From this WUWT thread, Gale Combs comments:
….. analyzed Egyptian records of annual Nile water levels collected between 622 and 1470 A.D. at Rawdah Island in Cairo. These records were then compared to another well-documented human record from the same time period: observations of the number of auroras reported per decade in the Northern Hemisphere….
“Since the time of the pharaohs, the water levels of the Nile were accurately measured, since they were critically important for agriculture and the preservation of temples in Egypt,” she said. “These records are highly accurate and were obtained directly, making them a rare and unique resource for climatologists to peer back in time.”
A similarly accurate record exists for auroral activity during the same time period in northern Europe and the Far East. People there routinely and carefully observed and recorded auroral activity, because auroras were believed to portend future disasters, such as droughts and the deaths of kings…
The researchers found some clear links between the sun’s activity and climate variations. The Nile water levels and aurora records had two somewhat regularly occurring variations in common – one with a period of about 88 years and the second with a period of about 200 years.
“The Nile River provides drainage for approximately 10 percent of the African continent. Its two main sources – Lake Tana in Ethiopia and Lake Victoria in Tanzania, Uganda and Kenya – are in equatorial Africa….
The authors suggest that variations in the sun’s ultraviolet energy cause adjustments in a climate pattern called the Northern Annular Mode, which affects climate in the atmosphere of the Northern Hemisphere during the winter. At sea level, this mode becomes the North Atlantic Oscillation, a large-scale seesaw in atmospheric mass that affects how air circulates over the Atlantic Ocean. During periods of high solar activity, the North Atlantic Oscillation’s influence extends to the Indian Ocean. These adjustments may affect the distribution of air temperatures, which subsequently influence air circulation and rainfall at the Nile River’s sources in eastern equatorial Africa. When solar activity is high, conditions are drier, and when it is low, conditions are wetter….
The abstract to the actual paper Title: Is solar variability reflected in the Nile River?
There is also Chiefio’s Of Time and Temperatures looking at ~ 1500 yr bond events and the demise of civilizations.
The Physical Evidence of Earth’s Unstoppable 1,500-Year Climate Cycle by S. Fred Singer and Dennis T. Avery
….It has long been accepted that the Earth has experienced climate cycles, most notably the 90,000-year Ice Age cycles. But in the past 20 years or so, modern science has discovered evidence that within those broad Ice Age cycles, the Earth also experiences 1,500-year warming-cooling cycles. The Earth has been in the Modern Warming portion of the current cycle since about 1850, following a Little Ice Age from about 1300 to 1850. It appears likely that warming will continue for some time into the future, perhaps 200 years or more, regardless of human activity. [This is where Chiefio disagrees]
Evidence of the global nature of the 1,500-year climate cycles includes very long-term proxies for temperature change — ice cores, seabed and lake sediments, and fossils of pollen grains and tiny sea creatures. There are also shorter-term proxies — cave stalagmites, tree rings from trees both living and buried, boreholes and a wide variety of other temperature proxies.
Scientists got the first unequivocal evidence of a continuing moderate natural climate cycle in the 1980s, when Willi Dansgaard of Denmark and Hans Oeschger of Switzerland first saw two mile-long ice cores from Greenland representing 250,000 years of Earth’s frozen, layered climate history. From their initial examination, Dansgaard and Oeschger estimated the smaller temperature cycles at 2,550 years. Subsequent research shortened the estimated length of the cycles to 1,500 years (plus or minus 500 years).
Dansgaard- Oeschger oscillations or warm events during glaciation known as interstadials also occur at ~ 1500 yr intervals.
On the 1470-year pacing of Dansgaard-Oeschger warm events by Michael Schulz
The oxygen isotope record from the Greenland Ice Sheet Project 2 (GISP2) ice core was reanalyzed in the frequency and time domains. The prominent 1470-year spectral peak, which has been associated with the occurrence of Dansgaard-Oeschger interstadial events, is solely caused by Dansgaard-Oeschger events 5, 6, and 7. This result emphasizes the nonstationary character of the oxygen isotope time series. Nevertheless, a fundamental pacing period of ∼1470 years seems to control the timing of the onset of the Dansgaard-Oeschger events…. During this interval the spacing of the Dansgaard-Oeschger onsets varied by ±20% around the fundamental 1470-year period and multiples thereof. The pacing seems unaffected by variations in the strength of North Atlantic Deep Water formation, suggesting that the thermohaline circulation was not the primary controlling factor of the pacing period.
Timing of abrupt climate change: A precise clock by Stefan Rahmstorf
Many paleoclimatic data reveal a approx. 1,500 year cyclicity of unknown origin. A crucial question is how stable and regular this cycle is. An analysis of the GISP2 ice core record from Greenland reveals that abrupt climate events appear to be paced by a 1,470-year cycle with a period that is probably stable to within a few percent; with 95% confidence the period is maintained to better than 12% over at least 23 cycles. This highly precise clock points to an origin outside the Earth system; oscillatory modes within the Earth system can be expected to be far more irregular in period.
