Niether.
The climate of any place on the western edge of a continent , and located approximately between latitudes 30 and 40 degrees, is determined by the Sub Tropical High Pressure Cells.
In years of higher rainfall (i.e what farmers would call a "good" year) agriculture has often been attempted in the more marginal areas of these zones (as was the case where I am currently working in South Australia). However, once the more normal rainfall pattern resumes, these efforts quickly fail - leaving behind evidence that could be interpreted as "the climate was once different."
The supernatural played little part in all this - and human activity not much more!
Bill.