(BBC): IT is expected that the US will unveil an updated carbon promise that will see their emissions almost halve by 2030.
Prior to the meeting, officials urged more ambition on countries considered to be climate laggards.
Referring to Australia, an official said “there would have to be a shift” in their approach.
President Biden has made climate change a key focus in the early days of his administration.
As well as rejoining the Paris climate agreement on his first day in office, he announced early on that he would gather about 40 world leaders for a global summit on Earth Day – 22 April.
Among those attending will be Chinese President Xi Jinping.
Despite serious tensions between the two countries on a host of issues, it seems both sides are keen to keep climate change separate from these disputes. Last weekend, the two countries issued a joint statement saying they would tackle the climate “with the seriousness and urgency it demands”.
Speaking before the meeting, Biden’s senior administration official spoke warmly about the potential for cooperation.
“There is a clear shared ambition. Both countries see this as a crisis. Both countries see the need for action in the 2020s. Both countries see the need to work towards holding the rise in global temperatures to 1.5C, ”he said.
“We certainly hope that President Xi will come to the meeting, and expand further on some of the additional efforts that China would choose to make. But I think we have a very strong foundation in the joint statement made by the two countries about the directions they seem to be moving. ”
But for other countries that have been slow to embrace action on climate change, the Biden team was less alert.
Brazil and Australia’s skeptical attitude towards the issue had gained favor in Trump’s White House. That is no longer the case.
“At the moment, I think our colleagues in Australia recognize that a shift will be necessary,” said one official.
“It is inadequate to follow the current trajectory, and hopefully they will be on a course of deep decarbonisation, reaching zero net emissions by the middle of the century.”
Speaking about Brazil, the same official said: “The expectation for all countries is that ambition must be increased immediately.”
But while the United States is talking loudly about ambition, the test of change will be for many observers in their new carbon-cutting promise for 2030 that they are expected to announce at the summit.
This will require some clever footwork from the US. They will have to go for a figure that is scientifically credible but also politically achievable.
Although Democrats have a majority in the House of Representatives, Parliament is essentially unlocked, making the passage of new climate legislation somewhat difficult.
“It seems to me that President Biden is in a bit of a bind, and he has to deal with the Congress he has,” said Samantha Gross of the Brookings Institution.
“But I think Congress, especially the Republicans, have not kept up with growing concern among the American public about the climate.”
For some in the international community, even the controversial 50% cut in emissions will not go far enough.
“The United States should cut at least 55% of 2005 levels by 2030 to inspire others to raise their ambitions,” said Quamrul Chowdhury, a Bangladesh and climate negotiator for the least developed group of countries. “Mitigation is the best adjustment and large economies must cut emissions quickly and steeply.”
Undoubtedly the pledge of the United States will be the head, whatever its size – but it is also expected that new actions will be announced by a number of countries.
“The three most likely beside the United States to step in at this summit are Canada, Japan and South Korea,” said Helen Mountford of the World Resources Institute (WRI).
“China… would be great, but I think[wewould[probablywanttothinkthatitwouldbeagoodideaforus”[ybyddemni[yndebygoliawnoarosynhirachnifyddwnyneiddisgwylarhynobryd”[we[quitelikelymightwaitlongerIwouldn’texpectitatthistime”
He added: “India is a real question mark, but whether they’re going to announce either a net zero target or a better plan, I’d say there’s less chance of that.”
For those who were involved in the negotiations that led to the 2015 Paris agreement, the key thing this week is not to deregulate the negotiations at the first hurdle.
This is the first major climate meeting of a decisive year that will culminate in a gathering of around 200 world leaders in Glasgow in November at COP26.
“I think for the US leaders’ summit to be a success, we need to have all 40 leaders in attendance and express their willingness to come to a strong agreement from Glasgow,” said Remy Rioux, a negotiator for France during the negotiations in Paris.
“And also for the United States to show that they are back and that they are back as convincing and strong as possible.”