Mysterious ‘warm blob’ breaks records in the North Pacific Ocean

North Pacific waters experienced their warmest summer on record, according to a BBC analysis of a mysterious marine heat wave that has baffled climate scientists.

Sea surface temperatures between July and September were more than 0.25°C above the previous 2022 maximum – a significant increase over an area about ten times the size of the Mediterranean Sea.

While climate change is known to increase the likelihood of marine heatwaves, scientists are trying to explain why the North Pacific Ocean has been so hot for so long.

But all that extra heat in the so-called “warm blob” could be having the opposite effect in the UK, possibly making a colder start to winter more likely, some researchers believe.

“There's definitely something unusual going on in the North Pacific,” said Zeke Hausfather, a climate scientist at Berkeley Earth, a research group in the US.

He said such a jump in temperature across such a large region was “quite remarkable.”

BBC analyzed the data European Climate Service Copernicus to calculate average temperatures from July to September over a large area of ​​the North Pacific Ocean, sometimes called the “warm blob”.

This region extends from the east coast of Asia to the west coast of North America, the same area used in previous scientific research.

The figures show that not only has the region experienced rapid warming over the past few decades, but in 2025 it will be noticeably higher than in recent years.

It's no surprise that the seas are getting hotter. Global warming caused by humanity's emissions of carbon dioxide and other gases has already tripled the number of days of extreme heat in oceans around the world, according to a study. study published earlier this year.

But temperatures were even higher than predicted by most climate models – computer simulations that take into account humanity's carbon emissions.

Analysis of these models Berkeley Earth group suggests that the chance of sea temperature change in the North Pacific in August was less than 1% during any given year.

Natural weather variability is believed to be one reason. For example, this summer the wind was weaker than usual. This means more heat from summer sunlight can remain at the sea's surface rather than mixing with the cooler waters below.

But according to Dr. Hausfather, this cannot explain the exceptional conditions.

“This is certainly not just natural variability,” he said. “There's something else going on here.”

One intriguing idea is that recent changes in marine fuels may be contributing to warming. Before 2020, dirty motor oil emitted large amounts of sulfur dioxide, a gas harmful to human health.

But this sulfur also formed tiny, solar-reflecting particles in the atmosphere known as aerosols, which helped curb rising temperatures.

So eliminating this cooling effect in shipping hotspots like the North Pacific could unlock the full effects of human-caused warming.

“Sulfur appears to be a leading candidate for the cause of regional warming,” Dr Hausfather said.

Another research shows that efforts to reduce air pollution in Chinese cities also played a role in the warming of the Pacific Ocean.

This dirty air did the same job as the ship, reflecting sunlight, while cleaning it could have the unintended consequences of warming the ocean even more.

The North Pacific marine heat wave has already impacted weather on both sides of the Pacific, likely boosting very high summer temperatures in Japan and South Korea, as well as storms in the United States.

“We've seen severe thunderstorms in California because the warm ocean waters of the Pacific provide warmth and moisture,” said Amanda Maycock, professor of climate dynamics at the University of Leeds.

“In particular, there are things we call atmospheric rivers… bands of air that hold very large amounts of moisture fed from ocean waters,” she added.

“So if we have warm ocean waters… they can bring a lot of moisture onto land, which then falls as rain and can fall as snow in the winter.”

Long-term weather forecasting is always a challenge, but a heat wave in the North Pacific could affect the UK and Europe in the coming months.

This is due to the relationship between weather in different parts of the world, known as telecoupling.

“Although the current warm conditions are located in the North Pacific, they can cause wave movements in the atmosphere that could change our weather downstream into the North Atlantic and into Europe,” Professor Maycock said.

“This could favor high-pressure conditions across the continent, giving us more influence from the Arctic, where we have colder air,” she added.

“This could be carried over Europe and bring us colder weather early in winter.”

The colder outcome is by no means certain, as this is a complex area of ​​science. Several other weather conditions also affect British winters, which are generally becoming milder due to climate change.

And the warm North Pacific Ocean appears to have a different effect in late winter, favoring milder and wetter conditions in parts of Europe.

Another factor to consider is what is happening further south in the eastern tropical Pacific.

There, the surface waters are unusually cool – a classic sign of the meteorological phenomenon known as Young woman.

La Niña and its warm brother El Niño are natural patterns, although study published this week stressed that global warming itself could influence the fluctuations between them.

Weak La Niña conditions are expected to persist over the next few months, according to NOAA, the US science agency.

All other things being equal, La Niña generally increases the risk of a cold start to the UK winter, but also increases the likelihood of a mild end. Met Office says.

“These two drivers in the northern and tropical Pacific will act together this winter,” Professor Maycock said.

“But since La Niña is quite weak this year, extreme warmth in the North Pacific may be more important in forecasting the coming winter.”

Additional reporting by Maskin Liddar and Libby Rogers