At www.sciencedaily.com/releases/2020/07/200731180717.htm … a sediment core from a Texas cave is said to solve the mystery of what set in motion the Younger Dryas event. Instead of the extraterrestrial impact event we have volcanic eruptions that set in motion the downturn in climate. For over 1300 years the temperatures are said to have dropped by an average of 3 degrees, one of the factors that has hampered the acceptance of the meteor storm as an explanation. Can volcanoes cause a prolonged downturn in climate. Well, they can spew an awful lot of dust, debris and gases into the upper atmosphere but usually the effects are relatively shortlived. We don't know what a meteor storm might do. It could certainly also put a lot of dust and debris, and presumably gases as well, into the upper layers of the atmosphere. A cooling phase of 1300 years might be a train ride too far. Not only that, at the end of the 1300 period the temperature suddenly warmed up by 5 degrees or more, rather suddenly (in geological terms). Fred Hoyle got round that by suggesting another impact, but this time into the ocean. The impact then caused an awful lot of water to ascend into the atmosphere, washing it clean of dust and debris. The suggestion came about as the Younger Dryas was reputed, at the time, to have been very dusty. There is no evidence the dust had an extraterrestrial origin otherwise the boundary impact people would have already homed in on the idea. The new article will no doubt be pawed over by the boundary impact people looking for flaws – just as the volcanic people pawed over the preceding paper (and papers).
Having said that the Younger Dryas boundary impact is hypothetical. It is a theory. It has not been proven conclusively, one way or the other. There is a lot of mileage to go. The new paper will provide another opportunity for the impact team to mangle and sift through the data once again. They require more evidence to back up their claims – or a way to trash the new paper. The problem is that cooling events, such as the Younger Dryas, litter the Late Pleistocene period. They are known as Heinrich events. This has always been the big problem for the catastrophists. How many impacts are required, and over what time span. Further, and most disturbing, the Heinrich events are usually preceded by warming periods known as the Dansgard-Oeschger events. Hence, there is a succession of sequences of a warming period of a thousand years, or possibly two or three thousand years, culminating in an abrupt cooling episode. It so happens the Younger Dryas was preceded by a couple of thousand years of warming, the Bolling-Alleroed phase of climate. Could this be a Dansgaard-Oeschger warming (with the Younger Dryas equivalent to a Heinrich event). Some geologists define Heinrich One as the Younger Dryas. Others define the Oldest Dryas as number One, or an even earlier cooling period. Not only that but one also has to wonder if such cycles are perhaps an artifact of a computer simulation – random numbers clustering into repetitive cycles. Cycles make nice graphs and many a scientist will provide such a graph – a perpetual motion graph of ups and downs.
How many impacts would you require to account for all the Heinrich events – and we still have the mystery of what might prompt the warmings (a much more prolonged period of change). The easy answer to that might be to invoke solar cycles. Periods of activity causing a warming and solar minimums creating the coolings. Could a grand solar minimum last 1300 years? Some people seem to think so. If we were to plump for tectoniics as a factor involved in the cooling events and then there is some evidence to suggest they may peak in periods of solar minima. There was certainly a lot of volcanoes going off in the Little Ice Age and that is usually blamed on a solar minimum (or minimums). However, there were also a lot of comet sightings. Big comets visible by naked eye. There were also some meteor showers that make current ones look like dud squibs – rather than a jumping jack flash. The most likely answer for the Little Ice Age was an opaque sky – as a result of volcanic and meteoric debris and dust particles in the upper atmosphere, replenished on a regular basis. Is that remotely possible as far as the Younger Dryas (and its Heinrich relatives) are concerned*. We may also remember that we are currently at solar minimum, in the trough between two 11 year solar cycles. There is little evidence of a temperature drop (except when dark clouds cross the sky above our heads) – and that might be another factor. Clouds. Solar minmums are supposed to encourage greater cosmic rays to enter the solar system (as a lack of solar activity is thought to weaken the magnetic bubble protecting our system from penetration from beyond). An increased flux of cosmic rays is thought to cause greater cloud formation. Rather, that is the theory presented by Henrik Svensmark and Nigel Clder in 'The Chilling Stars' .. which of course is not accepted by climate science alarmists. Neither are impact events, come to that.
