Controversy over comparing models with observations

Particular noteworthiness:

Rud Istvan’s comment [format edited for clarity] explaining Gavins Schmidt’s histogram version of Christy’s CMIP/Observation comparison:

Slide1

ristvan | April 5, 2016 at 4:05 pm

The histogram can be explained in less than one minute to a nontechnical audience.

  • Point to leftmost bar.
    • ‘the lowest of the CMIP5 runs , this one model out of 102, had an annual rate of increase from 1979 to 2015 of 0.008C/yr.’
  • Point to tallest bar.
    • ’23 models had an average rate of 0.018.’ Wave at the right side. ‘Many models had rates that were much higher.’
  • Now vertically wave at the colored horizontal lines, at the dots.
    • ‘The various satellited measured actual rates are lower than almost all the models’.
  • Then wave horizontally at the colored horizontal bars.
    • ‘That is even true considering the uncertainties in the various satellite measurements.’
  • Then wave again at the right side of the histogram.
    • ‘So we see that the models have generally run much hotter than reality over the past three and a half decades.
  • That is why it is hard to have any confidence in their longer term temperature and sensitivity estimates.’

Climate Etc.

by Judith Curry

My draft talk elicited an interesting conversation on twitter, that deserves some wider discussion.

View original post 815 more words

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