I Am Greta opens with a shot of the film’s titular activist sat on the bow of Malizia II – the racing yacht that took her from Plymouth, England to New York, USA for the UN Climate Summit in 2019. In many ways this is a perfect metaphor for the film’s subject. While waves and wind thrash Malizia, Greta stays focused and determined, figuratively detached from the chaos of her surroundings.

These refrains reappear throughout this excellent biopic. We begin our journey with Greta outside Parliament House in Stockholm with scenes of her first School Strike for Climate. For days she sits on her own, at best arousing only curious glances from passers-by. Later Greta will tell us that she doesn’t enjoy “small talk” and that she was bullied at school. These formative experiences must have helped her to become the independent activist we know her as today.

But how could the School Strike for Climate have taken off in such meteoric fashion? From those lonely days outside the Stockholm parliament, Greta’s movement has become a worldwide phenomenon. Yet Greta herself admits that she is no socialite, and at no point in this film do we see her at the head of a march calling out slogans through a loudspeaker. The key, it seems, lies in one of her core beliefs: that you lead by actions and not by words. The still and solitary nature of her early protests was a perfect reflection of the sombre seriousness of the issue she was highlighting and helped to intrigue and inspire others to join her movement.

Like Greta, the people who initially join her are young, and it is her interaction with adults that is one of the film’s most intriguing subplots. Even Emmanuel Macron – known for his smooth charm – appears uncomfortable in their meeting. When she speaks at climate summits, the film is transformed from a documentary into a piece of absurdism: Greta delivers gut-wrenching warnings about the future of the planet, and the adults respond with applause. Politicians, used to the language of spin, deception and misdirection, do not seem to be able to handle Greta’s straight-talking approach.

Which leads us to one final question: does the future of the planet depend on us finding more people like Greta who have a superhuman resolve to save it? Can mere mortals bring about the transformative changes that are necessary to avert climate breakdown? This is an issue we see emerge over the course of the film – and not just because of Greta’s awkward interactions with adult politicians. Even those who join her movement sometimes misunderstand her. They thank her, encourage her to keep going, and tell her that they have turned out at rallies for her. As she repeatedly reminds them, that is not the point. Greta wants us to act, not for her, but for the planet. She has a rational compassion for the environment and future generations that probably few will ever fully grasp.

Despite that, there is hope. What Greta has achieved is remarkable – even though the film shows her becoming increasingly tired and weary at politicians’ repeated failure to act on their promises. Climate awareness is, for many, a light-bulb moment: when they suddenly appreciate the gravity of the situation and the extent of action required to resolve it. Greta has switched on the light bulb for millions and given them a channel for action. That must count for something.

Matt Hawkins is a co-founder of Compassion in Politics.