Guest Post by Willis Eschenbach (@WEschenbach on X, my personal blog is here)
The IPCC describes computer climate models as follows:
“Climate models are mathematical representations of the climate system, expressed as computer codes and run on powerful computers. One source of confidence in models comes from the fact that model fundamentals are based on established physical laws, such as conservation of mass, energy and momentum, along with a wealth of observations.”
“The Atmosphere–Ocean General Circulation Models, Earth System Models and Regional Climate Models evaluated here are based on fundamental laws of nature (e.g., energy, mass and momentum conservation).”
And it’s a good thing that these models are “based on fundamental laws of nature” and are “run on powerful computers”, because they are being used to tell us to totally restructure the global energy system, change our personal lives, jack up our taxes, warn us that some weather event is made eleventeen times more likely because of “climate change”, and to require that we make endless costly sacrifices to an unknown climate god.
We are constantly assured that these models are the real deal, totally lit, not to be questioned. Zeke Hausfather says, “We found that climate models – even those published back in the 1970s – did remarkably well, with 14 out of the 17 projections statistically indistinguishable from what actually occurred.” What’s not to like?
So I thought I’d take a look at the latest crop of climate models, those used in the Climate Model Intercomparison Project 6 (CMIP6). I mean, if the 1970s models were as good as Zeke says, the more recent models must be bang-on, especially since they are ” based on established physical laws, such as conservation of mass, energy and momentum, along with a wealth of observations.”
To start with, Figure 1 shows what thirty-six of those recent CMIP6 models say about the global surface air temperature from 1850 to 2024. Note that for the period 1850-1914 they are fed with what we believe are the actual concentrations of greenhouse gases and aerosols, the solar and volcanic changes, and all the other input variables, so that period is a hindcast. The forecasts with predicted concentrations begin only after 2014.
Given that the models all have exactly the same inputs, we’d expect at least their hindcasts to be quite similar. However …
Figure 1. Absolute global average surface air temperatures from 36 CMIP6 climate models.
ZOWIE! Talk about a dog’s breakfast—it would be hard to be more jumbled than that. I wonder how many of these Zeke would claim are “statistically indistinguishable from what actually occurred”.
There’s a further oddity about Figure 1. I have no clue why the models that start out colder warm up more compared to the models that start out warmer. I thought it might be the result of the relationship between W/m2 and temperature, which involves temperature to the fourth power, so I checked. Turns out, it’s not from that—the temperature change is far too small for the fourth-power relationship to make a meaningful difference. So … what is causing it?
Next, note the huge differences in overall shape of the individual model outputs. In some there is a relatively steady increase in temperature from 1850 to 2024. Others run about level or even cool down from 1850 to around 1970 and then rise rapidly to 2024. And others are constantly going up and down over the entire period.
Now, I’m not expecting them to get individual years right. They’re not designed for that. But I certainly didn’t expect that variation in results in a 175-year run.
Call me crazy, but it seems to me that either the models or the modelers have very different ideas about what constitutes “established physical principles”. From my perspective, I’d say that these models are “based on established physical principles” in about the same way that a Hollywood blockbuster filled with CGI, flying dragons, and special effects is “based on a true story”.
Having been gobsmacked by the results in Figure 1, I moved on. Given the endless fascination with the warming since “pre-industrial times”, I thought I’d see what the models say about that. People keep saying that if we warm more than 1.5°C or 2°C since “pre-industrial times”, it will be Thermageddon™ and the oceans will boil. Well, perhaps not literally, but the UN Secretary-General António Guterres said, “the era of global warming has ended; the era of global boiling has arrived” … be very afraid.
Now, the average temperature from 1850 to 1899 is what is generally used by mainstream climate scientists as the “pre-industrial temperature”. (Although actually, it’s nothing of the sort. The Industrial Revolution is generally thought to have started around 1760, which was immediately preceded by the very cold depths of the Little Ice Age … but I digress …)
So following that standard practice, I took all the model outputs shown in Figure 1 above, expressed them as anomalies around their 1850-1899 average temperatures, and graphed the results. Figure 2 shows that stunning example of basic physics …
Figure 2. What the models say about the warming since “pre-industrial” times.
Have we surpassed the dreaded 1.5°C threshold? Fifteen models say yes, twenty-one say no. How about surpassing the 2°C threshold? Four say yes, thirty-two say no. Heck, you can find a model that tells us that it’s warmed since “pre-industrial times” at anything from 0.6°C all the way up to almost four times that, 2.3°C. Almost a four-fold variation in results, with a number of them saying the temperatures in ~1960 – 1980 were below the “pre-industrial” average … basic physics at its finest.
When I put on my hip boots and started wading through this digital disaster, I was planning to compare the model results to reality. But upon consideration, I realized that it would only get me embroiled in arguments about how models can’t be compared to reality because models are showing purely surface air temperatures, but historical reconstructions like Berkeley Earth or HadCRUT use ocean surface temperatures as a proxy for air temperatures, and the like.
I also realized that wasn’t really the issue. The real issue is the following:
If all of these wonderful models are “based on established physical laws, such as conservation of mass, energy and momentum, along with a wealth of observations”, then why do their results differ so greatly?
And of course, the corollary to that:
Why does anybody pay the slightest attention to this inaccurate, ludicrously unfit-for-purpose climate model farrago?
As Chester Nimitz said in his message to Bull Halsey … “The world wonders”.
My very best to everyone,
w.
As Is My Wont: I ask that when you comment, you quote the exact words you are discussing. It prevents endless misunderstandings.
Further Reading: In my post yclept Meandering Through A Climate Muddle, I engaged in haruspicy regarding the GISS climate model. TL;DR version? Lots of kludges and tunable parameters, not much in the way of “established physical laws“.
