No, the dating is wrong. The claim of is a dust veil c. 540. The barbarians had already detached the Western provinces by the end of the 5th century--hence the 'Fall of Rome' with the decision by Zeno to let Odovacar administer Italy in his name rather than having a Western Augustus.
The book I have, Exodus To Arthur, by Mike Baillie has a chart that shows a downward curve that begins before 540AD. 540AD is just the bottom of the curve. Something was going on prior to that date. Maybe a yearly pounding of Tunguska type events for a number of years before the earth moved out of the comet dust/boulder path?