So the gentleman is for turning. Well, maybe, anyway: after an outcry, Rishi Sunak may now attend the Cop27 climate summit in Sharm el-Sheikh after all. It would be easy to be churlish about this, given it follows reports that Boris Johnson was planning to go and hog the limelight instead, while doubtless giving the impression of caring so very much more deeply about the planet than his successor (imagine being out-serioused by Johnson, who made Kermit the Frog jokes during a rambling keynote address last year to the UN on the climate emergency, and a U-turn becomes easier to understand). But in this freakishly balmy autumn, amid apocalyptic warnings about just how far the world is from containing the global temperature rise to 1.5C, I’m mostly grateful for small mercies. Although even more so for big ones. Last weekend’s presidential elections in Brazil were described as one of the most consequential sets of elections in the world for the climate. The ejection of another toxic populist – Jair Bolsonaro goes the way of Donald Trump and Australia’s culture warrior Scott Morrison, hopefully quietly – and the return of Luiz Inácio Lula da Silva despite a corruption scandal some thought had finished him does at least bring some hope for the survival of the Amazon rainforest. “We will fight for a zero deforestation target in the Amazon,” Lula declared in his acceptance speech, reflecting campaign pledges to overhaul environmental policy and “green” the economy. “Brazil and the planet need an Amazon that’s alive.” Lula’s environmental record during his last spell in office was far from perfect, and who knows whether he can deliver. But there’s a pattern emerging in the US, Australia and now South America too: wherever rightwing populism is pushed back, environmentalism gets room to breathe. Joe Biden and Australia’s Anthony Albanese have their flaws, but they have at least opened doors that previously seemed slammed shut, indicating that changes of governments may be key to unlocking progress. Unfortunately, there’s little sign yet of Britain’s rapid turnover of prime ministers delivering. Albanese has also reportedly considered giving Sharm el-Sheikh a miss this year, which may be one of the reasons Downing Street thought it wouldn’t matter enormously for Sunak to skip it and focus instead on a critical not-quite-budget – which he would never ever be forgiven for bungling – being compiled at breakneck speed. Sunak may well have calculated, too, that his presence was unlikely to make much practical difference in Egypt; having been in office only a few days, it’s not as if he is some grizzled elder statesman to whom other world leaders look for their lead. But unlike Albanese, who campaigned on the premise that his predecessor hadn’t taken a series of floods and wildfires seriously enough, Sunak still needs to prove to his country that he gets why the climate matters. And that’s why he should have moved heaven and earth to be in the room. Our new prime minister is not a climate denier. He was quick to replace Jacob Rees-Mogg, the “climate dinosaur” Liz Truss so preposterously made business and energy secretary, with the Tesla-driving net-zero enthusiast Grant Shapps; his insistence on sticking to the 2019 manifesto also suggests less backsliding on targets than there might have been under Truss. He will listen to experts, and understands the growth potential of new green technologies. But Sunak is also by nature cautious not bold, and overly anxious about placating angry factions within the parliamentary party whose raison d’etre is refusing ever to be placated. In his desperation to win over party members during the summer, he boxed himself in badly, committing to block both onshore windfarms and farmers putting solar panels in their fields despite evidence that public opposition is visibly softening. (Nearly three-quarters wouldn’t oppose a new windfarm in their area, according to YouGov; Vladimir Putin has unwittingly helped make a powerful case for them, but I wonder if rural communities haven’t also just got more used to the sight of those whirling blades on the horizon). He must now avoid making a similar mistake with anti-net zero zealots on the backbenches. They may be noisy, but they’re as out of step with an alarmed British public on climate as they are on almost everything else, and setting a compass by them is madness; the situation cries out now for a prime minister who can lead, not follow, opinion. Perhaps the best lesson an inexperienced prime minister could draw meanwhile from the Cop27 episode is that always prioritising today’s urgent problem (in this case the budget) over tomorrow’s more distant but more existential one (the prospect of the entire planet frying) is roughly how we ended up in this burning mess. Sometimes, tomorrow needs to come before today. Gaby Hinsliff is a Guardian columnist