GLASGOW (BLOOMBERG) - It is hard to make progress on climate change when the biggest polluter doesn't show up.

Chinese President Xi Jinping was not among the dozens of world leaders there to open COP26, the ongoing climate talks organised by the United Nations in Glasgow, Scotland.

China also sent a much smaller delegation than usual and was uncharacteristically quiet during the first week of meetings.

In the few comments that officials did make, they mostly pushed back against calls to cut emissions more quickly.

The world's second-biggest economy also stayed out of pacts to tackle methane, a super-potent greenhouse gas, and reduce funding for fossil fuel - two measures that attracted widespread support and will likely end up among the biggest achievements of the entire summit.

Other world leaders are stepping into the gap.

United States President Joe Biden came in person to declare that the US is back after four years away from major climate diplomacy. Prime Minister Narendra Modi drew praise for an unexpected pledge to zero out India's emissions by 2070.

In contrast, Mr Xi sent a short note reiterating his country's stance.

"Developed countries not only need to do more in their own countries, but also need to provide support to developing countries in order to help them do better," he wrote.

That posture reflects China's long-held position that its emissions should be judged against the historical pollution from major economies that industrialised first such as the US and Britain.

But that line is ringing less and less true as China's economy booms and its toll on the warming planet continues to accelerate.

In less than three decades, China's cumulative carbon-dioxide emissions will exceed those of the US, according the Inevitable Policy Response project, if things continue on the same path.

China's emissions

By mid-century, in other words, China will become the biggest emitter in history if it does not do more to curb its pollution now.

China has already surpassed other historical giants of carbon emissions by other metrics.

Data from Rhodium Group shows that per capita emissions have already exceeded Europe's for years.

Last year, meanwhile, China's emissions rose above the average of all developed countries.

Almost every other country's emissions are around or below pre-pandemic levels - but China's soared in the first half of the year, according to the Global Carbon Budget.

Current policy, announced by surprise last years, sets out a plan for China to reach peak emissions by 2030 on the way to carbon neutrality by 2060.

These are goals China sees as the most dramatic reduction ever attempted, and thus from its perspective other countries shouldn't demand more. "We need to be realistic, to be pragmatic," China's lead climate negotiator Xie Zhenhua told reporters in a small briefing, according to state news agency Xinhua.

China's plans are "already ambitious", he said.

China had been building the case that its current goals are enough in the lead up to COP26.

Ye Min, the country's vice-environmental minster, said late last month that "developed nations' failure to fund poorer countries and win their trust has become the biggest barrier to the efforts to address climate change".

That funding shortfall has become a sore point in negotiations in Glasgow, but China is not among the developing countries that needs help from the UN.

The country already leads the world in renewable capacity and just kicked off a 100GW project in the desert.

The problem is that China's commitments on climate are selective and conditional, said University of Exeter postdoctoral research fellow Martin Thorley.

"The leadership would like to be seen as a global leader on climate in some respects such as technology," he said. "But they retain severe misgivings on international obligations that might restrict their options."

There are subtle signs that China does not want to draw attention to itself at COP26.

Unlike previous years, there is no government-backed pavilion where negotiators could network with delegates and observers.

China's team had just one low-profile briefing with state media and a few of foreign organisations selected by its British embassy.

In some ways, this year's minimalist engagement is a throwback to the Copenhagen climate summit in 2009, when Western media blamed its delegation for the breakdown.

Bad publicity

The sting of bad publicity eventually prompted China to become more constructive, said Chatham House associate fellow Sam Geall, who is also acting chief executive of non-profit China Dialogue.

That process culminated in the Paris Agreement in 2015, when a bilateral agreement between the US and China paved the way for a historic global deal to keep temperatures in check.

Geall recalls the unprecedented openness from the Chinese delegation in 2015.

State officials happily took questions from the media at the China pavilion.

"It's very unfortunate that China has made its presence so much smaller," he said.

Some China climate watchers suggested that the nation's leaders are more concerned with implementing measures at home than winning praise at COP26, which critics say can become a theatre for non-binding pledges from companies and countries.

"When Chinese diplomats look at many of these statements and declarations, the question in their mind is how much of this is PR that reflects the lack of substantive ambition beneath the existing headlines," said Greenpeace East Asia climate analyst Li Shuo. "If overpromising and underdelivering becomes a trend in global climate politics, Beijing can be forgiven for being cynical."