Just a reminder of what NASA said three years ago: Polar vortices and blocking events were even more common in the 1950s when CO2 was below 350 ppm.
See second chart below!
The following is NASA’s 2011 explanation why (my emphasis).
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Stalled Weather Systems More Frequent in Decades of Warmer Atlantic
11.03.11
Slow-moving winter weather systems that can lead to massive snowfalls are more frequent during the decades when the North Atlantic Ocean is warmer than usual, a new NASA study finds. The study demonstrates that the impacts of such systems, which are often fueled by an atmospheric phenomenon known as atmospheric blocking, go far beyond the atmosphere and can trigger changes in ocean circulation.
Blocking events occur when one of the jet streams —fast-flowing air currents traveling around the Earth in the upper part of the troposphere—pinches off large masses of air from the normal wind flow for an extended period. These kinks in the jet stream typically last at least five days but can persist for weeks. They can cause weather patterns to stall over one area and fuel floods, droughts, and other extreme weather events.
In the North Atlantic, atmospheric blocking centers generally form over Greenland and Western Europe. A blocking event that took place over Greenland in the winter of 2009-10 ultimately led to intense blizzards in the East Coast of the United States, in an episode popularly known as Snowmageddon.
A blocking event over Greenland led to intense blizzards in the East Coast of the United States in February 2010. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this true-color image on February 11, 2010, after a second snow storm had hit the East Coast in less than a week. CREDIT: NASA MODIS Rapid Response Team/Jeff Schmaltz
Now, a team of researchers lead by Sirpa Häkkinen, an oceanographer at NASA Goddard Space Flight Center in Greenbelt, Md., has reanalyzed atmospheric data from the 20th century and concluded that blocking events occurred up to 30 percent more often from the 1930s to the 1960s and during a period that started in the late 1990s and continues to the present.
At first, the researchers thought the increase in blocking events during these periods might be explained by a climatic phenomenon called the North Atlantic Oscillation (NAO). The NAO fluctuates between periods of high and low atmospheric pressure, without a predictable pattern, and strongly influences weather in Europe and the United States.
“The NAO is the usual suspect for all atmospheric changes in the northern hemisphere,” Häkkinen said.
But since 1996, the NAO has been in an almost a neutral state, while blocking events have continued to be abnormally frequent, especially after 2000.
Häkkinen’s team then looked at how a cyclical series of natural changes in sea surface temperatures, known as the Atlantic Multidecadal Ocean Variability (AMV), was behaving in the decades when there were more clusters of blocking events. The AMV switches phases every few decades.
The researchers observed the frequency of blocked weather events in the North Atlantic –from the equator to Greenland– over the entire twentieth century and compared it to the evolution of ocean surface temperatures for the same area. They then removed the effect that global warming has on water temperatures, and found that decades with more frequent, recurring blocking events in the North Atlantic corresponded to those decades when the North Atlantic Ocean was warmer than usual, as it is now.
The number of winter blocking events (black and blue lines) correlates strongly with fluctuations in the temperature of surface waters in the North Atlantic Ocean (red line). For their analysis, the researchers removed the effect global warming has on water temperatures. CREDIT: Sirpa Häkkinen (NASA GSFC), Peter Rhines (University of Washington) and Denise L. Worthen (Wyle Information Systems/NASA GSFC)
The team also found that these short-term weather blocking events impacts beyond the atmosphere and may ultimately alter ocean currents.
A series of connected changes begin because clusters of blocking events can divert the normal track of the storms crossing the Atlantic, which in turn can alter the twisting motion that the wind has on ocean waters, or wind curl. Depending on how wind curl works, it can speed up or slow down the large, circulating currents in the ocean known as gyres. When a blocking event reverses the rotation of the wind curl, the winds push against the direction of the whirlpool-like North Atlantic subpolar gyre, slowing its rotation. A slower, weaker gyre allows subtropical waters that would normally be trapped in the whirlpool-like flow to escape and move northward.
“These warmer and more saline waters then invade the subpolar ocean and cause a series of impacts,” said Peter Rhines, an oceanographer at the University of Washington, Seattle, and co-author of the new study. “They erode the base of glaciers, contributing to the melting of the Greenland ice sheet. And the change in temperature and freshness of the waters can alter subpolar ecosystems, too.”
A better understanding of the linkage between the Atlantic Multidecadal Ocean Variability and blocking events could lead to better weather forecasts and improved seasonal predictions.
“For example, knowing that there’s going to be a potential for more blocking events causing more snowfall would not only help people prepare better for the winter; it would be useful with water resources management,” said Häkkinen.
