Onset of the LIA

This looks interesting: a new paper from D’Andrea et al describes some climate fluctuations in Greenland at the end of the Medieval Warm Period and the beginning of the Little Ice Age.

Greenland's early Viking settlers were subjected to rapidly changing climate. Temperatures plunged several degrees in a span of decades, according to research from Brown University. A reconstruction of 5,600 years of climate history from lakes near the Norse settlement in western Greenland also shows how climate affected the Dorset and Saqqaq cultures.

H/T Messenger

Comments

[Nicholas Hallam]

“The record shows how quickly temperature changed in the region and by how much,” said co-author Yongsong Huang, professor of geological sciences at Brown, principal investigator of the NSF-funded project, and D’Andrea’s Ph.D. adviser. “It is interesting to consider how rapid climate change may have impacted past societies, particularly in light of the rapid changes taking place today.”

Of more interest, perhaps, is that the change was much greater and faster than any recent changes and that, whatever caused it it wasn't us. Though I suppose that if you are in this line of research it pays to draw out similarities with the dominant paradigm even when your research results points in the other direction.

[Don B]

A 1997 University of Alberta study of a Norse farm site in Greenland noted "The archaeobotanical remains are excellently preserved because the site was sealed by alluvium and permafrost." Also, there is a statement that the MWP was 1 - 4 degrees C warmer than the present.

(large file, 205 pages)
http://www.collectionscanada.gc.ca/obj/s4/f2/dsk2/ftp04/mq22551.pdf

[lapogus]

For anyone interested, some research on northern Greenland during the Holocene Optimum:

http://www.ngu.no/en-gb/Aktuelt/2008/Less-ice-in-the-Arctic-Ocean-6000-7000-years-ago/

and also:

http://ecotretas.blogspot.com/2010/09/arctic-in-holocene.html

As the name suggests, it seems that it was much warmer then also.

[lapogus]

another driftwood study:

http://hol.sagepub.com/cgi/content/abstract/14/4/607

and more paleoclimate research:

http://www.apex.geo.su.se/images/stories/apex2009.pdf

[Breath of Fresh Air]

rapid NATURAL climate change

is the key lesson, if it happened once with no known forcing then it can happen again without a known forcing.

[alistair]

We are presently getting fast natural climate change with significant cooling of the 400mB troposphere.

[BBD]

lapogus

The Holocene Thermal Maximum was the lagged response to peak Milankovitch forcing ~9kya. Temperatures rebounded sharply after the 8.2ky cooling event and rose until ~6kya. It is the direct consequence of the termination of the last glacial and cannot be compared to modern climate or climate change.

[BBD]

alistair

If you are getting your data from the AMSU-A site (AQUA Channel 06), you should be aware that Roy Spencer cautions against using it. He states that only Ch 05 and Sea Surface T are reliable.

[dusty]

Slightly OT but would anyone care to predict Sir John Beddington's reaction to today's announcement by the American Astrophysical Society?

[dusty]

Apologies, Astronomical not Astrophysical.

[ben]

I thought climate reconstruction was dead? Or is it just the combination of bristlecones and Team where things become unreliable? Does the method used in this study predict well out of sample?

[golf charley]

Dusty, I do not know Beddingtons response, but predict that ZDB will be quoting from John Cook's Skeptical Science blog.

If there is any similarity between Beddington's response and ZDB's, you will have to reach your own conclusion.

I do not think any of the climate models have a "cooling" programmed in, as this was never a possibility considered. They should all be scrapped. Next years average temperature, may be best approximated by a group of 10 year olds with calculators

[lapogus]

@ BBD - I think it is a bit of a sweeping statement to say that the Holocene Optima cannot be compared to modern climate or climate change, even if the Milankovitch forcing is a credible explanation (which I don't dispute). Even so, I have to ask why similar warm peaks (or even plateaux) did not occur following the previous glacials. My thoughts are that some other significant event occurred around 12,000 years ago, for example a change in heat-distributing ocean currents, which perhaps have made it more difficult for ice-sheets to grow again over Europe. This is conjecture, but something must have led to this interglacial being significantly prolonged compared to the 4 previous ones - http://www.foresight.org/nanodot/wp-content/uploads/2009/12/vostok.png - and the only thing I am confident about is that the variability we have seen in the Holocene, including specifically the Minoan, Roman and Medieval Warm periods, have got feck all to do with atmospheric CO2 concentration.

