Jy blaai in die argief vir climate change.

Climate Change: The debate in Geobulletin (continued)

31/01/2013 in Uncategorized

Climate change – The Short Story (William McClenney) (continued)

Between 6,000 and 7,000 years ago, a period known to geologists and paleoclimatologists as the Holocene Climate Optimum, sea levels peaked between 1.5 to a maximum-found 8 meters higher than today (average in the literature seems to be about 2.5-3.5 meters), and during the Eemian Optimum some 20 meters higher than today. During the seven post MPT ice ages sea levels dropped some 100 or more meters below present, the water tied up in the miles-thick ice sheets that have spread in North America as far south as Kansas. These are just some of the facts of the abrupt climate changes which we, as Homo sapiens, have experienced.

General Circulation Models, of which the IPCC references 20+, have yet to produce a single known abrupt paleoclimate change fed with the proxy data. The latest GCM models produce predictions based on a variety of input data and complex equations which few of us understand. But for all the complexity and investment, they are still only predictions.

Belief in, and acting as a result of, such predictions has opened up what may be the first chapter of faith-based science.The astonishing enormity of natural climate change provides a harrowing appreciation of massive sea level ‘noise’ that can range to over 400 feet (with a beat of lesser, rank-and-file swings, think D-O oscillations) and temperature shifts that lord over all future fantasies you have yet heard.

What might be quite ironic is that if GHG predicted global warming is in fact real, and, at half of a precessional cycle, we are near to the cliff of the next natural shift to an ice age, we may find ourselves needing to generate as much GHGs as possible to ease our transition into the next ice age. So as I said at the beginning, doing something about climate change is not necessarily a bad thing. Doing the right thing might prove to be quite another. The ice ages and associated interglacials are well known to be paced by the eccentricity, obliquity and precession cycles in earth’s rickety orbit. These we will do nothing about. D-O oscillations show strong evidence of being tied to the 1,500 year cycle of solar output,something we cannot change.

Be ever thoughtful of both facts and predictions before leaping to a conclusion. It was in fact a LEAP that terminated the last interglacial, the cold Late Eemian Aridity Pulse which lasted 468 years and ended with a precipitous drop into the Wisconsin ice age. And yes, we were indeed there. We had been on the stage as our stone-age selves about the same length of time during that interglacial that our civilization have been during this one.

 

Climate Change: The debate in Geobulletin (continued)

30/01/2013 in Uncategorized

Climate change – The Short Story (William McClenney) (continued)

The climb out from the Last Glacial Maximum of the Wisconsin ice age (called Termination 1with sea level bottoming out about 121 meters below present) into the Holocene is studded with the Younger Dryas, a 1,300 year near instantaneous return to ice age conditions. “Briefly, the data indicate that cooling into the Younger Dryas occurred in a few prominent decade(s)-long steps, whereas warming at the end of it occurred primarily in one especially large step of about 8 degrees C in about 10 years and was accompanied by a doubling of snow accumulation in 3 years; most of the accumulation-rate change occurred in 1 year (National Research Council,2002)”. Far more suddenly we came out of it: “Taylor et al (1997) found that most of the change in most indicators occurred in one step over about 5 years at the end of the Younger Dryas, although additional steps of similar length but much smaller magnitude preceded and followed the main step, spanning a total of about 50 years (NRC,2002)”.

Termination 1 went into top-fuel, carbon-free overdrive with what is referred to as melt water pulse 1a (mwp-1a) centered at about 14,680 years ago which resulted in a 24 meter rise in sea level believed to have occurred at the rate of 4.5 cm a year. It was followed around 12,260 years ago by mwp–1b with a 28 meter rise nearer 5cm a year. Recent model results predict that sea level is currently rising at 32cm/100 years. If we take the low-end of the natural ‘noise’ clocked at 4.5 cm/yr (or 450 cm/century) we will have to kick in some serious turbos (carbos?) to net one and a half orders of magnitude boost if we hope to trump mother nature’s bottom bracket.

Another variable worth devoting some cpu time to is just how astonishingly well the fourth cycle of eccentricity matches up with hominid evolution.

“An examination of the fossil record indicates that the key junctures in hominid evolution reported nowadays at 2.6, 1.8 and 1 Ma coincide with 400 kyr eccentricity maxima, which suggests that periods with enhanced speciation and extinction events coincided with periods of maximum climate variability on high moisture levels.” state Trauth et al (2009) in Quaternary Science Reviews. There is just nothing quite like having such a natural fly land in your climate change soup. As it turns out, periods of wet maximum climate variability (in modern lingo, global warming/global cooling correctly re-branded as climate change), cook-up the larger braincases. We went from 500-550 cc braincases 2.8 mya to the average of about 2,500 cc today in the most rapid encephalization of any mammal in the fossil record.

