What do you know? The Medieval Warm Period, which either “didn’t exist” or “only happened in Europe”, also hit Western Antarctica.
The climate models don’t know why the world was warmer 1000 years ago. They don’t know why it cooled into the Little Ice Age either. The models don’t do regional projections well, and they don’t do seasonal projections with any skill, and they (in the last ten years) don’t work on short decadal timeframes either, but surely when it comes to big global temperature changes the models have got all the major forces figured out? Surely they’d be able to predict large movements across the entire globe eh? — but the first test we come to, a mere thousand years ago, shows the models have a predictive ability not significantly different from a coin toss.
Just because it was warmer 1000 years ago (due to some other reason), doesn’t mean that CO2 isn’t responsible for this warming cycle, but when all the evidence for CO2′s guilt comes only from models that can’t get the last warming cycle right, and from argument from ignorance (“Our models don’t project this warm period without putting CO2 in!”) then we know that the “evidence” (such as it isn’t) is very weak. The mysterious forces that warmed us a thousand years ago could easily be at work right now. Worse, some entirely different factor could be too. The unknown unknowns eh?
During the “perfect stable idyllic climate” before SUV’s and power stations were invented and while the global population was one 20th of what it is today, ice on the Western Peninsula was at least as degraded as it is now, or possibly was even more so.
The timing of the warmest era 700 – 1000 years ago fits in very well with Craig Loehle’s reconstructions.
From NIPCC: Regarding Hall, B.L., Koffman, T. and Denton, G.H. 2010. Reduced ice extent on the western Antarctic Peninsula at 700-970 cal. yr B.P. Geology 38: 635-638.
“Is the recent warming of the Antarctic Peninsula unique in the Holocene?”
The three U.S. scientists report that “peat from the overrun sediments dates between 707 ± 36 and 967 ± 47 cal. yr B.P.,” leading them to conclude that “ice was at or behind its present position at ca. 700-970 cal. yr B.P. and during at least two earlier times, represented by the dates of shells, in the mid-to-late Holocene.”
In language pure and simple, Hall et al. say their findings mean that “the present state of reduced ice on the western Antarctic Peninsula is not unprecedented,” which leads them to pose another important question: “How widespread is the event at 700-970 cal. yr B.P.?”
In answering their own query, the researchers respond that (1) “Khim et al. (2002) noted a pronounced high-productivity (warm) event between 500 and 1000 cal. yr B.P. in magnetic susceptibility records from Bransfield Basin,” that (2) “dates of moss adjacent to the present ice front in the South Shetland Islands (Hall, 2007) indicate that ice there was no more extensive between ca. 650 and 825 cal. yr B.P. than it is now,” that (3) “evidence for reduced ice extent at 700-970 cal. yr B.P. is consistent with tree-ring data from New Zealand that show a pronounced peak in summer temperatures (Cook et al., 2002),” that (4) “New Zealand glaciers were retracted at the same time (Schaefer et al., 2009),” and that (5) their most recent findings “are compatible with a record of glacier fluctuations from southern South America, the continental landmass closest to Antarctica (Strelin et al., 2008).”
In light of these several observations, it would appear that much of the southern portion of the planet likely experienced a period of significantly enhanced warmth that falls within the broad timeframe of earth’s global Medieval Warm Period, which truly impressive interval of warmth occurred when there was far less CO2 and methane in the atmosphere than there is today.
See my map of the warmer empirical evidence from Africa, Asia, Europe, Antarctica and America. Which of course is provided in more lavish detail on CO2Science’s Medieval Warm Period database and map:
Medieval Warm Period Project
Was there a Medieval Warm Period? YES, according to data published by 912 individual scientists from 542 separate research institutions in 43 different countries … and counting! To access the entire Medieval Warm Period Project’s database, click here.
Cook, A.J. and Vaughan, D. 2009. Overview of areal changes of the ice shelves on the Antarctic Peninsula over the past 50 years. The Cryosphere Discussions 3: 579-630.
Cook, E., Palmer, J. and D’Arrigo, R. 2002. Evidence for a “Medieval Warm Period” in a 1100-year tree-ring reconstruction of past austral summer temperatures in New Zealand. Geophysical Research Letters 29: 10.1029/2001GL014580.
Hall, B. 2007. Late-Holocene advance of the Collins Ice Cap, King George Island, South Shetland Islands. The Holocene 17: 1253-1258.
Hall, B.L., Koffman, T. and Denton, G.H. 2010. Reduced ice extent on the western Antarctic Peninsula at 700-970 cal. yr B.P. Geology 38: 635-638.
Khim, B-K., Yoon, H.I., Kang, C.Y. and Bahk, J.J. 2002. Unstable climate oscillations during the Late Holocene in the Eastern Bransfield Basin, Antarctic Peninsula. Quaternary Research 58: 234-245.
Schaefer, J., Denton, G., Kaplan, M., Putnam, A., Finkel, R., Barrell, D.J.A., Andersen, B.G., Schwartz, R., Mackintosh, A., Chinn, T. and Schluchter, C. 2009. High-frequency Holocene glacier fluctuations in New Zealand differ from the northern signature. Science 324: 622-625.
Strelin, J., Casassa, G., Rosqvist, G. and Holmlund, P. 2008. Holocene glaciations in the Ema Glacier valley, Monte Sarmiento Massif, Tierra del Fuego. Palaeogeography, Palaeoclimatology, Palaeoecology 260: 299-314.
twitter shortlink: http://joannenova.com.au/?p=11239
UPDATE: Oct 2012 Loehle 2007 Graph replaced with Loehle 2008 corrected graph. Though it makes little difference to the height or amplitude of the curves. h/t “NiceOne”