The world is on a "catastrophic pathway" in terms of global warming, UN Secretary-General Antonio Guterres says.
According to a report by the UN climate agency on Friday, a warming of 2.7C is foreseeable.
"This is breaking the promise made six years ago to pursue the 1.5C goal of the Paris Agreement," Guterres said on Friday.
"Failure to meet this goal will be measured in the massive loss of lives and livelihoods."
Previously, the UN presented a climate report on the international community's plans for reducing global emissions.
The UN Climate Secretariat said "nations should submit a more ambitious" plan if they wanted to prevent global temperatures rising above 1.5C by the end of the century.
Experts agree much more needs to be done by 2030 if global warming is to remain well below 2C, as agreed by almost 200 countries in Paris in 2015.
The earth has already heated by 1.2C compared with pre-industrial times.
According to the UN, to reach the target, a 45 per cent cut in emissions by 2030 is necessary to reach carbon neutrality by mid-century.
"The fight against climate change will only succeed if everyone comes together to promote more ambition, more cooperation and more credibility," Guterres said.
The World Climate Conference will be held in Glasgow in November.
Australian Associated Press