UNITED NATIONS - A UN report published on Sunday said the world is falling badly behind in the race to avert climate disaster because of runaway warming, with the five-year period ending 2019 set to be the hottest ever.

It came ahead of a major United Nations climate summit opening on Monday to be attended by more than 60 world leaders, as Secretary-General Antonio Guterres pushes for countries to increase countries' greenhouse gas reduction targets.

The report "highlights the urgent need for the development of concrete actions that halt global warming and the worst effects of climate change," said its authors, the Science Advisory Group to the summit.

Average global temperature from 2015-2019 is on track to be the hottest of any five-year period on record, according to the report from the World Meteorological Organization.

The period "is currently estimated to be 1.1 C above preindustrial (1850-1900) times and 0.2 C warmer than 2011-15," it said.

The past four years were already the hottest since record-keeping began in 1850.

Guterres said last week the world was "losing the race" on climate change, and the latest report spells out the extent to which the gap between what is required and what is happening is widening.

Rather than falling, carbon dioxide grew 2 percent in 2018, reaching a record high of 37 billion tonnes.

More importantly, there is also no sign yet of reaching what is known as "peak emissions," the point at which levels will start to fall, though these are not growing at the same rate as the global economy.

The 2015 Paris Agreement saw countries lay out national targets to reduce their emissions in order to limit the long-term temperature rise to less than 2 C, or ideally 1.5 C, above preindustrial levels.

These are benchmarks that will limit in important ways the impact of warming on world weather systems.

But even if all countries meet the goals they set themselves, the world will warm by 2.9 C to 3.4 C, the report found.

The current levels of ambition would need to be tripled to meet the 2 C goal and increased fivefold to meet the 1.5 C goal - technically still possible.

"This reads like a credit card statement after a five-year long spending binge," said Dave Reay, a professor and chair in Carbon Management at the University of Edinburgh.

"Our global carbon credit is maxed out," he added. "If emissions don't start falling, there will be hell to pay."

Agence France-Presse