Editing Jet stream (section)

==Longer-term climatic changes==
[[File:Jetstream - Rossby Waves - N hemisphere.svg|thumb|right|400px|Meanders ([[Rossby wave]]s) of the northern hemisphere's polar jet stream developing (a), (b); then finally detaching a "drop" of cold air (c). Orange: warmer masses of air; pink: jet stream.]]
Since the early 2000s, climate models have consistently identified that [[global warming]] will gradually push jet streams poleward. In 2008, this was confirmed by observational evidence, which proved that from 1979 to 2001, the northern jet stream moved northward at an average rate of {{convert|2.01|km|mi}} per year, with a similar trend in the southern hemisphere jet stream.<ref>{{Cite journal |last1=Archer |first1=Cristina L. |last2=Caldeira |first2=Ken |date=18 April 2008 |title=Historical trends in the jet streams |journal=Geophysical Research Letters |language=en |volume=35 |issue=8 |doi=10.1029/2008GL033614 |bibcode=2008GeoRL..35.8803A |s2cid=59377392 |doi-access=free }}</ref><ref>{{cite web |date=2008-04-18 |title=Jet stream found to be permanently drifting north |url=http://komonews.com/news/local/jet-stream-found-to-be-permanently-drifting-north |publisher=[[Associated Press]] |language=en |access-date=7 October 2022 |archive-date=17 August 2016 |archive-url=https://web.archive.org/web/20160817133858/http://komonews.com/news/local/jet-stream-found-to-be-permanently-drifting-north |url-status=dead }}</ref> Climate scientists have hypothesized that the jet stream will also gradually weaken as a result of global warming. Trends such as [[Arctic sea ice decline]], reduced snow cover, [[evapotranspiration]] patterns, and other weather anomalies have caused the Arctic to heat up faster than other parts of the globe, in what is known as the [[polar amplification|Arctic amplification]]. In 2021–2022, it was found that since 1979, the warming within the [[Arctic Circle]] has been nearly four times faster than the global average,<ref name="Rantanen2022">{{Cite journal |last1=Rantanen |first1=Mika |last2=Karpechko |first2=Alexey Yu |last3=Lipponen |first3=Antti |last4=Nordling |first4=Kalle |last5=Hyvärinen |first5=Otto |last6=Ruosteenoja |first6=Kimmo |last7=Vihma |first7=Timo |last8=Laaksonen |first8=Ari |date=11 August 2022 |title=The Arctic has warmed nearly four times faster than the globe since 1979 |journal=Communications Earth & Environment |language=en |volume=3 |issue=1 |page=168 |doi=10.1038/s43247-022-00498-3 |bibcode=2022ComEE...3..168R |s2cid=251498876 |issn=2662-4435|doi-access=free |hdl=11250/3115996 |hdl-access=free }}</ref><ref name="4X2021">{{cite web |date=2021-12-14 |title=The Arctic is warming four times faster than the rest of the world |url=https://www.science.org/content/article/arctic-warming-four-times-faster-rest-world |website=[[Science Magazine]] |language=en |access-date=6 October 2022 |archive-date=8 November 2023 |archive-url=https://web.archive.org/web/20231108114005/https://www.science.org/content/article/arctic-warming-four-times-faster-rest-world |url-status=live }}</ref> and some hotspots in the [[Barents Sea]] area warmed up to seven times faster than the global average.