There is another interesting post at Cosmic Tusk (http://cosmictusk.com) which dates back to April 2010, a guest blog by Rodney Chilton, a Canadian climate scientist and the author of 'Sudden Cold: An examination of the Younger Dryas cold reversal' – go to web site and look down RH menu for past posts, a number of which are archived. The titles you want come under Guest Blogs, one of which is by Rod Chilton. Click link.
It was written in response to David Morrison of NASA who was critical of the Younger Dryas impact hypothesis, in the pages of Skeptical Enquirer. When Chilton discusses evidence of cosmic events, impacts or airbursts, he quotes a Dr Adrian Melott who suggested the source of high amounts of ammonium (spikes in ice cores) might be the 'Haber process' which literally cooks the atmosphere and produces ammonia as a side effect. Nitrates could be seen as a by product of moving bodies heating the atmosphere to ozone destroying levels.
Now, the problem with evidence of any cosmic impact, Younger Dryas or otherwise, is that most scientists not directly in the field are not reading the various papers and floated ideas. Comments at blogs and elsewhere are commonly along the lines, 'I thought the YD impact hypothesis had been debunked …' as if a couple of sceptic papers were the final resting place of the hypothesis. It will probably rumble on for a long time yet as new evidence is found in support of a cosmic dimension – but will the mass of scientists, in whatever field they operate, simply ignore the hypothesis as it does not sit easily with uniformitarianism. Climate scientists are not friendly towards the idea of a YD impact event (whether by comet strike or the atmosphere becoming clogged by cosmic dust and debris from the train of a comet) or of Heinrich events having a cosmic origin likewise. Why would they? The YD event serves a useful purpose as it keep alive the idea that climate can change rapidly – all part of the scary scenario attached to CAGW theory which they espouse in all seriousness. . It is in their interests to downplay the cosmic angle – even super solar flares, lightning from space, or any other kind of catastrophe. The idea therefore is to squash the YD impact hypothesis and keep the lid on other possible causes for dramatic climate change.
PS … Rod Chilton refers to the 'enigmatic' caches of animals and vegetation in Alaska and Siberia (the muck) and the possibility a huge tsunami was to blame. This, in combination with a rapid onset of cold weather and the destruction of the earth's ozone layer is a marker of something important – but what was it?