Jy blaai in die argief vir real science.

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.