In email a friend had asked if anything ‘interesting’ had happened 5200 years ago, and that sent me looking at some records. (The most interesting thing is the 5.9 Kilo Year event (Bond Event 4), but that’s not exactly 5.2 kyr ago…) I ended up looking at this chart.
The most interesting thing about it, to my eye, is the clear “pop and drop” character of the exit from the last Ice Age and our present very slow decent into the next one.
The article attached to the graph has a lot of mealy mouthed supplication to the Climate Religion of Global Warming, with the obligatory mutterings about how there must be something wrong with the proxies and it could not possibly have been that much warmer globally, really, in the past. But in its defense, it does say that the present warming rate might have happened in the past as the proxies all average many decades (centuries?) and that mutes short duration peaks. Then they emphasize a ‘hockey blade’ rise in recent temperatures. One that I think I’ve pretty well shown is a measuring artifact from bad thermometer choices (along with the typical hockey stick grafting data sets issues)
So you will notice a “2004 ->” arrow on the graph to show how it really is suddenly hotter now than it has ever been before. Yet we know it was warmer in those past times as the ice was missing from the North Pole about 7 k years BP and there are glaciers receding in the Andes in Peru where we are finding well preserved plant remains under them dating from about 5.4 k yrs BP (both slightly warm times on the graph above, and followed by cold excursions). We also know that Utze, the Ice Man, fell in a Swiss mountain pass about 5 k yrs BP and was buried in falling snow, to stay buried until now. So that places the present as being ‘close’ to about 5 k yrs BP, but not exceptionally warmer as the glaciers are not yet gone and the plants have not yet reclaimed those locations.
So first off, to answer the question about 5.2 k yrs BP: It looks like it was cold leading into it, got a little warm, then got a little cold, and eventually resumed the downward march. The most notable thing about it being the population move into the Nile valley and the start of the Egyptian period as that was where the cooling period had left water and life in North Africa.
Second, I’m pretty sure the inset graph does a very good job of showing that the Mann (and other folks) “Hockey Stick” is clearly out of touch with reality. The ‘facts on the ground’ just do not support the idea that we are massively warmer than 7 k yrs BP nor 5.2 k yrs BP when the Sahara had cooled enough to become a terrible desert and folks moved to Egypt to start the pharaonic period of Egypt. ( Covered in an earlier posting about the Sahara Pump theory that discussed how the Sahara forms when it cools enough to stop the rains). The physics that we know and the geologic and human history that we know simply to not match against the assertion of it being warmer now, than then.
The necessary conclusion is that the present measurements are not indicative of the actual trend. Yes, I’m being charitable. In theory there could be a decade or so spike that is in keeping with patterns of the past and not long enough in duration to show in past records. In theory we could have a warming spike, similar to those seen in the past, taking us back to about the same hight (as some of the individual proxy colored lines show).
In reality, to the extent we’ve put any warming into the system, it’s been a very good thing. Each of those prior warm periods has been a time of growth of civilization, prosperity, ample food supply, and the advancement of human knowledge. Each of the cold excursions has been a time of political turmoil and collapse of civilization. In essence: Warm, is good. Cold is bad. And always has been. That is why the warm periods have names like “Roman Optimum” and “Medieval Optimum” and “Holocene Optimum” while the cold periods have names like “Iron Age Cold Period” or “Iron Age Pessimum” (Bond Event 2) and “Migration Era Pessimum” also know as “The Dark Ages Cold Period” (and Bond Event 1).
For those wondering about Bond Event 3, it is:
≈4,200 BP (Bond event 3) — correlates with the 4.2 kiloyear event (correlates also with the collapse of the Akkadian Empire and the end of the Egyptian Old Kingdom)
Another time of troubles with the collapse of civilizations…
Bond events are roughly every 1470 years. The last one ended in about 900 AD. It began in 540 AD, or about 1470 years ago. Though some folks put the start closer to 450 AD and Bond Events can have a century or so of leeway on each side of the start. I’m sure we’ve got nothing to worry about. It’s not like the sun is suddenly going to drop in output and go all quiet on us… Oh, wait, it has…
So what can we see in this graph? A long slow decent toward a cliff, the drop into the next Ice Age (due any time now, geologically speaking) and a potential mitigation, but one that is likely far smaller than the present hysteria indicates. And certainly nothing near those colored peaks of other past temperature proxy excursions. We also have the sporadic cold dips of “Bond Events” and other cold excursions from time to time.