<ref name="Isaksen2022">{{Cite journal |last1=Isaksen |first1=Ketil |last2=Nordli |first2=Øyvind  |display-authors=etal |date=15 June 2022 |title=Exceptional warming over the Barents area |journal=Scientific Reports |language=en |volume=12 |issue=1 |page=9371 |doi=10.1038/s41598-022-13568-5 |pmid=35705593 |pmc=9200822 |bibcode=2022NatSR..12.9371I }}</ref><ref name="Carrington22">{{cite web |date=2022-06-15 |title=New data reveals extraordinary global heating in the Arctic |author=Damian Carrington |url=https://www.theguardian.com/environment/2022/jun/15/new-data-reveals-extraordinary-global-heating-in-the-arctic |website=[[The Guardian]] |language=en |access-date=7 October 2022 |archive-date=1 October 2023 |archive-url=https://web.archive.org/web/20231001165931/https://www.theguardian.com/environment/2022/jun/15/new-data-reveals-extraordinary-global-heating-in-the-arctic |url-status=live }}</ref> While the Arctic remains one of the coldest places on Earth today, the temperature gradient between it and the warmer parts of the globe will continue to diminish with every decade of global warming as the result of this amplification. If this gradient has a strong influence on the jet stream, then it will eventually become weaker and more variable in its course, which would allow more cold air from the [[polar vortex]] to leak [[mid-latitudes]] and slow the progression of [[Rossby wave]]s, leading to more persistent and more [[extreme weather]].<ref name="Francis 2012">{{cite journal |doi=10.1029/2012GL051000 |title=Evidence linking Arctic amplification to extreme weather in mid-latitudes |year=2012 |last1=Francis |first1=Jennifer A. |author-link=Jennifer Francis|last2=Vavrus |first2=Stephen J. |journal=Geophysical Research Letters |volume=39 |issue=6 |bibcode=2012GeoRL..39.6801F |pages=L06801|citeseerx=10.1.1.419.8599 |s2cid=15383119 }}</ref>

The hypothesis above is closely associated with [[Jennifer Francis]], who had first proposed it in a 2012 paper co-authored by Stephen J. Vavrus.<ref name="Francis 2012" /> While some paleoclimate reconstructions have suggested that the polar vortex becomes more variable and causes more unstable weather during periods of warming back in 1997,<ref>{{cite journal |doi= 10.1130/0016-7606(1997)109<0547:piotim>2.3.co;2|year=1997 |volume=109 |pages=547–559 |title=Paleoenvironmental implications of the insoluble microparticle record in the GISP2 (Greenland) ice core during the rapidly changing climate of the Pleistocene-Holocene transition |last1=Zielinski |first1=G. |last2=Mershon |first2=G. |journal=Bulletin of the Geological Society of America |issue=5 |bibcode=1997GSAB..109..547Z}}</ref> this was contradicted by climate modelling, with [[Paleoclimate Modelling Intercomparison Project|PMIP2 simulations]] finding in 2010 that the [[Arctic Oscillation]] (AO) was much weaker and more negative during the [[Last Glacial Maximum]], and suggesting that warmer periods have stronger positive phase AO, and thus less frequent leaks of the polar vortex air.<ref>{{cite journal |doi=10.1175/2010JCLI3331.1 |year=2010 |volume=23 |pages=3792–3813 |title=Arctic Oscillation during the Mid-Holocene and Last Glacial Maximum from PMIP2 Coupled Model Simulations |last1=Lue |first1=J.-M. |last2=Kim |first2=S.-J. |last3=Abe-Ouchi |first3=A. |last4=Yu |first4=Y. |last5=Ohgaito |first5=R. |journal=Journal of Climate |issue=14|bibcode=2010JCli...23.3792L |s2cid=129156297 |doi-access=free }}</ref> However, a 2012 review in the ''[[Journal of the Atmospheric Sciences]]'' noted that "there [has been] a significant change in the vortex mean state over the twenty-first century, resulting in a weaker, more disturbed vortex.",<ref>{{Cite journal|last1=Mitchell|first1=Daniel M.|last2=Osprey|first2=Scott M.|last3=Gray|first3=Lesley J.|last4=Butchart|first4=Neal|last5=Hardiman|first5=Steven C.|last6=Charlton-Perez|first6=Andrew J.