Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”


Last summer, we predicted that come this winter, any type of severe weather event was going to be linked to pernicious industrial activity (via global warming) through a new mechanism that had become a media darling—the loss of late summer/​early fall Arctic sea ice leading to more persistent patterns in the jet stream. These are known as “blocking” patterns, which generally means that the same type of weather (usually somewhat extremish) hangs around longer than usual.


This global‐​warming‐​leading‐​to‐​more‐​extreme‐​winter‐​weather mechanism has been presented in several recent papers, perhaps the most noteworthy of which was a 2012 publication by Jennifer Francis and Stephen Vavrus, which was the subject of one of our blog posts last summer. We noted then how their idea ran counter to much of the extant literature of the topic as well as a host of other newly published papers investigating historical jet stream patterns.


After running through a list of observations compiled from the scientific literature countering the Francis and Vavrus explanation of things, we nevertheless wondered:

It’ll be interesting to see during this upcoming winter season how often the press—which seems intent on seeking to relate all bad weather events to anthropogenic global warming—turns to the Francis and Vavrus explanation of winter weather events, and whether or not the growing body of new and conflicting science is ever brought up.

We didn’t have to wait long. After a couple of early winter southward Arctic air excursions, the familiar and benign‐​sounding “jet stream” had become the “polar vortex”[1] which “sucked in” the United States. Of course, the U.S. being sucked into a polar vortex was part and parcel of what was to be expected from global warming.


Since we had predicted this action/​reaction, we weren’t terribly surprised.


What did surprise us (although perhaps it shouldn’t have) is that the White House joined in the polar vortex horror show and released a video in which John Holdren, the President’s Science Advisor—arguably the highest ranking “scientist” in the U.S.—linked the frigid air to global warming:

In the video, Holdren boldly stated:

…a growing body of evidence suggests that kind of extreme cold being experienced by much of the United States as we speak is a pattern that we can expect to see with increasing frequency as global warming continues…

It seems that Holdren neither keeps up with our writings at Cato nor the scientific literature on the topic.


While perhaps it could be argued that Holdren’s statement is not an outright lie, it is, at its very best, a half‐​truth and even a stretch at that. For in fact, there is a larger and faster growing body of evidence that directly disputes Holdren’s contention.


In addition to the evidence that we reported on here and here, a couple of brand new papers just hit the scientific journals this month that emphatically reject the hypothesis that global warming is leading to more blocking patterns in the jet stream (and accompanying severe weather outbreaks across the U.S.).


The first paper is a modeling paper by a team of U.K. scientists led by Giacomo Masato from the University of Reading. Masato and his colleagues looked at how the magnitude and frequency of atmospheric blocking events in the Atlantic‐​Europe region is projected to change in the future according to four climate models which the authors claim match the observed characteristics of blocking events in this region pretty well. What they found was completely contradictory to Holdren’s claim. While the researchers did note a model‐​projected small future increase in the frequency of blocking patterns over the Atlantic (the ones which impact the weather in the U.S.), they found that the both the strength of the blocking events as well as the associated surface temperature anomalies over the continental U.S. were considerably moderated. In other words, global warming was expected to make “polar vortex” associated cold outbreaks less cold.


The second paper is by a research team led by Colorado State University’s Elizabeth Barnes. In their paper “Exploring recent trends in Northern Hemisphere blocking,” Barnes and colleagues used various meteorological definitions of “blocking” along with various datasets of atmospheric conditions to assess whether or not there have been any trends in the frequency of blocking events that could be tied to changes in global warming and/​or the declines in Arctic sea ice.


They found no such associations.


From their conclusions:

[T]he link between recent Arctic warming and increased Northern Hemisphere blocking is currently not supported by observations. While Arctic sea ice experienced unprecedented losses in recent years, blocking frequencies in these years do not appear exceptional, falling well within their historically observed range. The large variability of blocking occurrence, on both inter‐​annual and decadal time scales, underscores the difficulty in separating any potentially forced response from natural variability.

In other words natural variability dominates the observed record making it impossible to detect any human‐​caused global warming signal even if one were to exist (which there is no proof of).


So, the most recent science shows 1) no observed relationship between global warming and winter severe weather outbreaks and 2) future “polar vortex”-associated cold outbreaks are projected to mollify—yet the White House prepares a special video proclaiming the opposite with the intent to spread climate alarm.


Full scientific disclosure in matters pertaining to global warming is not a characteristic that we have come to expect with this Administration.


References:


Barnes, E., et al., 2014. Exploring recent trends in Northern Hemisphere blocking. Geophysical Research Letters, doi:10.1002/2013GL058745.


Francis, J. A. and S. J. Vavrus, 2012: Evidence linking Arctic amplification to extreme weather in mid‐​latitudes. Geophysical Research Letters, 39, doi:10.1029/2012GL051000.


Masato, G., T. Woollings, and B.J. Hoskins, 2014. Structure and impact of atmospheric blocking over the Euro‐​Atlantic region in present day and future simulations. Geophysical Research Letters, doi:10.1002/2013GL058570.