Swedish climate activist Greta Thunberg holds a sign reading, “School strike for the climate,” as she attends a rally in Hamburg on March 1. (Daniel Reinhardt/DPA/AP)

On Friday, children in some 100 countries are walking out of school to push for global action on climate change. Over the past four months, hundreds of thousands of young people from many countries participated in demonstrations against climate change. This is something quite unique — schoolchildren have never before instigated such far-reaching protests on a global scale.

The phenomenon ramped up with weekly school strikes, mainly in Western Europe, the United States and Australia, but also in low- and middle-income countries like Colombia, India and Uganda. The March 15 global strike reportedly involves more than 100 countries and over 1,600 separate events. In an open letter, the global coordination group of the movement demanded that all countries should meet their commitments outlined in the Paris agreement and demanded justice for all future victims of climate change.

How did this student-directed global protest movement get started, and where is it headed? Here are four things you need to know:

1. Why schoolchildren?

The world is accustomed to seeing university students take to the streets in protest. There are countless examples, from the U.S. civil rights movement in the 1960s, to student clashes with police in Paris in 1968, to the 1989 Tiananmen Square demonstrations in Beijing. Historically, university students have been an engine for social change worldwide. These older students might have been a far more likely group to lead a protest movement, given their greater resources and higher level of education.

But an unlikely climate hero emerged last fall.

2. Meet Greta Thunberg.

In September, a 15-year-old Swedish student named Greta Thunberg launched a climate change strike in front of the Swedish parliament building just before the national elections. Greta soon became a source of inspiration for strike participants worldwide and has just been nominated for the Nobel Peace Prize.

Based on prior studies, we believe there’s a simple explanation: In addition to concern for nature, schoolchildren readily identify with someone their own age.

This wouldn’t be the first time that a single act of civil disobedience helps launch a broad and sweeping social movement. Although facing threats of a completely different magnitude, Rosa Parks is one such iconic example. Her risky decision not to move to the back of an Alabama bus in 1955 helped launch the Montgomery bus boycott, an important catalyst in the U.S. civil rights movement.

Many broad-based social movements have evolved without cooperation with established organizations. In fact, people who seek social change may tend to see these organizations as too entrenched in the ruling political order.

Today’s young climate strikers appears to be organizing themselves in a grass-roots, bottom-up manner, focusing on building support within their school classes and other social networks. And they appear to get support from already established groups such as the adult-led U.K.-based climate protest movement Extinction Rebellion.

3. It’s no surprise to see this level of protest from young people in general.

According to surveys, young people give higher priority to climate change — often calling climate the paramount social issue of our time. Both schoolchildren and those in the 18-to-34 age range express more concern about climate issues than other age groups. There have also been clear signs for many years that youth climate activism is on the rise, with participants motivated by fear about the earth’s future, while at the same time they see hope in collective action.

In addition, a social movement is much easier to mobilize once participants identify a common target. It is apparent that young people around the world have such a target against whom to direct their anger on climate inaction, as their elected representatives, as well as CEOs and industry leaders, are all adults.

In the year after the Parkland high school shooting in Florida, school walkouts targeting gun laws in the United States were organized in a similar bottom-up way, evolving for the most part outside established gun-control groups. In 2018, states implemented 67 new gun-control laws. The student protests seem to have stimulated a new wave of political activism among young Americans.

4. Will this movement survive? Will it even expand?

A number of world leaders have invited Greta to sit down and talk. This move may suggest that the student-led climate movement has achieved the first necessary stage toward success — acceptance by its targets. Media coverage of Friday’s protests worldwide may also fuel further activism, involving schoolchildren as well as adults.

However, compared with the anti-gun-violence movement in the United States, the climate movement tackles goals that are more difficult to achieve — like all countries meeting their commitments outlined in the Paris agreement. These goals, expressed in the open letter written by the international leading group, may also be less clear-cut — for example, there are no established guidelines to determine justice for victims of climate change. Such challenges may make it more difficult for this movement to keep up the momentum.

Nonetheless, the climate-striking schoolchildren have gotten a crash course in activism and mobilization — and may emerge as the next generation of activists committed to mass mobilization against the threat of climate change.

Per Adman is an associate professor in political science at Uppsala University in Sweden.

Katrin Uba is an associate professor in political science at Uppsala University in Sweden and Tartu University in Estonia.