We have just finished the “Modern Optimum”, IMHO, and are now at an end of that turn of the cycle.
There have been prior such turns. Some back in the times of ancient Egypt:
THE ROLE OF SEA LEVEL AND BAY INFILLING IN THE CLOSING OF AN ANCIENT EGYPTIAN HARBOR
Ground penetrating radar, sediment coring, malacological and foraminiferal studies, radiocarbon dates, and rheological models demonstrate that the wadi bed adjacent to the terrace was once an open, protected bay. The base of the corraline / conglomerate terrace consists of a narrow coral-beach rock platform (dated at ~3500 BP) presently buried by anthropogenic, eolian, and colluvial sediments. Ubiquitous medium-fine wadi sediments underlie and extend beyond the beach rock. Malachological analyses, foraminifera distributions, radiocarbon dates, and sedimentological data indicate that these sediments were deposited in a protected tidal lagoon receiving infrequent freshwater inputs. Wave-cut notches along the seaward shoreline confirm a site-specific rheological model for the northern the Red Sea that indicates a sea-level highstand (~1 m above present MHW) during or immediately prior to occupation. Late during the period of occupation, the lagoon began to close as equatorial siphoning forced a regional sea-level fall while at the same time, riverine discharge through the wadi processes were infilling the bay at rates on the order of .25 cm/year.
Notice that One Meter above present mean high water mark? So much for “unprecedented sea level”…
One was the Medieval Optimum. There is an interesting little graph of what temperatures have historically been ascribed to that time in this article:
That got me wondering…
What happened in that circa 1300 “fall from warmth” into a cold Little Ice Age? And given that our present temperatures are not as high now as they were then, what will this time be like? ( We can know temperatures were warmer then from many sources. From Roman villas built without heating in places that now need it – and with Romans having evidenced their abilities to build in heating and closed space; to the fact that several historic ports from that era are now landlocked, abandoned by a receding sea.
So what does history say about that time of change? That end of the last “unprecedented warming”?
Well, looking around is a bit sparse. Folks don’t write a lot during times of social collapse…
is offering a book for sale.
This paper focuses on the climatic transition between the Little Climatic Optimum (approximately AD 750–1300 or 1200-650 cal yr BP) and the Little Ice Age (approximately AD 1300–1800 or 650-150 cal yr BP) in the Pacific Islands. This transition was marked by rapid temperature and sea-level fall, and perhaps by sharply-increased precipitation associated with an increase in El Nino frequency.
Examples from throughout the Pacific Islands demonstrate the possible and/or likely effects of sea-level fall at this time on inland horticulture through water-table fall; on coral reefs and lagoons through the emergence of reef surfaces and the consequent reduction of nearshore water circulation; on the emergence of reef islets and the conversion of tidal inlets to brackish lakes. The effects of such changes on human lifestyles are explored.
Well, we’ve certainly got the sea level headed for a standstill, to be followed by a drop. We’ve also had the start of heavy rains globally. Sure sounds like the same pattern. I’d love to read more, but that would take buying the book and spending a few hours. Hours I don’t have right now.
Another view of the same event is available here:
Almost all paleoclimate records for the Pacific Basin show a period of warmer-than-present climate known as the “Holocene Climatic Optimum,” approximately 6000-3000 B.P. in the central tropical Pacific (Nunn 1999). This period marked a time of maximum opportunity for biota, warm temperatures, and higher sea level, which produced a greater range of habitat diversity than today. In most parts of the Pacific Basin, mean annual precipitation also appears to have been greater than today. Since the Holocene Climatic Optimum ended, this region has generally experienced cooling, sea-level fall and, in places, a fall in precipitation and loss of biodiversity attributable to climate change.
