This summer was the hottest on record across the Northern Hemisphere, U.N. says The world's oceans were the hottest ever recorded, while Antarctica continued to set records for low amounts of sea ice, the World Meteorological Organization said.

This summer was the hottest on record across the Northern Hemisphere, the U.N. says

A man cools off at a temporary misting station deployed by the city in the Downtown Eastside due to a heat wave, in Vancouver, British Columbia, Aug. 16, 2023. DARRYL DYCK/AP hide caption

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DARRYL DYCK/AP

A man cools off at a temporary misting station deployed by the city in the Downtown Eastside due to a heat wave, in Vancouver, British Columbia, Aug. 16, 2023.

DARRYL DYCK/AP

GENEVA — Earth has sweltered through its hottest Northern Hemisphere summer ever measured, with a record warm August capping a season of brutal and deadly temperatures, according to the World Meteorological Organization.

Last month was not only the hottest August scientists ever recorded by far with modern equipment, it was also the second hottest month measured, behind only July 2023, WMO and the European climate service Copernicus announced Wednesday.

August was about 1.5 degrees Celsius (2.7 degrees Fahrenheit) warmer than pre-industrial averages, which is the warming threshold that the world is trying not to pass. But the 1.5 C threshold is over decades — not just one month — so scientists do not consider that brief passage that significant.

The world's oceans — more than 70% of the Earth's surface — were the hottest ever recorded, nearly 21 degrees Celsius (69.8 degrees Fahrenheit), and have set high temperature marks for three consecutive months, the WMO and Copernicus said.

"The dog days of summer are not just barking, they are biting," United Nations Secretary-General Antonio Guterres said in a statement. "Climate breakdown has begun."

So far, 2023 is the second hottest year on record, behind 2016, according to Copernicus.

Scientists blame ever warming human-caused climate change from the burning of coal, oil and natural gas with an extra push from a natural El Nino, which is a temporary warming of parts of the Pacific Ocean that changes weather worldwide. Usually an El Nino, which started earlier this year, adds extra heat to global temperatures but more so in its second year.

"What we are observing, not only new extremes but the persistence of these record-breaking conditions, and the impacts these have on both people and planet, are a clear consequence of the warming of the climate system," Copernicus Climate Change Service Director Carlo Buontempo said.

Copernicus, a division of the European Union's space program, has records going back to 1940, but in the United Kingdom and the United States, global records go back to the mid 1800s and those weather and science agencies are expected to soon report that the summer was a record-breaker.

Scientists have used tree rings, ice cores and other proxies to estimate that temperatures are now warmer than they have been in about 120,000 years. The world has been warmer before, but that was prior to human civilization, seas were much higher and the poles were not icy.

So far, daily September temperatures are higher than what has been recorded before for this time of year, according to the University of Maine's Climate Reanalyzer.

While the world's air and oceans were setting records for heat, Antarctica continued to set records for low amounts of sea ice, the WMO said.