|last7=Watson|first7=Peter|date=August 2012|title=The Effect of Climate Change on the Variability of the Northern Hemisphere Stratospheric Polar Vortex|journal=Journal of the Atmospheric Sciences|language=en|volume=69|issue=8|pages=2608–2618|doi=10.1175/jas-d-12-021.1|issn=0022-4928|bibcode=2012JAtS...69.2608M|s2cid=122783377 |doi-access=free}}</ref> which contradicted the modelling results but fit the Francis-Vavrus hypothesis. Additionally, a 2013 study noted that the then-current [[CMIP5]] tended to strongly underestimate winter blocking trends,<ref name="Masato 2013">{{cite journal |doi=10.1175/JCLI-D-12-00466.1 |title=Winter and Summer Northern Hemisphere Blocking in CMIP5 Models |year=2013 |last1=Masato |first1=Giacomo |last2=Hoskins |first2=Brian J. |last3=Woollings |first3=Tim |journal=Journal of Climate |volume=26 |issue=18 |pages=7044–7059|bibcode=2013JCli...26.7044M |doi-access=free }}</ref> and other 2012 research had suggested a connection between declining Arctic sea ice and heavy snowfall during midlatitude winters.<ref>{{Cite journal |last1=Liu |first1=Jiping |last2=Curry |first2=Judith A. |author-link=Judith Curry |last3=Wang |first3=Huijun |last4=Song |first4=Mirong |last5=Horton |first5=Radley M. |date=27 February 2012 |title=Impact of declining Arctic sea ice on winter snowfall |journal=PNAS |language=en |volume=109 |issue=11 |pages=4074–4079 |doi=10.1073/pnas.1114910109|pmid=22371563 |pmc=3306672 |bibcode=2012PNAS..109.4074L |doi-access=free }}</ref>

In 2013, further research from Francis connected reductions in the Arctic sea ice to extreme summer weather in the northern mid-latitudes,<ref>{{cite journal|author=Qiuhong Tang|author2=Xuejun Zhang|author3-link=Jennifer A. Francis|last3=Francis|first3=J. A.|date=December 2013|title=Extreme summer weather in northern mid-latitudes linked to a vanishing cryosphere|journal=Nature Climate Change|volume=4|issue=1|pages=45–50|doi=10.1038/nclimate2065|bibcode=2014NatCC...4...45T }}</ref> while other research from that year identified potential linkages between Arctic sea ice trends and more extreme rainfall in the European summer.<ref name="Screen 2013">{{cite journal|first=J A|last=Screen|date=November 2013|title=Influence of Arctic sea ice on European summer precipitation|journal=Environmental Research Letters|volume=8|issue=4|doi=10.1088/1748-9326/8/4/044015|pages=044015|bibcode=2013ERL.....8d4015S |doi-access=free|hdl=10871/14835|hdl-access=free}}</ref> At the time, it was also suggested that this connection between Arctic amplification and jet stream patterns was involved in the formation of [[Hurricane Sandy]]<ref>{{cite news|last=Friedlander|first=Blaine|title=Arctic ice loss amplified Superstorm Sandy violence|url=http://www.news.cornell.edu/stories/2013/03/arctic-ice-loss-amplified-superstorm-sandy-violence|access-date=7 January 2014|newspaper=Cornell Chronicle|date=4 March 2013|archive-date=11 June 2015|archive-url=https://web.archive.org/web/20150611114925/http://www.news.cornell.edu/stories/2013/03/arctic-ice-loss-amplified-superstorm-sandy-violence|url-status=live}}</ref>  and played a role in the [[early 2014 North American cold wave]].