[GrantB]

O/T (but only slightly) - another Maunder minimum

“We expected to see the start of the zonal flow for Cycle 25 by now, but we see no sign of it,” Hill said. “This indicates that the start of Cycle 25 may be delayed to 2021 or 2022, or may not happen at all.”......

I...f the models prove accurate and the trends continue, the implications could be far-reaching....

“If we are right, this could be the last solar maximum we’ll see for a few decades,” Hill said. “That would affect everything from space exploration to Earth’s climate.”

The Jones minimum, the Beddington minimum, the Ronald Oxburgh minimum...? It will need a name.

[Breath of Fresh Air]

The Jones minimum, the Beddington minimum, the Ronald Oxburgh minimum...? It will need a name.

And it will need a tax.

Sun tax, Ice tax, freeze your nuts off tax are a few.

[Edim]

I have heard it will be called Al Gore minimum. Cereal.

[BBD]

lapogus

Milankovitch forcing has a major cycle of ca 100ka. This triggered the Eemian interglacial ca 125kya and the present Holocene interglacial. The intervening period never quite got the energetic boost required to get up to Eemian or Holocene temperatures.

...the only thing I am confident about is that the variability we have seen in the Holocene, including specifically the Minoan, Roman and Medieval Warm periods, have got feck all to do with atmospheric CO2 concentration.

That's exactly the point argued by most climatologists. CO2 forcing is a component of climate. It was probably not dominant in past cyclical warming events (Dansgaard-Oeschger and Heinrich, collectively Bond Cycle) but modern levels of CO2 are sufficient to elevate it to the dominant forcing.

The big question is not if CO2 will warm the climate, it's by how much. All eyes on moist convective transport and low cloud over ocean basins.

[HotAir]

The paper also goes on to say that "temperature variations in West Greenland display an antiphased relationship to temperature changes in Ireland over centennial to millennial timescales"

Would seem to put a dampener on a global or Northern Hemisphere-wide MWP, no?

[BBD]

HotAir

Would seem to put a dampener on a global or Northern Hemisphere-wide MWP, no?

That's way, way too much interpretation for me.

Ireland isn't very big.

The correlation that matters (and is well established) is that temperatures on the Greenland ice sheet vary in phase with N Atlantic SST.

[HotAir]

BBD - a reasonable point. I was being a little tongue in cheek :-)

I'd be interested to look at the Greenland/Atlantic correlation though - on what data is this based, and how far does it stretch back? One of the novel things about this new paper is that fact that it attempts to reconstruct temperatures near Greenland settlements (rather than on top of ice caps).

If you have time a link your sources would be much appreciated. Plus, it might help me find out why Ireland temperatures might vary in antiphase with those SSTs...

[BBD]

HotAir

There are literally dozens of papers, so I have been hunting around for a synopsis and this is fairly good.

A comparison between the rapid temperature fluctuations measured in Northern Hemisphere ice sheets and the determination of North Atlantic sea surface temperatures for the past 90 kyr confirmed the predictions that marine sediments would be imprinted with the signature of D-O events (Bond et al., 1993). The connection between Greenland temperature and sea surface conditions in the North Atlantic has been expanded to include sites from the Scottish margin (Kroon et al.,
1997) and off the Norwegian coast (Lehman et al., 1992) both indicating that ocean surface waters warmed as Greenland temperature increased. In addition to D-O type variability, sediments from the North Atlantic show distinct episodes of Ice Rafted Debris (IRD), referred to as Heinrich Events, which occurred approximately every 7- 10 thousand years during the last glacial period and correspond with extreme cold temperatures in the Northern Hemisphere (Bond et al., 1992; Bond et al., 1995; Elliot
et al., 1998; Heinrich, 1988).

These are just some of the more relevant papers (sorry, I don't have time to hunt down links but they'll be out there I'm sure - Google Scholar is your friend ;-)

Bond, G. et al., Correlations between climate records from north-Atlantic sediments
and Greenland ice. Nature, 365(6442): 143-147, 1993.

Bond, G. et al., A pervasive millennial-scale cycle in North Atlantic Holocene and
glacial climates. Science, 278: 1257-1266, 1997.

Bond, G.C. and Lotti, R., Iceberg discharges into the north-Atlantic on millennial time
scales during the last glaciation. Science, 267(5200): 1005-1010, 1995.

Heinrich, H., Origin and consequences of cyclic ice rafting in the northeast Atlantic
Ocean during the last 130,000 years. Quaternary Research, 29: 143-152, 1988.

[BBD]

Sorry - I should have said - the data on which the correlation is based are derived from ocean bed cores and ice cores eg GISP2.