[aruanan]

The snippets I posted indicated that the calibrations from independent sources show that the error was in the opposite direction. Items dated prior to calibration for the changes in C-14 rates of absorption are much too young.

I'm not talking about rates of absorption but rates of production versus rates of decay. If the rate of production has not (for whatever reason) reached equilibrium with rate of decay, then something from an earlier period will have a smaller initial amount of C14 than expected. This will make it look a lot older than it actually is. For that matter, if there were a time with a greater rate of C14 production than seen at present, a plant (or animal via the plants it has eaten, etc.) will have a larger than expected initial complement of C14 and appear much younger than it actually is. There are also plants which selectively retain different ratios of carbon isotopes (corn and some other grasses). Animals that eat more of these plants have a different ratio of C14 to C13 than animals that do not and so have an different apparent C14 age.

[Jolly Rodgers]

The issues you raise are valid, and they are the reason why the C-14 dating performed in the 50's and 60's has been discarded. However, the process of calibration from independent sources accounts for the variability and makes more recent dating trustworthy.