<ref name=Time>{{cite magazine|first=Bryan|last=Walsh|title=Polar Vortex: Climate Change Might Just Be Driving the Historic Cold Snap|magazine=Time|url=https://science.time.com/2014/01/06/climate-change-driving-cold-weather/|date=6 January 2014|access-date=7 January 2014|archive-date=11 January 2018|archive-url=https://web.archive.org/web/20180111215416/http://science.time.com/2014/01/06/climate-change-driving-cold-weather/|url-status=live}}</ref><ref name=CSMonitor>{{cite news|last=Spotts|first=Pete|title=How frigid 'polar vortex' could be result of global warming (+video)|url=http://www.csmonitor.com/Science/2014/0106/How-frigid-polar-vortex-could-be-result-of-global-warming-video|access-date=8 January 2014|newspaper=The Christian Science Monitor|date=6 January 2014|archive-date=9 July 2017|archive-url=https://web.archive.org/web/20170709030842/https://www.csmonitor.com/Science/2014/0106/How-frigid-polar-vortex-could-be-result-of-global-warming-video|url-status=live}}</ref> In 2015, Francis' next study concluded that highly amplified jet-stream patterns are occurring more frequently in the past two decades. Hence, continued heat-trapping emissions favour increased formation of extreme events caused by prolonged weather conditions.<ref>{{cite journal|journal=Philosophical Transactions|title=Evidence linking rapid Arctic warming to mid-latitude weather patterns|doi=10.1098/rsta.2014.0170|pmid=26032322 |author1=Jennifer Francis |author2=Natasa Skific |date=1 June 2015|bibcode = 2015RSPTA.37340170F|volume=373|issue=2045|page=20140170|pmc=4455715}}</ref>

Studies published in 2017 and 2018 identified stalling patterns of Rossby waves in the northern hemisphere jet stream as the culprit behind other almost stationary extreme weather events, such as the [[2018 European drought and heat waves|2018 European heatwave]], the [[2003 European heat wave]], [[2010 Russian wildfires|2010 Russian heat wave]] or the [[2010 Pakistan floods]], and suggested that these patterns were all connected to Arctic amplification.<ref>{{cite journal|last1=Mann|first1=Michael E.|last2=Rahmstorf|first2=Stefan|date=27 March 2017|title=Influence of Anthropogenic Climate Change on Planetary Wave Resonance and Extreme Weather Events|journal=Scientific Reports|volume=7|pages=45242|doi=10.1038/srep45242|pmid=28345645|pmc=5366916|bibcode=2017NatSR...745242M}}</ref><ref>{{cite web|url=https://www.theguardian.com/environment/2018/jul/27/extreme-global-weather-climate-change-michael-mann|title=Extreme global weather is 'the face of climate change' says leading scientist|year=2018|work=The Guardian|access-date=8 October 2022|archive-date=13 April 2019|archive-url=https://web.archive.org/web/20190413154627/https://www.theguardian.com/environment/2018/jul/27/extreme-global-weather-climate-change-michael-mann|url-status=live}}</ref> Further work from Francis and Vavrus that year suggested that amplified Arctic warming is observed as stronger in lower atmospheric areas because the expanding process of warmer air increases pressure levels which decreases poleward geopotential height gradients. As these gradients are the reason that cause west to east winds through the thermal wind relationship, declining speeds are usually found south of the areas with geopotential increases.<ref>{{Cite journal|title = Amplified Arctic warming and mid latitude weather: new perspectives on emerging connections|volume = 8|issue = 5|pages = e474|publisher = 2017 Wiley Periodicals,Inc|url = http://web.mit.edu/jlcohen/www/papers/Francis_WIREsCC_2017_pub.pdf|journal = Wiley Interdisciplinary Reviews: Climate Change|author1 = Francis J|author2 = Vavrus S|author3 = Cohen J.