Climate change poses an "existential threat" to life on Earth, prominent scientists warned Tuesday, in an assessment on this year's avalanche of heat records and weather extremes that they said are hitting more ferociously than expected.

With expectations that 2023 will be the hottest year on record, regions across the planet have been scorched by deadly heat waves.

Others have been hit by floods, or in some cases, have suffered both extremes in quick succession.

"The truth is that we are shocked by the ferocity of the extreme weather events in 2023. We are afraid of the uncharted territory that we have now entered," said an international coalition of authors in a new report published in the journal BioScience.

Their stark assessment: "Life on planet Earth is under siege".

They said humanity had made "minimal progress" in curbing its planet-heating emissions, with major greenhouse gases at record levels, and subsidies for fossil fuels soaring last year.

The damning assessment comes just a month ahead of UN COP28 climate negotiations to be held in oil-rich United Arab Emirates.

"We must shift our perspective on the climate emergency from being just an isolated environmental issue to a systemic, existential threat," the authors said.

The study on the state of the climate looked at recent data on 35 planetary "vital signs" and found 20 of these were at record extremes this year. 

'Off the chart'

Just roughly 1.2 degrees Celsius of temperature rise above pre-industrial levels has triggered a range of calamitous and costly consequences.    

This year has also seen the beginning of a warming El Nino weather phenomenon. 

The European Union's Copernicus Climate Change Service has said that the three months to September were the hottest period ever recorded, and likely the hottest in approximately 120,000 years.