Countries agreed under the 2015 Paris Agreement on climate change mitigation to attempt to limit the rise in global temperatures to 1.5 degrees Celsius, the threshold scientists say would head off the worst impacts of warming. To do that, scientists say, the world needs to cut global emissions in half by 2030, and to net-zero by 2050.
"The difference between 1.5 degrees and 2 degrees is a death sentence for the Maldives," President Ibrahim Mohamed Solih told world leaders on Tuesday.
Guyana President Irfaan Ali criticised large polluters for not delivering on promises to curb emissions, accusing them of "deception" and "failure" and warning that climate change will kill far more people than the COVID-19 pandemic.
"We hold out similar hope that the world's worst emitters of greenhouse gases that are affecting the welfare of all mankind will also come to the realization that, in the end, it will profit them little to emerge king over a world of dust," Mr Ali told world leaders on Thursday.
He said small island states and countries with low-lying coastlines, like Guyana, will bear the full brunt of the impending disaster despite being among the lowest emitters of greenhouse gases.
"This is not only unfair, it is unjust," he said.
Richard Gowan, UN director at the International Crisis Group, said there had been a "sense of existential crisis" running through the annual gathering at the United Nations.
"Both Beijing and Washington want to show they are leading the fight against global warming. If the small islands' leaders can't get people to listen at this General Assembly, they never will," Mr Gowan said.
US President Joe Biden said on Tuesday he would work with Congress to double funds by 2024 to $11.4 billion USD per year to help developing nations deal with climate change.
The funding would help achieve a global goal set more than a decade ago of $100 billion USD per year to support climate action in vulnerable countries by 2020.
Chinese President Xi Jinping pledged to stop building coal-fired power plants overseas, a move widely welcomed.
'We must act now'
President Chan Santokhi of Suriname, where much of the coastal area is low-lying, called for "ambitious and actionable commitments" to be made at COP26, urging developed countries to recommit to the $100 billion per year.
Mr Santokhi said that ideals and political commitments do not mean much if not supported by new financial resources.
"In the case of my country, Suriname, and the countries with low-lying coastal areas, we are committed to fighting climate change because we are particularly vulnerable even though we have contributed the least to this problem," he told the General Assembly.
The Pacific archipelago nation of Palau warned the world is running out of time.
"Simply put, we must act now to ensure our children inherit a healthy and reliable future. We need to act now before further irreparable damage is made to our planet," Palau President Surangel Whipps Jr, said at the gathering.