The United Nations' Intergovernmental Panel on Climate Change (IPCC) has called for drastic and deep GHG emissions cuts to keep the average global temperature less than 1.5C above pre-industrial levels.
"There is a rapidly closing window of opportunity to secure a liveable and sustainable future for all," the report's authors write.
The report has been compiled by 93 authors from research done over the last six years by hundreds of the world's top climate scientists. It shows that human activities have already warmed the Earth by 1.1ºC, resulting in more frequent extreme weather and increased food and water scarcity for millions of people.
If no change occurs, current policies set to warm the Earth by a further 2ºC above pre-industrial temperatures by 2100, making the planet's climate "dangerously unstable".
However, the report's authors stress that it is not yet too late to take action. They argue that the technology needed to adapt to climate change and keep harmful emissions at bay is available, and could be implemented to avoid the worst-case scenario.
"If we act now, we can still secure a liveable sustainable future for all," said IPCC Chair Hoesung Lee.
The UN secretary general, António Guterres, added: "This report is a clarion call to massively fast-track climate efforts by every country and every sector and on every timeframe. Our world needs climate action on all fronts: everything, everywhere, all at once."
Global surface temperature has increased faster since 1970 than in any other 50-year period over the last 2,000 years, and in 2019 atmospheric CO2 concentrations were higher than at any time in at least two million years, according to IPCC analysts.
In order to limit the global temperature rise to 1.5ºC, CO2 emissions need to fall by 48 per cent by 2030, 65 per cent by 2035, 80 per cent by 2040 and 99 per cent by 2050.
"The report is pretty clear that we will, almost regardless of emissions scenarios, reach 1.5ºC in the first half of the next decade," said IPCC author Professor Peter Thorne.
"There is some uncertainty about that. The real question is whether our collective choices between now and then mean we reach and stabilise at or around 1.5C or whether we blast right through 1.5ºC, crash through 2C and keep going."
The conclusions coincide with the findings of Met Office analysis. These suggest that slashing global GHG emissions in half by 2030 would only leave a 50 per cent chance of limiting the global average temperature to 1.5ºC.
At the moment, between 3.3-3.6 billion people live in contexts highly vulnerable to climate change, the IPCC said, with those in the global south, small islands and the Arctic being the populations most at-risk.
The next IPCC report is not due to be published before 2030. Meanwhile, the IPCC report warns, there is "a rapidly closing window of opportunity to secure a liveable and sustainable future for all".
