Here are some general sources on the Medieval Warm Period (which the hockey stick chart denies occurred):
ldeo.columbia.edu
atmos.washington.edu
geo.arizona.edu
geo.arizona.edu
-----------
Here's another source supporting that the MWP was a global phenomema:
agu.org
GEOPHYSICAL RESEARCH LETTERS, VOL. 29, NO. 14, 1667, doi:10.1029/2001GL014580, 2002
Evidence for a ‘Medieval Warm Period’ in a 1,100 year tree-ring reconstruction of past austral summer temperatures in New Zealand
Edward R. Cook
Lamont-Doherty Earth Observatory, Palisades, NY, USA
Jonathan G. Palmer
Palaeocology Centre, Queens University, Belfast, Northern Ireland, UK
Rosanne D. D'Arrigo
Lamont-Doherty Earth Observatory, Palisades, NY, USA
Abstract
The occurrence of the Medieval Warm Period (MWP) in the Southern Hemisphere is uncertain because of the paucity of well-dated, high-resolution paleo-temperature records covering the past 1,000 years. We describe a new tree-ring reconstruction of Austral summer temperatures from the South Island of New Zealand, covering the past 1,100 years. This record is the longest yet produced for New Zealand and shows clear evidence for persistent above-average temperatures within the interval commonly assigned to the MWP. Comparisons with selected temperature proxies from the Northern and Southern Hemispheres confirm that the MWP was highly variable in time and space. Regardless, the New Zealand temperature reconstruction supports the global occurrence of the MWP.
Published 18 July 2002.
---------------
And another source on temperatures in central Alps (similar to today) during the MWP :
Reconstruction of temperature in the Central Alps during the past 2000 yr from a d18O stalagmite record.
Mangini et al. Earth and Planetary Science Letters
Vol. 235, Issues 3-4, Pages 741-751, 15 July 2005. doi:10.1016/j.epsl.2005.05.010
The precisely dated isotopic composition of a stalagmite from Spannagel Cave in the Central Alps is translated into a highly resolved record of temperature at high elevation during the past 2000 yr. Temperature maxima during the Medieval Warm Period between 800 and 1300 AD are in average about 1.7°C higher than the minima in the Little Ice Age and similar to present-day values. The high correlation of this record to ?14C suggests that solar variability was a major driver of climate in Central Europe during the past 2 millennia.
ncdc.noaa.gov
-----------------
And a source describing cereal cultivation in Greenland and a chart reconstructing central England temperatures :
Medieval Northern Europe - the Medieval Warm Period
From around 600 AD to 1250 AD there is clear evidence that Northern Europe was becoming warmer. Evidence comes from:
18O record from the Greenland Ice Sheet.
Limits of cultivation were higher on hills than they have been in later centuries.
The upper tree line was higher than earlier or later times.
During the 900s, there is evidence of several periods of prolonged drought, particularly from sequences of very narrow tree rings (the tree growth was reduced by lack of water). At the same time, there is evidence suggesting a predominance of "anticyclonic" weather over Northern Europe. This would give a rather "settled" type of weather with warm, dry summers and cold (but still dry) winters. For example, archaeological investigations in York reveal large numbers of bone skates from the Anglo-Scandinavian period.
During the following two centuries, rainfall increased significantly and tree rings are correspondingly wider.
Settlement of Iceland by the Vikings began around 860 AD, although Irish monks had been there already. The earliest explorers and settlers reported sea ice not far to the north of Iceland and some of the northern Icelandic fjords being choked by ice. However, later records make no mention of ice until the late 1190s and only after 1203 was significant ice reported. Grain was grown in Iceland from the time of the first settlement to the late 1500s, when it was abandoned.
In 986, the first Viking settlement of Greenland began. At first the settlement was successful and it was even possible to grow cereals. The settlers lived by rearing sheep and cattle. None of this is possible today. At its peak, the Norse population reached about 4000, with about 300 farms, 12 churches, a cathedral, a monastery. The settlers also traded with the Eskimos further north. After about 1300, the climate began to deteriorate. Stock rearing became unreliable, crops failed and the settlements were cut off from the outside world by sea ice for several years at a time. Unlike the Eskimos, the Norse settlers were unable to adapt to living off the sea (where fish were still plentiful). The last recorded contact was in 1410, although archaeological evidence suggests that one settlement hung on until about 1500. A recorded visited by a ship in 1540 notes only abandoned farms.
