BERLIN, April 29 (Xinhua) -- Record-breaking heatwaves and droughts in 2018 and recent years were connected to a newly identified pattern of the jet stream that encircles the Earth, according to a study by scientists at the Potsdam Institute for Climate Impact Research (PIK), the German institute announced on Monday.
The extreme weather conditions were "directly connected to the emergence of a re-occurring pattern in the jet stream that stretches around the entire Northern Hemisphere," said lead author Kai Kornhuber from the University of Oxford and the PIK.
At a height of about 10 kilometers within the atmosphere, the air current formed a stalled wave pattern, which made weather conditions more persistent and thus extreme in the affected regions, the PIK study found.
According to the study, the same pattern had also occurred during the heat waves in Europe that occurred during the summers of 2015, 2006 and 2003.
Under these conditions, warm sunny days could turn into a heat wave and drought while rainy days could create lead to floods. The study identified North America and Western Europe, South-East Europe and Japan as regions affected by the so-called "wave-7" phenomenon.
"Our study shows that the specific locations and timing of the 2018 summer extremes were not random," said Kornhuber.
The study warned that these extremes weather patterns have particularly high impacts "in terms of mortality, morbidity and agricultural losses" and therefore presented "major risks for society and global food production in particular".
Further research was needed to understand how this jet stream is triggered in the first place, but the extreme weather conditions connected to the wave-7 are becoming more frequent as well as increasing in duration.
"In the two decades before 1999, there were no summers that saw a stalling wave pattern lasting for two weeks or more, but since then we have seen already seven such summers," said the study's co-author Dim Coumou from Vrije Universiteit Amsterdam and the PIK.