Poor analysis has led climate scientists (and a gaggle of others) to see patterns where there are none. All this chatter regarding global warming causing cold snaps is the result of sloppy science.
You may have notice that the news media talking heads and TV weather presenters have discovered a new term recently—the Arctic Vortex. In a splendid demonstration of how the weak minded are quickly consumed by group think, and ill understood terms get repeated ad nauseum, the Arctic Vortex has dominated the news during the past week in the US. In truth, the phenomenon is not new. What is new is that its current foray south is being loudly attributed to global warming. For years the effects of a warming Arctic have been the subject of scientific speculation. Dubbed Arctic amplification, some claim it will enhanced extreme weather in the middle latitudes. The fact that such linkage is tenuous at best has not stopped ignorant politicians like the UK’s David Cameron and the US’s Barack Obama from blaming recent nasty weather on that old nugget, anthropogenic global warming. There is, however, some evidence to the contrary from one scientist who studies atmospheric dynamics and variability under different climates.
According to climate change alarmists the dreaded Arctic Vortex is responsible for frigid temperatures and abnormal weather patterns all across the Northern Hemisphere. Supposedly, global warming has caused the swirling cold air that circulates above the North Pole to wobble and dip to the south, setting a rash of new record cold temperatures across the continental United States. The cause of the shift is global warming, at least according to the ignorant and unimaginative. In a timely paper, Dr. Elizabeth A. Barnes from the Department of Atmospheric Science at Colorado State University, has published a paper in Geophysical Research Letters, titled “Revisiting the evidence linking Arctic amplification to extreme weather in midlatitudes.” Here is what Barnes found when looking more closely at the problem.
Previous studies have suggested that Arctic amplification has caused planetary-scale waves to elongate meridionally and slow down, resulting in more frequent blocking patterns and extreme weather. Here trends in the meridional extent of atmospheric waves over North America and the North Atlantic are investigated in three reanalyses, and it is demonstrated that previously reported positive trends are likely an artifact of the methodology. No significant decrease in planetary-scale wave phase speeds are found except in October-November-December, but this trend is sensitive to the analysis parameters. Moreover, the frequency of blocking occurrence exhibits no significant increase in any season in any of the three reanalyses, further supporting the lack of trends in wave speed and meridional extent.
The emphasis in the paragraph above was added to highlight the primary finding, that “previously reported positive trends are likely an artifact of the methodology.” Poor analysis has led climate scientists (and a gaggle of others) to see patterns where there are none. In other words, all this chatter regarding global warming causing cold snaps is the result of sloppy science. A look at the previous claims is in order.
Arctic amplification refers to the more rapid warming of the Arctic region as compared to the midlatitudes, which may alter midlatitude weather patterns by influencing the meridional temperature gradient and static stability. It should be noted that temperature gradients are what largely drive weather systems. This implies that changes in the temperature differential between the Arctic and lower latitudes should result in changes in weather. This all sounds logical and Dr. Barnes cites several recent studies that made positive claims in this regard.
Recent studies have investigated whether Arctic amplification has increased the frequency of observed extreme weather events [Liu et al.,2012; Francis and Vavrus, 2012]. Liu et al.  suggest that recent Arctic sea ice loss (which may be linked to Arctic amplification through a positive feedback process; see Screen and Simmonds  for details) has caused an increase in snowfall over the United States and Europe through an increase in the frequency of blocking events. These blocking patterns are slow-moving (or stationary) waves that can persist for days and up to weeks, often bringing extreme weather to nearby regions.
Others hypothesize that elongated Rossby waves propagate more slowly and favor more extreme weather conditions. They speculate that as Earth warms, Arctic amplification will increasingly influence the North Atlantic atmospheric circulation, potentially causing more extreme weather in association with the slower waves. So, according to the cited reports, it would seem that the climate alarmists are correct, a side effect of global warming should be worse winter weather, and the warmists have the computer models to prove it.
How some scientists think the Arctic Vortex functions.
Trouble is, the real data are a bit thin and models are not reality. Given the claims linking Arctic amplification to increased slow-moving Atlantic weather patterns, Dr. Barnes decided to ask the following three questions:
- Have wave extents increased over the past 30 years?
- Have the phase speeds of large-scale atmospheric waves decreased?
- Has the frequency of blocking events increased?
If the conditions outlined above are not met it means that nature is not behaving according to the dictates of climate science and the warmist theories are a bunch of hooey. To answer the questions Barnes studied the results of three reanalysis datasets: the European Centre for Medium-Range Weather Forecasts’s Era-Interim reanalysis [ Dee et al. , 2011], the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis [ Kalnay et al. , 1996], and NASA’s Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis [ Rienecker et al. , 2011].
Blocking frequency rate of change for three datasets.
Much of the paper’s analysis focuses on a pair of metrics—SeaMaxMin and DayMaxMin—and using a number of varied assumptions the author found no significant trends in wave extents for either. Moreover, No statistically significant increase in blocking frequency was found in any season. The erroneous trends reported by earlier studies were demonstrated to be due to the way the data were analyzed and that slight modifications to the methodology either removes or reverses the observed trends. The analysis itself is quite detailed and technical and I urge those interested to read the appropriate sections of the paper for deeper understanding. To answer the three questions posited by Dr. Barnes:
- The wave extents have remained relatively constant.
- There has been no slowdown in observed wave speeds.
- The frequency of blocking events has not changed.
Summing up the paper’s conclusions in Dr. Barnes’ own words: “We conclude that the mechanism put forth by previous studies [e.g., Francis and Vavrus, 2012; Liu et al.,2012], that amplified polar warming has led to the increased occurrence of slow-moving weather patterns and blocking episodes, appears unsupported by the observations.”
That, expressed in the carefully bland language of scientific discourse, means the other guys got it wrong. The moral is, when using computer models and statistics to look for anthropogenic global warming’s smoking gun it is easy to see trends that are not really there. As with other predictions used to “prove” AGW—more and stronger cyclonic storms, more drought, more wild fires, etc.—a careful look at long-term trends shows nothing to be alarmed about.
That’s right friend, it’s global warming at work.
To compensate, global warming activists have modified their predictions. Now global warming causes warmer winters and colder winters, more frequent storms and less frequent storms, more snow and less snow… you get the idea. Since scientific theories are judged by their predictive power, global warming has proven to be a particularly useless theory.