"The author is correct that historically, only the Barley mattered. Where he is slightly off is that reliance on the equinox was entirely post-dispersion. It was there from about 200 BCE at the time when the Pharisees came to power. The Talmud shows that there was reliance also on the equinox and the ripening of fruit trees as additional witnesses. The Talmud was redacted in the 3rd century CE, but to assume that its traditions all came from that era is not possible.
Torah simply says that the "month where there is Abib" is to be the first month of the year. It is not calling the month by the name Abib, but in Hebrew stating "the Chodesh where Abib exists".
Abib is a particular stage of ripening of the barley. When it is Abib, it will be harvest ready in 2 weeks time, thus there can only be ONE Chodesh per year where there is Abib barley in Israel. First Fruits can have slightly unripe barley, as Torah provides for grain roasted by fire, which is what you do with slightly unripe barley.
Nehemia has a good article on this at: http://karaite-korner.org/abib.shtml
There are a number of other articles related to this there also.
For me, it is a simple matter of pashat Torah. When there is abib at the chodesh, we are told to have the first month. A fairly simple Mitswot. Equinox is totally missing in Torah in this regard, since the focus was purely on agriculture.
The argument about the moon, stars, and sun having to be involved is misplaced. Nowhere in Torah is the FIRST Rosh Chodesh called a Moed, other than its place as a Rosh Chodesh - and we don't try to argue that the sun and stars are involved in any OTHER Chodesh, so why this one??
As to the diaspora argument, this is most likely what led the last Sanhedrin to have calculated reliance on the equinox in the first place. In the same way, the Sabbath and every Chodesh was lost too - to make it 'easy' to follow anywhere.
The year is the one Torah calendration which is completely focused on the land of Israel. The barley THERE and there ALONE is the determiner - "when you are come into the land..." - since First Fruits can only be of local Israeli crop.
Why assume that Noah must have had the same new year we do??? If that was the case, there would be no need for Torah to command the first month of the year at the time of the Exodus, and to clearly link it to the barley crop. Noah MIGHT have had the same new year, but such can not logically argue against a direct commandment in Torah. Noah was also a vegetarian until after the flood ;-)
Nope, clearly no 13th month this year [2010]- the barley in Israel was advanced Abib at the last Chodesh.
Hope that helps to simplify it a bit :-)
Also see:
http://karaite-korner.org/abib_faq.shtml and http://karaite-korner.org/abib_and_tekufah.shtml
David