The president of Cop28 has been forced into a fierce defence of his views on climate science, after the Guardian revealed his comment that there was “no science out there, or no scenario out there, that says that the phase-out of fossil fuel is what’s going to achieve 1.5C”. Sultan Al Jaber, who is also the chief executive of the United Arab Emirates’ state oil company, Adnoc, said at a hastily arranged press conference at the summit in Dubai: “I respect the science in everything I do. I have repeatedly said that it is the science that has guided the principles or strategy as Cop28 president. We have always built everything, every step of the way, on the science, on the facts.” Al Jaber made the controversial comments in ill-tempered responses to the former UN climate envoy Mary Robinson during an online event on 21 November. During the exchange, he also said: “Show me the roadmap for a phase-out of fossil fuel that will allow for sustainable socioeconomic development, unless you want to take the world back into caves.” At the press conference, Al Jaber said: “I have incredible respect for Mary Robinson.” He added: “I have said over and over the phase-down and the phase-out of fossil fuel is inevitable. In fact, it is essential.” More than 100 countries already support a phase-out of “unabated” fossil fuels – those where the resultant emissions are not captured – and whether the final Cop28 agreement calls for this or uses weaker language such as “phase-down” is one of the most fiercely fought issues at the summit. The former US vice-president Al Gore said a commitment to phase out fossil fuels would be Cop28’s only measure of success. Al Jaber said: “I know that there are strong views among some [countries], about the phase-down or phase-out of fossil fuels. Allow me to say this again: this is the first [Cop] presidency ever to actively call on parties to come forward with language on all fossil fuels for the negotiated text.” Cop26 in Glasgow in 2021 agreed for the first time to “phase down” coal use. Al Jaber did not refer to the Guardian story directly, but said: “One statement taken out of context, with misrepresentation and misinterpretation, that gets maximum coverage.” The Guardian story contains the full recording of his interaction with Robinson. “If anything, judge us on what we will deliver at the end [of Cop28],” he said. The issue of a phase-out or phase-down is complicated by the terms not having agreed definitions and by the highly uncertain role of technologies to “abate” fossil fuel emissions, such as carbon capture and storage (CCS). Al Jaber’s comments to Robinson prompted a strong reaction from climate scientists who had read the transcript, who described them as “incredibly concerning” and “verging on climate denial”. They also conflicted with the view of the UN secretary general, António Guterres, who told Cop28 delegates on Friday: “The science is clear: The 1.5C limit is only possible if we ultimately stop burning all fossil fuels. Not reduce, not abate. Phase out, with a clear timeframe.” Prof Johan Rockström, the director of the Potsdam Institute for Climate Impact Research in Germany, said: “I cannot see scientifically there being any other communication than that we need to phase out fossil fuels.” Alden Meyer, of the thinktank E3G, told the Guardian: “It was a mistake for Al Jaber to say ‘going back into caves’ – that’s an old trope of the fossil fuel industry. I bet, if he could, he would take that back.” Earlier in the day, youth climate activists mounted a protest at Cop28. Ina-Maria Shikongo, from Namibia, said: “We are here in response to [Al Jaber’s comments] making loud and clear. There is no debate whether we need a fossil fuel phase-out to stick with the Paris agreement. The science is clear.” Tina Stege, the climate envoy for the Marshall Islands, speaking before Al Jaber’s press conference, pointed out that he had called 1.5C his “north star”. She said: “We will hold him to that. If 1.5C is the north star, in practice what that means is a phase-out of fossil fuels; that is what the science has said. We can’t pretend there are other pathways to achieve 1.5C when so many lives are at stake.” Leo Roberts, an energy policy expert at E3G, said competing claims that the 1.5C target could be achieved only by a phase-out of fossil fuels, or by a phase-down while still burning some fossil fuels, resulted from the “translation of science into politics”. “I think, understandably, the climate movement is really concerned about [CCS] being deployed instead of phasing out fossil fuels, and it is a real concern,” he said. “It’s a slippery issue, because the actual amount of abated fossil fuel use [possible] in 2050 is almost zero. So getting to as close to zero as possible means that we have to aim for zero politically.” Mayer said: “Phasing down could mean 1% by 2040, but it’s not what we need. You have to get specific on timeframes and numbers, or it’s just gobbledegook.” Laurence Tubiana at the European Climate Foundation, one of the architects of the 2015 Paris climate deal, said on Monday: “Contrary to what some in the oil and gas sector claim, the deployment of CCS does not provide the industry with a reason to only ‘phase down’ fossil fuels. Not even close. While it can be helpful at the margins, CCS cannot possibly deliver reductions in greenhouse gas emissions on the scale needed to avert climate disaster.”