More than one world leader says humanity's future, even survival, hangs in the balance when international officials meet in Scotland to try to accelerate efforts to curb climate change. Temperatures, tempers and hyperbole have all ratcheted up ahead of the United Nations summit.

And the risk of failure looms large for all participants at the 26th U.N. Climate Change Conference, known as COP26.

Six years ago, nearly 200 countries agreed to individualized plans to fight global warming in the historic 2015 Paris climate agreement. Now leaders will converge in Glasgow for two weeks starting Sunday to take the next step dictated by that pact: Do more and do it faster.

It's not easy. Except for a slight drop because of the pandemic, carbon pollution from the burning of coal, oil and natural gas is increasing, not falling.

Between now and 2030, the world will spew up to 28 billion metric tons (31 billion U.S. tons) of greenhouse gases beyond the amount that would keep the planet at or below the most stringent limit set in Paris, the United Nations calculated this week.

"Everything is at stake if the leaders do not take climate action," young Ugandan climate activist Vanessa Nakate said. "We cannot eat coal. We cannot drink oil, and we cannot breathe so-called natural gas."

Her words were echoed by a man tasked with steering one of the world's richest economic blocs through the climate transition.

"We are fighting for the survival of humanity," European Commission Vice President Frans Timmermans said. "Climate change and the threatening ecocide are the biggest threats humanity faces."

Climate change is fueling heat waves, flooding, drought and nastier tropical cyclones. Extreme weather also costs the globe about $320 billion a year in economic losses, according to risk modeling firm AIR Worldwide. And people die.

"The unhealthy choices that are killing our planet are killing our people as well," said Dr. Maria Neira, director of public health and environment at the World Health Organization.

Humanity and the Earth won't quite go off a cliff because of global warming, scientists say. But what happens in Glasgow will either steer the world away from the most catastrophic scenarios or send it careening down a dirt road with tight curves and peril at every turn. It's a situation where degrees, even tenths of a degree, translate into added risk.

"We are still on track for climate catastrophe," United Nations Secretary-General Antonio Guterres said Tuesday, even after some countries' recent emission pledges.

For months, United Nations officials have touted three concrete goals for these negotiations to succeed:

— Countries must promise to reduce carbon emissions by 45% by 2030 compared with 2010.

— Rich countries should contribute $100 billion a year in aid to poor countries.

— Half of that amount must be aimed at adapting to climate change's worst effects.

World leaders have recently softened those targets a bit, and they say the goals may not quite be finished by mid-November, when negotiations end. U.S. Climate Envoy John Kerry told The Associated Press: "There will be a gap" on emission targets.

Under the Paris pact, nations must revisit their previous pledges to curb carbon pollution every five years and then announce plans to cut even more and do it faster. Delayed a year by the pandemic, this year's meeting is the first to include the required ratcheting up of ambitions.

The hope is that world leaders will cajole each other into doing more, while ensuring that poorer nations struggling to tackle climate change get the financial support they need.

The headline goal set in Paris was to limit warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit) since preindustrial times. The world has already warmed 1.1 degrees Celsius (2 degrees Fahrenheit) since then.

Former United Nations Secretary-General Ban Ki-moon said this month that the 1.5-degree mark "is the threshold for our survival, humanity, our planet Earth."

But every analysis of current climate-change pledges shows that they are not nearly enough to stop warming at that point but will instead lead to at least another degree or a degree and a half Celsius of warming (about 2 to 3 degrees Fahrenheit).

All five emissions scenarios studied in a massive UN scientific assessment in August suggest that the world will cross that 1.5-degree-Celsius threshold in the 2030s, though several researchers told the AP that it is still technically possible to stay within that limit or at least temporarily go over it and come back down.

Small island nations and other poor, vulnerable communities said in 2015 that 2 degrees would wipe them out, and insisted on the 1.5-degree threshold.

"Our way of life is at stake," said Tina Stege, the climate envoy for the Marshall Islands. "Our ability to provide our children with a safe and secure future is at stake. Atoll nations like the Marshall Islands do not have higher ground to retreat to."

In Glasgow, divisions between nations are big, and trust is a problem, say several United Nations officials and outside analysts.

Rich countries like the United States and European nations developed carbon-belching energy and caused most of the problem historically, but now they ask poor nations to cut or eliminate the use of fossil fuels. In return, they've promised $100 billion a year by 2020 to help developing countries switch to clean energy.

So far, the funding has fallen far short of that amount.

"Failure to fulfill this pledge is a major source of the erosion of trust between developed and developing nations," Guterres said.

The key to success may lie in the middle, with major emerging economies.

Three days before the meeting starts, China, the world's largest carbon emitter, submitted a new national target that is only marginally stronger than what was previously proposed.

China is so important that if every other nation cuts back in line with the 45% global emission reduction and China doesn't, the world's total will drop only by 30%, according to Claire Fyson, a top analyst at Climate Action Tracker, a group of scientists that monitor and analyze emission pledges.

In the end, every country, will be asked to do more in Glasgow, said United Nations Environment Programme Director Inger Andersen. But much of the effort, she said, comes back to China and the U.S.

"We need these two powers to put aside whatever else and to show true climate leadership because this is what it will take," Andersen told the AP.

But realistically, she added, leaders in Glasgow, will take anything "in terms of real, meaningful commitments that are backed by action — action that starts in 2022."

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Borenstein reported from Washington, Jordans from Berlin. Associated Press Writer Ellen Knickmeyer contributed from Washington. Follow Seth Borenstein on Twitter at https://twitter.com/borenbears and Frank Jordans at https://twitter.com/wirereporter.

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Read more of AP's climate coverage at http://www.apnews.com/Climate

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content.