yet it happened fast enough to kill off entire thriving human civilizations as well
Evidence for this human extinction event?
What is the certainty that gas trapped in ice may or may not melt and escape and leave a residue of much lower levels than actual above sea levels would contain?
Do you have a credible publication from an atmospheric chemist or biogeochemist that shows this to be true? I sounds an awful lot like you made it up.
So when a core is taken, how is it determined that the aeraton effect that adds CO2 is accurately reflecting the build up in the air itself above the sea level?
It's not just "air" they're measuring:
"It is possible to discern past air temperatures from ice cores. This can be related directly to concentrations of carbon dioxide, methane and other greenhouse gasses preserved in the ice. Snow precipitation over Antarctica is made mostly of H216O molecules (99.7%). There are also rarer stable isotopes: H218 O (0.2%) and HD16 O (0.03%) (D is Deuterium, or 2 H)[9]. Isotopic concentrations are expressed in per mil δ units (δD and δ18 O) with respect to Vienna Standard Mean Ocean Water (V-SMOW). Past precipitation can be used to reconstruct past palaeoclimatic temperatures. δD and δ18 O is related to surface temperature at middle and high latitudes. The relationship is consistent and linear over Antarctica[9].
Snow falls over Antarctica and is slowly converted to ice. Stable isotopes of oxygen (Oxygen [16 O, 18 O] and hydrogen [D/H]) are trapped in the ice in ice cores. The stable isotopes are measured in ice through a mass spectrometer. Measuring changing concentrations of δD and δ18 O through time in layers through an ice core provides a detailed record of temperature change, going back hundreds of thousands of years."
Secondly, do you have a particular gas chromatograph study whose isotope methodology you'd like to critique? I don't think anyone in this or other threads will have much faith in your fish tank expertise guiding expert analysis of ice core data.
I have also read the studies that claim that the modeling of thermal feed back loops has been proven to be wromg (sic), the ionosphere allows heat to escape more than we thought and the projection models have not proven themselves to be accurate.
This is not true in the slightest.
That's why I asked you what other causes created other significant moments of climate change in history... or if you think CO2 is the only cause.
Other events did create other significant climatic perturbations that caused extinctions. That's why this one is so exceptional. Our forcing envelope is balanced net negative due to several long-term oscillations that have been well studied, and one of the only (and by far the most overwhelming) positive forcings is anthropogenic CO2, which just so happens to coincide nicely with an unexpected uptick in global average temperatures.