Washington (CNN) - The year's most important meeting on climate change got underway in Poland this week with one glaring absence: a high-level US presence.
Global leaders and officials are gathering for two weeks of meetings at the 24th Conference of the Parties to the United Nations Framework Convention on Climate Change, or COP24, to create a rulebook that will turn the 2015 Paris climate agreement into a workable reality. They aim to establish rules, figure out financing and build ways to verify that nations are meeting their commitments.
But even as UN Secretary-General Antonio Guterres called for action Monday in Poland, telling gathered delegates that "we are in deep trouble with climate change," the United States has been emphasizing its rejection of the Paris agreement and global consensus.
COP24 comes on the heels of the G-20 gathering in Argentina, where 19 of the 20 leaders signed a communique reaffirming their commitment to fight global warming, but President Donald Trump insisted on a paragraph outlining his opposition and the US decision, under his administration, to withdraw from the 2015 Paris agreement.
Argentine President Mauricio Macri announced at a closing G-20 plenary session on Saturday that the gathered leaders had agreed on language about climate, a key sticking point in the leadup to the summit.
"We ratified the concern we all share with regard to climate change," Macri said.
The communique document obtained by CNN includes a section on climate, saying that signatories to the Paris climate accord reaffirm that the agreement "is irreversible and commit to its full implementation, reflecting common but differentiated responsibilities and respective capabilities, in light of different national circumstances."
"We will continue to tackle climate change, while promoting sustainable development and economic growth," the document reads.
Notably, however, a separate clause put the United States alone, saying it "reiterates its decision to withdraw from the Paris Agreement, and affirms its strong commitment to economic growth and energy access and security, utilizing all energy sources and technologies, while protecting the environment."
A senior US official said the communique was adopted by unanimous consensus, with the US still the only country not joining the section on the Paris climate accord. The separate language was required for Trump to sign off on the communique, the official said.
It's a 180-degree turn from the role the United States played in helping bring the climate pact into being, and it's happening at a time when global cooperation may be faltering, analysts said.
"It is an almost complete abdication. We have really, really dropped out of our leadership position," said Samantha Gross, a fellow at the Brookings Institution's Initiative on Energy and Climate.
The United States was a major driver in reaching the Paris agreement and afterward was particularly good at leading on issues of monitoring and verification, Gross said. But beyond that, there's a broader question.
"If we don't lead, who does?" Gross asked. "It's not clear who that's going to be and if anyone will fill that role."
Some observers float the idea of China taking up the baton, but Gross and others said that it's not clear that Beijing wants that kind of leadership role, adding that it has its own priorities shaped by domestic concerns and the country's terrible air pollution.
Trump has displayed a steady hostility to the Paris climate agreement and the very idea of climate change itself, responding to his own government's recent report about its potentially catastrophic impact by saying, "I don't believe it."
The US president's views also reflect a growing global nationalism and distrust of multilateral institutions that could make it all the harder to make progress on a complex, international challenge such as climate change, Gross noted in a call with reporters.
Many countries are preoccupied with domestic challenges: The UK is consumed by Brexit, Mexico is in the middle of its own presidential transition, a climate skeptic has just become president-elect of Brazil, and Australia too may be backing away from climate commitments.
"The global political environment is really challenging right now," Gross said. "It is a challenging time just for the idea of multilateralism in general."
The leadership vacuum on climate change comes as a recent study showed that CO2 emissions are falling woefully short of the Paris agreement goal to limit temperature rises during this century to no more than 2 degrees Celsius above pre-industrial levels.
In this environment, delegates from nearly 200 nations arrived in Poland, some of them starting meetings a day early to meet a year-end deadline to create a blueprint for the Paris agreement.
"I think it's fair to say it's the most important, consequential talk since Paris," said Todd Stern, a former US special envoy for climate change, now with the Brookings Institution.
The two-week gathering, deep in Polish coal country, is the first major climate meeting to follow a stark report by the Intergovernmental Panel on Climate Change that called for urgent change, saying that governments would have to cut emissions by 45% by 2030 to limit the global temperature increase to 1.5 degrees Celsius.
While the United States is not sending senior officials, a delegation of working-level staff is attending the meeting, as are representatives from US states and business.
"We will still be there," Gross said. "We just don't have the pull we used to."