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Extreme weather caused by shifts in a jet stream seems to have brought summers of fires, failed harvests and rampant disease across Europe over the past 700 years. That is the conclusion of an analysis of tree ring data, which also provides worrying clues for what the future holds under a changing climate.
Jet streams are bands of fast-moving winds high in the atmosphere, which blow around the world from west to east. The northern hemisphere polar jet influences weather conditions over Europe by…