July to be hottest month on record as UN warns of 'global boiling'

July is on track to be the hottest month in recorded history, scientists confirmed Thursday, as UN chief Antonio Guterres warned Earth has moved into an "era of global boiling".

Searing heat intensified by global warming has affected tens of millions of people in parts of Europe, Asia and North America this month, combining with fierce wildfires that have scorched across Canada and parts of southern Europe.

"Climate change is here. It is terrifying. And it is just the beginning," said Guterres, urging immediate and bold action to cut planet-heating emissions.

"The era of global warming has ended; the era of global boiling has arrived."

With the first three weeks of July already registering global average temperatures above any comparative period, the World Meteorological Organization and Europe's Copernicus Climate Change Service (C3S) said it is "extremely likely" that July 2023 will be the hottest month on records going back to the 1940s.

Carlo Buontempo, Director of C3S, said the temperatures in the period had been "remarkable", with an anomaly so large that scientists are confident the record has been shattered even before the month ends.

Beyond these official records, he said proxy data for the climate going back further -- like tree rings or ice cores -- suggests the temperatures seen in the period could be "unprecedented in our history in the last few thousand years".

Possibly even longer "on the order of 100,000 years" he said.

About 1.2 degrees Celsius of global warming since the late 1800s, driven by the burning of fossil fuels, has made heatwaves hotter, longer and more frequent, as well as intensifying other weather extremes like storms and floods.

The intense heat and devastating wildfires seen in July across parts of the northern hemisphere have caused alarm over the impact on health, ecosystems and economies.

With large swathes of the United States facing a record-breaking heatwave, President Joe Biden called the soaring temperatures from climate change an "existential threat".

"I don't think anybody can deny the impact of climate change anymore," he said at the White House, where he held a video conference with the mayors of heat-blasted Phoenix, Arizona, and San Antonio, Texas.

Biden, who said heat was the "number one weather-related killer" in the United States, causing 600 deaths every year, announced moves to bolster heat-related safety rules for workers, especially those labouring outdoors.

In Beijing, which saw a record-breaking streak of four weeks of highs above 35C, authorities urged the elderly to stay indoors and children to shorten outdoor playtime.

Wildfires raged in several countries across the Mediterranean region, where extreme heat has left landscapes tinder dry.

Hundreds of firefighters are struggling to contain deadly blazes across Greece that have raged for two weeks.