Protesters around the world have taken out rallies calling for action against climate change in advance of a United Nations Climate Action Summit in New York.

“The planet is getting hotter than my imaginary boyfriend,” read a poster, held by a teenager in Thailand on Friday.

Another girl in Bangkok seemed to feel guilty about skipping classes to demonstrate. Her placard read: “I’m missing school for this (Better be worth it!)”.

In Australia, placards read: “We’ll go to school when the earth is cool”, while raging wildfires prompted a pithy message from a woman in Melbourne, whose picture of a burning Australia was captioned: “We’re cactus mate!”

A group of protesters in Sri Lanka had a tough message: “Politicians who ignore climate change are climate criminals.”

Global warming caused by heat-trapping greenhouse gases from burning fossil fuels is already leading to droughts and heatwaves, melting glaciers, rising sea levels and floods, scientists say.

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.

The UN Climate Action Summit brings together world leaders to discuss climate change mitigation strategies, including the move from fossil fuels to renewable energy sources.