COP25 begins on Monday in a trade fair park in the Spanish capital, Madrid, days after the European Union collectively declared a "climate emergency", echoing a joint, equally grim crisis warning issued in early November by more than 11,000 scientists from 150 countries.
UN Secretary-General Antonio Guterres has appointed Mark Carney as his special envoy on climate action and finance, said Guterres' press office on Sunday.
Spain is hosting the event after Chile's cancellation due to unrest in the country.
The UN has reported that greenhouse gas levels in the atmosphere, the main driver of climate change, hit a record high past year.
The affected countries will unanimously demand compensation for the consequences of climate change on them during the COP 25 conference, said Environment, Forest and Climate Change Minister Shahab Uddin.
Around the world, extreme weather ranging from wildfires to floods is being linked to man-made global warming, putting pressure on the summit to strengthen the implementation of the 2015 Paris Agreement on limiting the rise in temperature.
Pelosi said she was proud to lead the congressional group - which includes Florida Rep. Kathy Castor, who Pelosi tapped to lead the House's select committee on climate change - "to reaffirm the commitment of the American people to combating the climate crisis".
Tens of thousands of protesters, primarily in Europe and Asia, hit the streets on Friday to make a fresh call for action against global warming, hoping to raise pressure on world leaders days before a United Nations climate summit.
Guterres flagged a United Nations report to be released Tuesday confirming the last five years are the warmest on record, with 2019 likely to be the second hottest ever.
Guterres said there may countries guilty of failing to meet commitments laid out in the Paris Agreement which seeks to the increase of global temperatures well below 2C, and ideally below 1.5C.
The UK's former clean growth minister, Claire Perry O'Neill, who is set to be president of next year's talks, will be attending the meeting in Madrid, along with Lord Duncan and delegates from government and devolved administrations.
Teenage climate activist Greta Thunberg has been named author of the year by British bookshop Waterstones.
The governor said he was "honoured" to be asked to take on the role.
She had travelled to NY by yacht with plans to make her way down to Chile to attend the talks in Santiago without flying, but had to find a way home when the meeting was moved.
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