Wednesday, January 2, 2013

December in Perspectve

Here is a scatter plot of mean temperature in December over the past 84 years. I've marked the year of the change in phase of the Pacific Decadal Oscillation (PDO), a long term variation in sea surface temperatures in the central and eastern Pacific Ocean. December 2010 and 2012 were unremarkable for a negative PDO phase.


  1. Averages can be misleading without attaching a description of variability. I know, we all do it because it's easy.

    Zero and 10 average 5, but so does 4 and 6. It's possible to have extreme -40 and below, and still end up with a unremarkable average given a couple of warm periods as well. Nobody minds the warm...few like the extreme cold.

    Rick, how about a plot of heating degree days similar to the above? Maybe by month, or cumulative to date from Sept 1? You may have done this already.


  2. Another thought in a row. How about a measurement of monthly cold that for example takes into account the daily differences between the record minimum temperatures for a day, and the observed minimum? Totaled over a monthly period, the lower the value between years might approximate the effect of cold for a particular month (or period).

    I guess what I'm trying to evaluate is this: the effect of cold (value and duration) has a greater impact for me than a few brief periods of above normal temps.


    1. Gary,

      I just put up a long post addressing (I think) your question, which I take as quantifying deep cold.