From New York to Guatemala City, Sydney to Kabul, and Cape Town to London, protesters in hundreds of cities around the world took the streets, demanding their governments take urgent steps to tackle the climate crisis and prevent an environmental catastrophe.
"The preliminary numbers say there are at least 3 million people in today's #ClimateStrike And that is before counting North and South America," tweet Greta Thunberg, the Swedish teen, who was in New York to lead the climate strike ahead of the UN Climate Action Summit, which is slated to bring together world leaders to discuss climate change mitigation strategies, including the move from fossil fuels to renewable energy sources.
The demonstrations started in the Pacific Islands before quickly getting started across Australia, Asia, Europe, Africa, the Middle East and North and South America.
'No Planet B'
As Friday's day of action got under way across the scattered Pacific communities, students holding placards in Kiribati chanted: "We are not sinking, we are fighting."
Children in the Solomon Islands rallied on the shoreline wearing traditional grass skirts and carrying wooden shields.
Hours later in Thailand, more than 200 young people stormed the Environment Ministry in Bangkok and dropped to the ground feigning death.
"This is what will happen if we don't stop climate change now," said 21-year-old strike organiser Nanticha Ocharoenchai.
Organisers estimated 300,000 people turned up for the "global climate strike" in Australia, the world's largest exporter of coal and liquid natural gas.
Protests were staged in 110 towns and cities across the country, with crowds calling on the government to commit to a target of net-zero carbon emissions by 2030.
In Canberra, the Australian capital, a 12-year-old primary school student told an estimated 10,000 people said she and her classmates had decided saving the planet was more important than classes.
"Politicians worry about us not going to school," said Alison. "But we're learning about the world, the danger we're in and what we can do about it. We know it's important to go to school and learn, but we know it is more important to save the planet for future generations to learn on."
Sixteen-year-old Elizabeth Whitbread attended the Canberra protest with a banner saying she was "hoping for a cooler death".
"I'm here because I want to live," she said. "We all have the right to the life we set out to have. I don't want to die young."
Acting Prime Minister Michael McCormack said students should be in school.
"These sorts of rallies should be held on a weekend where it doesn't actually disrupt business, it doesn't disrupt schools, it doesn't disrupt universities," McCormack told reporters in Melbourne.
"I think it is just a disruption," he added.
Australia's conservative government - while stopping short of outright climate change denial - has sought to frame the debate as a choice between jobs or abstract CO2 targets.
In Jakarta, the capital of Indonesia, students called for action against wildfires on the islands of Borneo and Sumatra, which have caused health problems for people across the region.
"The youth here are saying they want the government to deal with this issue more urgently and take more action," said Al Jazeera's Raheela Mahomed, reporting from the protest site.
In India's New Delhi, one of the world's most polluted cities, dozens of students and environmental activists chanted "We want climate action" and "I want to breathe clean" at a rally outside the Ministry of Housing and Urban Affairs.
They carried banners with some displaying messages like "There is no Planet B."
"I have come to this protest today because I live in the world's most polluted city and our government is doing nothing to change that," said Asheer Kandhari, a student. "Not taking action, a government doesn't realise that they are taking away our futures. It's my future that is being affected by the government's inaction regarding the climate change policy."
No protests were authorised in China, the world's biggest source of greenhouse gas emissions, but Zheng Xiaowen of the China Youth Climate Action Network said Chinese youth would take action one way or another.
"Chinese youth have their own methods," she said.
"We also pay attention to the climate and we are also thinking deeply, interacting, taking action, and so many people are very conscientious on this issue."
'Our home is burning'
Rallies were also held in Kenya's capital Nairobi, the South African capital, Pretoria.
Banners in Nairobi ranged from angry to playful, with one reading: "This planet is getting hotter than my imaginary boyfriend."
Al Jazeera's Nicolas Haque, reporting from Nairobi, said: "Out of the 10 countries most affected by climate change, seven of those are on the African continent. It has already started with hurricanes sweeping through Mozambique, flash floods in South Africa and Sierra Leone and droughts in the Sahel.
"Here in Kenya, 200 species are at risk of going extinct every day because of these droughts. So many young people here are going impatient with their leaders for not doing enough."
Global warming caused by heat-trapping greenhouse gases from burning fossil fuels has already led to droughts and heatwaves, melting glaciers, rising sea levels and floods, scientists say.
An estimated 100,000 people turned up on the streets of London.
