Credit: weather.com
A 2020 news report (H/T Belfast Telegraph) headlined Extreme weather being caused by jet stream ‘not because of Arctic warming’, with the sub-heading: ‘Any link is more likely to be a result of random fluctuations in the jet stream influencing Arctic temperatures, researchers say’ – cites a study that comprehensively contradicts the findings described in the article below. “The well-publicised idea that Arctic warming is leading to a wavier jet stream just does not hold up to scrutiny”, said Professor James Screen [University of Exeter]. “With the benefit of 10 more years of data and model experiments, we find no evidence of long-term changes in waviness despite on-going Arctic warming.” But the stated lack of evidence hasn’t deterred this new research. Are they flogging the proverbial dead horse?
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A quartet of researchers, two with the Nordic Institute for Theoretical Physics and two with Pukyong National University, has created a group of simulations of changes to the jet stream under global warming, says Phys.org.
In their paper published in Proceedings of the National Academy of Sciences, the group describes using math theory to describe wind motion under given circumstances to create their simulations.
Over the past several years, the jet stream has become wavier than it used to be. Both peaks and valleys have become more extreme.
This has led to changes in weather patterns—some places have grown wetter and some drier, and there have also been more extended hot and cold spells around the globe.
In this new effort, the researchers suspected that the reason for the increased waviness is due to the asymmetric rise in global temperatures. Global warming is heating up the Arctic much faster than it is heating up more southern areas. The result is big changes in winds in the upper atmosphere.
To test their theory, the researchers used math formulas to represent wind flow under historical patterns. They then added the impact of warming air, taking into account the differences above and below the jet stream.
They used their formulas to simulate wind flow across the northern part of the planet that make up the jet stream. The simulations showed what the researchers were expecting—more waviness.
Full article here.
Tallbloke's Talkshop 
It’s due to the current 30-year Meridional Phase of the 60-year Natural Climate Cycle.
Get used to it and adapt accordingly.
See also:
How do they measure and define waviness?
[…] Jet stream waviness theory of Arctic warming revived by modellers after scientific debunking | Tallb… […]
The journal editor for the featured research paper is Michael Mann.
Wavier jet streams driven by zonally asymmetric surface thermal forcing
September 12, 2022
https://www.pnas.org/doi/full/10.1073/pnas.2200890119
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The abstract is preceded by a short ‘significance’ section, authored by …. the journal editor perhaps??
Significance
Extreme midlatitude weather is strongly associated with the unusual meandering of jets. A central question is whether it is caused by or related to global warming. Here, we show that zonally asymmetric thermal forcing can drive a dramatic shift in planetary-scale atmospheric motion. As the zonal mean flow is reduced, a small-amplitude response confined near the surface shifts to a large-amplitude response reaching the upper atmosphere. As the high latitudes warm more rapidly under global warming, the reduction in zonal mean wind strength can trigger wavier atmospheric jets.
From the abstract:
‘The connection between midlatitude jet structure and extreme weather events is a focus area in contemporary climate science (1–5). As westerly mean flows decrease, jets become wavier and quasi-stationary high- and low-pressure blocking patterns form, causing severe flooding and drought (see ref. 6 for a recent review)’.
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Blocking patterns are part of standard meteorology. The discussion is about their magnitude and/or frequency in recent times.
‘We show that zonally asymmetric thermal forcing can drive a dramatic shift in planetary-scale atmospheric motion. As the zonal mean flow is reduced, a small-amplitude response confined near the surface shifts to a large-amplitude response reaching the upper atmosphere.’
I’m still going to drive my GT350R.
Do they really not see that building a model to prove their hypothesis is not remotely proving their hypothesis? Or is this just part of the game so that the media can keep pushing this tripe?
The data shows it’s not happening so what their model claims is utterly irrelevant.
The computer model has a lot to answer for. I’m sure that if they were done in good faith then some interesting things could be revealed but they all seem to suffer from input bias failure, then endlessly tweeked until they output the desired result.
Another dud year for Arctic sea ice alarmists.
Remarkably 2022 September ice extent averaged 5.1M over the first 17 days, and is likely to end the month with at least that amount for the entire month. For comparison, the 15 year average for Sept. 1-17 is 4.7M.
The melting season mid August to mid September shows 2022 melted slower than average and ended the period above the average.
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Even wavy jetstreams and extra CO2 molecules can’t cut the mustard.
I recall the Henri Coanda effect can flip-flop the Labrador cold current and Gulf Stream warm current from the bi-stable northern phase to its southern phase as a result of “unknown” ocean current or atmospheric polar vortex changes. This natural change might well push the UK (and Northern Hemisphere) into the next ice age. I guess these computer models and CO2 farts do the same magic?
Re. the 2020 research: ‘They found that the previously reported trend toward a wavier circulation during autumn and winter has reversed in recent years, despite continued Arctic amplification.
This reversal has resulted in no long-term trends in waviness, in agreement with climate model simulations, which also suggest little change in “waviness” in response to strong Arctic warming.’
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A reversal of a trend can’t be a trend.
In addition to waviness, the propagation speed of the waves must be considered. The slower the waves propagate the longer a high pressure region sits over a given area, and the longer draught conditions persist and the more severe the draught. It makes sense to me that meridional heat transport correlates with propagation speed. Indeed, waviness may be less important.
I believe it was HH Lamb who proposed that the jetstream would become more amplified when the planet cooled.
‘despite continued Arctic amplification’
Hmmm. Not much of that in evidence at the moment?