The UN's Intergovernmental Panel on Climate Change says keeping the Earth's temperature rise to only 1.5 degrees Celsius rather than the 2C target agreed to at the Paris Agreement talks in 2015, would have "clear benefits to people and natural ecosystems."

The IPCC report said at the current rate of warming, the world's temperatures would likely reach 1.5C between 2030 and 2052 after an increase of 1C above pre-industrial levels since the mid-1800s.

Keeping the 1.5C target would keep the global sea level rise 3.9 inches lower by 2100 than a 2C target, the report states.

That could reduce flooding and give the people that inhabit the world's coasts, islands and river deltas time to adapt to climate change.

The lower target would also reduce species loss and extinction and the impact on terrestrial, freshwater and coastal ecosystems, the report said.

"Every extra bit of warming matters, especially since warming of 1.5C or higher increases the risk associated with long-lasting or irreversible changes, such as the loss of some ecosystems," the IPCC's Hans-Otto Portner said.

The report is seen as the main scientific guide for government policymakers on how to implement the 2015 Paris Agreement during the Katowice Climate Change Conference in Poland in December.

To contain warming at 1.5C, manmade global net carbon dioxide (CO2) emissions would need to fall by about 45 per cent by 2030 from 2010 levels and reach "net zero" by mid-century.

The report summary said renewable energy would need to supply 70 per cent to 85 per cent of electricity by 2050 to stay within a 1.5C limit, compared with about 25 per cent now.

The report said the lower target would mean the Arctic Ocean would be free of sea ice in summer only once per century not at least once a decade under the higher target.

"The report shows that we only have the slimmest of opportunities remaining to avoid unthinkable damage to the climate system that supports life as we know it," said Amjad Abdulla, an IPCC board member.

Australian Associated Press