Thousands of people in Asia and Europe joined rallies demanding more action on climate change on Friday, aiming to force political leaders to come up with urgent solutions ahead of the United Nations climate summit in Madrid from Dec. 2-13.

Friday’s climate strikes were expected to take place in 2,300 cities in 153 countries around the world, according to the climate campaign group Friday For Future.

The protests come as experts warn that global temperatures could rise sharply over this century with destructive consequences after greenhouse gas emissions hit record levels.

Outside parliament in London, protesters flew a giant blimp in the shape of a baby with “Guess my weight in carbon dioxide” written on its vest.

Other protests took place in Mumbai, Tel Aviv, Vienna and Frankfurt. In Bangkok, young people chanted: “No more coal, no more oil, keep the carbon in the soil”, and staged a “drop dead” flash mob.

Students stage global strikes to pressure U.N. climate summit