'10 years - 1.5 degrees Celsius increase' is one of the key conclusions of the most comprehensive climate report ever released — produced by the world's most authoritative body on climate science, the Intergovernmental Panel on Climate Change (IPCC).

Globally, warming has now reached about 1.1C since industrialisation (1850-1900), according to the hundreds of scientists and governments that make up the IPCC. In Australia, warming has reached 1.4C.

The new report was a "code red for humanity", United Nations secretary-general Antonio Guterres declared.

"The alarm bells are deafening and the evidence is irrefutable: Greenhouse gas emissions from fossil fuel burning and deforestation are choking our planet and putting billions of people at immediate risk," he said.

"This report must sound a death knell for coal and fossil fuels, before they destroy our planet.

"The viability of our societies depends on leaders from government, business and civil society uniting behind policies, actions and investments that will limit temperature rise to 1.5 degrees Celsius."

The UK government immediately called for the rest of the world to take urgent action.

"I hope today's IPCC report will be a wake-up call for the world to take action now, before we meet in Glasgow in November for the critical COP26 summit," UK Prime Minister Boris Johnson said.

If it was not for aerosol pollution emitted by humans, which cools the Earth, they said the greenhouse gasses we have emitted would already have heated the world by 1.5C.

World likely to hit 1.5C by 2030 if nothing changes

The new report found that even in its most ambitious scenario, which the world is failing to stick to, global warming would likely hit 1.5C by about 2035.

On our current trajectory, we are likely to hit 1.5C of warming about 2030.

Even if we radically and immediately cut emissions now, the world is still likely to warm to 1.6C, before dropping again.

In all scenarios, getting the world back under that extra 1.5C would require massive reforestation, or technology to remove carbon dioxide from the atmosphere.

Technology like that has not yet been proven to work at scale.

In 2018, the UN body produced a report estimating that warming rates seen at the time meant the 1.5C barrier would be breached between 2030 and 2050, with the most likely time being around 2040.

The new report said many of the effects of that warming had particular relevance to Australia:

Australia committed to reaching net zero 'as soon as possible'

In 2015, as part of the Paris Agreement, the world's governments agreed to pursue efforts to stop warming at 1.5C — a promise they have now all but failed to come good on.

Australia is widely considered to be a laggard on efforts to stop climate change, and it was recently ranked last among 200 countries for its actions.

Minister for Emissions Reduction Angus Taylor said Australia was committed to reaching net zero "as soon as possible", preferably by 2050, but did not flag any changes to the government's approach.

He said the government's Technology Investment Roadmap would drive billions of dollars of investment in low-emissions technologies that would make net zero achievable.

"Our technology-led approach to reducing emissions will see Australia continue to play its part in the global effort to combat climate change without compromising our economy or jobs," he said.

One of the authors of the IPCC report is Malte Meinshausen, a climate scientist at the University of Melbourne and former scientific adviser to the German government's climate negotiators.

"I think everybody in the international community would laugh if they would hear that Australia thinks they're doing enough. Of course they're not doing enough," Dr Meinshausen told the ABC.

"They neither have upped their targets for 2030 nor have they put a net zero target onto the table. They are not invited to many of the talks where international climate diplomacy is now going on because they are seen — and rightly so — as a laggard."

1.5C limit a promise the world is set to break

Chair of the IPCC, Mark Howden from ANU, said to keep climate change at relatively safe levels, changes needed to be implemented quickly.

"We really need to be heading towards 45 per cent reduction by 2030 and keeping that going post 2030," he said.

"At the moment, those emission reduction commitments under the Paris Agreement are not sufficient to keep temperatures down to 2 degrees, let alone 1.5 degrees."

Reaching the target of net zero emissions needed to happen much earlier than most were considering, said Nerilie Abram, a climate scientist from ANU and the ARC Centre for Excellence for Climate Extremes.

"For Australia to be doing its fair share, actually we really should be trying to get to net zero emissions in the 2030s," she said.