Boris Johnson will give a press conference from the COP26 summit in Glasgow later today.
The Prime Minister is expected to field questions from journalists at 5pm as he rounds off the start of the global climate gathering.
Despite COP26 running for another 10 days, it's thought the Tory leader could seize the opportunity to claim he has made more progress than hoped.
Mr Johnson ruthlessly played down expectations ahead of the summit, warning world leaders could well "fail" in their bid to limit global temperature rises to 1.5C and society could fall like the Roman Empire.
But today Downing Street deliberately tried to strike a more positive tone. It could spark a debate about whether progress has been genuine or whether the PM was simply using expectation management.
The PM's spokesman said: “While there’s a long two weeks ahead of us and a good deal to nail down, some of the commitments we’ve seen over the last day and a half are very encouraging and building that momentum.”
Mr Johnson hailed an agreement to end the "great chainsaw massacre" of the world's forests by 2030, which has been signed by more than 100 world leaders including Brazil.
No10 said it was the biggest breakthrough on forests "in a generation" and a “massive success for COP”.
But the summit has also triggered accusations of hypocrisy as some delegates flew in on private jets, while urging people to cut their carbon emissions.
Mr Johnson himself will then jet off to London on a luxury Union flag-branded jet only hours after telling world leaders to stop "quilting the earth in an invisible and suffocating blanket of CO2".
The PM could also face questions about coronavirus after Parliament toughened up its restrictions in response to a surge in cases.
It is thought the UK believes progress has been made on emissions reductions by 2030 and on tracking temperature rises this century closer to 2100. Pledges on cutting methane are also expected.
But talks on climate finance to poorer nations are still tangled, described as the hardest piece of the puzzle with pinch points despite UK officials being confident the pledge to hand $100bn a year to poorer nations will be met in 2023, three years late.
UK officials are also disappointed G20 leaders did not agree to end coal power stations, with expectations talks could stretch out for years.
And despite being pleased that China's President Xi sent a written statement to the summit, UK officials believe more is needed from the world's largest emitter.
It comes after India announced a pledge to reach Net Zero emissions, but only by 2070, two decades after many other parts of the world.
A UK official branded the 2070 pledge "curious" and “an interesting political choice” that might lead to a U-turn.
However, it's understood UK officials are otherwise pleased with India's announcement - which could knock off one gigaton of the 28 gigatons that need to be reduced from global emissions by 2030.
India will also raise its non-fossil energy capacity to 500 gigawatts (GW) and get half its energy from renewable resources by 2030.
Prime Minister Modi pledged to reduce the carbon intensity of the economy by 45% by 2030. Mr Modi demanded developed countries makes one trillion US dollars available as climate finance "as soon as possible today".
No10 has not made a final decision about whether Boris Johnson will return at the end of the summit, to bring together a final agreement.
Asked if today's change of tone was more about PR and expectation management than a real breakthrough, he said: “The PM felt very much that at G20 some limited progress was made.
“What we’ve seen so far is some early signs that we are starting to make some progress.
“We are not complacent. This is not a done deal by any means and there is a huge amount of work left to do. Currently we’re at 2.7C.
“We’ve absolutely not done enough to get us to 1.5C by the end of this decade. The pressure will be kept up, absolutely.”
