The world’s climate scientists have issued what one expert said is a "final warning" before global warming exceeds 1.5 degrees Celsius.

"The climate time-bomb is ticking," said UN Secretary-General António Guterres, at a meeting of the Intergovernmental Panel on Climate Change (IPCC), which this week released its final "synthesis report", marking six years of work by about 700 scientists. 

"Today’s IPCC report is a how-to guide to defuse the climate time-bomb," he said. "It is a survival guide for humanity."

Representatives of 195 countries negotiated an agreed text for the summary report, after assessing tens of thousands of scientific studies.

Haven't we seen a lot of IPCC reports already?

The report, known as the AR6, is a synthesis of six other reports by the IPCC — taking enormous amounts of data and simplifying it so policymakers inside and outside governments can use it.

As you can probably guess, there's not a lot of good news.

However, the scientists say there is still time to avoid the worst impacts of climate change and every bit of carbon pollution makes a difference.

The authors concluded:

• It was now "unequivocal" that climate is changing as a result of human activity, and that it is a threat to human societies and the natural world
• Climate change is already making extreme weather events more frequent — with 3.3 to 3.6 billion people living in places “highly vulnerable” to these changes
• Cuts to emissions need to be "deep, rapid and sustained" if the world is to limit warming to 1.5 degrees Celsius this decade
• If warming goes above that, adaptation will likely be too much for some communities and ecosystems to survive.

On Australia's Torres Strait islands, Warraber man Daniel Billy has been taking photos of what has already been lost as the sea creeps up on his homeland.

"Just to see a lot of the land mass taken out from the islands, it's really sad," he said.

"It's destroying places.

"It's very sad and it's scary at the same time, as it's slowly coming up to the community."

Mr Billy is worried about the cemetery, metres from the shoreline, where his parents have been laid to rest.

"I don't want to pick up my parents' remains from the reef," he said.

"I don't want my children, or their children, my nieces and nephews to pick up my remains."

Mr Billy is one of eight Torres Strait Islanders who took their case to the United Nations Human Rights Committee, which found Australia had failed to protect the community from climate change.

"Stop digging into the ground, because we're copping it up here."

It's a call supported by the United Nations, the report's authors and climate scientists.

In launching the report, Mr Guterres specifically called on wealthy countries, such as Australia, to urgently stop approving new coal, gas and oil projects.

"Demanding others move first only ensures humanity comes last," he said.

The whole world needed to act quickly, he said.

"We have never been better equipped to solve the climate challenge — but we must move into warp speed climate action now," Mr Guterres said. "We don’t have a moment to lose."

University of New South Wales Associate Professor Sarah Perkins Kirkpatrick said it had to be done before 2030. 

"Bottom line, we need to stop burning fossil fuels — 80 per cent of anthropogenic greenhouse gas emissions actually comes from burning fossil fuels [such as] coal, oil and gas," she said.

"If we can stop doing that through various different methods — such as renewable energy, electric cars, no gas being burned at all — then that's a huge piece of the puzzle solved.

"It's not the entire piece, but it's a really massive piece solved."

Is this really a 'final warning' from the world’s scientists?

Dr Perkins-Kirkpatrick described this report — which completes the IPCC’s sixth round of assessments — as a “final warning” because a 1.5C rise in global temperature would threaten the planetary systems human life depends on.

AR7, the next assessment report, is expected to be issued after 2030, when global warming is on track to have already breached the 1.5C limit.

“This is the final warning to limit the climate warming,” Dr Perkins-Kirkpatrick said.

"In the next 10 years, we'll overshoot that 1.5-degree threshold, but then we can bring it back down again — with heavy climate mitigation, heavy investment in renewable energy and also carbon capture and storage,” she said.

Macquarie University's Professor Lesley Hughes said what happens in the next seven years would be vital if we're to leave a world that’s habitable for our children and grandchildren.

"One of the things this IPCC report emphasises is that the window of opportunity for a safer climate in the second half of this century is closing rapidly, but it's not yet closed," she said.

"So, what we do, particularly between now and 2030, is absolutely critical."

Is Australia doing enough?

Professor Hughes said Australia has a lot to lose from climate change — with the southern oceans warming at a faster rate than the global average.

"We have a population — 86 per cent of [whom] lives within 50 kilometres of the Australian coastline — so we have most of our people and most of our valuable infrastructure on the coast in harm's way from sea-level rises and storm surges," she said.