Humankind's role in the destructive warming of the planet is comparable to the meteor that wiped out the dinosaurs, UN Secretary-General Antonio Guterres said, calling for rapid steps including bans on fossil fuel advertising.
"Of the vast forces that have shaped life on Earth over billions of years, humanity is just one small blip on the radar," Mr Guterres said in a speech at New York's American Museum of Natural History.
"But like the meteor that wiped out the dinosaurs, we're having an outsized impact," he warned.
"In the case of climate, we are not the dinosaurs. We are the meteor. We are not only in danger. We are the danger."
He said that the European Commission's Copernicus Climate Change Service would officially report that May 2024 was the hottest May in recorded history.
Earlier, Met Éireann reported that Ireland has had the warmest May on record, according to Met Éireann, with an average temperature of 13.08C.
"This marks twelve straight months of the hottest months ever," Mr Guterres said.
However, he noted optimistically that humans "are also the solution" and called again for concerted global action to limit warming to 1.5 degrees Celsius.
That target, the most ambitious of the near-decade-old Paris Agreement, is "hanging by a thread," he said.
The UN's World Meteorological Organisation is set to report that there is an 80% chance the global annual average temperature exceeds the 1.5C limit in at least one of the next five years, he said.
"The battle for 1.5 degrees will be won or lost in the 2020s - under the watch of leaders today. All depends on the decisions those leaders take - or fail to take - especially in the next 18 months," he said.
Signatory countries of the Paris Agreement must submit new greenhouse gas emission reduction targets by early 2025.
Mr Guterres called for humanity to take an "exit ramp off the highway to climate hell," putting a particular target on the fossil fuel industry, which he labelled "Godfathers of climate chaos."
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He also denounced advertisers as "enablers" who have helped fossil fuel companies to delay climate action.
"Stop taking on new fossil fuel clients, from today, and set out plans to drop your existing ones," he told the "Mad Men fuelling the madness."
He also urged every country to ban advertising from fossil fuel companies, as many have done for "products that harm human health - like tobacco."
The UN chief repeated a call for a tax on fossil fuel companies' profits to finance the fight against global warming, while also mentioning unspecified "solidarity levies" on the aviation and shipping sectors.
Mr Guterres also demanded again that rich countries phase out coal by 2030 and reduce oil and gas consumption by 60% by 2035.
Wealthy countries which are historically more responsible for carbon emissions should increase their climate aid to poorer, more at risk countries, he pleaded.
"We cannot accept a future where the rich are protected in air-conditioned bubbles, while the rest of humanity is lashed by lethal weather in unliveable lands," he said.
