I am not sure what models you are referring to, and with respect to Egypt, but I will try to answer as best I can and hopefully it will cover your question.

Regarding tree rings, there are as far as I can recall, 4 long and continuous. The longest is the German chronology that extends back 12,410 years in total. This chronology is composed primarily of oaks, but far back it also contains Preboreal pines. The pine part of the chronology has had to be inserted into the master chronology by cross matching with the oak chronology. (see Friedrich et al. Radiocarbon 46, 1111-1122, 2004 [journals.uair.arizona.edu])

Then we have The "Irish oak chronology" AKA the Belfast chronology, which consists of primarily of Irish oaks, with some British oaks to bridge the gaps (and sometimes the gaps are interesting in themselves), extending back to around 7272 years. There is also the Swedish pine chronology which extends back a similar number of years (7400 or so). And we have Bristlecone pine, which goes back at least 5000 years (not sure if any work has been done to take it further back).

So when it comes to Radiocarbon dating, the calibration curve uses German and Irish Oak, as well as Bristle cone pine (at least the Northern Hemisphere curve does). So the radiocarbon calibration curve for the past roughly 5,000-7,000 years is well replicated. The main issue with radiocarbon dating is that the uncertainty in radiocarbon age, and hence the corresponding calendar age will increase the further back in time one goes, due to lower radiaoactivity of the sample (since most 14C will have decayed). This uncertainty would arise from low signal to noise. With counting statistics the uncertainty is given by +/- the square root of the count. So for example, if you counted 100 decays in a minute, the uncertainty would be +/- 10, i.e. a 10% error. If you counted 10,000 in a minute, the uncertainty would be +/- 100, i.e. a 1% error. So most accurate results come from large sample size, long integration times, and young samples (i.e. more decays per minute). This broadly simplistic of course, and other experimental factors come into play for a dating.

Another factor that can come into play is the shape of the calibration curve itself. The calibration curve at fine resolution has many fluctuations due to fluctuating cosmic ray rates, as well as dependence of the carbon reservoir, and CO2 out gassing etc. This can cause enrichment or depletion of the concentration of radiocarbon in the atmosphere (and hence biosphere). This link (<[books.google.co.uk]; page 110)shows an example of the radiocarbon calibration curve in the 16-17th century BC. Because it is essentially flat, then even if you had a sample of exactly known calendar age say 1628, then its radiocarbon age could not be interpreted better than between 1680 and 1530 BC. In other cases the radiocarbon curve is not so flat, and it is here that high precision wiggle matching can give precise dates to within +/-10-20 years.

So for dating ancient Egypt it can be useful but it depends upon the age of the sample and where this corresponds to the calibration curve. As you can see the dating for 16th-17th centuries can be very difficult and inaccurate (though some success has been met with dating a tree buried by Thera ash deposits to between 1627 and 1600 using the wiggle matching.

Jonny


The path to good scholarship is paved with imagined patterns. - David M Raup