This is interesting, somehow the Earth managed to reduce a good portion of the Arctic Ice Cap during the Holocene Climate Optimum from approximately 10,000-6,000 years ago without the help of the industrial revolution, fossil fuels, or automobile emissions.
This new paper published in Quaternary Science Reviews finds Arctic sea ice extent and thickness was much less than present-day conditions and according to the authors,
“Arctic Ocean sea ice proxies generally suggest a reduction in sea ice during parts of the early and middle Holocene (∼6000–10,000 years Before the Present) compared to present day conditions.”
The authors show how 8 different proxy studies reveal extended periods lasting hundreds of years without perennial sea ice in the Arctic [ice-free conditions], and find solar insolation explains these changes. See figure 4 from the paper below.
The top graph shows simulated annual mean sea ice thickness [orange curve] was much less during the Holocene Climate Optimum ~13,000-6,000 years ago compared to the end of the 20th century at right side of graph. The bottom graph shows multiple proxies of sea ice with darker green indicating periods of less sea ice. Modern sea ice is at high levels in comparison to the rest of the Holocene.
Annual mean sea ice thickness for the three different simulations (Panel a) compared with results from published paleo-sea ice studies (Panel b). Black curve: constant surface albedo; red curve: dynamic surface albedo parameterization. The simulation implemented with a dynamic surface albedo parameterization was run from present time and backwards to address the importance of the initial state of the sea ice cover. The annual mean sea ice thickness from this simulation (orange curve) reveals a hysteresis of ∼1000 years. The annual mean insolation at 80°N shown with a stippled curve is based on the algorithm presented by Berger (1978). To compare the results from different paleo-sea ice studies a scale of sea ice concentration was inferred using the approach by Jakobsson et al. (2010). This scale must be considered as highly qualitative because none of the paleo-sea ice proxies provide absolute measures of past sea ice concentrations.
The paper:
Arctic Ocean perennial sea ice breakdown during the Early Holocene Insolation Maximum
Christian Stranne, Martin Jakobsson, Göran Björk
Arctic Ocean sea ice proxies generally suggest a reduction in sea ice during parts of the early and middle Holocene (∼6000–10,000 years Before the Present) compared to present day conditions. This sea ice minimum has been attributed to the northern hemisphere Early Holocene Insolation Maximum (EHIM) associated with Earth’s orbital cycles. Here we investigate the transient effect of insolation variations during the final part of the last glaciation and the Holocene by means of continuous climate simulations with the coupled atmosphere–sea ice–ocean column model CCAM. We show that the increased insolation during EHIM has the potential to push the Arctic Ocean sea ice cover into a regime dominated by seasonal ice, i.e. ice free summers. The strong sea ice thickness response is caused by the positive sea ice albedo feedback. Studies of the GRIP ice cores and high latitude North Atlantic sediment cores show that the Bølling–Allerød period (c. 12,700–14,700 years BP) was a climatically unstable period in the northern high latitudes and we speculate that this instability may be linked to dual stability modes of the Arctic sea ice cover characterized by e.g. transitions between periods with and without perennial sea ice cover.
http://www.sciencedirect.com/science/article/pii/S0277379113004162?np=y
h/t to The Hockey Schtick
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Now we need to send in the archaeologist to find the coal fired power plants and GMC Yukons….
That is going to be one big dig. But hey people will be employed!
There were a lot of interesting things going on 6000 years ago, I saved some in http://wermenh.com/climate/6000.html
Most of my savings were about glaciers around the world (hello Oetzi!), but I also have this:
2008 Oct 20: Less ice in the Arctic Ocean 6000-7000 years ago
“Recent mapping of a number of raised beach ridges on the north coast of Greenland suggests that the ice cover in the Arctic Ocean was greatly reduced some 6000-7000 years ago. The Arctic Ocean may have been periodically ice free.”
This includes a ruined settlement left by the Independence I Culture in North Greenland abandoned at least 4,000 years ago.
Hey, the link still works, see http://www.ngu.no/sciencepub/eng/pages/Whatsup_20_10_08.html
We have never had to look any further than our Sun to see whichis the only force that matters when it comes to the Earths climate.