According to the UK Student Climate Network, which coordinated the strikes in this country, more than 200 demonstrations took place across the UK on Friday as workers were actively encouraged to join the young activists.
"I felt like climate change is so important, but I hadn't really seen anything to reflect that," Lola Fayokun, an 18-year-old from Avery in south London, told Al Jazeera at the protest.
"It's already killing people and having so many horrific impacts, especially in the global south. Yet nothing is being said. There is complete radio silence on the issue," she added.
Carbon emissions climbed to a record high last year, despite a warning from the UN-backed Intergovernmental Panel on Climate Change in October that output of the gases must be slashed over the next 12 years to stabilise the climate.
US President Donald Trump said in 2017 that he would pull the US out of the Paris Agreement under which countries have committed to cutting greenhouse gas emissions to tackle rising global temperatures.
"I'm here because Earth is our home and it's burning," said Carolyn Friedman, a 20-year-old Columbia University student with the Sunrise Movement.
"There are so many people from middle school and high school holding hands, walking through," she told Al Jazeera in New York.
In Guatemala, hundreds of students and activists march through the capital, Guatemala City.
Guatemala is consistently listed as one of the countries most vulnerable to the effects of climate change.
As students marched through the city, the Guatemalan government announced a national ban and regulation of single-use plastic products, including straws and utensils, and styrofoam products. The ban seeks to attempt to control rampant contamination of the environment.
Yet, protecting the environment has proven deadly in Guatemala.
"I'm here to make it known that there have been murders of environmental activists and of those who oppose mining and the extraction of natural resources," Mario Lopez, a 29-year-old resident of Guatemala City, told Al Jazeera. "All too often the killings are not investigated."
Most recently, on September 16, environmentalist Diana Isabel Hernandez was killed in the department of Suchitepequez on the country's southern coast.
Students also marched in major cities across Brazil, with many calling for greater action to protect the Amazon rainforest, which has seen a surge in fires and deforestation this year.
"The [Brazilian] federal government wants to turn the Amazon in an area for exploitation, to put cattle and soy over the forest," said university student Fabiana Amorim.
"The first action to save the climate in the case of Brazil is to tackle the interests of agribusiness, the Brazilian economic model based on selling commodities and seeing the environment as a product only," the 21-year-old told Al Jazeera.
Student Rebeca Gaspar, worried about the fate of her generation.
"I am 18 years old, so thinking about climate change is to think of my future," she said.
"We, young people, are the most affected by climate change," she added. "I hope these manifestations have an impact on the global policy for the environment, and that the government listens to the students," she added.
Protesters in the Colombian capital of Bogota also focused their attention on the Amazon and deforestation.
"Young people can create a presence and give a message near politicians and big establishments. They know we are here and know in their conscience they're not doing something," said Antonio Ehrlich, 18, a student at University at Los Andes.
"Colombia should be a leader in this march against climate change because we are the second most biodiverse country in the world," he told Al Jazeera.
Many students also showed up to take a stand against climate change sceptics.
High school student Sofia Gutierrez, 17, said, "they are insensitive to the topic of climate change. They don't think it's a real problem."
In Argentina, small demonstrations took place across the country, with a bigger march planned for next Friday in Buenos Aires.
A couple dozen people gathered in Plaza de Mayo, in front of the Casa Rosa presidential palace, Friday afternoon, holding hands and forming a circle, with signs that urged people to "wake up". Some people called environmental awareness a "blind spot" in their country, overshadowed by economic and political crises, but they vowed to gather and bring more attention to the issue again.
"The things people generally say around the climate here is: 'why should I care, I'm already old, and I'm not going to be here tomorrow," said 21-year-old Valentina Pacino.
"That's what our parents say, what our grandparents say. They don't believe that it's an emergency, because it's not treated as such, so I think the primary responsibility here rests with the media - that the media be present and that they broadcast this, so it can reach people," she told Al Jazeera.
Arantxa Avila joined the calls demanding governments take greater action.
"They have to do something," the 20-year-old told Al Jazeera.
"Because I can do something on my own, it's a small change, it helps. But the real change is going to come if governments start working on this," she added.
Additional reporting by Kate Walton in Canberra, Bilal Kuchay in New Delhi, Ylenia Gostoli in London, Ben Piven in New York City, Jeff Abbott in Guatemala City, Flavia Milhorance in Rio de Janeiro, Pu Ying Huang in Bogota and Natalie Alcoba in Buenos Aires.