Governments are to face renewed calls for dramatic action to tackle climate change as a major report on limiting global temperature rises to 1.5C is published.
Scientists and representatives of 195 governments meeting in South Korea have approved a report on the impact of a rise of 1.5C above pre-industrial levels and the action needed to limit global warming to that level.
The finalised report, to be published on Monday, will sound a warning about the speed and scale of measures required to keep temperature rises to a level beyond which many vulnerable countries say their survival is at risk.
It will prompt new calls for dramatic and urgent steps to cut emissions to zero by 2050.
That would mean an end to burning fossil fuels to generate power, the replacement of petrol and diesel cars with electric vehicles or other clean alternatives and no more gas boilers to heat homes, in just a few decades.
Scientists have also warned that protecting and restoring forests will be key to cutting carbon and drawing down excess emissions from the atmosphere.
In addition, concerns have been raised about relying on unproved technology to take emissions out of the atmosphere to bring down temperatures again if the world exceeds the 1.5C mark.
The world is already experiencing around 1C of global warming, and events such as floods, storms and heatwaves like the one in the UK this summer have become increasingly likely as a result of climate change, according to experts.
While previous assessments looked at a range of scenarios for greenhouse gas emissions and what they would mean for the planet, this new study will spell out to governments that they are not doing enough – and what they need to do.
With the promises countries have made so far to cut their emissions putting the world on track for 3C of warming by the end of the century, the report will throw into stark relief the scale of the challenge.
The science shows letting temperature rises climb more than 1.5C will lead to sea level rises, an increase in heavy rainstorms and heatwaves, more people facing water scarcity and drought, greater spread of diseases and more economic losses.
Ahead of its publication, Neil Thorns, director of advocacy at charity Cafod, said: “This report proves that keeping global temperatures to 1.5C is a necessity, not an ambition.
“Faced with such information we cannot leave poor communities standing on the front-line of this potential storm, we must act urgently.”