|year = 2017|doi = 10.1002/wcc.474|doi-access = free|bibcode = 2017WIRCC...8E.474F|access-date = 8 October 2022|archive-date = 21 March 2023|archive-url = https://web.archive.org/web/20230321223150/http://web.mit.edu/jlcohen/www/papers/Francis_WIREsCC_2017_pub.pdf|url-status = live}}</ref> In 2017, Francis explained her findings to the ''[[Scientific American]]'': "A lot more water vapor is being transported northward by big swings in the jet stream. That's important because [[Greenhouse gas#Role of water vapor|water vapor is a greenhouse gas]] just like carbon dioxide and methane. It traps heat in the atmosphere. That vapor also condenses as droplets we know as clouds, which themselves trap more heat. The vapor is a big part of the amplification story—a big reason the Arctic is warming faster than anywhere else."<ref>{{cite web|url=https://www.scientificamerican.com/article/the-arctic-is-getting-crazy/|title=The Arctic Is Getting Crazy|year=2017|work=Scientific American|first=Mark|last=Fischetti|access-date=8 October 2022|archive-date=22 April 2022|archive-url=https://web.archive.org/web/20220422105448/https://www.scientificamerican.com/article/the-arctic-is-getting-crazy/|url-status=live}}</ref>

In a 2017 study conducted by climatologist Judah Cohen and several of his research associates, Cohen wrote that "[the] shift in polar vortex states can account for ''most'' of the recent winter cooling trends over Eurasian midlatitudes".<ref>{{Cite journal|last1=Kretschmer|first1=Marlene|author1-link=Marlene Kretschmer|last2=Coumou|first2=Dim|last3=Agel|first3=Laurie|last4=Barlow|first4=Mathew|last5=Tziperman|first5=Eli|last6=Cohen|first6=Judah|s2cid=51847061|date=January 2018|title=More-Persistent Weak Stratospheric Polar Vortex States Linked to Cold Extremes|journal=Bulletin of the American Meteorological Society|language=en|volume=99|issue=1|pages=49–60|doi=10.1175/bams-d-16-0259.1|issn=0003-0007|bibcode=2018BAMS...99...49K|url=http://centaur.reading.ac.uk/92432/3/01Sep2020manuscript_BAMS_revised_round3.pdf|access-date=8 October 2022|archive-date=9 October 2022|archive-url=https://web.archive.org/web/20221009050237/https://centaur.reading.ac.uk/92432/3/01Sep2020manuscript_BAMS_revised_round3.pdf|url-status=live}}</ref> A 2018 paper from Vavrus and others linked Arctic amplification to more persistent hot-dry extremes during the midlatitude summers, as well as the midlatitude winter continental cooling.<ref>{{Cite journal|last1=Coumou|first1=D.|last2=Di Capua|first2=G.|last3=Vavrus|first3=S.|last4=Wang|first4=L.|last5=Wang|first5=S.|date=2018-08-20|title=The influence of Arctic amplification on mid-latitude summer circulation|journal=Nature Communications|volume=9|issue=1|page=2959|doi=10.1038/s41467-018-05256-8|pmid=30127423|pmc=6102303|bibcode=2018NatCo...9.2959C|issn=2041-1723}}</ref> Another 2017 paper estimated that when the Arctic experiences anomalous warming, [[primary production]] in North America goes down by between 1% and 4% on average, with some states suffering up to 20% losses.<ref>{{Cite journal |last1=Kim |first1=Jin-Soo |last2=Kug |first2=Jong-Seong |last3=Jeong |first3=Su-Jong |last4=Huntzinger |first4=Deborah N. |last5=Michalak |first5=Anna M. |last6=Schwalm |first6=Christopher R. |last7=Wei |first7=Yaxing |last8=Schaefer |first8=Kevin |date=26 October 2021 |title=Reduced North American terrestrial primary productivity linked to anomalous Arctic warming |url=https://www.nature.com/articles/ngeo2986 |journal=Nature Geoscience |volume=10 |issue=8 |pages=572–576 |doi=10.1038/ngeo2986 |osti=1394479 |access-date=15 October 2022 |archive-date=28 November 2022 |archive-url=https://web.archive.org/web/20221128184826/https://www.nature.com/articles/ngeo2986 |url-status=live }}</ref> A 2021 study found that a stratospheric polar vortex disruption is linked with extreme cold winter weather across parts of Asia and North America, including the [[February 2021 North American cold wave]].