi Jinping. It came three days after a joint US-China agreement in Glasgow that Mr Jochen Flasbarth, who headed Germany's delegation at COP26, described as the summit's "high point".

Yet if that deal was the peak, the low point for many delegates also involved China, as it aligned with India to secure a last-minute change to the conference conclusions on coal, watering down the language calling for an end to its use.

China - the world's biggest emitter - was the main driver behind the push, according to several country representatives. And the US let it go.

Backstage showdown

The final text contains the first ever reference to fossil fuels in a quarter century of COP summits. But China's intervention - via India - effectively undermined COP26 President Alok Sharma's goal to "consign coal to history".

Mr Sharma, the US, the European Union, India and China went backstage to thrash out the line on fossil fuel subsidies, according to a senior EU official. China threatened to dig in and take down the talks, and the US deal was what stopped it from pushing too hard and scuppering the whole summit, the official said.

The US had in any case signalled its acceptance of the weaker language in question, according to a separate person familiar with its stance. The result was that the world's three biggest polluters - China, India and the US - overrode the concerns of the vulnerable nations most at risk of climate change.

Places like the Maldives, whose president, Mr Ibrahim Solih, was among the many representatives of small and island states who travelled thousands of miles to appeal for help to avert an existential threat.

"What will it take for you to listen to us?" he demanded.

An email sent to the Chinese delegation seeking a response went unanswered on Sunday.

Mr Sharma, in an interview with the BBC, said that China and India will have to "justify" themselves to vulnerable nations.

'Pulse is weak'

The eleventh-hour drama reflected the fundamental disconnect between national interest and painful action needed to save the planet that detracted from a sense of historic progress made at the two-week United Nations climate conference.

Success at COP26 was always going to be subjective. Delegates said the outcome, known as the Glasgow Climate Pact, was flawed but pushed the boundaries of what was possible. The summit also concluded rules on global carbon markets and commitments to toughen up national climate plans, maintaining the key goal of limiting global warming relative to pre-industrial levels to 1.5 degrees Celsius.

"We can now say with credibility that we have kept 1.5 degrees alive," Mr Sharma said in the closing plenary session on Saturday, fighting back tears. "But, its pulse is weak."

Expectations of participants going into the meeting were raised by science showing the unequivocal impact of climate change, with the last seven years the hottest on record. Global protests at the emergency facing the planet piled on pressure.

Energy crisis

Yet even as activists demanded immediate and drastic action to try and save the planet from catastrophic warming, it was clear that the political and economic calculations for governments were more complex.

Outside realities intruded from Day One, as COP26 opened against the backdrop of an energy crisis that has seen gas prices at record highs and surging demand for coal. Saudi Arabia was painted by activists and NGOs as the villain for much of the summit, prompting an outburst by Energy Minister Prince Abdulaziz bin Salman rejecting accusations that his country had been the main block on progress as "a cheat and a lie".

In the end, the world's largest oil exporter was content to stay out of the argument over coal and let China and India take the flak, according to a person familiar with the events. Russia, too, stayed out of the line of fire. For Riyadh, the key was that the focus was on coal rather than oil.

Domestic politics

US Energy Secretary Jennifer Granholm attended only to be asked about oil prices and whether Mr Biden was going to release America's strategic reserves, after OPEC+ nations led by Saudi Arabia snubbed the president's call to pump more crude.

China hit fresh records for daily coal production during the course of the talks. Mr Biden's limited ability to secure his climate goals has been graphically illustrated by his dependence for passage of key legislation on Democratic Senator Joe Manchin of coal-producing West Virginia. And with Mr Xi laying the ground for an unprecedented third term next year, domestic considerations were always to the fore for China's delegation.

While Mr Biden brought little new to Glasgow, at least he attended. Mr Xi and Mr Vladimir Putin of Russia were among the high-profile no shows, as political developments elsewhere threatened to overshadow the talks.

Still, the US-China agreement announced on Nov 10, which outlined efforts to raise climate action in this decade, was the product of protracted diplomacy, with more than 30 meetings over the space of 10 months, including virtual visits as well as sessions in London, China and Glasgow.

Warm rapport

Mr Kerry and Mr Xie have developed a rapport over years, and the atmosphere at their meetings was described by China as very good. During lengthy talks, they shifted easily from casual, warm conversation about family to in-depth exchanges on climate, said a US person familiar with the negotiations.

They met almost every day in Glasgow before the joint statement. With negotiating teams working on two tracks - one focusing on the formal COP26 talks and another focused on forging their bilateral statement - it was quite taxing, according to a senior US official.

Not as taxing as for the Chinese side, though. China didn't have a government-backed pavilion this year, due to Covid-19 worries, and people familiar said it was one of the delegation's top objectives to not get Covid-19 in Glasgow.

With 40,000 registered participants, COP26 was among the largest UN climate summits ever. Whereas several members of the US team stayed in a hotel next door to the conference venue, the Chinese delegation failed to secure accommodation for everyone in Glasgow, and many had to make the hour-long commute from Edinburgh before dawn each morning.

Room roulette

With negotiators working as late as 5am, any room they were able to secure in Glasgow on any given day was allocated to the person with the most important mission, according to two people familiar with the delegation's activities.

Mr Kerry spoke with a hoarse voice on Tuesday after a late-night negotiating session he said ran to at 3am that morning. The deal was announced the following evening.

Only a small circle of negotiators were read in to the US-China talks, so that it came as a surprise to some other nations notified about an hour before the joint statement was issued, according to a person familiar with the process. The EU's climate chief, Mr Frans Timmermans, was one of those notified one hour before.

British Prime Minister Boris Johnson, as the summit host, arrived earlier that day to urge delegations to show more ambition - only for his calls to be drowned out within a matter of hours by the US-China announcement.

For all the choreography, within 48 hours a senior Communist Party official in Beijing was rowing back. Briefing reporters on China's climate commitments, Mr Han Wenxiu said it was necessary to avoid "rushing for success", and invoked the Great Leap Forward, Mao's campaign of rapid economic and social change that resulted in millions of deaths.

'Climate guy'

China needs to learn the lessons of that era, "and move forward one step at a time to achieve carbon peaking and carbon neutrality and in promoting common prosperity," said Mr Han.

Mr Kerry said the key to the US-China talks was being "honest about the differences" between them and staying scrupulously focused on the subject matter of COP without being derailed by other tensions.

"My job is to be the climate guy," he said.

Throughout the summit, there were bleak assessments from those on the front line, who pointed out that scientists gave the world 98 months to halve global emissions. It was a message taken up by NGOs and activists including Ms Greta Thunberg, who dismissed the proceedings as "greenwash".

With Covid-19 related restrictions leading to long queues, the organisers were accused of keeping out campaigners and making COP26 unnecessarily exclusive.

An estimated 100,000 people marched through Glasgow last weekend at the summit's midway point to demand urgent climate action.

"Young people say there's a lot of 'blah, blah, blah' here," said Mr Wang Yi, a member of China's delegation, channelling Ms Thunberg. "To some degree it's true."

How the summit outcome is perceived probably matters less than the concrete actions nations take once their delegations are back home.

As Slovakia's president, Ms Zuzana Caputova, said: "The carbon footprint from the planes we arrive on cannot be the only output."