Denise Worthen, a researcher with Wyle Information Systems/NASA Goddard Space Flight Center contributed to this study, which NASA funded.
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Note how the second chart shows that blocking events were more common in the 1940s, 50s and 60s.
The recent warm-Arctic/polar-vortex claims obviously are nothing but a load of bull-manure designed to keep the AGW theory out of the fairy tale books.
National weather service has a page that show where blocking are present.
This site has had several pages not worked, for several days; the snow page has been down all week.
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/block.shtml
The “root cause” is not carbon dioxide but natural climate cycles, one of about 1,000 years and another of 60 years superimposed on the first. The current slight cooling since 1998 will continue for another 14 or 15 years, and about 500 years of long-term cooling is due to start within the next 100 years or so.
These natural climate cycles are compellingly correlated with the inverted plot of the scalar sum of the angular momentum of the Sun and all the planets, possibly because of planetary magnetic fields which reach to the Sun and may affect its radiation and cosmic ray flux.
Because the temperature gradient in a planet’s troposphere is the state of thermodynamic equilibrium which the Second Law of Thermodynamics says will evolve, the planet’s supported surface temperature is autonomously warmer than its mean radiating temperature, so warm in fact on Earth that we need radiating gases (mostly water vapour) to reduce the gradient and thus cool the surface from a mean of about 300K to about 288K, this being confirmed by empirical evidence (as in the study in my book) which confirms with statistical significance that water vapour cools rather than warms, all these facts thus debunking the greenhouse conjecture.
Pierre,
The origin of blocking events is beautifully described in a book by prof. Marcel Leroux.
Zero propaganda, a lot of knowledge…
These climatologist should be better used as museum managers: Jet streams are not the cause of all big events ! Jet streams run at high altitude (10km), are therefore very cold (-50 to -65°C) and do not contain water vapour: They are totally devoid of energy, excepts for kinetic energy; But their low desity (0.25) make this inefficient.
Jet streams results from slow collision between huge, large zones of cold high pressure systems (larger than Canada) issued daily from North Pole and slowly going spiralling towards medium latitudes where they might dilute themselves after mixture with equatorial humid air systems. Jet stream mass is hundreds of time smaller than these massive cold systems….
Exclusively looking at jet streams and neglecting their cause is as tupid as considering only the small linear sea waves instead of the massive oiler ship creating them…!
This frozen idea is there for almost a century in climatic science.
It seems to be an ultra conservative idea-frozen science totally hermetic to reality ! Just look at present persistent global warming hoax
Prof. Leroux uses a concept of Mobile Polar Highs – MPH (observed big blobs of cold air moving from polar areas to median latitudes) to explain the blocking factors, as well as other observed meteorological features (eg, flush floods).
Also questions a lot the jet streams as responsible for climate, and laughs at tele-connections.
In his theory of MPH I see the connection to standing Rosby waves (so jet-stream-like behaviour) – from these Rosby-waves the MPH depart, in well described places on the Earth surface, thus shaping the weather and climate of main Earth areas (like Siberia, Great Plains, or Rockies)
The match is better with levels of solar activity than for the AMO.
Sometimes the AMO is in phase with solar activity and sometimes it isn’t.
There was lots of blocking during the LIA and much less during the MWP and recent warm period.
Blocking is a function of jet stream meridionality as opposed to zonality.
The AMO is but one factor when it comes to blocking. As Stephen said in the previous post solar plays a much bigger role. It is surprising that blocking was so prevalent from the late 1930’s to early 1960’s given the strong solar activity if taken at face value..
However I submit that if solar activity during that time frame had been at minimum values those rather high values of blocking relative to other time periods before and after that particular period would have been much higher.
In addition the increase in blocking during that time frame came off very low values and as Stephen alluded to blocking during the Little Ice Age was much greater then the blip in blocking from the late 1930’s to early 1960’s.
I would go so far to say that the blocking shown from the 1930’s to 1960’s if it occurred during the Little Ice Age would have been considered a period of very little blocking.
It is all so relative when dealing with the climate.
More blocking events within meridional circulation flows and less blocking within more zonal circulation flows are a consequence of the interplay between bottom up oceanic and top down solar effects on the global air circulation.
However, the bottom up oceanic effect is itself a delayed system response to the global cloudiness changes caused by the top down solar effect.
Sometimes both are in phase and sometimes they are out of phase.
No use trying to pin any of this on the puny amount of CO2 in the atmosphere.