Arctic warming not making jet stream ‘wavier’

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Rapid Arctic warming has not made the jet stream “wavier” around the mid-latitudes, according to research by the UK’s University of Exeter.

The scientists have studied the extent to which Arctic amplification – the faster rate of warming in the Arctic compared to places further south – has affected the jet stream’s course over the Northern Hemisphere.

Studies had suggested the warming Arctic region has led to a “wavier” jet stream – which can cause extreme weather in the USA and Europe.

Research by Dr Russell Blackport and Professor James Screen shows that Arctic warming does not drive a more meandering jet stream, and that it is more likely that random fluctuations in the jet stream are influencing Arctic temperatures.

Dr Blackport, lead author of the study, said, “While there does appear to be a link between a wavier jet stream and Arctic warming in year-to-year and decade-to-decade variability, there has not been a long-term increase in waviness in response to the rapidly warming Arctic.”

For two decades, the jet stream was observed to have a “wavier” flow, coinciding with greater Arctic warming through climate change, causing extreme weather conditions.

The new study looked at climate model simulations but also the observed conditions going back 40 years.

They found that the previously reported trend toward a wavier circulation during autumn and winter has reversed in recent years despite continued Arctic amplification.

The reversal has resulted in no long-term trends in waviness, in agreement with climate model simulations, suggesting little change in “waviness” in response to strong Arctic warming.

The scientists say that the observed and simulated link between jet stream waviness and Arctic temperatures do not represent a casual effect of Arctic amplification on the jet stream.

Professor Screen, associate professor in climate science at Exeter university, said, “The well-publicized idea that Arctic warming is leading to a wavier jet stream just does not hold up to scrutiny. With the benefit of 10 more years of data and model experiments, we find no evidence of long-term changes in waviness despite ongoing Arctic warming.”

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