The Piora Oscillation is a term given to the short duration cold period that marked the boundary between the warmer and wetter Atlantic Climate Regime and the Sub-Boreal Climate Regime we are in today. The strongest evidence of this oscillation comes from the Val Piora (Piora Valley) in Switzerland where there is evidence of the glacier increasing in size during this period.
There had been a gradual decrease in the annual rainfall totals in North Africa and the Arabian Peninsula since 7000 years before present (BP). Climatologists attribute this to the precession of the axis of rotation of the Earth. (Think about how a spinning top moves in a small circle.) This precession has a 26,000 year cycle. The climate maps of this region demonstrate this gradual drying out of the Sahara Desert and the Arabian Peninsula:
7000 BP:
5000BP
Today
The loss of the savanna regions drove the nomadic hunters and herdsmen to the major river valleys where the first great civilizations were born. (Nile, Tigris & Euphrates, Indus, and Yellow Rivers)
The Piora Oscillation occurred at the beginning of the first great civilization in each of these river valleys. The cause of the Oscillation has not been determined, but one of the theories put forth is a short duration decline in solar output.
I have seized this explanation in my novel as both the cause of the Piora Oscillation and the reason the Star Liner Atlantis visited the Sol system. I identified it as “The Andromeda Resonance” and have tied its cycle to the Long Count Calendar.
From "The Star People Arrive":
Imhotep was nervous. I saw him look around the pool room and then he started to speak in hushed tones. “I overheard your argument yesterday with the Captain. I haven’t heard you that angry since you confronted that fool who ordered that ill-advised attack in the Rigel system battle. What was that all about?”
“You’re right! I was more than just a little angry, I was furious! Imhotep, Captain Kratos has consented to Praetorian Zeus’ request to divert to the Sol system. Zeus insisted that we divert to the Sol system in order to experience the effect of the gravitational/ space-time distortion wave during the Sol system’s transition through the Andromeda resonance. I reminded the Captain that system is in a quarantined sector, but that didn’t seem to matter to him.”
....
Later that night:
After the first round of drinks, Azspit asked Jushur “what’s so special about this backwater system. I thought this cruise is supposed to be a Wonders of the Galaxy Tour.”
“This system is about to transit through the Andromeda Resonance. Many people experience a physical rush from the gravity/space-time distortion wave a system encounters when it passes through the Resonance. The rush is greatest when they are near the star. It is also interesting to view the changes at the core of that star. We will be displaying Sol’s core scans on the monitors tonight during our fly-by.”
The woman to my left asked, “How long will the shows last tonight?”
Jushur didn’t know, so I spoke up. “We will come out of hyperspace-jump inside the orbit of the tenth planet in about an hour, and then we will transit through the system for about six hours.”
Isis looks at me. “Patrick, how do you know so much about this quadrant? You’ve said it is in a quarantined sector. Have you been here before?”
“Yes I have.”
.....
The effect on Sol:
The real work of the Council of Elders began the next day. I opened the morning session by a presentation of the data I had gathered about the reduced solar output. I warned them that even the predicted two percent decrease solar output would lead to a drop in average Terrene temperatures. I posted the climate change estimate I had developed using Phoenix’s computer.
“I have been told that the first killing frosts have been early this year. I believed we should expect a longer and harder winter followed by cooler temperatures next summer.”
Q’uq’umatz asked, “Papo, how long do you think the reduction in solar output will last?”
“I am not completely certain, but as far as I know, the space-time distortion affects a star’s magnetosphere. It should only last for one stellar maximum cycle. For the Sol system, that will be about eleven years.”
.....