Pledges by nations to cut carbon emissions will fall far short of those needed to prevent global temperatures rising by more than the crucial 2C by the end of the century, warned climate experts.
A rise of 2C is considered the most the Earth could tolerate without risking catastrophic changes to food production, sea levels, fishing, wildlife, deserts and water reserves.
Even if rises are pegged at 2C, scientists say this will still destroy most coral reefs and glaciers and melt significant parts of the Greenland ice cap, bringing major rises in sea levels.
Researchers have had a global temperature rise of almost 1C since the industrial revolution and have already seen widespread impacts that have had real consequences for people, said climate expert Professor Chris Field of Stanford University.
Field added that people should therefore be striving to limit warming to as far below 2C as possible. However, that will require a level of ambition that we have not yet seen. In advance of the COP21 United Nations climate talks to be held in Paris from 30 November to 11 December, every country was asked to submit proposals on cutting use of fossil fuels in order to reduce their emissions of greenhouses gases and so tackle global warming.
The deadline for these pledges was 1 October. A total of 147 nations made submissions and scientists have since been totting up how these would affect climate change.
They have concluded they still fall well short of the amount needed to prevent a 2C warming by 2100, a fact that will be underlined later this week when the Grantham Research Institute releases its analysis of the COP21 submissions.
This will show that the world's carbon emissions, currently around 50bn tonnes a year, will still rise over the next 15 years, even if all the national pledges made to the UN are implemented. The institute's figures suggest they will reach 55bn to 60bn by 2030.