1/8.》 As it happens, I was part of that 2021 conversation, and I remember it. Zeke effectively accused Spencer of cherry-picking. That was untrue: Spencer used all of the available data. https://twitter.com/ncdave4life/status/1444435462165344261…

2/8.》 Here's a more recent comparison: https://www.heritage.org/environment/report/global-warming-observations-vs-climate-models…

3/8.》 And a discussion of it: https://www.drroyspencer.com/2024/01/new-article-on-climate-models-vs-observations/…

4/8.》 Here's a graph from it: https://www.heritage.org/sites/default/files/inline-images/BG-observed-warning-vs-climate-models-charts-page3_0.gif…

5/8.》 Most of the GCMs run way too hot -- and Jim Java and Zeke don't want to admit it, because they prioritize the political narrative ahead of the scientific facts. The bottom line is that the climate models are not fit for purpose.

6/8.》 In fact even @Zeke Hausfather Zeke's BEST data shows ECS sensitivity is much lower than most GCMs assume, though he'll never admit it. https://twitter.com/ncdave4life/status/1336701210468945923…

7/8.》 The CMIP6 GCMs have widely varying baked-in assumptions for ECS sensitivity. The high-end CMIP6 model (CanESM5) uses an estimate which is 208% higher than (i.e., 3.08×) the ECS estimate used by the low-end model (INM-CM4-8). (But "the science is settled," doncha know?)

8/8.》 The best way of estimating ECS is by comparing measured temperature change to the GHG level changes we've already seen. (The climate industry doesn't like that approach, because it inevitably results in ECS estimates at or below the low end of the range of ECS values assumed in the CMIP6 models.) Measured (already realized) warming reflects a "practical sensitivity" which is probably about halfway between TCR and ECS. If ECS = 1.5 × TCR (a common estimate), then TCR is probably 80% of the portion of realized/measured warming which is due to CO2, and ECS is about 1.5 × that (i.e., 120%). Here's how to calculate an estimate of ECS, based on measurements starting with preindustrial CO2 at about 280 ppmv: Step 1. Note that globally averaged temperature has risen about 1.2 ±0.2°C since the ("pre-industrial") Little Ice Age. Step 2. Note that if we assume it was ALL caused by human activity (which I doubt), at most 80% of it was due to the rise in CO2 (280 → 421 ppmv). Step 3. Calculate that we've had log2(421/280) = 59% of the "radiative forcing" that we'd get from a doubling of CO2. Step 4. Calculate that "practical sensitivity" = 1.2 × 0.8 / 0.59 = about 1.63°C/doubling. (If a portion of the warming since the "preindustrial" Little Ice Age was natural, as I suspect, then sensitivity was even less.) Step 5. Calculate that ECS (Equilibrium Sensitivity) is about 1.2× that, which makes it about 1.95°C/doubling. (You can also do calculations like these using a shorter time period, with similar results; be sure to use endpoints during ENSO-neutral conditions.) Conclusion: If the CO2 rise (from 280 to 421 ppmv) accounts for 80% of warming to date, and warming to date is about 1.20°C, and CO2 forcing to date is 59% of a full doubling (log2(421/280)), that makes ECS = about 1.95°C/doubling, and TCR about 2/3 of that. Note: Aerosol & particulate air pollution were reducing / masking warming until about 1980. Since then, air pollution abatement has been reducing the masking/cooling effects of aerosol & particulate pollution, which accounts for part of the rise in temperatures over the last 45 years. (The IMO 2020 low-sulfur shipping rules just reduced aerosol pollution again, quite significantly.)