ANALYSIS OF THE ABRIDGED TIMELINE AND CLIMATE DATA

            The historic events of the abridged timeline are graphed with the master chronology (Figure 6.3).  There are definite groupings of events around AD 250s to 270s and the 360s to 380s when examining the abridged timeline illustrating the first year of historic events.  The grouping is much more distinctive and simplified than in the annotated timeline with all historic events included (Figure 6.1).  This abridged timeline is a way of filtering “noise” in a climate-migration study.  In this manner it becomes possible to evaluate the historic events and the

changes in the tree ring chronology simultaneously.  It is hoped that a clearer image of these ancient events will be presented by utilizing this methodology of filtering out continuations of long events and non-climate influenced events.

            The number of years that were determined to have an historical event that was not directly tied to a previous event or direct political action is 46 (Figure 6.4a).  There is a 201-year span in this study (AD 200 – 400).  This means that about 23% of the second and third centuries display initial movement phases or new invasions.  93.4% of these years occur in either a period below the mean or a period above the mean, leaving the remaining 6.6% in average periods or in a period with no predominant climate signal.

In the third century AD, 25 years have pertinent historic events that are included in the abridged timeline.  In the fourth century AD, 21 years have pertinent historic events that are included in the abridged timeline.  Of these 46 years under evaluation, only 16 years or 34.8% of the historical events occur in above mean years.  Thirty of the events occur in below mean years, which is 65.2% of all events in the 3^rd and 4^th centuries AD (Figure 6.4a).  These data suggest that historic events started in years below the mean than in years above the mean in 3^rd and 4^th century Germania.  These data appear even more informative when evaluating the state (above or below mean) of the period in which these historic events occur.  The number of events that occur in periods below the mean is 35 or 81.4%, leaving only 8 or 18.6% occurring in periods above the mean (Figure 6.4b).  These numbers support the hypothesis of a direct coincidence between documented Germanic tribe activity and periods below the mean growth rate displayed in the tree ring record.

            If the centuries are evaluated individually, the 25 third century events coincide with above mean years about 44%, and 56% of the years coincide below mean years (Figure 6.5a).  These numbers do not seem too significant if only the conditions of the years are examined.  If the periods in which these events occurred are evaluated, only 26.1% of these events occur in a period above the mean, while the remaining 73.9% occur in periods that are below the mean growth rate in the tree ring chronology (Figure 6.5b).  This is explainable because the continuation and origin of new attacks after the long drought period of AD 214-232 that were in above mean years but in a period below the mean.

            Of the 21 historical event years in the fourth century AD, only 23.8% occur in years that are above mean tree ring growth and the remaining 76.2% occur in years that are below the mean (Figure 6.6a).  Just 10% of these first year historic events are in a period that is above the mean, while 90% of these events are in a period that is below the mean tree ring growth rate (Figure 6.6b).  These events of the 4^th century show a stronger coincidence with periods and years that are below the mean growth rate of the standardized master tree ring chronology.

            This statistical approach to identifying migration and invasion events with the tree-ring chronology is simply a method of evaluating the data from a subjective angle that should be reproducible.  If all events were included in the annotated timeline, the criteria for eliminating the events should yield the abridged timeline.  In any case, if there are other events are uncovered and new documents found and added to the timelines, the percentages will most likely not deviate too greatly from this overview of the 3^rd and 4^th centuries AD Germania.  This gives a strong implication that the historical events of the agrarian-based Germanic tribes started in periods that were below the mean growth rate of the tree ring chronologies.  Especially in the 3^rd century AD, these movements did continue into periods that were above the mean growth rate and may have further fueled these attacks due to the increase in agricultural sustainability (Figure 6.7).