Just to get a new thread going here are the basic bones. Firestone et al (too many names to reproduce quickly) came out with their theory several years ago that some kind of cosmic object struck the Earth or burnt up in the atmosphere at the beginning of the Younger Dryas Event and this caused global temperatures to plunge dramatically. Various people, in particular climate scientists, were not impressed and have remained largely outside the debate. This is due to the fact it complicates what they are striving to achieve, that modern global warming is a result of fossil fuel emissions. Anything that might interupt the flow of the dialogue is seen as unwanted and subsequently they are unenthusiastic. Hence, the YDB event has barely touched the radar of the mainstream - just a couple of news flashes. This is especially true in the UK where the debate is muted.
The main criticism of the theory is that the Younger Dryas was a very long event lasting up to 1300 years (although the length does vary from scientist to scientist, between 900 and 1300 years). Therefore, it was a lengthy period and led to the obvious point of criticism, how could a cosmic object have such a lengthy effect - to wit, the consensus view that it was all to do with the ocean circulation system switching into a negative mode seemed much more likely. However, Wally Broecker, the main proponent of the ocean circulation model is himself not so sure and has toned down his criticism. In addition, Bill Napier came out with a paper a couple of years ago, at the height of the furore, with mainstream misrepresenting the details of the YDB event and in a nutshell said that the Earth may have entered a particularly dense Taurid stream (which has now widely dispersed). Obviously, if the orbit of the Earth did encounter such a stream of cometary material the question might be asked, how long would it take the atmosphere to lose all the dust and debris it had collected - could it possibly have lingered for as long as 1300 years?
The history and most of the papers involved in the YDB event controversy, on both sides, are available at George Howard's web site http://cosmictusk.com and you can read them for free - including the important Napier paper. They are available on the LH side of the menu. It is therefore advisable for anyone wanting to dip their fingers into this debate to familiarise themselves with the various arguments. George Howard doesn't actually debate the issue but posts an occasional update at the web site. He is running a business so he is a fairly busy person and is often slow to respond. He is however very friendly to SIS - but not necessarily a Velikovskian. Other contributors at the site (comments section) are not always worth reading but a couple of the names are familiar from Benny Peiser's CCNeT debate on the 1995 SIS conference where catastrophism was largely discussed.
Now, ignoring for the moment the merits or otherwise of catastrophism versus a purely terrestrial explanation for the Younger Dryas cooling event we need to bear in mind that it is not a one off. There are seven earlier events that closely resemble the Younger Dryas, penetrating deeply within the last Ice Age (as it is defined in the consensus model, some 100,000 years in duration). The earliest event is around 70,000 years ago - which is very near where a super volcano is supposed to have blown and plunged the world into a similar cold epoch - colder than it had been in that part of the Ice Age. This was followed by a succession of other cooling episodes ending in the Oldest Dryas Event which brought the Ice Age to an end around 17000BC (a rough figure without checking the current opinion on this). Therefore, if Bill Napier's argument is valid do we assume the Earth has encountered a succession of heavy Taurid streams - does this even fit into the Clube and Napier model? In Napier's favour we have several short cooling episodes in the Holocene (post Younger Dryas) wherefore the continuing break-up of the hypothetical comet was ongoing and according to the Clube and Napier model was still causing periodic problems for humans on the surface of the Earth as recently as the Little Ice Age (when the atmosphere accumulated, they suggested, periodic bouts of cometary dust as the orbit of the Earth weaved its way through the now dispersed elements of one of the Taurid streams. Orthodox opinion has recently put these things down to solar changes - a lack of sun spots during at least one part of the Little Ice Age, the point at which it was coldest. Previously the Sun was thought to be constant, as far as temperatures on Earth were concerned, but as Lawrence can explain to us the Chinese and Koreans, among others, had noticed such correlations prior to modern western science. Now, we are all aware of Moe Mandelkehr's articles in SIS journals (sadly he has now died so can't take part in the debate) and his correlation of the Taurid stream with the events between 2300 and 2000BC. We can further speculate something similar happened (orthodox dates and no point here in raising the scientific dating issue as that would be a separate subject) around 3100BC and 6200-6000BC, so these two periods are open to discussion in this forum debate as they are essential in the grander scheme devised by Clube and Napier, ongoing streams of Taurid dust with an origin in a comet that was breaking up and gradually getting smaller and smaller - or split into various segments. Also part of the debate might be the identification of the comet and parts thereof in perceived mythology, such as Set and Horus etc. The theory is most attractive as it explains the origin of religions - or myths that developed into religions. We also know the Ice Age painters of caves in Europe were very interested in the Pleiades and generally the Taurus constellation. Therefore we can proceed with several strands that might appeal to different people