Climate activist "Rocky" says:
       "We’ve already experienced 1C of warming Dave."
https://twitter.com/Rocky35418823/status/1578520519648759808

I presume he means 1°C of human-caused global warming.

That's a plausible number, albeit near the high end of plausibility.
So, let's start with that assumption.

We've already had CO2 forcing = about 58% of a "doubling" of CO2;
here's how you calculate it:
log2(419/280) = 0.5815
https://www.google.com/search?q=log2(419%2F280)+%3D

The usual estimate is that about 2/3 of anthropogenic warming is from CO2.
Myhre (1998) estimated 58%.

Let's use the 2/3 figure. Then if, as Rocky says, we've had 1°C of anthropogenic
warming, that means only 2/3 °C is from CO2.

If 58% of a doubling yields 2/3 °C, that means "practical sensitivity" S is:
(2/3)/0.58 = 1.15°C/doubling.

So, if:

"Practical sensitivity" S is 1.15°C (as we just calculated)

and ECS = 1.5 × TCR (a typical estimate)

and S is midway between ECS and TCR
(because TCR is much "faster" than reality, and ECS is much "slower" than reality.)
Note: definitions for TCR and ECS climate sensitivity can be found here:
https://sealevel.info/glossary.html#sensit

Then we have two equations in two unknowns (TCR and ECS):

S = (ECS + TCR) / 2
ECS = 1.5 × TCR

Solving:

S = (2.5 × TCR) / 2 = 1.25 × TCR

TCR = S / 1.25
         = 1.15 / 1.25
         = 0.92°C

ECS = 1.5 × TCR
         = 1.5 × (S / 1.25)
         = 1.2 × S 
         = 1.2 × 1.15
         = 1.38°C

Each of those are about half of the IPCC's AR6 central estimates (1.8°C and 3.0°C, respectively).

∴ The IPCC's climate sensitivity estimates are incompatible with observed warming.