Last week, Larry Kummer posted a very thoughtful article here on WUWT:
At first glance, this did look like “a successful 10-year forecast:
The observations track closer to the model ensemble mean (P50) than most other models and the 2016 El Niño spikes at least a little bit above P50. Noticing that this was CMIP3 model, Larry and others asked if CMIP5 (the current Climate Model Intercomparison Project) yielded the same results, to which Dr. Schmidt replied:
CMIP5 version is similar (especially after estimate of effect of misspecified forcings). pic.twitter.com/Q0uXGV4gHZ
— Gavin Schmidt (@ClimateOfGavin) September 20, 2017
The CMIP5 model looks a lot like the CMIP3 model… But the observations bounce between the bottom of the 95% band (P97.5) and just below P50… Then spike to P50 during the 2016 El Niño. When asked about the “estimate of effect of misspecified forcings, Dr. Schmidt replied:
As discussed here: https://t.co/0d0mcgPq0G
(Mostly misspecification of post-2000 solar and volcanoes)
— Gavin Schmidt (@ClimateOfGavin) September 21, 2017
Basically, the model would look better if it was adjusted to match what actually happened.
The only major difference between the CMIP3 and CMIP5 model outputs was the lower boundary of the 95% band (P97.5), which lowered the mean (P50).
CMIP-5 yielded a range of 0.4° to 1.0° C in 2016, with a P50 of about 0.7° C. CMIP-3 yielded a range of 0.2° to 1.0° C in 2016, with a P50 of about 0.6° C.
They essentially went from 0.7 +/-0.3 to 0.6 +/-04.
Progress shouldn’t consist of expanding the uncertainty… unless they are admitting that the uncertainty of the models has increased.
Larry then asked Dr. Schmidt about this:
Small question: why are the 95% uncertainty ranges smaller for CMIP5 than CMIP3, by about .1 degreeC?
— Fabius Maximus (Ed.) (@FabiusMaximus01) September 22, 2017
Dr. Schmidt’s answer:
Not sure. Candidates would be: more coherent forcing across the ensemble, more realistic ENSO variability, greater # of simulations
— Gavin Schmidt (@ClimateOfGavin) September 22, 2017
“Not sure”? That instills confidence. He seems to be saying that the CMIP5 model (the one that failed worse than CMIP3) may have had “more coherent forcing across the ensemble, more realistic ENSO variability, greater # of simulations.”
I’m not a Twitterer, but I do have a rarely used Twitter account and I just couldn’t resist joining in on the conversation. Within the thread, there was a discussion of Hansen et al., 1988. And Dr. Schmidt seemed to be defending that model as being successful because the 2016 El Niño spiked the observations to “business-as-usual.”
— Gavin Schmidt (@ClimateOfGavin) September 5, 2017
I asked the following question:
So… the monster El Niño of 2016, spiked from ‘CO2 stopped rising in 2000’ to “business as usual”?
— David Middleton (@dhm1353) September 25, 2017
No answer. Dr. Schmidt is a very busy person and probably doesn’t have much time for Twitter and blogging. So, I don’t really expect an answer.
In his post, Larry Kummer also mentioned a model by Zeke Hausfather posted on Carbon Brief…
El Niño events like 1998 and 2016 are not high probability events. On the HadCRUT4 plot below, I have labeled several probability bands:
|Standard Deviation||Probability Band||% Samples w/ Higher Values|
Yes… I am assuming that HadCRTU4 is reasonably accurate and not totally a product of the Adjustocene.
I removed the linear trend, calculated a mean (P50) and two standard deviations (1σ & 2σ). Then I added the linear trend back in to get the following:
The 1998 El Niño spiked to P02.5. The 2016 El Niño spiked pretty close to P0.01. A strong El Niño should spike from P50 toward P02.5.
All of the models fail in this regard. Even the Mears-ized RSS satellite data exhibit the same relationship to the CMIP5 models as the surface data do.
The RSS comparison was initialized to 1979-1984. The 1998 El Niño spiked above P02.5. The 2016 El Niño only spiked to just above P50… Just like the Schmidt and Hausfather models. The Schmidt model was initialized in 2000.
This flurry of claims that the models don’t “run hot” because the 2016 El Niño pushed the observations toward P50 is being driven by an inconvenient paper that was recently published in Nature Geoscience (discussed here, here and here).
Claim of a substantial gap between model projections for global temperature & observations is not true (updated with 2017 estimate): pic.twitter.com/YHzzXtbhs9
— Gavin Schmidt (@ClimateOfGavin) September 20, 2017
21 September 2017 0:27
Factcheck: Climate models have not ‘exaggerated’ global warming
A new study published in the Nature Geosciences journal this week by largely UK-based climate scientists has led to claims in the media that climate models are “wrong” and have significantly overestimated the observed warming of the planet.
Here Carbon Brief shows why such claims are a misrepresentation of the paper’s main results.
All (95%) of the models run hot, including “Gavin’s Twitter Trick”. From Hansen et al., 1988 to CMIP5 in 2017, the 2016 El Niño spikes toward the model ensemble mean (P50)… Despite the fact that it was an extremely low probability weather event (<2.5%). This happens irrespective of then the models are initialized. Whether the models were initialized in 1979 or 2000, the observed temperatures all bounce from the bottom of the 95% band (P97.5) toward the ensemble mean (P50) from about 2000-2014 and then spike to P50 or slightly above during the 2016 El Niño.