<ref>{{cite news |title=Climate change: Arctic warming linked to colder winters |url=https://www.bbc.com/news/science-environment-58425526 |access-date=20 October 2021 |work=BBC News |date=2 September 2021 |archive-date=20 October 2021 |archive-url=https://web.archive.org/web/20211020112818/https://www.bbc.com/news/science-environment-58425526 |url-status=live }}</ref><ref>{{cite journal |last1=Cohen |first1=Judah |last2=Agel |first2=Laurie |last3=Barlow |first3=Mathew |last4=Garfinkel |first4=Chaim I. |last5=White |first5=Ian |title=Linking Arctic variability and change with extreme winter weather in the United States |journal=Science |date=3 September 2021 |volume=373 |issue=6559 |pages=1116–1121 |doi=10.1126/science.abi9167 |pmid=34516838 |bibcode=2021Sci...373.1116C |s2cid=237402139 |url=https://doi.org/10.1126/science.abi9167 |url-access=subscription |access-date=8 October 2022 |archive-date=16 April 2023 |archive-url=https://web.archive.org/web/20230416155730/https://www.science.org/doi/10.1126/science.abi9167 |url-status=live }}</ref> Another 2021 study identified a connection between the Arctic sea ice loss and the increased size of [[wildfire]]s in the [[Western United States]].<ref>{{Cite journal |last1=Zou |first1=Yofei |last2=Rasch |first2=Philip J. |last3=Wang |first3=Hailong |last4=Xie |first4=Zuowei |last5=Zhang |first5=Rudong |date=26 October 2021 |title=Increasing large wildfires over the western United States linked to diminishing sea ice in the Arctic |journal=Nature Communications |volume=12 |issue=1 |page=6048 |doi=10.1038/s41467-021-26232-9 |pmid=34702824 |pmc=8548308 |bibcode=2021NatCo..12.6048Z |s2cid=233618492 }}</ref>

However, because the specific observations are considered short-term observations, there is considerable uncertainty in the conclusions. [[Climatology]] observations require several decades to definitively distinguish various forms of natural variability from climate trends.<ref>{{cite journal |doi=10.1007/s00376-012-1238-1 |year=2012 |volume=29 |pages=867–886 |title=Impacts of multi-scale solar activity on climate. Part I: Atmospheric circulation patterns and climate extremes |last1=Weng |first1=H. |journal=Advances in Atmospheric Sciences |issue=4|bibcode = 2012AdAtS..29..867W |s2cid=123066849 }}</ref> This point was stressed by reviews in 2013<ref>{{cite journal|title=Atmospheric science: Long-range linkage|date=December 8, 2013|author=James E. Overland|journal=Nature Climate Change|volume=4|pages=11–12|doi=10.1038/nclimate2079|issue=1|bibcode=2014NatCC...4...11O}}</ref> and in 2017.<ref>{{Cite journal|last=Seviour|first=William J.M.|date=14 April 2017|title=Weakening and shift of the Arctic stratospheric polar vortex: Internal variability or forced response?|journal=Geophysical Research Letters|volume=44|issue=7|pages=3365–3373|bibcode=2017GeoRL..44.3365S|doi=10.1002/2017GL073071|url=https://research-information.bris.ac.uk/en/publications/weakening-and-shift-of-the-arctic-stratospheric-polar-vortex(caf74781-222b-4735-b171-8842cead4086).html|hdl=1983/caf74781-222b-4735-b171-8842cead4086|s2cid=131938684 |hdl-access=free}}</ref> A study in 2014 concluded that Arctic amplification significantly decreased cold-season temperature variability over the northern hemisphere in recent decades. Cold Arctic air intrudes into the warmer lower latitudes more rapidly today during autumn and winter, a trend projected to continue in the future except during summer, thus calling into question whether winters will bring more cold extremes.