Editing Polar vortex (section)

==Extreme weather==
A study in 2001 found that stratospheric circulation can have anomalous effects on weather regimes.<ref name="Baldwin 2001" /> In the same year, researchers found a statistical correlation between weak polar vortex and outbreaks of severe cold in the Northern Hemisphere.<ref name="Song 2001">{{cite web|title=Stratospheric Polar Vortex Influences Winter Cold|author=NASA|url=http://earthobservatory.nasa.gov/Newsroom/view.php?id=22082|archive-url=https://web.archive.org/web/20100316223817/http://earthobservatory.nasa.gov/Newsroom/view.php?id=22082|url-status=dead|archive-date=March 16, 2010|access-date=January 7, 2014|publisher=Earth Observatory|date=December 21, 2001}}</ref><ref name="Song 2004" /> In later years, scientists identified interactions with [[Arctic sea ice decline]], reduced snow cover, [[evapotranspiration]] patterns, [[North Atlantic oscillation|NAO]] anomalies or weather anomalies which are linked to the polar vortex and [[jet stream]] configuration.<ref name="Baldwin 2001">{{cite journal |doi=10.1126/science.1063315 |title=Stratospheric Harbingers of Anomalous Weather Regimes |year=2001 |last1=Baldwin |first1=M.P. |journal=Science |volume=294 |issue=5542 |pages=581–584 |pmid=11641495 |last2=Dunkerton |first2=TJ|bibcode = 2001Sci...294..581B |s2cid=34595603 }}</ref><ref name="Song 2004">{{cite journal |doi=10.1175/1520-0469(2004)061<1711:DMFSIO>2.0.CO;2 |year=2004 |volume=61 |pages=1711–1725 |title=Dynamical Mechanisms for Stratospheric Influences on the Troposphere |last1=Song |first1=Yucheng |last2=Robinson |first2=Walter A. |journal=Journal of the Atmospheric Sciences |issue=14|bibcode = 2004JAtS...61.1711S |doi-access=free }}</ref>

===Climate change===
{{excerpt|Jet stream#Longer-term climatic changes|paragraphs=1-8|file=yes}}