Owing to the imprecision of methods for calculating paleotemperature over short time periods, few such records for the Pacific span the past 1,200 years or so (Figure 1A). Of those that have been compiled, most show that temperatures reached close to modern levels around 750 and then rose slowly throughout the Medieval Climate Anomaly until around 1300. Around or shortly after this time, temperatures fell rapidly, reaching levels below their modern levels early in the Little Ice Age, or about 1450. Sea-level change has proved to be a useful proxy for temperature change during the past 1,200 years along tropical Pacific coasts. Evidence shows that sea levels rose slowly during the Medieval Climate Anomaly before falling as much as 135 centimeters (typically 70-80 centimeters) during the A.D. 1300 Event (Figure 1B). During the ensuing Little Ice Age, sea levels appear to have remained below their present levels before they began to rise again around A.D. 1800-1850. Although direct evidence is not widely available, it has been inferred that the A.D. 1300 Event was, compared with the preceding Medieval Climate Anomaly, a period of increased storminess (Bridgman 1983; Nunn and Britton 2001), marking an increased incidence of El Nino events (Figure 1C) and ushering in greater climate variability during the Little Ice Age (M. E. Mann and others 2005).
So we’ve not gotten back to as warm as it was during that Egyptian time, 4000 BC to 1000 BC; and we’ve had a cold plunge from an intermediate level warm period, and not quite recovered all the way from it… And not it looks like we are about to enter the next leg down, given the present solar funk and rapid global cooling with excessive rains. But how fast?
Only a few studies allow one to deduce the timing and the magnitude of temperature fall during the A.D. 1300 Event. Dendrochronological investigations in southern Alaska show a multidecadal warm interval centered on 1300 and a corresponding cool interval centered on 1400 (Barclay, Wiles, and Calkin 1999). In the Columbia Icefield of western Canada, similar research showed a rapid temperature fall of around 1.2[degrees]C beginning around 1290 (Luckman and others 1997). Depletion of [.sup.18.O] during the A.D. 1300 Event found in ice cores from Quelccaya in the Peruvian Andes shows that this transition was very rapid there, occurring about 1380 within a few decades (Thompson and others 2003). In northern Patagonia the event began around 1250 and reached a temperature minimum around 1340 (Villalba 1990). In China’s Henan Province temperature fall during the event, which began around 1264, was at least 0.9-1.0[degrees]C (Zhang 1994). In a nearby area the event lasted approximately a century, between a time of maximum dryness about 1260 and maximum coldness about 1470 (Chu and others 2002). Analysis of phenological data from the Huanghe and Yangtze Valleys reveal rapid…
A bit scattered in time of onset (perhaps errors, perhaps it just hits different places over time as the global process unwinds. It would be worth it to make a time line of those places and watch for parallels now.) But fairly rapit in each place as it hits. And accompanied by excessive rains as the hydrological cycle pumps heat to the stratosphere and off the planet, then the water condenses falling as snow, hail, rain, …
Another link was more interesting, but hard to figure out how to give attribution. Connection to the top level domain gives a ‘page not found’, so I don’t know what the site is. Yet their description of the time is compelling:
CRISIS, 1300 AD – 1350 AD
Poor harvests had already brought hardship by the 1290s but there were even more bad years at the beginning of the new century and in a disastrous series of wet summers in 1315, 1316 and 1317 caused a famine. At least half a million people died; and land sales on an unprecedented scale combined with a crime wave, are clear evidence of social distress. In some places the population recovered after the Great Famine but numbers usually stagnated or declined. By 1340 much land in the midlands lay uncultivated and reclaimed wetlands on the south and east coasts were being invaded by the sea. In 1348 – 1349 the Black Death killed about half of the population. These were not just a series of unfortunate accidents caused by bad weather and the arrival of a new bacteria. Growth was ending before the disasters – land was no longer available on a large scale and after reaching a peak in 1300 AD, the volume of trade began to shrink. New towns and markets were no longer being founded. When the famine came it struck an already undernourished population. Prosperous, confident societies recover from natural disasters. The crises of the 14th Century exposed the principle weakness of Medieval development – it had left millions of smallholders in the country and the laborers in the towns who could hope to earn no more than 30 shillings in a year and that was not enough to support a family. They could make ends meet in good years with wives and children contributing to their earnings but any large rise in the price of grain threatened their lives. Had the Black Death been a simple outbreak of disease, there would have been rapid recovery; instead the plague recurred in the 1360s and there seems to have been no sustained rise in births to replace the losses.