It is positively ludicrous to propose the a minute increase or decrease in CO2 can have any significant effect.,
Consequently one must accept the only logical explanation, That this preposterous hypothesis is all about political control,,and science be damned.
Good, Decent well done science. Can’t fault it really. Suprised it got published as it doesn’t fit the its warmer than ever and were all going to die MEME.
Sooo disappointing….. “Our work points to the strong surface albedo feedback as the common denominator between the sea ice minimum before 6000 years ago and the present diminishing trend. However, at the same time as our simulations show the importance of the surface albedo feedback, there are likely two distinctly different underlying causes for the feedback to kick in: increased insolation (past) and increased GHG levels (present). We also speculate that climatically unstable periods such as the Bølling–Allerød period (c. 12,700–14,700 ”
If increased insolation caused reduced ice in the past, whi do they assume its GHG levels in the present.
ARGHHHHHHHH
Skeptics proven right again.
We have been questioning the validity of the AGW claim that Arctic sea ice is
1- at unprecedented low levels
2- dangerous to the climate when it is low
now we see this is the case.
Hyping AGW is lucrative, and popular, but that does make it correct.
cnxtim says:
March 24, 2014 at 5:17 am
We have never had to look any further than our Sun to see whichis the only force that matters when it comes to the Earths climate.
It is positively ludicrous to propose the a minute increase or decrease in CO2 can have any significant effect.,
Consequently one must accept the only logical explanation, That this preposterous hypothesis is all about political control,,and science be damned.
____________________________
Well, you are correct about the political part. Perhaps you could provide links to historical data which show the Sun’s link to climate and you’ll be right about that, too. Do any such studies hold under scrutiny? To say the Sun is the primary source of energy is one thing, but saying the Sun is the primary driver of Climate is another thing, unproven to date.
Yup, sea level was 2 meters higher 4-6000 years ago.
As Ric Werme says, this is old-hat, and I think now stuffed with a few new feathers by computer modellers. Norwegian real scientists found the north Greenland beach structures – showing evidence of wave action on a coastline where there is now ‘permanent’ ice, and carbon-dated it to the period 8000-6000BP (reviewed in my book Chill, 2009). For the same time-period, other real scientists in my home country of Somerset discovered that the lake-village dwellers ate Pelicans for breakfast (European birds now found only in Greece and the Danube delta)! Recent flooding may bring the lake-villages back, but it will take a lot of global warming to encourage the Pelicans to return. Greenpeace campaigners please note: this previous Arctic meltdown did not release methane hydrates that fried the planet.
Notice these types of papers don’t go into fearmongering mode when talking about previous natural changes. It’s only when talking about similar changes that might happen now that the fearmongering emerges. What about the poor polar bears back then? The poor seals? The delicate Arctic ecosystem?
To cnxtim:
The radiative energy reaching the Earth from the Sun varies both cyclically and randomly, but so far, the changes don’t correlate to historical climate change. It may well be that the Sun, in concert with other forces we don’t yet understand, such as the Solar wind influence > cosmic radiation > cloud formation is a major factor in our changing climate. There is just too much going on that we don’t yet understand.
It’s 99% modeling results with a tiny bit of support from other studies using paleo data, some of which the authors say is contradictory. The only thing worthwhile coming from it is that models can cut both ways, which hardly supports the paper’s conclusion.
The truth is the hysteria of the ice caps is based upon such a miniscule window into the behavior of the ice caps that no logical conclusions can be drawn. Yet those seeking to advance their alarmist agenda still use it as some sort of absolute measuring stick.
Climate philosophy – about as `scientific` as say alchemy, astrology or reading palms. The corrupt Cult of Globaloneywarming just highlights the poverty of modern critical thinking. Truly a dark age in some ways.
Well at least now we don’t have to worry about any emails being sent from Michael Mann to Phil Jones inquiring whether they can get one of the editors at Quaternary Science Reviews sacked.
Maybe.
Ferdinand (@StFerdinandIII) says:
March 24, 2014 at 5:52 am
__________________
Engelbeen, is that you?
Although generally preferring more direct data than model simulations, there are quite a number of studies showing the Holocene Climate Optimum had greater warmth than now, higher sea level, more arctic vegetation (fitting the warmth), etc. Some are listed within co2science.org
And naturally solar forcing was high then.