<ref>{{cite journal|first=James A.|last=Screen|date=15 June 2014|title=Arctic amplification decreases temperature variance in northern mid- to high-latitudes|doi=10.1038/nclimate2268|journal=Nature Climate Change|url=https://www.sciencedaily.com/releases/2014/06/140615143834.htm|volume=4|issue=7|pages=577–582|bibcode=2014NatCC...4..577S|hdl=10871/15095|hdl-access=free|access-date=8 October 2022|archive-date=23 February 2022|archive-url=https://web.archive.org/web/20220223230945/https://www.sciencedaily.com/releases/2014/06/140615143834.htm|url-status=live}}</ref> A 2019 analysis of a data set collected from 35 182 weather stations worldwide, including 9116 whose records go beyond 50 years, found a sharp decrease in northern midlatitude cold waves since the 1980s.<ref>{{Cite journal |last1=van Oldenborgh |first1=Geert Jan |last2=Mitchell-Larson |first2=Eli |last3=Vecchi |first3=Gabriel A. |last4=de Vries|first4=Hylke |last5=Vautar |first5=Robert |last6=Otto |first6=Friederike |date=22 November 2019 |title=Cold waves are getting milder in the northern midlatitudes |journal=Environmental Research Letters |language=en |volume=14 |issue=11 |page=114004 |doi=10.1088/1748-9326/ab4867|bibcode=2019ERL....14k4004V |s2cid=204420462 |doi-access=free }}</ref>

Moreover, a range of long-term observational data collected during the 2010s and published in 2020 suggests that the intensification of Arctic amplification since the early 2010s was not linked to significant changes on mid-latitude atmospheric patterns.<ref>{{cite journal |last1=Blackport |first1=Russell |last2=Screen |first2=James A. |last3=van der Wiel |first3=Karin |last4=Bintanja |first4=Richard |title=Minimal influence of reduced Arctic sea ice on coincident cold winters in mid-latitudes |journal=Nature Climate Change |date=September 2019 |volume=9 |issue=9 |pages=697–704 |doi=10.1038/s41558-019-0551-4|bibcode=2019NatCC...9..697B |hdl=10871/39784 |s2cid=199542188 |url=https://pure.rug.nl/ws/files/96090906/s41558_019_0551_4.pdf |hdl-access=free }}</ref><ref>{{cite journal |last1=Blackport |first1=Russell |last2=Screen |first2=James A. |title=Insignificant effect of Arctic amplification on the amplitude of midlatitude atmospheric waves |journal=Science Advances |date=February 2020 |volume=6 |issue=8 |pages=eaay2880 |doi=10.1126/sciadv.aay2880|pmid=32128402 |pmc=7030927 |bibcode=2020SciA....6.2880B |doi-access=free }}</ref> State-of-the-art modelling research of PAMIP (Polar Amplification Model Intercomparison Project) improved upon the 2010 findings of PMIP2; it found that sea ice decline would weaken the jet stream and increase the probability of atmospheric blocking, but the connection was very minor, and typically insignificant next to interannual variability.<ref>{{Cite journal |last1=Streffing |first1=Jan |last2=Semmler |first2=Tido |last3=Zampieri |first3=Lorenzo |last4=Jung |first4=Thomas |date=24 September 2021 |title=Response of Northern Hemisphere Weather and Climate to Arctic Sea Ice Decline: Resolution Independence in Polar Amplification Model Intercomparison Project (PAMIP) Simulations |journal=Journal of Climate |language=en |volume=34 |issue=20 |pages=8445–8457  |doi=10.1175/JCLI-D-19-1005.1|bibcode=2021JCli...34.8445S |s2cid=239631549 |doi-access=free }}</ref><ref>{{cite web |date=2021-05-12 |author=Paul Voosen |title=Landmark study casts doubt on controversial theory linking melting Arctic to severe winter weather |url=https://www.science.org/content/article/landmark-study-casts-doubt-controversial-theory-linking-melting-arctic-severe-winter |website=[[Science Magazine]] |language=en |access-date=7 October 2022 |archive-date=9 March 2023 |archive-url=https://web.archive.org/web/20230309190222/https://www.science.org/content/article/landmark-study-casts-doubt-controversial-theory-linking-melting-arctic-severe-winter |url-status=live }}</ref> In 2022, a follow-up study found that while the PAMIP average had likely underestimated the weakening caused by sea ice decline by 1.2 to 3 times, even the corrected connection still amounts to only 10% of the jet stream's natural variability.<ref>{{Cite journal |last1=Smith |first1=D.M. |last2=Eade |first2=R. |last3=Andrews |first3=M.B. |display-authors=etal |date=7 February 2022 |title=Robust but weak winter atmospheric circulation response to future Arctic sea ice loss |journal=Nature Communications |language=en |volume=13 |issue=1 |page=727 |doi=10.1038/s41467-022-28283-y|pmid=35132058 |pmc=8821642 |bibcode=2022NatCo..13..727S |s2cid=246637132 }}</ref>

Additionally, a 2021 study found that while jet streams had indeed slowly moved polewards since 1960 as was predicted by models, they did not weaken, in spite of a small increase in waviness.<ref>{{Cite journal |last1=Martin |first1=Jonathan E. |date=14 April 2021 |title=Recent Trends in the Waviness of the Northern Hemisphere Wintertime Polar and Subtropical Jets |url=https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JD033668 |journal=Journal of Geophysical Research: Atmospheres |language=en |volume=126 |issue=9 |doi=10.1029/2020JD033668 |bibcode=2021JGRD..12633668M |s2cid=222246122 |access-date=8 October 2022 |archive-date=15 October 2022 |archive-url=https://web.archive.org/web/20221015073038/https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JD033668 |url-status=live }}</ref> A 2022 re-analysis of the aircraft observational data collected over 2002–2020 suggested that the North Atlantic jet stream had actually strengthened.<ref>{{Cite journal |last1=Tenenbaum |first1=Joel |last2=Williams |first2=Paul D. |last3=Turp |first3=Debi |last4=Buchanan |first4=Piers |last5=Coulson |first5=Robert |last6=Gill |first6=Philip G. |last7=Lunnon |first7=Robert W. |last8=Oztunali |first8=Marguerite G. |last9=Rankin |first9=John |last10=Rukhovets |first10=Leonid |date=July 2022 |title=Aircraft observations and reanalysis depictions of trends in the North Atlantic winter jet stream wind speeds and turbulence |url=https://onlinelibrary.wiley.com/doi/10.1002/qj.4342 |journal=Quarterly Journal of the Royal Meteorological Society |language=en |volume=148 |issue=747 |pages=2927–2941 |doi=10.1002/qj.4342 |bibcode=2022QJRMS.148.2927T |s2cid=250029057 |issn=0035-9009}}</ref> Finally, a 2021 study was able to reconstruct jet stream patterns over the past 1,250 years based on Greenland [[ice core]]s, and found that all of the recently observed changes remain within range of natural variability: the earliest likely time of divergence is in 2060, under the [[Representative Concentration Pathway]] 8.5 which implies continually accelerating greenhouse gas emissions.<ref>{{Cite journal |last1=Osman |first1=Matthew B. |last2=Coats |first2=Sloan |last3=Das |first3=Sarah B. |last4=McConnell |first4=Joseph R. |last5=Chellman |first5=Nathan |date=13 September 2021 |title=North Atlantic jet stream projections in the context of the past 1,250 years |journal=PNAS |language=en |volume=118 |issue=38 |doi=10.1073/pnas.2104105118|pmid=34518222 |pmc=8463874 |bibcode=2021PNAS..11804105O |doi-access=free }}</ref>