President Joe Biden kicked off global talks on climate change on Thursday by announcing the US will aim to halve its carbon emissions over 2005 levels by 2030.
The ambitious goal from the world's second-biggest polluter after China marks a stark reversal from the policies of Mr Biden's predecessor Donald Trump, whose tenure was marked by inaction on climate change, a withdrawal from the Paris climate accord and loosening of pollution rules.
Additionally, Mr Biden announced that by 2024, the US would double its annual assistance to help developing countries cope with the effects of climate change.
The UN Green Climate Fund is falling well short of its goal of providing $100 billion per year to low-income countries, and Mr Trump halted contributions to the fund after withdrawing from the Paris Accord.
Mr Biden also called on the rest of the world to join the US in reducing carbon emissions to keep global warming below 1.5°C above pre-industrial levels.
“The world beyond 1.5°C means more frequent fires, floods, draughts, hurricanes tearing through our communities, sweeping away lives and livelihoods, increasingly dire impacts to our public health,” Mr Biden said.
"The signs are unmistakable. The science is undeniable, and the cost of inaction just keeps mounting.”
The US wants other nations to follow suit and scale up plans for cutting pollution and preventing future climate-related challenges. China, Russia, Canada, India, Germany, the UK, Saudi Arabia, the UAE and other big economies are among those attending the summit.
Underscoring the sense of urgency, UN Secretary-General Antonio Guterres said the world stood at "the verge of the abyss".
"Mother Nature is not waiting. Last summer was the hottest on record … Meanwhile, we see ever-rising sea levels, scorching temperatures," he warned.
Chinese President Xi Jinping laid out Beijing's goals, which included "strictly" limiting coal consumption in the coming years.
"China will strive to peak carbon dioxide emissions before 2030 and achieve carbon neutrality before 2060," Mr Xi said.
"China has committed to move from peak carbon to carbon neutrality in a much shorter time span than might take many [developing] countries and that requires extraordinary hard efforts from China.”
Turkish President Recep Tayyip Erdogan spoke on Ankara's initial 2015 commitments under the Paris climate accord during his opening remarks at the summit, praising Turkey as "a leading country in its region when it comes to renewable energy".
"Within the framework of our nationally determined contribution that we had presented in 2015, we are expecting a reduction of our greenhouse gas emissions up to 21 per cent until 2030," said Mr Erdogan.
"We will be increasing our electricity generation from solar power to 10 gigawatts until 2030 and from wind energy to 16 gigawatts."
Sheikh Mohammed bin Rashid, UAE Vice President and Ruler of Dubai, will represent the Emirates at the talks. He will join US climate envoy John Kerry and others for a session on "unleashing climate innovation".
Discussions will feature Pope Francis, Saudi Arabia's King Salman bin Abdulaziz, Russian President Vladimir Putin and Israeli Prime Minister Benjamin Netanyahu.
After a brief technical glitch in the opening session, Mr Putin promised to carry out a large-scale campaign for renewable energies, including a pilot project on carbon reduction.
King Salman also touted Saudi Arabia's investments in clean energy, vowing that renewables would comprise half of the oil-rich kingdom's energy needs by 2030.
French President Emmanuel Macron, British Prime Minister Boris Johnson and Canadian Prime Minister Justin Trudeau – whose countries are among those that contribute most to emissions – also addressed the summit.
Mr Johnson said that tackling climate change was not "some expensive, politically correct green act of bunny-hugging", and instead insisted "this is about growth and jobs and I think the president was absolutely right to stress that".
The event involves pre-recorded messages and live interactions between leaders from 40 countries and other luminaries before a UN meeting in Glasgow, Scotland, in November, called Cop26.
Microsoft co-founder and philanthropist Bill Gates will address the talks on Friday.
Celebrities are involved, too. Actor Leonardo DiCaprio, singer Katy Perry and other stars this week wrote to Mr Biden asking him not to sign any environmental deals with Brazil’s President Jair Bolsonaro, who will also address the meeting.
Mr Bolsonaro's government, widely criticised for its lack of action in preventing the destruction of the Amazon rainforest, is demanding $1 billion from the US to cut deforestation in the rainforest by 40 per cent.
Even as the White House aims to ensure the world meets a goal of limiting planetary warming to 1.5°C compared with pre-industrial levels, activists and UN climatologists say we are badly off-track.
The planet has so far warmed by 1.2°C and is headed for at least 3°C this century, increasing the risk of bush fires, droughts, floods, hurricanes and other weather disasters that could one day force millions of people from their homes.
A Biden administration official involved in planning the talks told The National that Gulf oil exporters such as Saudi Arabia and the UAE were key to keeping global temperature increases within acceptable limits.
“Some of these countries which have historically been relegated to a second tier of either unimportant or problem nations, I think may be part of the solution,” he said.
He highlighted the UAE’s advanced water management technology and Saudi’s transition from being a crude exporter to capturing solar energy and powering its $793 billion economy with hydrogen.
“It doesn't matter if you’re in Australia or the US, the UAE or Saudi Arabia, you’re going to have to figure out how you move an economy, which is partially reliant on carbon-intensive activities, to one that is not,” the official said.
The US and China, the world's two biggest carbon polluters, agreed to boost co-operation on climate change before the summit, even as Washington and Beijing clash over everything from trade to cybersecurity and human rights.
The European Union on Wednesday reached a tentative deal that aims to make the 27-nation bloc climate-neutral by 2050, with member states and the parliament agreeing on new carbon reduction targets on the eve of Mr Biden's summit.
Still, climate activists and some UN climatologists say the pledges being announced are too little, too late.
Teenage environmental activist Greta Thunberg this week cast doubt on the US climate summit, saying world leaders were not truly treating the “crisis as a crisis”.
“Lots of insufficient climate ‘targets’ and ‘pledges’ being presented … they equal surrender on the 1.5°C target," the Swedish activist said on Twitter on Wednesday.
"Same facts pretty much apply to all high income nations.”