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.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) Climate strike A protester at Millbank in London held up a poster of climate activist Greta Thunberg (Gareth Fuller/PA) Climate strike Thousands gathered on the unseasonally hot September day in Victoria Park Gardens to warn against global warming (Jonathan Brady/PA) Climate strike A younger protester needed a lie-down as handmade posters warned of the need to tackle climate change (Gareth Fuller/PA) Climate strike Students at a large protest in Manchester expressed their anger at Donald Trump (Peter Byrne/PA) Climate strike There was a big turn-out at the protest in Cambridge (Joe Giddens/PA) Climate strike Protesters in the city later held a ‘die-in’ to warn about the threat to the planet (Joe Giddens/PA) Climate strike Young and old also took to the streets of Birmingham (Jacob King/PA) Climate strike Protesters in Cullercoats, Tyneside, staged their protest at the seaside (Owen Humphreys/PA) Climate strike Pupils from Colaiste Bride School made their point with striking posters at a protest in Dublin (Brian Lawless/PA)