The young people of the world have a message for adults. This Friday, they will go on strike to make sure their views on climate change are heard.

Tens of thousands of students from more than 80 countries and territories - including the United States, Malaysia and Hong Kong - plan to skip school that day to urge adults to treat climate change as a crisis, and for governments to take action now.

The global youth movement was kick-started last year by Swedish teenager Greta Thunberg, who had refused to go to school in order to pressure her government to take more drastic climate action.

Her move has inspired many other young people to do the same.

Friday's protest, however, is the first global one.

"This is of course nothing that I expected," Ms Thunberg, 16, told The Straits Times.

"None of this would have happened without all the channels of the global environmental community. Millions of people have been fighting for the climate for decades, and without them nothing would have happened."

Young people point to several reasons for their anger: The raft of recent scientific reports highlighting the perils of unabated global warming for future generations, and the inaction over implementing available climate solutions.

American teenager Kate Anchondo, who is organising a school strike in San Diego, California, said: "I am worried and angry that we let it get this far. The science has been clear for a really long time, but we've never really faced the issue head on."

Speaking to The Straits Times on Sunday near Chula Vista City Hall, where Friday's strike will be held, she pointed to a report last October by the Intergovernmental Panel on Climate Change (IPCC) as an urgent call to action.

The IPCC report highlighted the differences between the impact of a 1.5 deg C global warming scenario and a 2 deg C one, with the latter having catastrophic effects on earth systems, human livelihoods and biodiversity.

The report also laid out pathways for nations to keep warming to the lower limit, but these involve drastic action to cut fossil fuel use and major changes to lifestyles.

"If we act by ourselves, there is limited impact. But striking as a whole nation, as a whole bunch of youth from all over the world, creates a very strong message. It makes the adults face the issue and hopefully prompt them to do something about it," said Ms Anchondo. The 17-year-old's parents are supportive of her plans to strike.

There has been success in other areas.

Ms Sara Wanous, 23, from US activist group Citizens Climate Lobby (CCL), told The Straits Times her group recently invited 17-year-old student Piper Christian to its climate education board for her efforts to get the state of Utah to commit to climate action.

In another inspirational story, a group of high school students in Michigan successfully urged their congressman to hold a face-to-face meeting with CCL, said Ms Wanous, when the group had been trying to do so for years, to no avail.

She added: "After that meeting, he committed to joining the climate solutions caucus, a group in Congress committed to working on climate solutions. Getting that meeting is something that no adults would have been able to do."

As Mr Daniel Driscoll, a sociology doctoral candidate studying climate change movements and policy at the University of California, San Diego, noted: "It's tough to say, but saying 'no' to thousands of children isn't easy and it's not great for public image."

Said Ms Thunberg: "I hope the youth movement will help governments, the media and individuals start treating the crisis like a crisis. Because we really can't solve a crisis without treating it like one."