The United Nations has slammed the world’s efforts to stop climate change as “utterly inadequate”, as it pleaded for countries to stop humanity’s “war against nature”.

Secretary-General Antonio Guterres said global warming could pass the “point of no return” and called for the world to find more political will to combat climate change.

“Our war against nature must stop, and we know that it is possible,” Mr Guterres said on Sunday ahead of the two-week global climate summit in Madrid.

Insisting that his message was “one of hope, not of despair”, the UN chief said the world has the scientific knowledge and the technical means to limit global warming.

“We simply have to stop digging and drilling and take advantage of the vast possibilities offered by renewable energy and nature-based solutions,” Mr Guterres said.

Around the world, extreme weather ranging from wildfires to floods is being linked to man-made global warming, putting pressure on the summit to strengthen the implementation of the 2015 Paris Agreement on limiting the rise in temperature.

Former prime minister Malcolm Turnbull has urged Liberal Party members to be “loud Australians” on climate change.

Mr Turnbull told moderates at a farewell function last week the government’s current climate change policy was incoherent, The Daily Telegraph reported.

“It was hard not to read it as a dig at (current Prime Minister Scott) Morrison,” one attendee told the tabloid.

Cuts in emissions of greenhouse gases – mostly from burning carbon-based fossil fuels – that have been agreed so far under the Paris deal are not enough to limit temperature rises to a goal of between 1.5 and 2 degrees Celsius above pre-industrial levels.

Many countries are not even meeting those commitments, and political will is lacking, Mr Guterres said.

President Donald Trump for his part has started withdrawing the United States from the Paris Agreement while the deforestation of the Amazon basin – a crucial carbon reservoir – is accelerating and China has tilted back towards building more coal-fired power plants.

Seventy countries have committed to a goal of “carbon neutrality” or “climate neutrality” by 2050.

This means they would balance out greenhouse emissions, for instance through carbon capture technology or by planting trees.

But Mr Guterres said these pledges were not enough.

“We also see clearly that the world’s largest emitters are not pulling their weight, and without them, our goal is unreachable,” he said.

Last year’s UN climate summit in Poland yielded a framework for reporting and monitoring emissions pledges and updating plans for further cuts. But sticking points remain, not least over an article on how to put a price on emissions, and so allow them to be traded.

“I don’t even want to entertain the possibility that we do not agree on article 6,” Mr Guterres said.

“We are here to approve guidelines to implement article 6, not to find excuses not to do it.”

Bank of England governor Mark Carney has accepted an invitation to become UN special envoy on climate action and climate finance from January 1, Mr Guterres said.

-with AAP