“Hopeless and broken”: that is how a top scientist interviewed by the Guardian described feeling as she and hundreds of other climate experts shared harrowing predictions of the future of the planet this week. I resonate with her feelings of despair. Even as the former head of the UN climate change convention that achieved the Paris agreement in 2015, I, like many, can succumb to believing in the worst possible outcome. Just after I assumed the role of UN climate chief in 2010, I said to a room full of reporters that I didn’t believe a global agreement on climate would be possible in my lifetime. Now, scientists say we are on track to shoot through the 1.5C temperature ceiling enshrined in the Paris agreement, leading to a dystopian world plagued with famine, conflict and unbearable heat. Climate impacts have hit so fast that worst-case scenarios predicted by scientists are in some cases already coming true. This isn’t scaremongering: these climate scientists are doing their job. They are telling us where we are, but now it’s up to the rest of us to decide what this moment requires of us and to radically change the direction of travel. Collective doubt in our ability to respond to the climate crisis is by now dangerously pervasive. Beyond climate scientists, it’s shared by politicians and some young people. It’s also shared by some philanthropists who fund climate NGOs, and by many who work in those NGOs. It is shared by some financiers, and some of those who work in companies struggling to reduce their emissions. A sense of despair is understandable, but it robs us of our agency, makes us vulnerable to mis- and disinformation, and prevents the radical collaboration we need. Doubt holds us back from taking bold action, which is why it is strategically seized upon by incumbents, who have invested millions of dollars (probably much more) in sowing uncertainty around the climate crisis and its solutions among the general public. We all have a right to grieve the loss of a future free from the climate crisis. It is a deep, hard loss. And it’s particularly painful, because those of us who read these reports bear a great responsibility in passing an unsafe planet on to our children and future generations. But grief that stops at despair is an ending that I and many others, most notably those on the frontlines, are not prepared to accept. We also have the responsibility – and the opportunity – to shape the future differently. We must take stock of the science, triple down on our efforts and deploy the perspective of possibility. For example, what has been achieved in transforming the energy system to this point, pushing against a fossil fuel industry deliberately intent on delaying progress, and within a lacklustre policy environment, is extraordinary. We also learned this week that we have just reached a crucial turning point towards powering our world with clean energy. Last year saw a record absolute increase in solar generation. With renewables in the energy mix now at 30%, fossil fuel generation is expected to fall this year and then decline rapidly in the near future. Solar, in particular, is accelerating faster than anyone thought possible: last year it was the fastest growing source of electricity generation for the 19th year in a row. This really is the beginning of a different kind of future. Not enough, by itself, of course, but it shows a reality that is exponentially changing day by day. While we grapple with the current lack of political will, and the abhorrent inequities of the climate crisis, we can take some comfort that so many of those who are key to designing our future have heard climate scientists’ urgent warnings and are channelling their spirit by taking positive action in response: think of the engineers reforming our grids, the architects, the social entrepreneurs, the regenerative farmers restoring our soil, the legal advocates, and the millions of people everywhere who are advancing new systems of care, repair and regeneration. It will take much more courageous collective action to turn the seemingly impossible into the new normal. But we are on the brink of positive societal tipping points. I believe that the children of children born this year will be the first fossil-fuel-free generation in modern history. Their generation, just a few years from now, will benefit from development and smart climate adaptation based on the certainty of abundant, homegrown and distributed clean energy. It doesn’t mean they will live in a utopian future – we know too much climate change is already baked into the system – but enormous positive change is coming. I mentioned earlier telling the press that I didn’t believe a global agreement on climate was possible back in 2010. What I didn’t share is that I immediately afterwards had to change my attitude. And that made all the difference. It was a candle in the darkness that I used to light a spark in many others. I am still using the candle of stubborn optimism today – and I’m not the only one. A world in which we pass 1.5C is not set in stone. Christiana Figueres was the head of the UN climate change convention from 2010 to 2016, and is the co-host of the climate podcast Outrage + Optimism