- Experts led by the University of Arizona took ice samples from Greenland
- They studied how ice layers had accumulated over the past 1,250 years
- From this, they reconstructed the jet stream’s past locations and intensities.
- They found that climate change has not yet outpaced its natural variability.
- But if greenhouse emissions continue to accelerate, we will see change in decades
- This will lead to more extreme weather such as floods, droughts and heatwaves
One study warns that extreme weather could become more common across Europe and North America by 2060 as climate change shifts the North Atlantic jet stream.
North Atlantic jet steam is a band of prevailing, westerly winds that circle the Arctic, and are known to propel planes flying from the Americas to Europe.
While the jet stream airliner flies hardest at cruising altitude, it also reaches the ground, and plays an important role in local weather conditions.
In fact, 10–50 percent of the variation in annual precipitation and temperature in eastern North American and western Europe comes from the jet stream.
A heat wave in the Pacific Northwest this summer and flooding in Europe are just a few examples of how jet steam variations can affect the weather.
However, despite its importance, not much is known about how the jet stream was different in the past and how it may change in the future.
Experts from the University of Arizona who drilled into Greenland’s ice sheets extracted a record of past weather conditions some 1,250 years ago.
They found that, so far, the effects of human-caused warming on the jet stream have been less than those observed in the recent history of wind.
However, their projections suggest that business-as-usual greenhouse emissions will push the jet stream north, causing significant changes in only decades.
Extreme weather could become more common across Europe and North America by 2060 as climate change shifts the North Atlantic jet stream (pictured), warns a study
Experts from the University of Arizona who drilled into Greenland’s ice sheets extracted a record of past weather conditions some 1,250 years ago. Image: A borehole from which an ice core was sampled for study. Snow comes from depths up to 1,000 feet
In eastern North American and western Europe, 10–50 percent of the annual precipitation and temperature variation comes from the jet stream. Image: After heavy rain in Verviers, Belgium earlier this year. Jet stream change could make extreme weather events like this a more common occurrence
Historical Impact of the Jet Stream
Based on reconstructions of the jet stream over the past 1,250 years, the team was able to link changes in stream strength and position with historical meteorological disasters.
For example, in 1374, a northward shift in the jet stream caused drought and famine on the Iberian Peninsula.
Similarly, two famines across Britain and Ireland in 1728 and 1740 resulted in a 50 percent drop in wind intensity, causing a drop in temperature and less rainfall.
It is later estimated to have killed about half a million people, including 13–20 percent of Ireland’s population.
According to Osman and his team, future jet stream changes could have similar weather, ecosystem and social impacts.
“For most places on Earth, direct climate observations usually take no more than a few decades,” said paper author and climate scientist Matthew Osman of the University of Arizona.
‘Therefore, we don’t have a very good understanding of how or why the jet stream changes over long periods.
“What we do know is that extraordinary changes in the jet stream can have serious social impacts – such as floods and droughts – due to its effect on weather patterns,” he continued.
‘Therefore, in the context of thinking about the future, we can now begin to use the past as a prelude.’
In their work, Dr Osman and his colleagues analyzed ice cores collected from about 50 sites in the Greenland ice sheet.
From these natural records, the team was able to reconstruct changes in the air in the North Atlantic on a year-to-year basis going back to the eighth century.
They did this by looking at the amount of snowfall that accumulates each year, as well as the chemical makeup of the water molecules that make up each ice layer.
“These layers tell us how much precipitation occurred in a given year and also about the temperature,” Osman explained.
The team found that, to date, fluctuations in jet stream intensity and position are within the limits of natural variation.
However, he calculated, if global warming continues to accelerate, significant changes will emerge within a few decades, with the jet stream expected to shift its mean position northward.
“Variations like these have a huge impact on the types of weather that people can experience in a place,” Osman said.
‘For example, when the jet stream is located further south, the normally arid Iberian Peninsula experiences mild, moist conditions.
‘But, as the jet stream migrates north, much of that moisture also moves from Iberia to already wetter regions of Scandinavia.
‘A polar-shifting jet stream could have similar, but more permanent, consequences in the future.’
That said, the team found evidence of socially significant changes in the history of the jet stream, sometimes drifting north, only to be more than 10° south only years later.
North Atlantic jet steam (pictured above Canada) is a band of prevailing, westerly winds that circle the Arctic – and are known to propel planes flying from the Americas to Europe. While the jet stream continues…