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Associations to climate and climate change

Associations to various climate and environmental trends exist. For example, an increase in the sea surface temperature of source region (e.g. Gulf of Mexico and Mediterranean Sea) increases moisture content, potentially fueling an increase in severe weather and tornado activity, particularly in the cool season.<53>

Although insufficient support exists to make conclusions, evidence does suggest that the Southern Oscillation is weakly correlated with some 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.<54>

Climatic shifts affect tornadoes via teleconnections 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 that the climate change phenomenon of global warming may affect tornado activity, 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.<55>

http://en.wikipedia.org/wiki/Tornado