KATOWICE, Poland (AP) — As leaders attending the U.N.'s annual climate summit heard fresh warnings about the dire consequences of leaving global warming unchecked, a new issue emerged Monday as a pressing concern: how to persuade millions of workers their industry can't have a future if humanity is to have one.

Hosting the talks in the heart of its coal region of Silesia, Poland tried to set the tone for the two-week meeting by promoting the idea of a "just transition" for miners and other workers facing layoffs as countries adopt alternative energy sources.

"We are trying to save the world from annihilation, but we must do this in a way that those who live with us today in the world have the best possible living conditions," Polish President Andrzej Duda said. "Otherwise they will say, 'We don't want such policy.'"

The issue of a "just transition" isn't restricted to workers in energy industries who might lose their jobs. Many economists argue that ambitious curbs on greenhouse emissions require raising the cost of carbon fuels — one of the measures that triggered large-scale protests in France by motorists feeling the squeeze at the pump.

Scientists say the only way to keep average global temperatures from rising above 1.5 degrees Celsius (2.7 F) by the end of the century is to phase out the use of fossil fuels by 2050. That is the most ambitious goal set in the 2015 Paris agreement, which negotiators from nearly 200 countries have come to Katowice to finalize.

U.N. Secretary-General Antonio Guterres issued a dramatic appeal to leaders Monday to take the threat of global warming seriously, calling it "the most important issue we face."

"Even as we witness devastating climate impacts causing havoc across the world, we are still not doing enough, nor moving fast enough, to prevent irreversible and catastrophic climate disruption," Guterres told delegates from almost 200 countries on the second day of talks.

Famed British naturalist Sir David Attenborough echoed his warnings, telling the gathering that the "collapse of our civilizations and the extinction of much of the natural world is on the horizons" if no urgent action is taking against global warming.

The 92-year-old TV presenter blamed humans for the "disaster of global scale, our greatest threat in thousands of years."

Without naming specific countries, Guterres chided the nations most responsible for greenhouse gas emissions for failing to do enough to meet the goals set in Paris.

Citing a recent scientific report , the U.N. chief urged governments to aim for net zero emissions by 2050. Net zero emissions mean that any greenhouse gases emitted need to be soaked up by forest or new technologies that can remove carbon from the atmosphere.

Such cuts would require a radical overhaul of the global economy. But Guterres said governments should embrace the opportunities of shifting to a "green economy" rather than cling to fossil fuels such as coal, which are blamed for a significant share of man-made greenhouse gas emissions.

U.S. officials have kept a low profile at the talks so far. President Donald Trump has announced Washington's withdrawal from the Paris accord, saying it's a bad deal for Americans, and repeatedly questioned the science behind climate change.

By contrast, action film star and former California Governor Arnold Schwarzenegger drew crowds and applause at the U.N. conference Monday for insisting that many in the United States remain committed to the agreement.

"America is more than just Washington or one leader," he said, calling Trump "meshugge" — Yiddish for "crazy" — for deciding to withdraw from the Paris accord. Schwarzenegger said he wished he could travel back in time — like the cyborg he portrayed in "The Terminator" — to stop fossil fuels from being used.

The Netherlands, a country with a long history of pumping oil and gas from the ground, is also among the places most at risk from rising sea levels caused by global warming.

With millions of people in the Netherlands living in low-lying areas, "you have your evidence and your case in point to make, sure, that you prevent sea levels from rising even further" Dutch Prime Minister Mark Rutte told The Associated Press.

Asked about the recent protests in France, one of which turned into a riot in Paris on Saturday, Rutte said politicians must work to get all of society to back the measures needed to tackle climate change.

"That means talking, talking, talking," he said. "With all societal organizations, politicians, all citizens being involved if they want to."

More talk is doubtlessly necessary, including at the international level. Poland's President Duda told reporters that his country, which relies on coal for 80 percent of its energy, would work to reduce its reliance on coal but never entirely give up its "strategic fossil fuel."

Among those addressing conference participants this week is a 15-year-old Swedish activist, Greta Thunberg, who has inspired students around the world to campaign against global warming.

Thunberg criticized leaders, such as Trump and German Chancellor Angela Merkel, who failed to come to the climate talks.

"I think that in the future we will look back and we will either laugh at them or we will hate them," she told The Associated Press. "It's very sad, but if they don't do anything right now that is the truth."

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