High Pacific surface temperatures fuel record warm year

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Sea surface temperatures remained unusually high across many regions in the Pacific Ocean in November, leaving the world on course for a record warm year, the European Earth observation agency said.

The month of November was the second-warmest on record on land and at sea, with air temperatures at 1.62C above pre-industrial levels, data from Copernicus showed. The average sea surface temperature for the month was 20.58C.

This produced more rainfall than normal in many parts of the world last month, causing flooding, as the warmer air holds more moisture.

The cooling effect of the naturally occurring La Niña weather cycle across the central and eastern Pacific Ocean that was expected to provide a short-term brake on the pace of global temperature rises has failed to emerge with any strength.

Samantha Burgess, deputy director of Copernicus, reiterated the agency’s “virtual certainty” that 2024 would be the warmest on record, and that it would be the first calendar year above 1.5C.

It does not, however, represent a breach of the Paris Agreement threshold of 1.5C, which refers to a long-term average measured over a period of decades. But it meant that “ambitious climate action is more urgent than ever,” Burgess said.

Copernicus also identified short-term and localised variations in the weather last month, including colder than usual temperatures across the western US, parts of northern Africa, far eastern Russia, and across most of Antarctica.

In some parts of the world this cold snap was caused by “dips” in the jet stream, the narrow current of air flowing west to east high across the globe, said Julien Nicolas, a senior scientist at Copernicus.

One such “dip” over the western US last month carried cold polar air with it, while propelling warmer tropical air to other parts of the country.

Some parts of western Europe also experienced the cold, he said. “The jet streaming was skewing this [cold] air towards Europe, and warmer air east,” he added.

Despite these weather variations, scientists emphasise that the global temperature trend remains upwards over the long term, driven by the relentless greenhouse gases released from the burning of fossil fuels.

“Climate change is happening in the background,” Nicolas said. “Air from polar regions is not as cold as it used to be, and air from the tropics is warmer than it used to be.”

In one sign of this, snowfall across the Alps has fallen 34 per cent between 1920 and 2020, with snow increasingly turning to rain at lower altitudes, according to Eurac Research, a private facility based in northern Italy. Michele Bozzoli, environmental meteorologist, said in an online post last week that the “notable decrease” in snow had been particularly evident after 1980.

There was more rain than normal in regions of the US last month, as well as much of Australia and South America, Copernicus said.

Typhoons in the western Pacific Ocean led to heavy rainfall in Asia, with more than a million people ordered to evacuate in the Philippines because of a typhoon on its main island of Luzon.

Hotter seas lead to more rain as water evaporates from their surface. The average sea surface temperature for last month was 20.58C, just 0.13C below a record peak in November 2023, Copernicus also said.

In Europe, eastern Spain, southern UK and the Balkans also experienced wetter-than-average conditions last month. The rain, winds and snow brought by Storm Bert wreaked havoc across parts of Wales, Scotland and England, prompting calls for more money to be spent on flood defences.