Archive for the ‘smooth’ Category


Comments on “To Tell The Truth: Will the Real Global Average Temperature Trend Please Rise?

March 18, 2008

I appreciate the detailed write-up that Basil Copelanddid for Anthony Watts’ “Watts Up With That” over the last several days.  However, I think the temperature data is being dangerously over analyzed.  I must agree with Christopher Monckton, as reported here, when considering the recent low tempertures:

“… for goodness sake the one thing we mustn’t do is crow,” he said in an interview. “Yes, the temptation of course is to get excited and say this proves the alarmists wrong. But a single extreme weather event in either direction does not prove anything.” 

We have been rightly critical of the global warming alarmist for years for seizing upon every climate extreme as evidence for climate change.  Let’s not seize on these last few months or low temperatures as the basis for a counter argument.

I have reproduced Basil’s smoothing using the Hodrick-Prescott filter (which I got here) for the UAH temperature data.   The UAH data temperature data runs from 1979 to February of 2008.  But I also repeated the smoothing by ending three months early (Nov. ’07), six months early (Aug. ’07), nine months early (May ’07), and 12 months early (Feb. ’07).  The entire run, starting in 1979 can be seen if figure 1, below.  Figure 2 zooms in on just the last ten years, and shows the temperature trend at the end of each smoothing run.  This simply demonstrates that this smoothing technique, like most others, can be quite unstable near the beginning and end of a time series.


Figure 1.  Reproduction of Basil Copeland’s Hodrick-Prescott smoothed UAH temperature data.


Figure 2.  Smoothed UAH data zoomed in to last 10 years.  Note how the final slope varies as each 3 month period is removed from the data.

If the recent cold temperatures hold, or continue to drop, then we will have plenty of time to point this out as the trend becomes more obvious.  If the temperatures go back up over the next year or so, then the alarmists will gleefully point out how wrong this analysis is, ultimately giving us less credibility. 

 Thanks again to Anthony Watts and Basil Copeland.  Watts’ “Watts Up With That” is on the front-lines in the battle between hysteria and sanity.  I made a donation to his tip jar today, and recommend that readers give what they can.