BAKU - United Nations Secretary-General Antonio Guterres told world leaders at the COP29 summit on Tuesday to "pay up" to prevent climate-led humanitarian disasters, and said time was running out to limit a destructive rise in global temperatures.

Nearly 200 nations have gathered at the annual UN climate summit in Baku, focused this year on raising hundreds of billions of dollars to fund a global transition to cleaner energy sources and limit the climate damage caused by carbon emissions.

But on the day of the summit designed to bring together world leaders and generate political momentum for the marathon negotiations, many of the leading players were not present to hear Guterres' message.

After victory for Donald Trump, a climate change denier, in the US presidential election, President Joe Biden will not attend. European Commission President Ursula von der Leyen is not attending because of political developments in Brussels.

"On climate finance, the world must pay up, or humanity will pay the price," Guterres said in a speech. "The sound you hear is the ticking clock. We are in the final countdown to limit global temperature rise to 1.5 degrees Celsius and time is not on our side."

This year is set to be the hottest on record.

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Scientists say evidence shows global warming and its impacts are unfolding faster than expected and the world may already have hit 1.5 degree Celsius of warming above the average pre-industrial temperature - a critical threshold beyond which it is at risk of irreversible and extreme climate change.

As COP29 began, unusual east coast US wildfires that triggered air quality warnings for New York continued to grow. In Spain, survivors are coming to terms with the worst floods in the country's modern history and the Spanish government has announced billions of euros for reconstruction.

'Economy killer'

The summit opened on Monday with a technical deal seen as critical to launching a UN-backed global carbon market that would fund billions of dollars of projects that reduce greenhouse gas emissions.

That success was marred by a row over the summit priorities - a procedural tug-of-war that pitched European and small island countries against the Arab group of nations on how prominent the future of fossil fuels should be on the agenda.

The opening procedures were delayed by at least five hours, ending in an eventual compromise reluctantly accepted by the EU and other aligned nations.

At a press conference on Tuesday, COP29 officials sought to refocus attention on the summit's primary goal - agreeing a deal for up to $1 trillion in annual climate finance for developing countries.

"Enabling every country to take strong climate action is 100 percent in all countries' interests, even the largest and wealthiest. Why? Because the climate crisis is fast becoming an economy killer," said Simon Stiell, head of the UNFCCC climate body that facilitates the summit.

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"Unless all countries can slash emissions deeply, every country and every household will be hammered even harder than they currently are. We'll be living in a permanent inflationary nightmare."