UNITED NATIONS, United States -- UN Secretary-General Antonio Guterres is set Wednesday to host a climate meeting marred at its outset by the absence of speakers from the world's top two emitters, China and the United States.

Despite increasing extreme weather events and record-shattering global temperatures, greenhouse gas emissions continue to rise and fossil fuel companies reap handsome profits.

Guterres has thus billed the "Climate Ambition Summit" as a "no nonsense" forum where leaders or cabinet ministers will announce specific actions that deliver on their commitments under the Paris Agreement.

The bar for making the podium was set high, with the UN chief making clear that only leaders who had made concrete plans to achieve net-zero greenhouse emissions would be allowed to speak.

After receiving more than 100 applications to take part, the UN finally released a list on Tuesday night of 41 speakers which did not include China, the United States, the United Kingdom, Japan or India.

"Tomorrow, I will welcome credible first movers and doers to our Climate Ambition Summit," Guterres said Tuesday.

Several major leaders didn't bother making the trip to New York for this year's UN General Assembly, including President Xi Jinping of China and Prime Minister Rishi Sunak from the United Kingdom, who said he was too busy.

US President Joe Biden, who addressed the General Assembly on Tuesday, sent his climate envoy John Kerry to the meeting -- though Kerry won't be permitted to speak.

"There's no doubt that the absence of so many leaders from the world's biggest economies and emitters will clearly have an impact on the outcomes of the summit," Alden Meyer of climate think tank E3G said.

He blamed competing issues -- from the Ukraine conflict to US-China tensions and rising economic uncertainty.

"But I think it's also the opposition in many of these countries from the fossil fuel industry and other powerful interests to the kind of transformational changes that are needed," said Meyer.

Catherine Abreu, executive director of nonprofit Destination Zero, said it was "perhaps a good-news story that we see Biden not being given a speaking slot at the summit" because the United States is continuing to expand fossil fuel projects even as it makes historic investments in renewables.

"I think about this as being a correction from past summits, where leaders have been given the opportunity to take credit for climate leadership on the global stage, while they continue to pursue plans to develop fossil fuels, and continue driving the climate crisis back at home," she added.

While the United States won't take the rostrum, California will be represented by Governor Gavin Newsom. From Britain, London Mayor Sadiq Khan will also attend.

- Growing anger -
The event is the biggest climate summit in New York since 2019, when Greta Thunberg stunned the world with her "How Dare You" speech before the UN.

Anger is building among climate activists, particularly younger people, who turned out in thousands last weekend for the "March to End Fossil Fuels" in New York.

Observers are eager however to see what Canadian Prime Minister Justin Trudeau and European Union President Ursula von der Leyen say both on their own goals and on financing commitments for the developing world.

The failure of advanced economies, responsible for the majority of historic emissions, to honor their promises to the worst affected lower-income nations has long been a sore point in climate talks.

There are some bright spots, including the announcement that Colombia and Panama are joining a grouping called the Powering Past Coal Alliance -- particularly notable as Colombia is the world's sixth biggest coal exporter.

Wednesday's summit comes weeks ahead of the COP28 climate talks in the United Arab Emirates, where goals include tripling renewable energy by 2030, and ending by 2050 the generation of fossil fuel energy that isn't "abated" by carbon capture technology.