The nature broadcaster delivered his message while speaking on behalf of the UN’s ‘People’s Seat’ initiative which gives ordinary people a voice at the international talks by gathering their thoughts, ideas and concerns through social media and polling in the past two weeks.

Attenborough said the world is facing its “greatest threat in thousands of years: climate change”.

“If we don’t take action, the collapse of our civilisations and the extinction of much of the natural world is on the horizon.”

“The continuation of our civilisations and the natural world upon which we depend, is in your hands,” 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.

“They’re supporting you in making tough decisions but they’re also willing to make sacrifices in their daily lives.”

The world is currently on course to overshoot by far the limits for global warming agreed in the landmark 2015 Paris accord on climate change, which were intended to prevent more extreme weather, rising sea levels and the loss of plant and animal species.

The talks are billed as the most important UN conference since Paris, coming ahead of an end-of-year deadline to agree a ‘rule book’ on enforcing action.

To mark the event the UN has launched an ActNow.bot which helps people discover simple everyday actions they can take to tackle climate change.

The speeches come after four former presidents of the annual UN climate talks warned the “world is at a crossroads” and decisive action in the next two years would be crucial to tackle the threat of climate change.

In a joint statement, France’s Laurent Fabius, Frank Bainimarama from Fiji, Salaheddine Mezouar from Morocco, and Peru’s Manuel Pulgar Vidal said: “The challenges are there, as are the solutions.

“We require deep transformations of our economies and societies to build a better world for all. This must be powered by multilateral co-operation.”

They called for ambitious decisions that are sufficiently detailed and comprehensive to enable the effective operation of the Paris Agreement, secured three years ago in the French capital to curb global warming.

A process to enable countries to announce efforts by 2020 to ramp up their domestic ambition on cutting greenhouse gas emissions must be launched, they said, as current efforts are not enough to prevent dangerous temperature rises.

They also called for further progress on the goal of mobilising $100bn (£78bn) a year for poorer countries to drive clean growth.

Michal Kurtyka, Poland’s deputy environment minister and president of the talks, said that without success in Katowice, Paris would not be a success, as it had only decided what was needed, not how it could be done.

Moreover, the wider political environment had changed.

“The wave of optimism and global cooperation that carried us to and through Paris has now crested, broken and is now tumbling,” he told delegates.

The nature broadcaster delivered his message while speaking on behalf of the UN’s ‘People’s Seat’ initiative which gives ordinary people a voice at the international talks by gathering their thoughts, ideas and concerns through social media and polling in the past two weeks.

Attenborough said the world is facing its “greatest threat in thousands of years: climate change”.

“If we don’t take action, the collapse of our civilisations and the extinction of much of the natural world is on the horizon.”

“The continuation of our civilisations and the natural world upon which we depend, is in your hands,” 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.

“They’re supporting you in making tough decisions but they’re also willing to make sacrifices in their daily lives.”

The world is currently on course to overshoot by far the limits for global warming agreed in the landmark 2015 Paris accord on climate change, which were intended to prevent more extreme weather, rising sea levels and the loss of plant and animal species.

The talks are billed as the most important UN conference since Paris, coming ahead of an end-of-year deadline to agree a ‘rule book’ on enforcing action.

To mark the event the UN has launched an ActNow.bot which helps people discover simple everyday actions they can take to tackle climate change.

The speeches come after four former presidents of the annual UN climate talks warned the “world is at a crossroads” and decisive action in the next two years would be crucial to tackle the threat of climate change.

In a joint statement, France’s Laurent Fabius, Frank Bainimarama from Fiji, Salaheddine Mezouar from Morocco, and Peru’s Manuel Pulgar Vidal said: “The challenges are there, as are the solutions.

“We require deep transformations of our economies and societies to build a better world for all. This must be powered by multilateral co-operation.”

They called for ambitious decisions that are sufficiently detailed and comprehensive to enable the effective operation of the Paris Agreement, secured three years ago in the French capital to curb global warming.

A process to enable countries to announce efforts by 2020 to ramp up their domestic ambition on cutting greenhouse gas emissions must be launched, they said, as current efforts are not enough to prevent dangerous temperature rises.

They also called for further progress on the goal of mobilising $100bn (£78bn) a year for poorer countries to drive clean growth.

Michal Kurtyka, Poland’s deputy environment minister and president of the talks, said that without success in Katowice, Paris would not be a success, as it had only decided what was needed, not how it could be done.

Moreover, the wider political environment had changed.

“The wave of optimism and global cooperation that carried us to and through Paris has now crested, broken and is now tumbling,” he told delegates.