Does This Warm Winter Tell Us Anything?
Weather records date back to the year 1895 in the United States. Six of the top ten warmest winters have occurred since 1998. While there have been some warm winters lately the overall winter temperature trend in the United States is going down. In the last ten years the United States winter temperature has been falling at the rate of nearly 2 degrees per decade even with this past warm winter is figured in. The cost of energy is doing the opposite, it is rising. Understanding the large variability of winter temperature will be important in helping us form prudent policy that insures a stable and secure energy future.
No doubt about it, this was a very mild winter across the United States. Traditionally winter starts on the winter solstice, around December 21st but the winter season, as defined by the National Oceanic and Atmospheric Administration (NOAA), is the months of December, January and February. The average temperature for this past winter across the country was 36.84 degrees or the 4th warmest since the weather records began in 1895. The warmest winter on record was in 2000 with an average temperature of 37.17 degrees or 0.33 degrees warmer than this past winter. In terms of anomaly it was especially warm in the upper Great Lakes region. Readings there were 6 to 8 degrees higher than the 1981 to 2010 base period average.
The benefits of this warm winter were in the energy cost savings to Americans. With gas prices rising to near record levels and a deep recession continuing to drain bank accounts and close businesses, any savings in the cost of energy would be welcome and Mother Nature provided some much needed relief. This is especially true in light of the fact that this winter came on the heels of two very cold and snowy winters. The winter of 2011 was at or below average cold over nearly the whole country with only three states, Maine, Nevada and California having above average temperature for the winter. The winter of 2010 was even tougher on heating bills with near record cold in the south and only 6 states having above average temperature. With an ongoing recession and continuing tension in the Middle East and elsewhere upward pressure on energy costs will likely persist. A helping hand from a mild winter was a welcome surprise.
Most of the long range forecasts for this past winter were calling for colder than average temperature in the west, into the Great Lakes region and into Northern New England. In a typical La Nina winter, that pattern is the norm but not this winter, at least not here. It was not warm everywhere. Europe had its worst cold wave in twenty five years starting around January 27th and continuing for three weeks. Brutal cold and record amounts of snow dominated a large portion of Europe. One town in the central highlands of Italy, Urbino had 11 feet of snow from January 31st to February 5th! Around 650 deaths were a direct result of below zero cold, impassable roads with towns and villages cut off from supplies. Many of the great rivers froze solid stranding ships in place for weeks.
A legitimate question would be just how unusual was this winter? The winter of 2012 ranked 114th out of 117 so only three other winters since 1895 were warmer than this one. However the range of variability of winters in short periods of time can be very large. We only need to go back to the winter of 2010 to find the 15th coldest winter on record. The winter of 2002 ranked 112th warmest but the winter before, 2001 was 27th coldest.
Here in the United States the year 1934 is particularly interesting when it comes to temperature. The annual average for that year is 54.83 degrees ranking it 115th warmest out of 117 years. Since 1895 only two years are warmer than 1934 and they were 1998 and 2006. Actually up to 1999 the year 1934 was the warmest year on record but “adjustments” made to the data over the last few years have changed that. Why those changes were made to the data is a story for another day. Currently the average temperature difference between 1998 and 1934 is 0.25 degrees meaning they are only 1% different from each other. They are virtually the same.
The average winter temperature for 1934 was 35.98 degrees ranking it 107th or 0.86 degrees cooler than this past winter. The average temperature of the winter of 1934 and this past winter differ by only 2%. Although the average temperature of these winters was very close to each other, the regional differences were enormous. February of 1934 ranks in the middle of the pack at number 66 out of 117 winters. However, when you look at the regional differences you see that nature can be very tricky and averages can be very deceiving. The western United States was much above average in the winter of 1934 with Idaho having its warmest February on record. In the east it was a very different story. Every state from Michigan to South Carolina eastward was much below average temperature and every state east of Pennsylvania to Maryland had its coldest February on record. Averages don’t always tell the whole story.
You might think that since there has been a general warming since 1895 that the coldest winter was a long time ago near the beginning of the temperature record. It was not. The coldest winter of the last 117 was 1979 with an average of 27.29 degrees. This coldest winter on record was at the end of a general cooling of the earth that started in the middle 1940s. Beginning in the late 1970s there was a warming period that peaked around 1998. Since then there has been no upward trend in the measured average temperature of the earth. The temperature data from the Hadley Center in England says there has been a slight cooling for the last 10 years. Either way, if this lack of warming persists or if a cooling trend is developing there will continue to be very large variations of winter temperature in the United States. The winter of 1934 is ranked 107th warmest out of 117 but just two years later the winter of 1936 was 7.5 degrees colder and ranks 2nd coldest. This past winter was ranked 114th warmest but just two years ago the winter of 2010 was 5.7 degrees colder and was the 15th coldest. The tremendous natural variability in winters that existed in the past continues to exist today and will into the future.
We should not fixate on one winter or a series of winters. The past tells us that even in very mild winters there can be regional cold waves that can strain energy systems and budgets. A large natural variability in winter temperature exists in the United States and we must be ready for its annual swings. In the last 33 years the average winter temperature in the United States has varied by 10 degrees. That’s a large amount of natural variability. In fact the coldest and the warmest winters occurred in the space of just 21 years. The coldest was 1979 and the warmest was 2000. Next winter’s average temperature could be the same as this past one but it could end up record cold in some places and record warm in others. Just because the average is warm doesn’t mean that there couldn’t be large regional differences. Those differences could produce severe upward pressure on the price of energy especially if the cold were in the east where most of the population is. If the general downward trend in winter temperature continues we will see increasing upward pressure on energy prices.
Snowfall across the country also exhibits a large range of variability. Satellite mapping of snow cover started in the winter of 1967. Since that time the least amount of snow on the ground was in the winter of 1981. That low amount of snowfall was just two years after the greatest snow cover in 1979. Every winter since 2007 has recorded above average snow cover across the country with the winter of 2010 equaling the record of 1979 for total coverage. Four of New York cities snowiest months since 1869 have been in the last 9 years. Across the nation this past winter was substantially below the average snow cover of the last 45 years. Last winter New York City had 61 inches of snow, this winter 7.4 inches. Boston had 79 inches of snow last winter, this winter a mere 9.3 inches. Chicago was buried under 57 inches of the white stuff last winter but only 20 inches this winter. As with temperature the United States snow cover varies tremendously from year to year and from decade to decade. Expect more of this in the future.
The winter of 2012 was surprisingly warm with little snow across the most of the country. Next winter could be the exact opposite. The winter of 2012 should tell us that each winter we should be ready for anything from severe cold and snow to the kind of winter we just had. Large variability in temperature and snowfall has always existed in the past and it will in the future, be ready for it.