Editing Tornado (section)

===Associations with climate and climate change===
[[File:Tornado US annual count.svg|thumb|U. S. annual count of confirmed tornadoes. The count uptick in 1990 is coincident with the introduction of doppler weather radar.]]
Associations with various [[climate]] and environmental trends exist. For example, an increase in the [[sea surface temperature]] of a source region (e.g. Gulf of Mexico and [[Mediterranean Sea]]) increases atmospheric moisture content. Increased moisture can fuel an increase in [[severe weather]] and tornado activity, particularly in the cool season.<ref name="Edwards GoM">{{cite conference|first1=Roger|last1=Edwards|first2=Steven J.|last2=Weiss|author-link1=Roger Edwards (meteorologist)|title=Comparisons between Gulf of Mexico Sea Surface Temperature Anomalies and Southern U.S. Severe Thunderstorm Frequency in the Cool Season|book-title=18th Conf. Severe Local Storms|publisher=American Meteorological Society|date=1996-02-23|url=http://www.spc.noaa.gov/publications/edwards/sstsvr.htm|access-date=2008-01-07|archive-date=2008-05-03|archive-url=https://web.archive.org/web/20080503230451/http://www.spc.noaa.gov/publications/edwards/sstsvr.htm|url-status=live}}</ref>

Some evidence does suggest that the [[Southern Oscillation]] is weakly correlated with changes in tornado activity, which vary by season and region, as well as whether the [[ENSO]] phase is that of [[El Niño]] or [[La Niña]].<ref name="AGU ENSO tor">{{cite conference|first1=Ashton Robinson|last1=Cook|first2=Joseph T.|last2=Schaefer|title=The Relation of El Nino Southern Oscillation (ENSO) to Winter Tornado Outbreaks|book-title=19th Conf. Probability and Statistics|publisher=American Meteorological Society|date=2008-01-22|access-date=2009-12-13|url=http://ams.confex.com/ams/88Annual/techprogram/paper_134378.htm|archive-date=2008-12-06|archive-url=https://web.archive.org/web/20081206065655/http://ams.confex.com/ams/88Annual/techprogram/paper_134378.htm|url-status=live}}</ref> Research has found that fewer tornadoes and hailstorms occur in winter and spring in the U.S. central and southern plains during El Niño, and more occur during La Niña, than in years when temperatures in the [[Pacific]] are relatively stable. Ocean conditions could be used to forecast extreme spring storm events several months in advance.<ref>{{Cite journal|url= http://nature.com/|journal= Nature|title= El Niño brings fewer tornados|volume= 519|date= 26 March 2015|access-date= 27 March 2016|archive-date= 19 July 2016|archive-url= https://web.archive.org/web/20160719125259/http://www.nature.com/|url-status= live}}</ref>

Climatic shifts may affect tornadoes via [[teleconnection]]s in shifting the jet stream and the larger weather patterns. The climate-tornado link is confounded by the forces affecting larger patterns and by the local, nuanced nature of tornadoes. Although it is reasonable to suspect that [[global warming]] may affect trends in tornado activity,<ref name="agw tstm">{{cite journal|first1=Robert J.|last1=Trapp |first2=NS|last2=Diffenbaugh |first3=H. E.|last3=Brooks |first4=M. E.|last4=Baldwin|first5=E. D.|last5=Robinson|first6=J. S.|last6=Pal  |name-list-style=amp |title=Changes in severe thunderstorm environment frequency during the 21st century caused by anthropogenically enhanced global radiative forcing|journal=Proc. Natl. Acad. Sci. U.S.A.|volume=104|issue=50|pages=19719–23|date=2007-12-12|doi=10.1073/pnas.0705494104|bibcode=2007PNAS..10419719T|pmc=2148364|doi-access=free }}</ref> any such effect is not yet identifiable due to the complexity, local nature of the storms, and database quality issues. Any effect would vary by region.<ref name="IPCC4-WGI">{{cite book|first=Susan|last=Solomon |title=Climate Change 2007 – The Physical Science Basis |series=Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change |publisher=Cambridge University Press for the [[Intergovernmental Panel on Climate Change]] |year=2007 |location=Cambridge, UK and New York |access-date=2009-12-13 |url=http://ipcc-wg1.ucar.edu/wg1/wg1-report.html |isbn=978-0-521-88009-1 |display-authors=etal |url-status=dead |archive-url=https://web.archive.org/web/20070501031449/http://ipcc-wg1.ucar.edu/wg1/wg1-report.html |archive-date=2007-05-01 }}</ref>