Various explanations have been offered for this reversal of fortunes. It is argued that the commercial growth which had sustained the expansion ended because the market was glutted: in other words, that society which could support an urban proportion of roughly 20% and no more, and that only a further rise in productivity could break the impasse; that was not forthcoming. Alternatively, it is suggested that the problem was associated with an over-extension of cultivation which had taken in poor land and had caused imbalances between pastoral and arable farming, to the detriment of grain crops deprived of fertilization. On the other hand, technical solutions could have been found for such problems and the recession was not confined to arable – it hit regions specializing in pastoral farming. Perhaps, in that case, the high level of rents prevented the peasants from escaping from the trap of low productivity. Or perhaps the heavy taxation from the 1290s added a last straw to the burden of rent. Or perhaps society had become too hierarchical with the urban and rural elites holding back more enterprising spirits. Or as a final possibility, could the aristocrats have served as unproductive role models, encouraging the rest of society to spend rather than invest?
It is hard to form a clear answer. It is a search for explanations of a complex social malaise which affected the whole of western Europe and which lasted for more than a century. The crisis must be compared in the complexity of its causes with the fall of the Roman Empire in the 5th Century.
Just so eerily similar to how one would describe our society today. Folks just getting by, with two earner families, and the rich not really caring other than to hold down the peasants. Spending rather than investing.
That same site goes on, with some jiggling of “back” buttons to find it, to this:
New labor laws attempted to peg wages at the pre-plague level and to force workers to accept contracts for employment. Specially appointed justices vigorously enforced the law in localities. On their manors lords held to the old rules, enforcing serfdom and resisting rent reductions. They actually increased the revenues for their courts putting a great deal of financial pressure on the reduced number of tenants. The poll taxes pf 1377 – 1380 insisted that everyone should pay a sum equal to a craftsman’s daily wage and when mass evasion of this tax was investigated in the summer of 1381 the people of the southeast rose in revolt.
So dramatic was the uprising, rightly called the ‘Great Revolt’, that those in authority thought that the lower classes had gone mad. But close examination of the reasoning behind the Revolt suggests that it had rational basis: it drew on ideas that went back centuries and also expressed the frustration of the tense 30 years that had followed the Black Death.
Very interesting times indeed…
It looks to me like we are in a pattern of “lower lows and lower highs”. Each rise, does not rise as far. Each dip, dips further. The cyclicality looks like it’s about a 1/2 Bond Event pace, but with full 1470 year stronger patterns too. Will this one be a ‘smaller one’ or a larger? Only time will tell…
I think we need to, collectively, brush up on our 1300 AD history. What worked, what did not. Which societies fell, which survived. What places had the worst of it, and which places had an OK time.
Perhaps even a bit of “how did the pattern move around the globe?”. If China was hit in 1264, but Patagonia in 1250, one could, perhaps, choose to be in Peru and areas near it where the ice cores show a time closer to 1380. A good 40 years after the ‘minimum’ in Patagonia. Perhaps a huddle at the equator for a generation is in order…
I also note that China has recently had some very bad droughts. And what did that article say?
“In China’s Henan Province temperature fall during the event, which began around 1264, was at least 0.9-1.0[degrees]C (Zhang 1994). In a nearby area the event lasted approximately a century, between a time of maximum dryness about 1260 and maximum coldness about 1470 (Chu and others 2002)
So it has floods and heavy rains in the Pacific (and Europe) at the onset, but droughts in China… then spends a century getting colder.
Update: 24 June 2011
Added this Carbon 14 graph from wiki.
As Pyromancer76 talks about it. Interesting that it shows a strong C14 correlation with known temperature cycles of history, very high C14 now, and we presently are having a warm period rather like during the MWP when C14 was also high. Looks like a much better fit to me than the CO2 thesis.