Cold And Snow Will Make A Comeback This Winter
By Art Horn
Last winter’s weather was a nice break for Americans. After a series of severe winters, last year’s winter weather was unusually mild with much less snow than has fallen on North America during the last five years. With gasoline prices staying consistently high, the mild weather of last winter helped Americans pay a little less for energy during this prolonged economic slump. One year ago the average price of a gallon of gasoline in the United States was $3.47, today it is around $3.69 per gallon, an increase of 22 cents. Diesel fuel is around $4.12 per gallon or 29 cents higher than one year ago. Will we be as lucky with the winter weather this year as last? Probably not.
Winters in the United States are getting colder and snowier. In fact over the last 15 years, winters (December, January and February) in United States have been getting colder at a rate of -1.99 degrees Fahrenheit since 1998. Why pick 1998 as the year to begin measuring this rapid decline in United States winter temperature? The reason is that up until 1998 winters in the United States had been warming at the rate of +1.92 degrees per decade since 1977. That two decade warming of US winters peaked in 1998. The year 1977 marked the approximate start of the warm phase of the Pacific Decadal Oscillation (PDO). This roughly 20 to 30 year long warming and cooling of the Pacific Ocean has strong linkage to 20 to 30 year long warming and cooling periods of earth’s global average temperature. The PDO had been in its cool phase since the middle 1940s. In 1977 it shifted into the warm phase and at that point, United States winter started warming. There is evidence that the PDO has shifted back into the cool phase. In fact it appears this shift took place around 1998.
As a result of this shift our winters have begun to cool and snowfall has been increasing. The winters of 2008 to 2011 were the four snowiest consecutive winters in the last 45 years in North America. Some tried to blame the record breaking Mid-Atlantic snows of these winters on global warming. These assumptions were made with no mention of the natural climate cycles inspired by the shifts in the PDO. The fact is that the downward trend in temperature and the upward trend in snowfall were even greater prior to last winter. If we exclude last winter and look at the trend in the US since 1998, winters were getting colder at the almost unsustainable rate of -3.20 degrees per decade. Last winter was a good example of how large natural variability is. What I mean by natural variability is the tendency of the atmosphere to swing back and forth from year to year within a general trend. The result of this variability is that what happened last winter is no indication of what will happen this winter.
So what does all of this mean for winter 2012/13? It is likely that the long term trends in United States temperature and snowfall will resume the path they were on prior to last winter. The National Oceanic and Atmospheric Administration (NOAA) uses El Nino (warmer water) and La Nina (cooler water) events in the Pacific Ocean as guides, along with other atmospheric phenomena, to make their winter forecasts. There were indications that an El Nino was going to develop this fall and have a significant impact on this winters weather. That El Nino has failed to live up to its billing and may not happen at all. It is typical that during the cool phase of the PDO that there are fewer and weaker El Nino events. This has caused confusion at NOAA so that they have basically thrown in the towel with respect to the forecast temperature for the central and eastern part of the nation this winter.
Without El Nino or La Nina this winter it appears that a return to the longer term trend dictated by the shift of the PDO into its cooler phase will dominate this winter in the United States. With world tensions and gas prices high a cold and snowy winter will add significantly to Americans economic plight this winter. One interesting bit of speculation on my part is that nature tends to swing the pendulum back and forth. With such a mild winter last year during an overall downward trend in temperature, is it possible the temperature and snowfall pendulum could swing the other way this winter? Only time will tell but in any event don’t expect a repeat of last winter.