India and China will “have to explain themselves to poor nations” after watering down the Glasgow climate pact, warned the Cop26 president, Alok Sharma, adding that their actions had left him “deeply frustrated”. He told the Guardian: “We are on the way to consigning coal to history. This is an agreement we can build on. But in the case of China and India, they will have to explain to climate-vulnerable countries why they did what they did.” Boris Johnson, the prime minister, also said the Glasgow deal, even with the weaker wording, “sounded the death knell for coal power”. He told a press conference in Downing Street on Sunday: “The conference marked the beginning of the end for coal. For the first time ever, the conference published a mandate to cut the use of coal power.” In the closing stages of the Cop26 summit, Sharma told the Guardian he feared that the deal would be lost when China and India – both heavily dependent on coal power – attempted to reopen the text of the deal by objecting to a commitment to “phase out” coal. They proposed instead the slightly weaker “phase down”, which implies that they could still carry on using coal in some way. The commitment, contained in the “cover decision” from the Cop26 summit, does not attach any deadline to the use of coal, but is regarded as significant as it marks the first time such a resolution has been agreed by a UN climate conference. Sharma accepted the compromise, he said, because “it was my view that otherwise we might end up with no deal at all. We would have lost two years of really hard work, and would have ended up with nothing to show for it for developing countries.” At the Cop26 summit, the UK as host nation set the goal of “keeping 1.5C alive”, meaning setting a roadmap for the world to cut greenhouse gas emissions by the 45% by 2030 that scientists say is needed to cap global temperature rises at 1.5C above pre-industrial levels. That threshold marks the limit of safety, beyond which the impacts of the climate crisis, such as heatwaves, floods, droughts and sea level rises, are likely to become catastrophic and irreversible. The national plans on emissions set out at the conference would take the world to about 2.4C of heating, according to an analysis presented in Glasgow, but that was expected before the summit began. “People who know Cops say they are not about one big bang solution to climate change, they are a building block,” said Sharma. At the summit, nations agreed to return next year to revise their national targets in line with the 1.5C goal, which was regarded by most countries as a good outcome. Johnson acknowledged that his “delight at this progress is tinged with disappointment”. He said some countries were not willing to “go there” to a high level of ambition at the summit, frustrating “those for whom climate change is already a matter of life and death” from vulnerable island nations. “We can lobby, we can cajole, we can encourage, but we cannot force sovereign nations to do what they do not wish to do,” he said. “It’s ultimately their decision to make and they must stand by it.” Sharma told the Guardian, speaking from the train as he returned to London, that he was told during the conference that the commitment he wanted on coal was “never going to get in” the final outcome, so having the commitment present even with watered down language was “important”. “It wasn’t quite the wording I wanted, but I have been saying for quite some time I want us to consign coal to history [at this Cop]; therefore having this wording about coal is incredibly important,” he said. Other experts agreed that the “Glasgow package” sent a strong message on coal around the world. Nicholas Stern, the peer and climate economist, said: “The last-minute watering down of this statement is unfortunate but is unlikely to slow down a strong momentum past coal, a dirty fuel of an earlier era.” John Kerry, the UN climate envoy, was also visibly annoyed, telling journalists afterwards: “Did I appreciate we had to adjust one thing tonight in a very unusual way? No. But if we hadn’t done that, we wouldn’t have a deal. I’ll take ‘phase it down’ and take the fight into next year. Developing countries told the Guardian the deal reached in Glasgow was “imperfect” but that it contained many good elements. Milagros de Camps, the deputy environment minister of the Dominican Republic, a member of the Alliance of Small Island States, said: “Although this is far from a perfect text, we have taken important steps forward in our efforts to keep 1.5 alive and deliver the much-needed outcomes on adaptation. We acknowledge it was not an easy task.” But she said a key developing country demand, for finance to address the “loss and damage” that poor countries have suffered from the impacts of the climate crisis, had not been met. “Instead, what we got was a ‘dialogue’. How is this climate justice?” Tina Stege, the climate envoy for the Marshall Islands, which chairs the High Ambition Coalition of developed and developing countries at the talks, praised the deal for delivering a doubling of the finance available for poor countries to adapt to the impacts of the climate crisis. “Countries like mine have to fight for every outcome we get. We did that on adaptation financing, and securing that commitment to double adaptation finance took a huge effort. A year ago many developed countries I spoke to really didn’t understand, I think, why this dominated every speech, meeting, interview by many Pacific Island leaders – we just couldn’t let it go. And in the end we didn’t. I hope that aspect of the package gets the attention it deserves, because it really will provide a lifeline for so many people around the world.” Some developing country observers were less positive. Mohamed Adow, the director of the Power Shift Africa thinktank in Nairobi, said: “Sadly, this wasn’t a good Cop for developing countries. It was a developed country Cop that reflected developed countries’ priorities.” Saleemul Huq, the director of the International Centre for Climate Change and Development in Bangladesh, accused the UK of failing to ensure strong provisions for loss and damage made it into the final text: “This was absolutely unacceptable as a process for arriving at a decision and has made the Cop outcomes a death sentence for the most vulnerable communities in the most vulnerable developing countries.”