This afternoon an international sensation is taking to the stage in central London. She’s young, admired around the world and her name is Greta Thunberg. She’s a 16-year-old climate hero and I couldn’t be more proud to be co-hosting her visit.

Greta’s rise to fame has been vertiginous. Last year she skipped school and sat in front of the Swedish parliament in protest against inaction on climate change – and now she is one of the figureheads of a school climate strike movement that has swept the globe, which more than a million young people taking to the streets last month to demand that world leaders step up to this monumental challenge.

The success of the strike is not incidental. Every red light is flashing on the Earth’s dashboard. The 20 warmest years on record all happened in the last 22 years. Nature and wildlife populations are at crisis levels across the world. Wildfires and droughts are becoming increasingly common – with people in the global south already dying from the effects of climate change which were mostly caused by countries in the north. Here in the UK, communities are under serious threat from flooding, sea level rises, extreme heat and more.

Of course Greta had to act. And of course thousands followed her.

Play Video 1:59 ‘We will never stop fighting’: Greta Thunberg addresses London climate protests – video

In the UK, Extinction Rebellion is also making waves. By putting their bodies on the line in protest against climate change, its members aren’t just creating headlines, they are showing moral courage at a time when too many politicians are taking us backwards. Greta arrives today in a country that talks the talk on climate, but simply won’t walk the walk. Not only are the government cheerleaders for dirty fossil fuels like fracking, but they’ve cut support for renewables like wind and solar. When we look back at this moment in a generation’s time, the real criminals won’t be seen as those blockading bridges – it will be those who understood the science of climate change, yet consistently blocked action to prevent its worst effects.

Yet despite government intransigence, there are real grounds for hope. We have the means to start to tackle this crisis – from renewable energy to clean and sustainable public transport. It is cheap and it is here; we just need to the political will to scale it up and roll it out, the first steps towards utterly transforming the global economy. And we need to take every step together, in a new, genuinely inclusive politics.

There is hope in a generation of people who are demanding from their leaders not just what seems politically possible but what is scientifically necessary to prevent total climate breakdown. That generation builds on longstanding struggles, particularly from environmental defenders who have risked – and given – their lives defending their land, water and rights against the power of fossil fuel firms who have stopped at nothing in their pursuit of the bottom line.

Extinction Rebellion protest day eight – in pictures Read more

So when Greta takes to the stage today, she will see in front of her hundreds of people of her age who aren’t afraid to take a stand, and she will stand on the shoulders of the many environmental defenders who have stood before her.

Make no mistake, the climate movement has broken into the mainstream – and it is here to stay. Our task now is to meet every promise by a politician with a demand to go further, to scale up our ambition as those at the top seek to appease us with warm words and rousing rhetoric. We must be deadly serious about getting the work done to avoid the worst of this climate catastrophe.

If we don’t rise to this task,and don’t rise to it now, then we condemn Greta’s generation, and generations to follow, to a future framed by wildfire and drought – it’s as simple as that.

• Caroline Lucas is MP for Brighton Pavilion