Global Warming: A Trend or Step Changes?

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Thanks so much for reading our publication. We hope you find it informative and useful. Happy charting and may the data always support your position.


Dr. Bill McNeese
BPI Consulting, LLC

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Comments (2)

  • AnonymousJune 29, 2020 Reply

    Interesting analysis. I know you’ve done many more of these charts then I have, but I think I disagree with your final statement that the latter part of the temperature trend is best made up of a series of shorter horizontal segments. When I constructed this using your entire data set, starting at 1880 and not 1997, I get the following chart. For about 100 years, the process continued in two horizontal regimes. Thereafter, the horizontal steps were barely a decade long.The shift from long undisturbed segments to short segments is itself a process change. In fact, it is more of a process mechanism change than merely a process shift. Even within these shorter steps, one can imagine that the points follow a slope. And the changed mechanism has to be related to the runaway increase of greenhouse gases.Given this change in mechanism, I have changed the latter part of the chart to a ramp, and selected the transition where the sloped centerline intersects the horizontal mean of the previous segment.In light of the changing mechanism of warming, and the reasonable fit of the points to the centerline, this approach makes more sense to me.

    • billJune 30, 2020 Reply

      Thanks for your great input and analysis.  I don't disagree with your analysis.  There are points that show out of control conditions in the long patterns you have – I think those are different periods of homogeneity and it is valid to split the control limits there.
      It is definitely true that the step changes (if you go that route) have been much shorter in recent years.  I believe it is two different ways in looking at the data.  The trend is what most people would say is going on because of the correlation to greenhouse gases increase.  I still find the pattern of step changes interesting and provides another way to look at the data.

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