Renowned nature broadcaster Sir David Attenborough has added his voice to the chorus of warning that scientists and experts that have been aired recently.
Scientists have been warning us that destruction of biodiversity and ecological loss and climate change caused by environmental damage could spell disaster sooner than we think.
Atat the opening ceremony of the COP24 UN climate conference, in Katowice, Poland, Attenborough called climate change "our greatest threat in thousands of years."
In the run-up to the event, the UN asked people to send their thoughts on climate change. Attenborough was there to represent the public, by taking the "People's Seat" at the conference.
He said: "The world's people have spoken. Their message is clear. Time is running out. They want you – the decision makers to act now.
"Leaders of the world you must lead," he added. "The continuation of our civilizations and the natural world on which we depend is in your hands."
COP stands for Conference of Parties. COP 21, in 2015, led to the landmark Paris Agreement. It's a legally binding agreement to fight climate change, where nations committed to keeping global warming well below 2 degrees Celsius above pre-industrial levels and, if possible, below 1.5 degrees.
But a recent study showed that CO2 emissions are on the rise again after a plateau of four years.
An urgency was seen at the event, however.
In an unprecedented move, four former UN climate talks presidents issued a statement on Sunday, calling for urgent action.
They say "decisive action in the next two years will be crucial."
Meanwhile, the discrepancy between what countries say they are doing and what needs to be done has never been wider. It’s amazing how little has been done lately. It’s high time leaders woke up.