Protests have taken place around the world calling for action to avert environmental catastrophe.
From London to Sydney, here's a look at some of the millions of people joining the global youth climate strike.
A 'polar bear' joined children from the Terra Nova secondary school in Cheshire to demand action to stop global warming (Peter Byrne/PA)
A protester at Millbank in London held up a poster of climate activist Greta Thunberg (Gareth Fuller/PA)
Thousands gathered on the unseasonably hot September day in Victoria Park Gardens to warn against global warming (Jonathan Brady/PA)
A younger protester needed a lie-down as handmade posters warned of the need to tackle climate change (Gareth Fuller/PA)
Students at a large protest in Manchester expressed their anger at Donald Trump (Peter Byrne/PA)
There was a big turn-out at the protest in Cambridge (Joe Giddens/PA)
Protesters in the city later held a 'die-in' to warn about the threat to the planet (Joe Giddens/PA)
Young and old also took to the streets of Birmingham (Jacob King/PA)
Protesters in Cullercoats, Tyneside, staged their protest at the seaside (Owen Humphreys/PA)
Pupils from Colaiste Bride School made their point with striking posters at a protest in Dublin (Brian Lawless/PA)
Thousands of miles away in the Philippines, activists displayed their message in front of 'a human globe' formation (Bullit Marquez/AP)
South Korean protesters held portable LED lamps to show the need for renewable energy (Lee Jin-man/AP)
In India, young protesters gathered outside the Ministry of Housing and Urban Affairs in New Delhi (Manish Swarup/AP)
Activists blocked a road in Frankfurt, Germany, during rush hour (Michael Probst/AP)
A large inflatable globe was bounced through the crowd as thousands protested in Sydney (Rick Rycroft/AP)
People shared some of their favorite signs on Twitter as well:
This may be my favourite #ClimateStrike sign from Sydney. https://t.co/Hds507rDOF— Mikey Nicholson (@Mikey Nicholson) 1568951444.0
Melbourne’s out in force. #ClimateStrike https://t.co/NicTHGmzKs— ℭ𝔬𝔲𝔯𝔱𝔫𝔢𝔶 (@ℭ𝔬𝔲𝔯𝔱𝔫𝔢𝔶) 1568954751.0
#ClimateStrike #ClimateStrikeperth My Favorite sign of the day! https://t.co/vNKiin9Umu— PureMarble (@PureMarble) 1568961307.0
Junior school children tell climate rally: "The world is like an ice cream and no-one likes a melted ice cream."… https://t.co/9GkKIqlCVB— BBC East Midlands (@BBC East Midlands) 1568981725.0
The climate strike is good https://t.co/a8yGNK7fer— Katie McDonough (@Katie McDonough) 1568990080.0
Some cracking signs at today's climate strike in Sheffield. "Hold in ur farts" the current favourite @SheffieldStar https://t.co/nezpElpBBl— Ellen Beardmore (@Ellen Beardmore) 1568992533.0
The best signs from the global climate strike https://t.co/rlA9qOeUkn https://t.co/yxvM9GABE0— Mashable (@Mashable) 1568980581.0
The @lizzo X #ClimateStrike sign this world deserves. https://t.co/bEdJdaW1ej— Alex Anastassiou (@Alex Anastassiou) 1568947084.0