About 12,800 years ago, the last Ice Age was coming to an end, the planet was warming up. Then, inexplicably, the planet plunged into a deep freeze, returning to near-glacial temperatures for more than a millennium before getting warm again. The mammoths disappeared at about the same time, as did some Native American cultures that thrived on hunting them. That climatic event is known as The Younger Dryas.
Many explanations for the event point to the impact of a comet or an asteroid, but now there is a new study suggests the driver/trigger was all from terrestrial based events.”
According to the article in Science Magazine, they find no evidence for an impact:
The study “pulls the rug out from under the contrived impact hypothesis quite nicely,” says Christian Koeberl, a geochemist at the University of Vienna. Most evidence for the extraterrestrial impact hypothesis, he says, was conjured up “out of thin air.”
The notion was popularized in television documentaries and other coverage on the National Geographic Channel, History Channel, and the PBS program NOVA.
…
Now comes what some researchers consider the strongest attack yet on the Younger Dryas impact hypothesis. In a paper published online this week in the Proceedings of the National Academy of Sciences, a team led by David Meltzer, an archaeologist at Southern Methodist University, Dallas, in Texas, looks at the dating of 29 different sites in the Americas, Europe, and the Middle East in which impact advocates have reported evidence for a cosmic collision.
Only three of the 29 sites actually fall within the time frame of the Younger Dryas onset
http://news.sciencemag.org/archaeology/2014/05/what-caused-1300-year-deep-freeze
From the publication:
A key element underpinning the controversial hypothesis of a widely destructive extraterrestrial impact at the onset of the Younger Dryas is the claim that 29 sites across four continents yield impact indicators all dated to 12,800 ± 150 years ago. This claim can be rejected: only three of those sites are dated to this window of time. At the remainder, the supposed impact markers are undated or significantly older or younger than 12,800 years ago. Either there were many more impacts than supposed, including one as recently as 5 centuries ago, or, far more likely, these are not extraterrestrial impact markers.
Chronological evidence fails to support claim of an isochronous widespread layer of cosmic impact indicators dated to 12,800 years ago
David J. Meltzer, doi: 10.1073/pnas.1401150111
David J. Meltzera, Vance T. Holliday, Michael D. Cannon, and D. Shane Miller
Abstract
According to the Younger Dryas Impact Hypothesis (YDIH), ∼12,800 calendar years before present, North America experienced an extraterrestrial impact that triggered the Younger Dryas and devastated human populations and biotic communities on this continent and elsewhere. This supposed event is reportedly marked by multiple impact indicators, but critics have challenged this evidence, and considerable controversy now surrounds the YDIH. Proponents of the YDIH state that a key test of the hypothesis is whether those indicators are isochronous and securely dated to the Younger Dryas onset. They are not. We have examined the age basis of the supposed Younger Dryas boundary layer at the 29 sites and regions in North and South America, Europe, and the Middle East in which proponents report its occurrence. Several of the sites lack any age control, others have radiometric ages that are chronologically irrelevant, nearly a dozen have ages inferred by statistically and chronologically flawed age–depth interpolations, and in several the ages directly on the supposed impact layer are older or younger than ∼12,800 calendar years ago. Only 3 of the 29 sites fall within the temporal window of the YD onset as defined by YDIH proponents. The YDIH fails the critical chronological test of an isochronous event at the YD onset, which, coupled with the many published concerns about the extraterrestrial origin of the purported impact markers, renders the YDIH unsupported. There is no reason or compelling evidence to accept the claim that a cosmic impact occurred ∼12,800 y ago and caused the Younger Dryas.
What about theory that solar system travels through densier dustarea in milkyway?
Looks like an upside down and backwards hockey stick to me.
The LIA and MWP are mislabelled. If you look at the timescale below you can work out the issue. He has the LIA sitting between the RWP and MWP at 1500 YBP.
Get the feeling not much advancement of knowledge here.
@ur momisugly Bloke down pub and JohnMarshall
You are both making the same category error, I think.
Because no alternative explanation is suggested does not nullify the findings of a report like this or in any way degrade its reliability.
Some things that happened during the Younger-Dryas:
1. It got colder yet sea level continued to rise dramatically.
2. Melt-water from the Laurentide ice sheet switched from flowing South into the Gulf of Mexico suddenly shifted to dumping into the North Atlantic.
3. The Clovis culture and large land mammals pretty much disappeared in the fossil record. There is a mysterious black mat above which mega-fauna and the Clovis no longer exist.
As more evidence comes out, personally I am becoming convinced that earth got slammed by a fragmented comet that blasted a good portion of North America Tunguska-style, taking a good portion of the ice sheet with it (which explains why sea levels continued to rise). A man named Dennis Cox put a really good overview of the impact theory. http://cometstorm.wordpress.com/2011/04/06/a-different-kind-of-climate-catastrophe/
Though I am having trouble accepting his theory on the formation of the Carolina bays, I think he is on the right track with everything else.