At https://wattsupwiththat.com/2020/08/01/younger-dryas-impact-hypothesis-t… … we have a cascade of comments. However, a couple of the commenters seem to dominate the proceedings and have composed so many comments they virtually don't allow a proper debate. Some commenters appear to be furtive in reply, almost like a squeak, as the vitriol against the catastrophists is quite deafening. Never the less we have to applaud the host of the web site for allowing such debates on his web site, and they are ongoing. The commenters are very often different people but as there have been a number of posts on the YD boundary event papers over the last several years, it is amazing that the host has continued to pick up on the subject once more. In fact, on this occasion, it is not so much a misrepresentation on what is being claimed by the impact people, as it was by some earlier commenters, but a clear case of one group appearing to favour the idea of the cold water pulse. This is surprising as even Wal Broecker, who came up with the idea in his book (and articles), 'The Ocean Conveyor Belt' some years ago, has said some surprisingly positive things about the impact theory. In other words, he knows that his proposal was a theory. It was an explanation that may have credence, or otherwise. It was a seminal piece of climate science in its time. At least one of Broecker's team was a former colllaborator with him in his research back in the day. It is interesting how the arguments of those opposed to the idea of impacts changes each time there is a post on the subject. In this one a couple of the posters seem to have gone overboard in their support of a cold water pulse, even while admitting there was no evidence of such a pulse along the course of the St Lawrence river. The idea was then switched, perhaps the cold water went another way, along the McKenzie river system and out into the Arctic, a rather desperate attempt to sustain the theory, and the same couple of commenters present this as if it was irrefutable evidence when in actuality it was just an idea to get around the lack of evidence of such a pulse into the North Atlantic. Not only that they also ignore the fact that the water from the Great Lakes that now flows over Niagara Falls was not full throttle until after 6200BC. Two thirds of that flow was going out via the St Lawrence river. On top of that there is archaeological evidence of humans living on the shores of the lakes from very early in the Holocene. Was there really such a massive body of cold water sitting there for hundreds of thousands of year (Lake Agassiz) with the Great Lakes representing its residue. This is something else that is hypothetical and unproven. Somebody saying it as a possible explanation does not make a fact. It is an explanation. A hypothesis. In reality it is not known why the Younger Dryas cooling event occurred – or the 6200BC (shorter) cooling period. The idea of cold water pulses is as valid as an impact – or a massive volcano. They are all ideas and it would be nice for them to be discussed without one side of the argument becoming dictatorial and attempting to suppress the alternative ideas. It is also a fact that most of the ice melt travelled south by way of the Mississippee and Ohio river system – and this occurred fairly rapidly after the end of the Late Glacial Maximum. We should also bear in mind there are even more alternative ideas out there, some of which are classified as pseudo science by uniformitarians.
It is also worth pointing out the Younger Dryas was not universally cold. It had warm episodes within the 1300 year period. It also tended to be coldest in the first half of that period. The 3 degrees is an average fall in temperature. Sometimes it was more than 3 and sometimes less than 3 degrees. It is a bit like the Little Ice Age. It had some really cold decades, with specifically cool summer weather. However, other decdes were not a lot different in temperature than today, even to the fact that heat waves did occur. One might expect this if the upper atmosphere was the problem, some decades colder as a result of substantial volcanice aerosols or even debris left behind by meteor showers. as opposed to other decades when there was little tectonic activity (and a decided lack of comet sightings).
There is also another factor mentioned by a commenter, magnetic anomalies, even a possible reversal of polarity. It so happens the Gothenburg excursus occurred roughly at the Younger Dryas boundary (or within a couple of hundred years). Little is known about wandering magnetic poles, magnetic excursions, or reversals, but the subject is now a field of research as the northern magnetic pole appears to have moved a considerable distance in recent decades. A couple of years ago and the idea of a connection would have been shouted down. It was even claimed the Gothenburg excursion was a mirage and did not exist. How times change. It is now a recognised fact of life – but difficult to define as it was found in sediments rather than in rock with an origin in lava. Even the 8th century BC magnetic excursion is being treated seriously and a connection made with solar minimums. In this instance, the cold and wet weather of the Iron Age in Europe appears to have preceded the actual excursion event – which raises a question mark before the solar minimum idea, posited no doubt as an explanation but later touted as evidence of a solar minimum (which may not have happened). Lots of roundabout thinking involved.
Having said all that, the idea that a single comet (as in the Clube and Napier theory) was responsible for a whole cluster of disruptions through the Holocene, may be stretching a theory too far – although astronomers do not rule out the possibility that Comets such as Halley or Encke could have been visiting the inner solar system for thousands of years. See also https://phys.org/news/2020-07-texas-cave-sediment-upends-meteorite.html … and https://advances.sciencemag.org/content/6/31/eaax8587/tab-pdf
* If the Boundary event was caused by a heavy meteoric bombardment with a root cause in a large comet shedding a lot of material on its orbit around the Sun and then it is perhaps feasible that a great deal of debris was left in an earth crossing orbit that was encountered regularly (annually) during late spring or early summer. That would account for a series of cool summers. The supposition here might be that at the end of the 1300 years the earth's orbit extricated itself from such encounters, or the debris had been dispersed more widely in near space. The problem still remains in that 1300 years is a very long time, and secondly, how would earth have extricated itself from such a meteor stream (even if it gradually dissipated). The earth annually encounters several Taurid meteor streams, some of which are thought by astronomers to have an origin thousands of years ago – dwarfing the 1300 years. Even so, the atmosphere is fairly clear nowadays, unlike what it was in the Little Ice Age. I suppose the answer may lie in how dense the meteor stream is when encountered and how quickly such streams dissipate in order to become less dangerous. We must not forget that periods of disruption continued to be a factor in the early to mid Holocene.