In Downing Street’s elegant White Room overlooking St James’s Park, Prime Minister Boris Johnson, attended by a gaggle of maskless aides, has swapped much of his trademark bonhomie for an unblinking passion; he has become a climate change evangelist.

With the eyes of the world on Glasgow for the next two weeks and a majority of international leaders attending, this will be the biggest stage of Mr Johnson’s political career. He appears to be relishing the opportunity but he fully recognises the stakes are high; indeed, they could not be higher.

However, this is not a time for political showmanship but international statesmanship. Interestingly, in an interview with The Herald, Mr Johnson gives the impression that delivery of a comprehensive deal to achieve the 2015 Paris accord target of limiting global warming to 1.5C will ultimately not be achievable by the end of COP26 on November 12. Rather, Glasgow will more likely become a significant staging post to getting that agreement on delivery. Hopeful minds will look to next year’s COP27 in Egypt for more progress as time continues to run out of the global hourglass.

The Prime Minister was his usual effusive self but the optimism gauge was turned down. He was at pains to point out he would not give a “kind of rosier, optimistic gloss to this… I’m saying this is extremely difficult but countries can achieve extraordinary things”. He referred to recent conversations with two world leaders, which gave him hope that delivering the Paris accord was possible.

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“I was talking to Joko Widodo, the President of Indonesia, and we were expecting him to say he could phase out the use of coal by 2056 or thereabouts. In fact, he readily agreed to do it by 2040. So, Indonesia is a massively important economy in that part of the world and it can be done.

“[Russian President Vladimir] Putin I talked to a couple of days ago, who surprised me with his determination to get to net zero by 2060 if not earlier,” he said. “This negotiation is going to be incredibly difficult and what it’s going to take is the developed world really engaging with the developing countries and persuading them they can make the changes they need to make and find the cash to do it.”

Yet only this week it emerged that the long-promised goal of wealthy countries creating a $100 billion a year fund to help the poorer ones go green and cope with global warming has been dissipated as the date for delivery has been put back again to 2023.

While Mr Johnson was understanding towards Mr Putin’s absence in Glasgow – Covid case numbers are rising again in Russia – it was interesting there was no equivalent understanding towards China’s President Xi Jinping, who, we now learn, will address COP26 via video-link. Indeed, No 10 let it be known yesterday that our PM and Mr Xi had an “extensive conversation” on the phone about climate change and other issues.

Mr Johnson “acknowledged” China’s new emissions plan, its so-called nationally determined contribution [NDC], and stressed how important it was for all countries to “step up their ambitions,” transition to renewables and phase out coal.

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It has to be said Beijing’s new NDC looks remarkably like the old one, that’s because it is the old one; namely, China’s emissions are set to peak by 2030 and then be reduced to net zero by 2060. Li Shuo, from Greenpeace Asia, said there had been a lot of resistance within China to embrace higher ambitions and added: “If we wait until 2030... the curve [for CO2 cuts] between 2030 and 2060 is so steep… some people think this is science fiction.”

The numbers of late have been truly frightening. The UN Environment Programme report this week warned the world was on track for a “climate catastrophe,” facing disastrous temperature rises of at least 2.7C if countries failed to strengthen their climate pledges. Current pledges will reduce carbon by about 7.5 per cent by 2030, far less than the 55% cut scientists say is needed to limit global temperature rises to 1.5C.

UN Secretary-General Antunio Guterres described the findings as a “thundering wake-up call” to world leaders. The UN, which sponsors COP summits, pointed out only around half of the countries supposed to submit NDCs had done so and they had presented weak plans that were no improvement on their 2015 Paris pledges.

An assessment of all the available plans from all 192 parties to the UN climate process showed the world is set to see a 16% increase in global greenhouse emissions by 2030.

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Everyone agrees that China, by far the world’s biggest polluter – its share of CO2 emissions is almost 30%, the UK’s is 1% – is key to limiting global warming to 1.5C. The PM said there were “reasons for confidence about what countries can achieve” and added: “The Chinese are obviously very important. They have now committed to no more financing of coal overseas. What does that mean for Chinese coal-fired generation in China? We need to hear.”

When it was pointed out to Mr Johnson that China, which burns half of the world’s coal, is planning to build 43 new coal-fired power plants and 18 new blast furnaces and that across Asia nearly 600 coal-fired power plants were set to be built, his forehead visibly shifted backwards.

It has been suggested that Beijing would have to close 600 of its own coal-fired power stations before 2030 to meet its 2060 net zero target. So, when the PM said the challenge was massive, he was not exaggerating.

In the coming days, Glasgow might not secure fully delivery on the Paris accord to limit global warming to 1.5C but minds are at last beginning to be focused. It is hoped the floods and fires that will surely ravage the planet in the coming months and years will focus them some more.