2014 will be remembered for the range of weather extremes persistent storms that battered the country at the beginning of the year, to record high temperatures at the end of October. Scientists now have evidence that these persistent extreme weather patterns are increasing in their frequency, due to the rapid heating up of the Arctic that is changing the behaviour of the jet stream.
Dr. Jennifer Francis who is one of the leading scientists in the U.S. studying the relationship between Arctic warming and changes in the jet stream, says:
“The Arctic is generally very cold and the areas farther south are warm and that difference in area between those two areas is really what fuels that vast river of weather moving high over our head that we call the jet stream.
The jet stream in turn creates the weather that we feel all around the northern hemisphere and the middle latitudes, so anything that affects this jet stream is going to affect weather patterns. So as the Arctic warms up much faster than the areas farther south, we’re seeing this temperature difference between these two regions get smaller. This means the force that drives those winds in the jet stream are getting smaller and that means the winds themselves in the jet stream are getting weaker.
When that happens, the jet stream tends to take a wavier path as it travels around the northern hemisphere and those waves are actually what create the stormy patterns [and] the nice weather patterns. As those waves get larger because of this weakening of those winds of the jet streams, they tend to move more slowly from west to east. That means it feels like the weather patterns are sticking around longer, because those patterns are moving much more slowly and this then makes it more likely to have the kind of extreme events that are related to persistent weather patterns.”
Are critical findings influencing policy?
These changes in climate have huge implications as Dr. Francis points out, there are “people who worry about whether there is enough fresh water to supply cities, whether there is enough snowpack on mountains to supply reservoirs, and for agriculture… Drought and agriculture is a big problem. Storminess in certain areas is another big problem. Yes, it has a huge impact for a whole range of issues that affect the way we live.”
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