Major UN climate report set for release

Rarely does a gathering of scientists pouring over thousands of pages of complex data generate so much buzz.

But when the science in question concerns global warming, and those pages will form the world's most important report on climate change in years, the hype becomes more understandable.

On Friday, the United Nations' Intergovernmental Panel on Climate Change (IPCC) will hand down its fifth major assessment on climate science in Stockholm.

The report, six years in the making, brings together the latest findings from thousands of experts worldwide to form the scientific basis of climate change, and its impacts and future risks.

The vast 2000-page trove is condensed into a slim 20-page summary digestible for policymakers, which is then scrutinised line by line by hundreds of scientists until they all agree both documents can be published.

The level of rigour involved in the IPCC process is famously slow and painful, but proponents insist it's necessary given the influence the final report has on policy decisions.

The findings of past IPCC reports steered action on ratifying the Kyoto Protocol, and pushed global leaders into agreeing that avoiding a two-degree temperature rise was in the world's best interests.

"It is the benchmark used by all the world's governments in deciding on the level of action that collectively we should all be taking," the Climate Institute's Erwin Jackson told AAP.

"It is put under intense amounts of scrutiny, simply because of the political nature of the outcomes which inevitably flow from it."

The last IPCC assessment in 2007 - the fourth since the UN climate body's inception 25 years ago - proved sober reading.

The world was warming, scientists concluded, and human activity was the primary driver. Allowing global temperatures to rise above two degrees was "dangerous" and risked more extreme weather events.

This upcoming assessment - the first of three parts - isn't expected to offer any rosier projections, with the global consensus on climate science only strengthening in the past six years.

There's more worrying evidence about surface temperatures, sea levels and the state of the Arctic ice caps, and new chapters with fresh science on clouds, sea level change and climate phenomena.

More than 600 authors from 32 countries - including experts from the CSIRO and Bureau of Meteorology - contributed to the first section on the physical science, with subsequent parts on the impacts and mitigation of climate change to follow.

The IPCC itself does not conduct its own research, instead tasked with collecting and assessing the latest global science.

It also doesn't make any policy recommendations but just presents the facts which are then endorsed by the IPCC member governments.

A string of leaks - inevitable when the draft document was sent out to 195 nations - prompted rumours that scientists got their numbers wrong in 2007 and were planning on downgraded their warnings in this report.

Professor Andy Pitman, a review editor of the IPCC report at the University of NSW, said efforts to discredit the IPCC were to be expected given the influence the report wielded.

Efforts being considered by the IPCC to control leaks and damaging misinformation would likely fall on deaf ears given some interest groups and sections of the media had adopted an anti-science agenda, he added.

"There would be nothing that the scientific community could do to override that agenda because they've already decided what they want to report," Prof Pitman said.

Making heads or tails of the dense jargon within the report will fall to groups like the Climate Institute, the Climate Change Authority and Tim Flannery's new Climate Council.

The council's Professor Will Steffen said they hoped to cut through the complexities that made the report "exceptionally confusing" for the average punter.

Environment Minister Greg Hunt is expected to receive a briefing from the Bureau of Meteorology.