A climate action summit on Monday opens a week of high-level talks at the United Nations General Assembly, with world leaders being asked to significantly reduce greenhouse gas emissions following commitments first made in Paris in 2015.
Although the event in New York aims to pressure countries to do more to combat climate change the gathering could instead highlight the ambivalence of some nations to the UN initiative.
The United States – which early in the Trump administration announced plans to withdraw from the Paris Climate Accord – will not be among 64 countries that take to the podium. A low-level US delegation will attend the day-long talks while President Donald Trump hosts a separate event around the time UN Secretary General Antonio Guterres opens the climate summit.
Also missing will be Brazilian President Jair Bolsonaro, like Mr Trump a climate science sceptic, who has been castigated for failing to combat huge fires that continue to rage in the Amazon rainforest.
Each speaker at the climate summit has been allotted three minutes. While some nations are expected to make commitments on emissions, progress may be deemed inadequate by many of the estimated four million people that took to the streets in global protests against climate change on Friday, thousands of whom thronged the UN at the weekend.
The summit is also a major personal test for Mr Guterres, the top official at the UN since the beginning of 2017. The former prime minister of Portugal’s tenure has been plagued by global conflict. Wars in Syria and Yemen have intensified during that time and a UN peace process in Libya that he personally spearheaded collapsed earlier this year, calling the world body's relevance into question.
Mr Guterres has said that while there is limited ground for the UN to solve conflicts, climate change is an issue where the world body can prove its value and take a global leadership role. Monday's summit will put that statement to the test, said Richard Gowan, UN director at the International Crisis Group.
“The secretary general has struggled to find a really powerful case for why the UN matters, emphasising issues like conflict prevention and fairer migration rules that have not resonated globally,” said Mr Gowan.
“His efforts to mediate in cases such as Cyprus and Libya have failed, but his new focus on climate change this year has won a lot of political and media attention, and he has smartly tied his diplomatic work to the Climate Strike movement.
“There has been a sense that the fight against global warming has been adrift since the Paris agreement. I think Guterres has found a cause that he can use to prove the UN's relevance.”
The Paris pact was intended to keep temperatures from rising to more dangerous levels. It called on almost 200 countries to set voluntary targets to reduce their emissions, but many large nations, including the US, are off track.
Heat waves that killed hundreds in Europe this summer, as well as floods and the Amazon fires have reawakened the opportunity for collective action. There is a broad scientific consensus that warmer oceans are supercharging hurricanes, making Category 4 and 5 storms more common. The latest research also suggests that warming may be affecting global atmospheric currents, increasing the frequency of ultra slow-crawling hurricanes such as last month's Dorian and 2017's Harvey.
But the evidence has not yet resonated in US policymaking.
Mr Trump has rolled back dozens of environmental regulations, saying they place an intolerable burden on the American economy. Reiterating his resistance he last week blocked the state of California's attempt to set its own rules on auto emissions. The case is now headed for the Supreme Court, with 23 other US states joining California in suing the Trump administration.
In Brazil, Mr Bolsonaro wants to open the Amazon to greater commercial activity, with activists saying that forest clearing caused by fires is aiding that goal. And in China, state-owned companies want to increase the number of coal-fired energy projects, although the country has said it is seeking to reduce carbon emissions in other ways.
Speaking to reporters on Friday, Mr Guterres stressed that cities and businesses would be attending Monday's summit, noting that they were pushing ahead in efforts to assess climate risks and respond accordingly, even if some governments are not.
The goal of the summit is that a "very meaningful number of countries" announce their commitment to a goal of carbon neutrality by 2050, said the secretary general.
Under such a pledge, nations would aim to achieve a carbon footprint of zero by minimising their emissions and offsetting any that remain through such actions as planting trees that absorb excess carbon dioxide.
Mr Guterres also hinted that China, represented by Foreign Minister Wang Yi, may be among the attendees who commit to new measures.
“I believe that China will be one of the few countries that will be ahead of time in relation to the commitments made, those nationally determined contributions made in Paris," he said.