Variation in solar forcing at Earth, both from Milankovitch cycles and from variation in solar activity itself, is the prime driver of climate on most timescales, including through influence on cosmic rays (also affected by geomagnetic variation and movement around the galaxy):
As a Dergachev et al 2004 paper flatly notes, known data “proves that cosmic rays were the main factor affecting the weather and climate during tens of thousands of years.”
References and far more are within my usual http://tinyurl.com/nbnh7hq link.
Such includes implicit debunking of various common Big Lies; for example, one common falsehood is that solar activity was flat during the 1970s->1990s warming, aided by rewriting ACRIM data with PMOD, but there were too many more independent neutron monitors to get those rewritten, so observe what a plot 2/3rds of the way down in the prior link shows.
re: cnxtim says: March 24, 2014 at 5:17 am
————————————————————————————————————————
Please do not confuse TSI and insolation. The chart shows higher insolation at 80 N because approx 10,000 years ago obliquity was 24 degrees and perihelion was at summer solstice. One would certainly expect less northern sea ice under those conditions which are a result of Earth’s orbit not changes in the Sun’s output.
It’s the wobble, precession of the axis. The Earth was closest to the sun in the Northern Hemisphere summer (July through September) during that period causing the insulation minimum. The sea ice extent and thickness should have been at a maximum in the Southern Hemisphere approximately 13000 to 8000 BP. We are now at perihelion in early January, therefore moderating NH winters. The asymmetrical distribution of continental crust complicates the matter.
I see this paper doesn’t get the “Claim:” characterization added to the blog post title. I guess someone likes some aspect of the paper. That’s interesting, since the conclusion comes from modelling:
Climate models are OK now?
Later it is noted that the paleo-sea ice records don’t necessarily support ice free conditions found in the model, while they do support a reduction in ice extent:
But yes, they are arguing that it is possible the Arctic could have been ice free during some part of the period from 6000-12000 years ago based on their models. So do the authors of this paper think this means the current decline in Arctic sea ice has a natural cause? Nope. In their own words:
Not very surprising. Hardangervidda in Norway was a forest back then.
its open knowledge?
Holocene climatic optimum
‘Of 140 sites across the western Arctic, there is clear evidence for warmer-than-present conditions at 120 sites. At 16 sites where quantitative estimates have been obtained, local HTM temperatures were on average 1.6±0.8 °C higher than present. Northwestern North America had peak warmth first, from 11,000 to 9,000 years ago, while the Laurentide ice sheet still chilled the continent. Northeastern North America experienced peak warming 4,000 years later. Along the Arctic Coastal Plain in Alaska, there are indications of summer temperatures 2–3 °C warmer than present.[5] Research indicates that the Arctic had substantially less sea ice during this period compared to present.’
“The Hans Tausen Iskappe (ice cap) in Peary Land (northern Greenland) was drilled in 1977 with a new deep drill to 325 m. The ice core contained distinct melt layers all the way to bedrock indicating that Hans Tausen Iskappe contains no ice from the last glaciation; i.e., the world’s northernmost ice cap melted away during the post-glacial climatic optimum and was rebuilt when the climate got colder some 4000 years ago.”
http://en.wikipedia.org/wiki/Holocene_climatic_optimum
better take a snapshot of that before the co2ers realise there is a wiki page they forgot to
‘improve’.
if the co2ers contextualised the warming within icce age cycles no one would take any notice of them which is why they have to sex it up so the press [who don’t care either way- they love sensation] have a headline.
Tom, thank you. Our Earth wibbles, wobbles, whirls, and varies its own intrinsic atmosphere and oceans in a fluidly dynamic dance around the ever present Sun. And I am unimpressed with these “discoveries” being marched out in front of us in order to proclaim that this has been the past but has now ceased to exist as the prime behavior of Earth, overtaken as it is by the breath of man.
Idiots.
So then Polar Bears as a species only emerged within the last 6,000 years? Because we know current ice conditions are driving them to extinction, so the ice conditions in the paper would have killed them all off. Meaning the current species must postdate those lower ice conditions.
The skeptics may be right. It’s worse than we thought.