Gavin Schmidt and Reference Period “Trickery”

Posted: April 20, 2016 by tallbloke in solar system dynamics

Still hiding the decline. They never learn.

Climate Audit

In the past few weeks, I’ve been re-examining the long-standing dispute over the discrepancy between models and observations in the tropical troposphere.  My interest was prompted in part by Gavin Schmidt’s recent attack on a graphic used by John Christy in numerous presentations (see recent discussion here by Judy Curry).   christy_comparison_2015Schmidt made the sort of offensive allegations that he makes far too often:

@curryja use of Christy’s misleading graph instead is the sign of partisan not a scientist. YMMV. tweet;

@curryja Hey, if you think it’s fine to hide uncertainties, error bars & exaggerate differences to make political points, go right ahead.  tweet.

As a result, Curry decided not to use Christy’s graphic in her recent presentation to a congressional committee.  In today’s post, I’ll examine the validity (or lack) of Schmidt’s critique.

Schmidt’s primary dispute, as best as I can understand it, was about…

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  1. oldbrew says:

    ‘Christy’s misleading graph’

    Pot calls kettle black?

  2. I thought it was a trivial spat until I realised just how appalling the “baseline” chosen by Gavin was. If you are going to arbitrarily use a 20 average for the baseline, then you ought also at least display the 20 year averaged data over the period and do otherwise would be dishonest.

    What he could have done, is to simply remove the average and have the lines crossing at the centre. This would allow a comparison of trends. Otherwise, he should have averaged the data and the baseline using the same time period.

    That is to say, if it is yearly data, then the first year should coincide. If the average were 5 years, then the point representing the first five years should coincide, Likewise decadal. But when you get to two decades, you don’t have a graph at all.

    At the very least he ought to have marked the mid-point of the baseline – without that his graph is very misleading.

  3. oldbrew says:

    Scottish Sceptic says: ‘without that his [Schmidt’s] graph is very misleading’

    I rest my case.

  4. catweazle666 says:

    “In sum, a strategy must recognise what is possible. In climate research and modelling, we should recognise that we are dealing with a coupled non-linear chaotic system, and therefore that the long-term prediction of future climate states is not possible.”

    IPCC Working Group I: The Scientific Basis, Third Assessment Report (TAR), Chapter 14 (final para.,, p774.

  5. oldbrew says:

    “the long-term prediction of future climate states is not possible.”

    But if we call them ‘projections’ instead, we can wind people up with our preferred climate scare stories anyway 😉

  6. tom0mason says:

    People making pretty graphs of chaotic climate systems by sophisticated averaging of short term measurements, in order to extrapolate a long-term trend are — to my mind — nuts!
    Such calculation might give you illusory confidence in manufacturing a medium term indication of a general or probable direction that global temperature may take but nothing very definitive. If you think otherwise then use the best (adjusted) data, and just move the start point back a couple of hundred years, then look for a consistent 60 year (or shorter) period that accurately predicts the next hundred or two hundred years by sophisticated averaging.
    Surely this storm in teacup is possibly the most overblown cry of ‘Don’t Rain On My Parade’ in the history of virtual climate science. As such a distraction it will run and run.

  7. ren says:

    Jupiter and Saturn come close to each other. The sun still active.