In essence: Nothing very major is happening now, but things were pretty wild in the past. And we’ve luckily ended up in a minor “modern optimum” when things are pleasant, plants and animals grow well, and we are not under a mile of ice. Nor even in the depths of the Little Ice Age seen in the graph as those downward excursions of 200 or so years BP. The cold dips that were the lowest on that black average line in since 11,000 BP. If this is Global Warming, I’m all for it. And hope Bond Event Zero has a long cycle…
Some quotes from the Holocene article:
The main figure shows eight records of local temperature variability on multi-centennial scales throughout the course of the Holocene, and an average of these (thick dark line). (to 10000 BC-(from 0 — 12000 BP)) The records are plotted with respect to the mid 20th century average temperature, and the global average temperature in 2004 is indicated. An inset plot compares the most recent two millennia of the average to other recent reconstructions
Note that it says ‘recent reconstructions’ not ‘temperature record’. This leads me to believe this is based on the pretty well shown to be bogus tree ring Hockey Stick for the 2004 inset. The references given include Jones and Mann and have the look of a ‘tree ring with grafted on temperature series’ trick as used in the Mann reconstruction.
(orange 200-1995): P.D. Jones and M.E. Mann (2004). , Reviews of Geophysics, 42: RG2002. doi:10.1029/2003RG000143
(red-orange 1500-1980): S. Huang (2004). , Geophys. Res Lett., 31: L13205. doi:10.1029/2004GL019781
(red 1-1979): A. Moberg, D.M. Sonechkin, K. Holmgren, N.M. Datsenko and W. Karlén (2005). , Nature, 443: 613-617. doi:10.1038/nature03265
(thin black line 1856-2004): Instrumental global annual data set TaveGL2v : P.D. Jones and A. Moberg (2003). , Journal of Climate, 16: 206-223.
There are some notes on how the temperature construction was done:
To construct this plot, eight data sources (listed below) were selected on the basis of good temporal resolution (preferably ~100 years or less per data point) and coverage of the last 12 kyr. Six of the eight specifically reported temperature and were used as is. The other two reported unscaled temperature proxies and were scaled as described in Notes below. Each curve was smoothed by a Gaussian weighted filter to produce a history of the Holocene temperature variations at that site with approximately 300 year resolution (one exception, see notes). These smooth curves were adjusted to have the same mean over the interval 100-6000 years BP. The average of these curves was then constructed, and the alignment relative to modern day determined by comparing the average over the interval 250-1900 AD relative to the three short-term proxies shown in inset (for details on those plots, see: Image:2000 Year Temperature Comparison.png). Note that the short-term proxies are not at all used in constructing the average itself.
And I must give them some kudos for recognizing that it will be 150 years before we can know if the present really is an odd decade or two; or not… (I’ve bolded the interesting bits):
Because of the limitations of data sampling, each curve in the main plot was smoothed (see methods below) and consequently, this figure can not resolve temperature fluctuations faster than approximately 300 years. Further, while 2004 appears warmer than any other time in the long-term average, and hence might be a sign of global warming, it should also be noted that the 2004 measurement is from a single year (actually the fourth highest on record, see Image:Short Instrumental Temperature Record.png for comparison). It is impossible to know whether similarly large short-term temperature fluctuations may have occurred at other times, but are unresolved by the available resolution. The next 150 years will determine whether the long-term average centered on the present appears anomalous with respect to this plot.
My take on all this is that if we’ve managed to side step a new Ice Age Glaciation, that’s all for the good. If we’ve managed to move ourselves from a Little Ice Age to an Optimum, that’s all for the good. And if it takes 150 years to find out, well, I’m fine with that. Call me in 100 years and we’ll see if we need to do something about the climate then…