Ha! Good link,
but, woe is me, what an almost rude commentary! This is not scientific rigour, this is someone challenged and reacting emotionally ("gavin"). The denigration of other people who disagree (quote)
"... from many of the usual suspects
(my emphasis, GG) e.g. Singer (2005), and Baliunas (in 2003)." (unquote), was certainly not what I was taught as "scientific". I take it that "gavin" disagrees?
"gavin" enters several non sequiturs - what Henry VIII in 1500 + has to do with 800 to 1300 I'm not quite sure; nor do the Black Death and the working class preference for beer have the least bearing on the issue. It is persiflage.
We all have our blind-spots. Gavin has his opinion and is utterly convinced of its veracity, this appears (from that link) to exclude even the vaguest doubt that there may be other opinions. That, is not scientific rigour, again.
My personal position is that we DO have Global Warming; that this may be caused by the burning of fossil fuels since 1850 (say); I do know, having sailed mid-ocean, that we are polluting our environment willfully. I do note that this has all happened before - albeit from different causes.
However I am willing to play Devil's Advocate - to see if Matilda can perhaps question the shibboleths. My old viti' lecturer (Max Loder at Wagga in the 70s), would ask that his students "thought" about grape vines and would award high marks to original thought - even though he thought it - or even knew it - to be wrong.
"Vineyards are not a proxy for warm periods."
No, I would hesitate to align them completely, however, we know that vines will not grow and fruit below a certain level of accumulated temperature. The vines growing in what is now Newfoundland (aka "Vineland") were in all likelihood Vitis riparia
which will survive winter chilling to minus 30 C. In addition, vines "don't care" if they don't set fruit every year - this is a function they have to complete only once in what may be a lifetime of some 100s of years.
So we have two examples. That vines grew at Ely and in Newfoundland. The latter don't grow there now - but let us exclude this as an example due to the variety; this leaves Ely - and it has to be Vitis vinifera
because young Eric the Red did not choose to bring botanical samples back home. Thus the European grape.
Modern scientific research has basically established what we term Growth Degree Days and the level of all except some very specialised (and of modern breeding), varieties seem to need in excess of 900 GDD to ripen fruit on traditional Vitis vinifera
. Currently, London has a modal GDD of <850 - Ely being significantly further north, will have fewer. Yet the monastic gardens at Ely cropped their grapes, we have written history (of that time) to verify this.
Then we enter into a paragraph that quotes the only reliable lay source (the Doomsday Book) and we have 46 vineyards. This confirms Bede and others and concurs with a line drawn at Ely. The factor that there are now 400 (and counting) English vineyards begs the simple point I made above and that is almost all in the northern parts are planted in Mueller Thurgau (bred, 19th/20th century, bred for short cycle and cold climates), and similar varieties all short cycle plants e.g. Breidecker, bursts roughly with Cabernet, harvest before Pinot noir, or Scheurebe etc. These were not available to our monkish forebears.
It is only really the final two paragraphs of that link that really have good weight (IMO).
To your first point:
I agree and there is a huge volume of scientific data available that supports your contention.
In broad-brush terms - a warm N hemisphere appears to cool the S hemisphere. These are sedimentary cores take from Sptizbergen, Canada, Antarctica and many other places. One may be in error, several may be, but not dozens.
Thus I feel that we can be confident that the "Little Optimum" (aka Medieval Warm Period) was indeed one degree celsius warmer than 2005 (source of data), the temperature predicted for 2050/60.
^ Khim, B-K; Yoon H.; Kang C.Y.; Bahk J.J. (November 2002). "Unstable Climate Oscillations during the Late Holocene in the Eastern Bransfield Basin, Antarctic Peninsula". Quaternary Research 58 (3): 234–245(12). doi:10.1006/qres.2002.2371. http://www.ingentaconnect.com/content/a ... 3/art02371
^ Cobb, Kim M.; Chris Charles, Hai Cheng, R. Lawrence Edwards (July 8, 2003). "The Medieval Cool Period And The Little Warm Age In The Central Tropical Pacific? Fossil Coral Climate Records Of The Last Millennium". The Climate of the Holocene (ICCI) 2003.
Both of which illustrate your point of considerable temperature variance from N to S hemispheres (1) and even from coast to coast in N. American continent (2).
This still only adds intrigue to what is indisputable - they farmed in Greenland at this time
... arable farming. They don't do that currently.
Of general interest:-
^ "Medieval Warm Period, Little Ice Age and 20th Century Temperature Variability from Chesapeake Bay". USGS. http://geology.er.usgs.gov/eespteam/Atlantic/GPCabs.htm
For Australia: # ^ Allen, Robert J.; The Australasian Summer Monsoon, Teleconnections, and Flooding in the Lake Eyre Basin; published 1985 by Royal Geographical Society of Australasia, S.A. Branch; ISBN 0909112096
The continental Antarctic ice-sheet is currently thickening (Weddel and Ross sea ice shelves are calving rapidly as more weight is exerted from the pressure of the continental sheet. This is indicative of a regional cooling.
For us, in Australia and NZ there are four major sources of our weather
1. Central Brazil; 2. Equatorial Africa; 3. Antarctica; 4. Equatorial Indonesia/Malaya - and the inter-relationships of these. Of course the Indian, and sub Antarctic Oceans have a bearing too - as collectors of the weather patterns.
Here is a fascinating (active) recent weather link:-
http://www.ssec.wisc.edu/data/comp/cmol ... _mpeg.html
and you can see the recent cloud forming in Brazil/Congo and moving down over Aust and NZ. You can also see it streaming north (an aerial Gulf Stream), and dumping on Canada, the northern states, UK and Europe. Yep, they got a bit of snow.
Also note that it has been deep overcast and raining
over the Sahara.