At http://wattsupwiththat.com/2013/06/02/multiple-intense-abrupt-late-pleis… … is a post by Dan Easterbrook, a geologist at Western Washington University (bellingham). There is nothing especially important about it, and it certainly isn't anything new. However, what it does is clarify in a very simple fashion what was going on at the end of the Ice Age, and the five thousand years following it, by using data from Alley (2000) and Cuffy and Chow (1997). It outlines the series of ups and downs in temperature in the Late Pleistocene – through the Oldest, the Older, and the Younger Dryas cooling periods and the Bolling and Alleroed warming periods, using graphics in Years BP. The scale of the fluctuations are plotted in clearest detail. Anyone thinking the Earth shifted at the Poles in a single event can see what else is involved – and it is a very complex story. For example, the Younger Dryas cooling was not just a single climatic event. Warming and cooling not only occurred before and after the Younger Dryas but there were significant temperature fluctuations within the Younger Dryas (platted as roughly a 1300 year period which is the general consensus). These fluctuations are not confined to Greenland ice cores and appear to be global as they recur in Antarctic ice cores and various mountain glaciers in Patagonia, Scandinavia, the Rockies, Russia, the European Alps, the New Zealand Alps, the Cascade Mountains, and even in Scotland and N Wales. Whatever caused the end of the Ice Age itself, roughly around 16,000 years ago, tends to be on the backburner – the Younger Dryas overshadows it. Perhaps the evidence is not so easy to come across – buried geology, a C14 plateau, the magnitude of the Oldest Dryas cooling event, are all contributing factors. Looking at Easterbrook's graphs one can see why the Younger Dryas has such a dominant position in Pleistocene research – there is plenty of enough here to keep scientists occupied.
Although the author is focussed on proving the poind modern co2 fed warming is insignificant in comparison with what was happening in the natural world in the Late Pleistocene, the data is essential to understand if catastrophic possibilities exist – or is it all down to cycles of the Sun. Easterbrook teases out a succession of 100 year periods (some more and some less than a 100) which provide an interesting graph (the third in the series). Easterbrook also makes the point that single events such as impacts or big volcanoes cannot be responsible for the abrupt warming and cooling events because they happen so frequently over several thousand years (and even within the Holocene, afterwards, or the Ice Age, before the period being examined.
He also says the absence of time delay between N and S hemisphere glacial fluctuations in the ice cores precludes an oceanic cause (the favourite consensus theory in the literature, overturning global ocean currents, especially favoured as a mechanism by climate scientists). The very fact the changes are abrupt, he says, mean they can't also be put down to the Croll-Milankovitch orbital forcing model, you know – the eureka moment when Milankovitch was seen to fit with Wegener (both sidelined until the 1950s) after the discovery of magnetic stripes on the Atlantic sea floor.
Presumably, Easterbrook in his next post will outline the solar role in all this. However, he has dismissed the impact idea without exploring the Clube and Napier model which involves the Taurid meteor streams (of dust and debris emitted by a comet or comets in the Late Pleistocene). For the moment, the solar model is looking good – periods of high activity followed by periods of low activity, even quietude. We have experienced this over the last couple of decades – a very active Sun in the 1990s and early 2000s, and a largely quiet Sun thereafter.
Steve Garcia, who regularly comments at http://cosmictusk.com also has a comment at this post, mentioning the Taurid complex – but nobody took him up. Watts Up readers are fixated on the CAGW bubble – why would they? I find it surprising that they see one consensus as being awry but fail to appreciate that other sciences might also be overblown. People don't really want to question what is perceived knowledge – which is how the CAGW doomsaying caught hold of the public imagination.
Easterbrook has had earlier posts published by Anthony – see for example http://wattsupwiththat.com/2011/01/24/easterbrook-on-the-magnitude-of-gr… and for a general overview of the important Younger Dryas event http://wattsupwiththat.com/2012/06/19/the-intriguing-problem-of-the-youn…