I'm looking at this IAU WGCCRE Report: http://aa.usno.navy.mil/publications/reports/Archinaletal2011a.pdf
It gives expressions for Earth orientation relative to the International Celestial Reference Frame in terms of right ascension and declination of the north pole.
The numbers say that the declination of the Earth rotation axis starts from 90 degrees and decreases by 0.557 degrees every century:
δ0 = 90.00 − 0.557T
Which means that in about 16000 years (and 16000 years ago) Earth rotation axis will lay in ecliptic plane. It doesn't make any sense to me.
Is it because this model should be applied on short time scales only? I didn't find any information on the time range for which the model is adequate.
Update: my question is not about how Earth actually rotates, but about the model and how it should be used.