(CNN) Young people around the world are not interested in excuses when it comes to dealing with climate change.

Every year of their lives has been one of the warmest recorded . Extreme weather events, including floods, wildfires and heat waves , are becoming the new norm. Many believe that, if nothing is done to stop global warming, their generation will be left to deal with catastrophic consequences.

That's why, on March 15, tens of thousands of students worldwide will be cutting class and taking to the streets to demand that elected officials act.

Here's what you need to know about their movement.

How we got here

The global climate strike on March 15 is an offshoot of the #FridaysForFuture movement, which has been active around the world for months.

It began with Greta Thunberg, the 16-year-old environmental activist, who in August 2018 started skipping school on Fridays to protest outside Sweden's parliament.

You might remember how she roasted the global elite at the World Economic Forum by telling them they were to blame for the climate crisis. Before that, she delivered a damning speech at the United Nations' climate conference COP24, telling climate negotiators they weren't "mature enough to tell it like it is."

Thunberg has said she won't stop her sit-ins until Sweden is in line with the Paris Agreement, an accord that aims to limit a global temperature rise this century to 1.5 degrees Celsius.

Her protests have inspired thousands of young people around the world. Students in countries including Australia, Thailand, Uganda and the United Kingdom have already skipped school to demand that their governments act against climate change.

Students in more than 90 countries and more than 1,200 cities around the world plan to join the strike in what could be one of the largest environmental protests in history.

Why they're striking

The question many student protesters have for officials who might scold them for cutting class is: What's the point in going to school if climate change might destroy all hope of a future?

Right now, they say, they've got bigger things to worry about.

That's because world leaders only have 11 more years to avoid disastrous levels of global warming, according to a 2018 report from the UN Intergovernmental Panel on Climate Change (IPCC).

If human-generated greenhouse gas emissions continue at the current rate, the planet will reach 1.5 degrees Celsius above pre-industrial levels as soon as 2030. That threshold is critical.

Global warming at that temperature would put the planet at a greater risk of events like extreme drought, wildfires, floods and food shortages for hundreds of millions of people, according to the IPCC report.

According to the report, curbing global warming would require "rapid and far-reaching" changes in land use, energy sources, infrastructure and industrial systems. The students who are protesting don't think enough is being done.

In an open letter published in The Guardian newspaper, a group of youth-led climate activists called climate change "the biggest threat in human history" and said young people will no longer accept the inaction of world leaders. They're taking matters into their own hands, "whether you like it or not."

"We have the right to live our dreams and hopes," the letter reads. "Climate change is already happening. People did die, are dying and will die because of it, but we can and will stop this madness."

Young climate activists are hoping to spark a widespread dialogue about climate change, following in the footsteps of their peers in Parkland, Florida, who led a national conversation about gun control after a mass shooting at their school.

What they want

The demands of students vary from country to country, but one common thread among them is that countries cut greenhouse gas emissions.

Kids in the US want a radical transformation of the economy. Here's what that agenda includes, according to the Youth Climate Strike website

a national embrace of the Green New Deal

an end to fossil fuel infrastructure projects

a national emergency declaration on climate change

mandatory education on climate change and its effects from K-8

a clean water supply

preservation of public lands and wildlife

all government decisions to be tied to scientific research

Who's on their side

The kids leading the March 15 strike don't yet have high school diplomas. But a whole bunch of grown-up scientists say these kids know what they're talking about.

A group of more than 100 US-based climate scientists released a letter last week in support of the US strike, saying that students' demands for immediate action on climate change are consistent with the latest science.

"They need our support, but more than that, they need all of us to act. Their future depends on it; and so does ours," the letter said.

Scientists in other countries have released similar letters of support for past strikes.

Democratic Rep. Ilhan Omar has also expressed support, saying she will attend the national strike in Washington, D.C. Omar's 16-year-old daughter, Isra Hirsi, is one of the national organizers of the strike, along with 12-year-old Haven Coleman and 13-year-old Alexandria Villaseñor.

But not everyone has been on board.

A spokesperson for UK Prime Minister Theresa May criticized student protests in February, saying that striking "increases teachers' workloads and wastes lesson time," adding that kids should be in school training to be scientists and engineers so that they can tackle the problem. That same month, an Australian education minister warned students and teachers that they would be punished if they went on strike during school hours.

How to get involved

There are strikes happening in more than 90 countries. For information about upcoming strikes around the world, check out this map on the Fridays for Future website.

In the US, a national strike is planned in Washington, D.C., along with strikes in nearly 50 states. To find one in your area, check out this map on US Youth Climate Strike's website.