In an attempt to discredit Judith Curry, Gavin at RealClimate shows how bad climate models really are

From the “whoopsie, that’s not what I meant” department

Guest essay by Thomas Wiita

A recent poster here wrote that they had stopped looking at the Real Climate web site, and good for them. It has become a sad, inwardly focused group. It’s hard to see anyone in the Trump Administration thinking they’re getting value for money from their support of that site.

I still check in there occasionally and just now I found something too good not to share with the readers at WUWT.

Gavin has a post up in which he rebuts Judith Curry’s response to comments about her testimony at the Committee hearing. Let me step aside – here’s Gavin:

“Following on from the ‘interesting’ House Science Committee hearing two weeks ago, there was an excellent rebuttal curated by ClimateFeedback of the unsupported and often-times misleading claims from the majority witnesses. In response, Judy Curry has (yet again) declared herself unconvinced by the evidence for a dominant role for human forcing of recent climate changes. And as before she fails to give any quantitative argument to support her contention that human drivers are not the dominant cause of recent trends.

Her reasoning consists of a small number of plausible sounding, but ultimately unconvincing issues that are nonetheless worth diving into. She summarizes her claims in the following comment:

… They use models that are tuned to the period of interest, which should disqualify them from be used in attribution study for the same period (circular reasoning, and all that). The attribution studies fail to account for the large multi-decadal (and longer) oscillations in the ocean, which have been estimated to account for 20% to 40% to 50% to 100% of the recent warming. The models fail to account for solar indirect effects that have been hypothesized to be important. And finally, the CMIP5 climate models used values of aerosol forcing that are now thought to be far too large.

These claims are either wrong or simply don’t have the implications she claims. Let’s go through them one more time.

1) Models are NOT tuned [for the late 20th C/21st C warming] and using them for attribution is NOT circular reasoning.

Curry’s claim is wrong on at least two levels. The “models used” (otherwise known as the CMIP5 ensemble) were *not* tuned for consistency for the period of interest (the 1950-2010 trend is what was highlighted in the IPCC reports, about 0.8ºC warming) and the evidence is obvious from the fact that the trends in the individual model simulations over this period go from 0.35 to 1.29ºC! (or 0.84±0.45ºC (95% envelope)).”

The figure was copied straight from RC. There is one wonderful thing about Gavin’s argument, and one even more wonderful thing.

The wonderful thing is that he is arguing that Dr. Curry is wrong about the models being tuned to the actual data during the period because the models are so wrong (!).

The models were not tuned to consistency with the period of interest as shown by the fact that – the models are not consistent with the period of interest. Gavin points out that the models range all over the map, when you look at the 5% – 95% range of trends. He’s right, the models do not cluster tightly around the observations, and they should, if they were modeling the climate well.

Here’s the even more wonderful thing. If you read the relevant portions of the IPCC reports, looking for the comparison of observations to model projections, each is a masterpiece of obfuscation on this same point. You never see a clean, clear, understandable presentation of the models-to-actuals comparison. But look at those histograms above, direct from the hand of Gavin. It’s the clearest presentation I’ve ever run across that the models run hot. Thank you, Gavin.

I compare the trend-weighted area of the three right hand bars to the two left hand bars, which center around the tall bar of the mode of the projections. There is way more area under those three bars to the right, an easy way to see that the models run hot.

If you have your own favorite example that shows that the models run hot, share it with the rest of us, and I hope you enjoyed this one. And of course I submitted a one sentence comment at RC to the effect that the figure above shows that the models run hot, but RC still remembers how to squelch all thoughts that don’t hew to the party line so it didn’t appear. Some things never change.