article_snippet: The extreme contrast in temperatures has been put down to global warming and the melting sea ice in the Arctic by some experts, according to NASA's Earth Observatory.
article_snippet: Researchers were reportedly exploring a number of possible causes behind the contrasting weather patterns seen across the US last.
article_snippet: NASA's Earth Observatory said: 'Most meteorologists attribute the sharply contrasting temperatures to the combination of a persistent ridge of high pressure—
article_snippet: the northeastern Pacific Ocean, and an equally persistent trough that has funneled chilly air from the Arctic into central North America. '
article_snippet: But why that resilient ridge has appeared over the northeastern Pacific during the last few winters is a more complicated and controversial question among experts. '
article_snippet: A new line of research suggests that the loss of the Arctic sea ice associated with global warming may be causing the jet stream to slow down and become wavier, thus setting up the unusual pattern over North America. '
article_snippet: Other researchers think there could be a link between Siberian snowfall and mid-latitude weather extremes. '
article_snippet: Still others think changes in the Arctic have little to do with mid-latitude weather extremes; instead others see periods with an anomalously sharp gradient in sea surface temperature in the far western Pacific as the key factor.