I first learnt about climate change when I was eight years old. I learnt that this was something humans had created. I was told to turn off the lights to save energy and recycle paper to save resources.

I remember thinking it was very strange that we were capable of changing the entire face of the Earth and the precious thin layer of atmosphere that makes it our home.

Because if we were capable of doing this, then why weren’t we hearing about it everywhere? As soon as you turned on the television, why wasn’t the climate crisis the first thing you heard about? Headlines, radio programmes, newspapers, you would never hear about anything else, as if there was a world war going on.

Yet our leaders never talked about it.

If burning fossil fuels threatened our very existence, then how could we continue to burn them? Why were there no restrictions? Why wasn’t it illegal to do this? Why wasn’t anyone talking about the dangerous climate change we have already locked in? And what about the fact that up to 200 species are going extinct every single day?

I have Aspergers syndrome so, for me, most things are black or white. I look at the people in power and wonder how they have made things so complicated. I hear people saying that climate change is an existential threat, yet I watch as people carry on like nothing is happening.

We can no longer save the world by playing by the rules because the rules have to be changed

We can no longer save the world by playing by the rules because the rules have to be changed.

Countries like Sweden need to start reducing our emissions by at least 15 per cent every year if we consider the aspect of equality or climate justice – a principle that is clearly stated everywhere in the Paris Agreement. And that is just so we can stay below 2 degrees, which we now know will still create misery for so many people and ecosystems around the world.

For Australia – given its even larger carbon footprint – that percentage is likely to be higher still. Now the Secretary General of the United Nations argues that we should aim for 1.5 degrees. Change on a scale we’ve never imagined.

If I live to be 100, I will be alive in 2103. Adults often don’t think beyond the year 2050. But by then, I will, in the best case, not have lived half of my life. What we do or don’t do right now will affect my entire life and the lives of my friends, our children and their grandchildren.

When school started in August this year, I decided enough was enough. Sweden had just experienced its hottest summer ever. The election was coming up. No one was talking about climate change as an actual consequence of our way of life.

So I decided to walk out of school and sit on the ground outside the Swedish parliament to demand our politicians treat climate change for what it is: the biggest issue we have ever faced.

Because if climate change has to stop, then we must stop it. It is black and white. There are no grey areas when it comes to survival. Either we continue as a civilisation or we don’t. One way or another, we have to change. Countries like mine and Australia must start reducing our emissions dramatically if we believe in equality and climate justice.

But instead of talking about this, all our politicians go on about is economic growth, energy prices and shareholder value. What value is there in a future where hundreds of millions of people suffer?

According to the Swedish Uppsala University, countries like Sweden and Australia must get down to zero emissions within six to 12 years so that people in poorer countries can have a decent future and build some of the infrastructure that we already enjoy. How can we expect countries such as India or Nigeria to care about the climate crisis if we, who already have everything, are not living up to our commitments?

Australia is the world’s biggest exporter of coal, one of the leading causes of climate change. Your politicians want to help Adani build one of the biggest coal mines in the world. Right now, there are no policies to change this. There are no rules to keep coal in the ground.

And it has to start today. As a student, one way I can push for urgent change is to go on strike from school. I’ll be sitting outside the Swedish parliament every Friday from now until my country is in line with the Paris agreement.

I urge other students to join me: Sit outside your parliament or local government wherever you are and demand that they get on track to keep the world below 1.5 degrees.

Some say I should be in school. But why should any young person be made to study for a future when no one is doing enough to save that future? What is the point of learning facts when the most important facts given by the finest scientists are ignored by our politicians?

We are running out of time. Failure means disaster. The changes required are enormous and we must all contribute to the solutions, especially those of us in rich countries like Australia.

The adults have failed us. And since most of them, including the press and the politicians, keep ignoring the situation, we must take action into our own hands, starting today.

• Greta Thunberg is 15 years old and lives in Stockholm, Sweden

This article was amended on 27 November, 2018, to clarify a point made by the author