“Many explanations for the event point to the impact of a comet or an asteroid, but now there is a new study suggests the driver/trigger was all from terrestrial based events.” ”
So, what were the terrestrial events? Exactly what did the new study “suggest.”
It sounds like the paper was nothing more than a massive correction to the proxy dating. Which is good, if it turns out their math and methodology are correct. However, to assume that the Younger Dryas Period therefore was created solely by terrestrial events is going a bridge too far.
@Nick Stokes,
The Anthropologist, Brian Fagan, uses the same theory in one of his books on Climate and Civilization. I checked Wiki when I read the book about 5 years ago. I went back looking for it a few months ago I couldn’t find it. Interesting.
I never liked the idea of an asteroid or comet impact occurring at regular intervals correlating with ice-ages.
MikeB says:
May 13, 2014 at 4:46 am
“Did no one else think it strange that, according to the labelling on the headline graph, present day global warming appears to be colder than the little ice age?
You’re right MikeB that’s because it’s a typical climatological graph… 😉
richard says:
May 13, 2014 at 4:29 am
what caused the rapid warming?
====
That’s the question I would be asking too…
because temps went back down to the same base line
There’s two step ups in warming…..and now we’re on a slow trend down again
Comet strikes are totally different from asteroid strikes. Yes, the Siberian Tunguska strike shows how devastating a comet explosion can be and if an ice ball hits the Atlantic Ocean, this can cause an ocean rise (tsunamis).
The Younger Dryas could also be caused by the comet striking the Southeast US plus Yellowstone and other continental volcanic events happening in quick succession. If this coincides with a cooler irradiation from the sun…tip into severe Ice Age conditions are quite possible.
A requiem to the Younger Dyras Impact Hypothesis was already announced three years ago.
But there was a consensus! Impact! It was settled science! Is this paper written by DENIERS?
I rather like the premis of this article. Take someone else’s “[name]mometer” data or “[name] driver” data and beat the crap out of it to see if it stands up to close scrutiny. Do I care they do not propose a replacement theory? Nope. This is called replication and I love it.
hell_is_like_newark says:May 13, 2014 at 5:10 am
Thanks for the Dennis Cox Link, a good read.
@Pamela Gray
You said it much better than I did.
In my opinion it was the sun that causes glacial periods such the Younger Dryas and interglacial periods like the present.
I’ve been working on a mechanism (which fits current solar theory) of how this can work, and its very interesting! (just a heads up).
Depending on what you read you can make pretty much anything up. Such as “The mammoths disappeared about the same time [12,800 years ago]”. Nick Stokes also adds in the usual “Fresh water influx is the likely cause for the cold events [of 12,800 years ago]”.
Problem is mammoths did not go extinct until about 3,750 BCE. Hunters were camped alongside the Great Lakes about 9,000 years ago when water levels were only 40 feet lower than today, Alaskan hunters were hunting mammoth about 12,000 years ago, and so on.
So how could the planet be plunged into a deep-freeze while the Alaskan hunters went merrily about hunting mammoth and the mammoth went merrily about being non-extinct for another 8,000 years (in Siberia no less)? And how could the ice sheets of North America grow so quickly and melt so fast? The low water levels were blamed on a continental scale dry period, not a massive discharge into the ocean.
Contradictory conclusions are one thing. But evidence that flies in the face of your theory is something else. Yuka, the incredibly preserved baby mammoth, was living almost 3,000 years after mammoths went extinct. WUWT?
http://www.dailymail.co.uk/sciencetech/article-2124991/Siberian-mammoth-Yuka-Ice-Age-creatur-perfectly-preserved-10-000-years.html
There were several Dryas periods, the first being some 15-18K years BP. Also, there is evidence of previous Dryas-like events at the end of previous glacial periods. Thus, an extraordinary event such as a comet or asteroid strike as the cause doesn’t seem logical. We may never know, but some sort of shutdown of the thermohaline or similar terrestrial reaction seems the most likely cause.
its a mystery?…..so they don’t understand how climate processes work? i thought we knew with 95% certainty how it all worked?
“those bad ol’ Neanderthals caused it by burning tons upon tons of mammoth chips”
I’m no expert, but wouldn’t those be carbon neutral?
Steve from Rockwood says:
May 13, 2014 at 5:46 am
Right on. In fact there is a trend: the more northerly the species’ habitat, the more likely it was to survive; e.g., arctic fox, musk ox, polar bear. All the evidence points to human predation.
–AGF
The great thing about being a skeptic is the fun to be had from reading the comments and bashing the alarmist nonsense . Having read a few of the alarmist ones everyone has to remain ” oh so serious”
Whoa!
According to that graphic, we are cooler now then we were in the LIA!
That can’t be right.
Ah, much better:
http://www.ncdc.noaa.gov/paleo/pubs/alley2000/alley2000.gif
Thanks to MikeB above.