Droughts are often associated with cooler temperatures since the energy is not there to drive evaporation cycle. Also as the Feynman paper indicated you see a shift in the jet streams à la Stephen Wilde.
A but further down the thread, Chiefio adds some flesh to Gale’s reference to him:
Best I’ve been able to figure it out, there was a large “rock fall from space” about 2200 BC / 2000 BC related to the Taurid Meteor / Comet Encke breakup. A LOAD of ancient cities and civilizations all “go poof” at the same time. (And it isn’t dated off pharaoh lists. Lots of ‘stuff in the ground’…)
Sadly, we don’t get to breathe a sigh of relief over this. The debris is subject to orbital resonance effects that concentrate a “lump” in the debris fields. Most of the mass is still up there. So we get pretty good Taurid meteor displays every year, but the mutual timing of earth intersection with the “lump” being where we are only comes around about once every 3000 years. (It’s a little more complicated in that there are really two major streams and two lumps with a couple of hundred years offset, so we get a double tap – part of why it is BOTH 2000 BC and 2200 BC…)
Separately, there is a 1500-1800 year Bond Event / DO event cycle that is most likely related to lunar resonance effects (but could have a cross relationship with the Taurids as both are “coordinated” by the same orbital resonance effects).
There is also some impact on a 180 or so year cycle from solar changes. These three things interact to cause much of the natural variation ( though on a longer term, changes of axial tilt and orbital circularity along with precession of the equinox, causes ice age glacials to come and go).
So where are we now? We’re on the edge of the Taurid stream and don’t get back to the middle until about 2300. The sun is in a ‘cool phase’ (‘sleepy sun’) but sans the added dust and stuff from a thick Taurid blanket may not have enough to make a full on Bond Event. So it’s a bit of a ‘dice roll’ for “this cycle”. Timing for “now” is pretty good on the 1470 year repeat, but sometimes it’s more of an 1800 year repeat – or 2300 A.D. ( The 1500 year cycle is an average of what looks like 2 nodes – one of which is 1800 or so years). But since we don’t know how much stuff is in the streams nor just how it is bunched up, the exact “when” of much bigger comet / meteor storms is a rough estimate…
So I think we’re “up for” a Bond Event “now”, or in 2300 A.D., depending on how much the Taurid contribution matters… But even if this time is a ‘skip beat’ to 2300 time, there are often periods of modest drought and famine on the 180 year cycle points when we get low solar contribution. It’s not very precise ( the data have lots of confounders, so some famine is caused by cold, but some by wars or political things). The Great Famine of 1315 A.D. lands on a low solar cycle… as do some famines with dates like 17 A.D. and 400 AD. But there are also some ‘misses’ so it’s not a great match.
One thing that is Very Clear when you start looking at history and weather together: Things Change all the time and far far more than we’ve seen in the last 100 years. Sometimes rapidly and dramatically. There’s a very thick dust layer in the sediments from Egypt to Iran for that 2000 BC event. It has onset in weeks to months, not years; then stays for decades… up to 200 years. Just as rapidly, the sediments go back to normal mud…
And this did not just happen once. There is a roughly 2000 year sequence of them ( the 8.2 Kilo Year Event, the 6.2 Kilo Year Event, this one in 2000 BC or 4000 Year Event B.Present, then the famine of 17 A.D. and / or the start of the Dark Ages in 540 AD. And if the 540 AD event was ‘the biggy’, then add 1500 to it and you get 2040 A.D. as the next one…
BTW, just prior to those major cold ‘dips’, there is typically a run up to a much warmer period… Heinrich Events being very strong examples ( if more rare as they show up during the Ice Age Glacials…) So everything about the present is perfectly normal. Including our pleasant very comfortable reasonably warm times. But it won’t last. We will have the inevitable turn back to cold again. Just like all the other times… The overall profile of the Holocene is a peak in temps about 8 ky ago, then a ‘wobbly down’ since. We get excited about the ‘wobbles’ (and right now the wobble is ‘up a little bit’ out of the Little Ice Age) but the overall trend is slowly downward into the next glacial. We’ve got about 2000 more years, max, to the start of persistent ice accumulation up north… Axis tilt and precession are already in the “cool off’ position and getting more so. It’s only a matter of time once that stage is reached.
But a tiny bit of geologic time ( 1 to 2 thousand years ) is an eternity for a politician, so ignored… Heck, even the 30 years of cooling from 1940 to 1970 was ‘almost forever’ and we had “new ice age coming’ scares then. Then we were in the other half cycle from 1970 to 2000 and had the Global Warming Scare. Now the PDO has swapped and the sun has gone sleepy and they are trying to mutate it to a “Climate Chaos” scare. It’s just a tiny little wiggle on a 1500 year wobble on an 8,000 year slide into a glacial…