However, little is known about how the jet stream varied during the past, or how it might change in the future. The reconstructions suggest that natural variability has thus far masked the effect of human-caused warming on mid-latitude atmospheric dynamics across annual and longer timescales.
What we do know is that extraordinary variations in the jet stream can have severe societal implications, such as floods and droughts, due to its impacts on weather patterns and so, in terms of thinking about the future, we can now begin to use the past as a sort of a prologue. The work reveals that although natural variability has largely controlled the position of the North Atlantic jet stream, continued warming could cause significant deviations from the norm.
In particular, model projections forecast a northward migration of the North Atlantic jet stream under 21st-century warming scenarios. Such migration could render the jet stream significantly different within a matter of decades. Although the polar jet stream blows most swiftly near the typical cruising altitudes of planes, the band of winds actually extends all the way to the ground. While of lesser intensity, Osman explains, near the ground the winds are often referred to as storm tracks.
By analyzing year-to-year variations in the amount of snowfall archived in Greenland ice cores, as well as the chemical makeup of the water molecules comprising those annual snow layers, the researchers were able to extract centuries-old clues into how the jet stream changed. But, as the jet stream migrates northward, much of that moisture also moves away from Iberia towards already-wet regions of Scandinavia.
A poleward-shifted jet stream in the future thus might have similar, but more permanent, consequences.
The team was able to match certain changes in wind speed and geographical shifts to historical weather-related calamities. For example, during a famine that gripped the Iberian Peninsula in , the jet stream was situated unusually far north.
Similarly, two famine events in the British Isles and Ireland in and coincided with years that winds blew at nearly half their usual intensity, dramatically cooling temperatures and reducing precipitation. The latter of these events, in , is estimated to have cost the lives of nearly half a million people.
Osman and his coauthors expect that any future shifts in the North Atlantic jet stream would also have dramatic implications on day-to-day weather and ecosystems, with trickle-down effects affecting national economies and societies. The world faces converging environmental crises: the accelerating destruction of nature, and climate change.
Natural climate solutions NCS — investment in conservation and land management programmes that increase carbon storage and reduce carbon emissions — offer an important way of addressing both crises and generate additional environmental and social benefits.
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A new study finds that the jet stream could shift outside the bounds of its historic range within just a few decades — by the year or so — under a strong warming scenario. The findings were published last week in the journal Proceedings of the National Academy of Sciences. The effect of climate change on the jet stream is a hot topic among scientists.
The jet stream has a powerful influence on weather and climate patterns throughout the Northern Hemisphere, and changes in the strength or the position of the air current can have big ripple effects around the world.
The current exists because of the strong difference in temperatures between the icy North Pole and the warm equator. This temperature gradient affects the thickness of the atmosphere, giving rise to wavy air currents that flow from west to east around the globe. Today, these air temperatures are steadily climbing. But not all parts of the world are warming at the same rate. And as some regions heat up faster than others — the rapidly warming Arctic, in particular — scientists believe they may cause shifts in the atmosphere that affect the flow of air.
But not everyone agrees on exactly how the jet stream might change — or whether climate change has had any noticeable effect on it yet. The jet stream tends to move around a lot as it is, shifting north and south and wiggling up and down as it moves around the globe. It can be hard to parse out whether recent fluctuations are within its normal boundaries or not. The new study, led by Matthew Osman of the University of Arizona, aimed to get to the bottom of it. They did so using a handy scientific trick, chemically analyzing samples of ancient ice drilled from deep within the Greenland ice sheet.
Ice cores, as scientists call them, work a bit like a scientific time machine. They contain all kinds of information about what the climate was like thousands of years ago. And because the jet stream has such a strong effect on regional weather and climate patterns, scientists can use this information to map out the flow of the jet stream through history.
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