Greta Thunberg and leading youth strikers for climate action from across the world have called for all adults to join a global general strike on 20 September.

They are asking citizens to walk out of work just before a crucial UN summit at which nations are being urged to declare much stronger ambitions to tackle the climate emergency.

The call was issued as young people prepared for what organisers have claimed will be one of the biggest student strikes so far on Friday, with protests expected in 1,594 cities and towns in 118 countries, according to the Fridays for the Future website.

Thunberg, the Swedish teenager who sparked the global movement with a solo protest last August, and 44 fellow protesters from across the globe, issued the call for a general strike in an article in the Guardian.

“We’re asking adults to step up alongside us … today, so many of our parents are busy discussing whether our grades are good, or a new diet or the Game of Thrones finale – whilst the planet burns,” they write. “But to change everything, we need everyone. It is time for all of us to unleash mass resistance … if we [demand change] in numbers we have a chance.”

Facebook Twitter Pinterest Greta Thunberg speaks at the Extinction Rebellion group’s protest at Marble Arch in London in April. Photograph: Tolga Akmen/AFP/Getty Images

The global strike is intended to start a week of climate action around the world.

“We’re asking adults to step up alongside us,” the youth strikers write. “Step out of your comfort zone to make this a turning point in our history. This is about crossing lines – it’s about rebelling wherever one can rebel.”

The youth protesters are demanding that governments immediately provide a safe pathway to stay below a maximum temperature rise of 1.5C. The world’s scientists say sharp cuts in carbon emissions are urgently needed to deliver a 50% fall by 2030 and avoid worse droughts, floods, extreme heatwaves and poverty for hundreds of millions of people. However, emissions are still rising.

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Wildlife is also being annihilated by human activity, with animal populations having fallen by an average of 60% since 1970. Human society is threatened by the decline of natural life-support systems, according to another landmark report published earlier in May, with half of natural ecosystems now destroyed and a million species at risk of extinction.

Play Video 1:51 Students around the world go on climate strike – video

Some adults have already joined the youth strikes, with thousands of workers protesting across Belgium in March, along with a delegation from the European Federation of Public Service Unions. Some parents have also mounted protests in the UK and across Europe.