Climate Change: The debate in Geobulletin (continued)

28/01/2013 in Uncategorized

Climate Change – The Short Story ( William McClenney). (continued)

A reconstruction from fossil algae in sediments from Drought Lake in North Dakota of the past 2,000 years found that dry conditions were far and away the rule in the High Plains, with the Dust Bowl conditions of the 1930’s one of the lesser dry spikes found in the record. Half of the warming that brought us out of the last ice age (the Wisconsin) occurred in less than a decade. There were 24 Dansgaard-Oescher oscillations between this interglacial, the Holocene, the interglacial in which all of human civilization has occurred, and the last one, the Eemian, in which the first fossils of Homo sapiens are to be found. D-O oscillations average 1,500 years, and have the same characteristic sawtooth temperature shape that the major ice-age/interglacials do, a sudden, dramatic, reliable, and seemingly unavoidable rise of between 8-10 degrees C on average, taking from only a few years to mere decades, then a shaky period of warmth (less than interglacial warmth), followed by a steep descent back into ice age conditions. Each D-O oscillation is slightly colder than the previous one through seven oscillations, then there is an especially long, cold interval, followed by an especially large, abrupt warming up to 16 degrees C (a Bond cycle). During the latter part of the especially cold intervals, armadas of icebergs are rafted across the North Atlantic(Heinrich events), their passage recorded reliably by the deep ocean sediment cores which capture the telltale signature of these events in dropstones and detritus melted out of them.

We know with absolute certainty that these events happen, with evidence of D-O oscillations extending back some 680 million years. We do not know, yet, precisely what causes them. What we do know is that the past six interglacials (dating back to Mid Pleistocene Transition) have lasted roughly half of a precessional cycle, or currently 11,500 years, which just happens to be the present age of the Holocene. What we know is that N65 latitude insolation values are very close now to what they were at the close of the Eemian. What we also know is that GHGs (Green House Gases), like us, seem to have played only a spectator role to all of these alarming natural transitions, with temperature changes leading GHG concentrations by a considerable margin of time (800-1,300 years). What we do not know is if the reverse could occur, anthropogenic sourced GHGs triggering a climate change event, for perhaps the first time ever. What we do know is that earth’s climate is bimodal, cold 90% and warm 10% of the time for the past million years or so, with the transition times (such as at the end of an interglacial) well known from proxy records to be quite sensitive to forcings we do not yet understand, and the forcings we have identified seemingly incapable of producing the responses we see in the paleoclimate record. Including the recent paleoclimate record.

(to be continued)

Climate Change: The debate in Geobulletin (resumed)

28/01/2013 in Uncategorized

Anna het oor die naweek in die Kaap gekuier en is op pad terug op die Interkaap-bus, trek nou seker al verby Springbok. Soos ‘n groot hond is ek geneig om so vas te slaap dat ‘n wekker of selfoon-oproep my nie sommer sal steur nie. Terwyl ek nou wakker is is dit ‘n goeie geleentheid om te blog, terwyl normale mense nog slaap.

Ek het in ‘n reeks poste berig oor ‘n debat in die “Geobulletin”, kwartaalblad van die Geologiese Vereniging van S.A., oor klimaatsverandering. Dit het in die Desember-uitgawe begin met ‘n brief deur Rose Prevec wat meen “deniers” hoort nie in die debat nie. In die Maart-uitgawe het John Trusswell (skrywer van universiteitshandboeke oor geologie) en ek (word genoem in “A Century of Geological Endeavour in Southern Africa, 1895-1995”), haar standpunt aangeval. Sy het repliek gelewer in die Junie-uitgawe, waarop my en John Trusswell se replieke in September geplaas is. In September was daar ook ‘n bydrae deur emeritus-professor John Geissman (VSA) en ‘n verwysing deur die redakteur van “Geobulletin” -albei glo in AGW. In die Desember 2012-uitgawe lees die laaste paragraaf in ‘from the editor’s desk’ soos volg:

“The ongoing saga of the threat that climate change poses to our earthly paradise is continued in another letter from Deon le Roux and in an article from William McClenney. Both contributions question the role of carbon dioxide as a cause of climate change, and are rather technical. However they highlight the dangers of thinking that the causes of climate change are easily understood.”

Ek wil lesers nie verveel met holrug-geryde argumente oor die aangeleentheid nie. William McClenney, “a California Licensed Professional Geologist and Registered Environmental Assessor” se artikel verskaf egter data wat minder algemeen bekend is en word hier in aflewerings geplaas.

Climate Change – The Short Story

In some ways, I applaud the sense of urgency that accompanies the perceived need to do something to affect climate change. The need is there in more ways than you presently know. But the means could be another matter entirely.

The Akkadian Empire under Sargon (2,300-2,200 BC), mankind’s first empire ever, succumbed to climate change that happened rather suddenly. A 300 year long period of drought struck this nascent civilization and toppled what turned out to be only a 100 year empire. The Old Kingdom of Egypt and the Harappans of the Indus Valley suffered a similar fate 4.200 years ago, succumbing to an abrupt drought that ended those civilizations, with Egyptians “forced to commit unheard of atrocities such as eating their own children and violating the sacred sancity of their own dead (Fekri Hassan, 2001)”.  The Mayans had pretty much the same luck with three periods of extreme drought at 810, 860 and 910 AD. Sadly just two years after the last drought, which saw 95% of the Mayan population gone, wet years returned to the Yucatan.

(to be continued)