Guest contribution by Willis Eschenbach
The new UN IPCC Assessment Report 6 (AR6) has been published and is available here. They make it clear that a good part of the report is not science. Instead, it’s the opinions of scientists. They describe what they use, for example as:
… structured expert judgment (i.e. a formal, calibrated method for combining quantified experts)
Assessments that include all potential processes)
First of all, there is no way of knowing if they contain “all potential processes”. We don’t know much about the climate and new discoveries are made every month. What is a “quantified expert assessment” at home next? A numerical guess you’ve thought about a lot?
And what is the “formal, calibrated method” of combining a series of numerical guesses from “experts”?
Here is the description of how you rate the likelihood of something and how much confidence you have in this assessment of the likelihood (emphasis mine).
In this Technical Summary, the main assessment results are reported using the IPCC language for calibrated uncertainty (Chapter 1, Box 1.1). Two calibrated approaches are used to communicate the level of confidence that important findings are based on Reviews of the writing teams of the underlying scientific understanding:
(1) Trust is a qualitative measure of the validity of a finding based on the type, amount, quality and consistency of evidence (e.g. data, mechanistic understanding, theory, Models, expert judgment) and the degree of agreement; and
(2) The probability is a quantified measure of the confidence in a probabilistically expressed finding (e.g. based on a statistical analysis of observations or model results or both, and Expert judgment by the team of authors or from a formal quantitative survey of expert opinions, or both.
A couple of notes on this quote. First, “evidence” in their world is not just data, observation, and mechanistic and theoretical understanding. For them, “evidence” also includes models and expert judgments. As a man who has programmed computer models of a wide variety of systems, I can assure you that the model output is only “proof” in the simplest of systems. This is why Boeing and Airbus use wind tunnels to test scale models of proposed aircraft that are designed based on computer model outputs … because model outputs are not evidence.
And “expert judgment”, be it from an expert or “expert judgment of the team of authors or from a formal quantitative survey of expert opinions”, is in no way proof. It’s valuable, but a hundred years ago “expert judgment” said that malaria is caused by poor hygiene and fresh air, ulcers are caused by stress, and that continental plates cannot move … was that “proof”?
It is hubris at the highest level to believe that this is not happening now in a variety of areas.
In any case, I thought I’d see how good your “expert judgment” could be. I noticed that they have a new “sea level projection tool” to give us their expert judgment on how sea levels might rise in different areas around the world.
Figure 1. Screenshot of the sea level projection tool of the UN IPCC. For a number of locations (blue dots), both future levels and future rates of increase per decade from the 2020s are given.
I’ve written about sea level before, including discussing one of the best and longest records in the world. This is the San Francisco record, measured about an hour and a half south of where I am writing this. Here is this record.
Figure 2. San Francisco sea level record.
As with about 80% of long-term sea level records, there has been no evidence, overall or in the last half century, of any acceleration in sea level rise in San Francisco. Sea level rise has been stable at 2mm per year for a century and a half, which is just under 8 inches per century.
So what would be the simplest forecast for future sea level rise in San Francisco? I would say given that there has been a steady 2mm increase for 170 years, the first estimate wouldn’t differ much from 2mm per year … especially in the current decade, the 2020s.
And what do the models of the UN IPCC and the “expert judgment” tell us about future sea level rise in San Francisco? It depends on the “scenario”. The UN IPCC uses five different scenarios. In the order of increasing CO2 and other greenhouse gas emissions and thus after increasing theoretical temperature increases, they are designated as “1.9”, “2.6”, “4.5”, “7.0” and “8.5” scenarios. In addition, there are two “low confidence” scenarios for sea level rise. They say:
Two low-confidence scenarios are also provided that show the potential impacts of ice sheet processes with low probability and large impacts that cannot be ruled out. … A rise in global mean sea level above the probable range – approaching 2 m by 2100 and 5 m by 2150 under a very high greenhouse gas emission scenario (SSP5-8.5) (low confidence) – cannot be ruled out due to the great uncertainty involved in ice sheet processes .
With that as a prologue, here are your median (50% quantile) projections of the rate of future sea level rise in San Francisco after ten years for these seven different scenarios.
Figure 3. The UN IPCC predicted rates of sea level rise after decades. These are the median values.
(I would like to note that this reveals one of the great advantages of this type of analysis for your “experts” – almost regardless of what sea level will do in the future, they can truthfully say, “Look, that’s what we projected!” But I digress …)
However, there is a deeper and much more serious problem. To emphasize, here are the four least extreme scenarios, 1.9 through 7.0.
Figure 4. As in Figure 3, but for the four least extreme scenarios. Again, these are the median values.
I am sure you can see the problem. In their “expert judgment” of the model results, the median result (50% quantile) of the models for the sea level rise in San Francisco for the current decade is 4 mm per year… you say what? Has it been half for 170 years and will this decade suddenly double?
Now, right now, we are 2 years in the decade of the 2020s … for the entire decade at an average of 4mm per year the rate should start to accelerate today and continue to accelerate to the point where it is about 7, 5 mm per. reaches year until 2029. Only then would the decade average 4 mm per year.
It gets worse. The high estimates of sea level rise (the 95% quantile) give San Francisco rates of rise of 6.4 to 11.6 mm per year … for the current decade.
Sorry, but this is not science in any way. This is a joke. There is no way on earth that in the 2020s the average sea level rise in San Francisco will be either 4mm per year or 8mm per year.
Remember that this is the result of “a formal, calibrated method of combining quantified expert assessments that includes all potential processes”. Isn’t that why you’re feeling completely warm and fuzzy about the rest of the UN IPCC’s AR6 claims?
So think of that monumental sea-level rise madness when someone points out that “the IPCC is saying something about the future” … spit.
My best to all – even in these turbulent, hectic times, life is good.
My immutable request: Please quote the exact words you are referring to in your comment. It avoids endless misunderstandings.
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