Guest post by Willis Eschenbach
(The image above shows the Cray Ecoplex NOAA GAEA supercomputer, which can generate impossible future climate scenarios much faster than we simple humans can…)
Someone online is praising the capabilities of early climate models by referencing the study Evaluating the performance of past climate model forecasts by Zeke Hausfather, Henri F. Drake, Tristan Abbott and Gavin A. Schmidt.
And yes, according to their research, climate models are amazing in their ability to tease out the past and predict the future. They provide many tables and graphs to prove it.
But I’m interested in something different. I wanted to see what the transient climate response (TCR) of each model was. The Intergovernmental Panel on Climate Change (IPCC) defines the transient climate response (TCR) as the change in global temperature at which carbon dioxide (CO2) doubles in an experimental increase of 1 % each year.
In other words, it is the temperature change corresponding to an increase in forcing of 1 W/m2, times the increase in forcing of 3.7 W/m2 that the IPCC says will occur when CO2 doubles.
So I looked at the model data that the authors have responsibly posted online in an Excel spreadsheet at GitHuband calculated the TCR for each model they analyzed.
Then, in addition to TCR, I want to calculate ECS, Equilibrium Climate Sensitivity. To do that I looked at the TCR and ECS of 23 word models this paper. Here is that data, along with the smoothness of the LOW data.
Figure 1. Scatter plot, equilibrium climate sensitivity (ECS) versus transient climate response (TCR), 23 CMIP models.
So I converted the TCR values from the model performance study to ECS values, using the LOW line to do the conversion. Details in the notes section.
Below are the results for the different models.
Figure 2. TCR and ECS for the 12 models studied in the model performance paper.
Now, the interesting part of this is that the climate sensitivity (ECS) of the models has a very wide range, from two to four degrees to double CO2… however, they all do the same job. the extraordinary job of hindering the planet’s historic temperature.
And IF they are all “physics-based” as people claim, I’m sorry but that’s impossible.
I call this “Dr. Kiehl’s Paradox” because in 2007, in an article published in GRL titled “Modeling 20th century climate responses and climate sensitivity” Jeffrey Kiehl first noticed this strange thing. He say:
The question is: if climate models differ by a factor of 2 to 3 in climate sensitivity, how can they all simulate the global temperature record with a reasonable level of accuracy? physical?
A good question indeed. In response to that article, I wrote a post titled “Dr. Kiehl’s Paradox“. In that post, I discussed Dr. Kiehl’s answer to that question, as well as my own answer to that question. I followed that up with a few more analyzes titled “A Zero Point Is Three Times The Force” And “Life is like a box of dark chocolate“.
In those posts, I showed that although they are very complex, the global temperature outputs of climate models can be simulated very accurately by a simple, one-line equation. Simply hysteresis and scaling of forcings are used as input to the models.
Oh, yes, one last strange thing. In the Hansen 1981 model, TCR and ECS are not constant. From 1981 to 2024, ECS increases from about 1.6°C/2xCO2 to about 2.5°C/2xCO2. ECS then continues to increase until 2040, decreases slightly to 2075, and by 2100 it reaches 2.8°C/2xCO2. That’s almost double its original value.
What did you say?
Figure 3. TCR and ECS of the Hansen 1981 model. Each year’s TCS is calculated using the change from forcing and temperature in 1950 to forcing and temperature in that year.
So I have to say that I’m not impressed with the apparent fit between the models and reality. They are not based on physics. Instead, they are simply adjusted to fit the past… and in the case of Hansen 1981, adjusted to exaggerate future warming.
And as my sincere genius brother once said, “It’s easy to predict the future… as long as it’s like the past.”
Unfortunately, as I stated in my previous article titled Now you are sea ice, now you are notThe climate is sometimes and quite unpredictable, very different from before…
Best regards to all of you,
w.
Yes, you’ve heard it before: When commenting, quote the exact words you are discussing. It avoids endless problems.
For those who love math: The function I used in Excel to convert TCR to ECS is based on an approximation of the LOW curve in Figure 1. It is:
= IF(TCR < 1.6, 1.39 + 0.8 * TCR, IF(TCR < 2, -1.04 + 2.32 * TCR, 1.4 + 1.1 * TCR))
This defines three nearly straight-line sections of the LOW smooth line and uses their formula to calculate ECS depending on the value of TCR
Related