Fig. 7.1. Norse settlements in Greenland
The peak of the Medieval Warm Period seems to have come later in Europe than in Greenland, with numerous records from the late 1200s of cultivation at higher levels than ever before.
7.2 Central England Temperature
Huge numbers of historical reports pieces of climate evidence have been combined into numerical indices which indicate the relative numbers of reports of warm or cold months in summer and winter for the central part of England. Similar indices have been compiled for rainfall. Although these are not considered to be very reliable for individual years or even decades in Medieval times, 50 year averages are considered to be reliable. These indices have been translated into the so-called Central England Temperature (CET) which gives a good indication of past climates. N The figure below shows the CET for the whole year since 900 AD.
Fig. 7.2 Central England Temperature since 900 AD, estimated from historical records. The dashed lines indicate the likely uncertainty. Adapted from H.H. Lamb, Climate History and the Modern World, 2nd Ed., Routledge, 1995. Note the Medieval Warm Period peaking around 1200 AD in England.
env.leeds.ac.uk
--------------------------
And another source showing warmer temps in China during the MWP than anytime since:
CHINA'S 2000-YEAR TEMPERATURE RECORD DISCREDITS CLIMATE ALARMISTS
CO2 Science Magazine, 19 November 2003
co2science.org
A 2000-Year Temperature Record of a Big Chunk of China
Controversy abounds over the temperature history of the earth, particularly that of the past one to two millennia. The origins of the debate date back only a few years to the papers of Mann et al. (1998, 1999), which describe an analysis that challenged the long-accepted view of most climatologists and prompted the Intergovernmental Panel on Climate Change to disavow their original presentation of the temperature history of the Holocene (Houghton et al., 1990, reproduced in Earth's Climatic History: The Last 10,000 Years). This earlier presentation had clearly indicated there was nothing unusual or unnatural about earth's current temperature, with many prior periods of time having experienced temperatures significantly higher than those of the past few decades.
The revisionist history of Mann et al. depicts a slightly undulating 1700-year temperature decline that ends with a dramatic 20th century warming that raises the mean surface air temperature of the Northern Hemisphere to a level that is unprecedented over the past 1800 years, although the same cannot be credibly claimed for the entire planet, unless the proxy-based record of the globe is extended at its end with modern instrumental data in an "apples and oranges" type of assumed equivalency [see our Journal Review of Mann and Jones (2003)].
This revisionist history of earth's climate was recently challenged by Soon and Baliunas (2003) and Soon et al. (2003a), who in turn were challenged by Mann et al. (2003a), who in turn were challenged by Soon et al. (2003b), who in turn were challenged by Mann et al. (2003b), who in turn were, well, you get the idea: the end of the debate is nowhere in sight. In addition, the revisionist climate history of Mann et al. was even more recently challenged on totally different grounds by McIntyre and McKittrick (2003), who in turn have been challenged by Mann and others (this time on the Internet), who in turn have been challenged in the same medium by McIntyre and McKitrick, and on and on it goes, again with no end in sight, even on the distant horizon.
Nevertheless, what had a beginning must eventually have an end; and so will this debate someday be decided, most likely by the ever-accumulating masses of data that allow ever more temperature histories of ever more parts of the world to be produced with ever more reliability. Hence, we continue to report on the many new developments in this field that will someday settle the issue once and for all, highlighting the two-millennia temperature history of central east China just published by Ge et al. (2003).
Working with 200 different sets of phenological and meteorological records extracted from a number of historical sources, many of which are described by Gong and Chen (1980), Man (1990, 2004), Sheng (1990) and Wen and Wen (1996), Ge et al. produced a 2000-year history of winter half-year temperature (October to April, when CO2-induced global warming is projected to be most evident) for the region of China bounded by latitudes 27 and 40°N and longitudes 107 and 120°E. They describe their findings thusly.
"From the beginning of the Christian era, climate became cooler at a rate of 0.17°C per century," which correlates well with the fact that this is the period of time when the planet slipped out of the Roman Warm Period and entered into the Dark Ages Cold Period, "and around the AD 490s temperature reached about 1°C lower than that of the present (the 1951-80 mean)."
"Then, abruptly, temperature entered a warm epoch from the AD 570s to 1310s with a warming trend of 0.04°C per century; the peak warming was about 0.3-0.6°C higher than present for 30-year periods, but over 0.9°C warmer on a 10-year basis." This finding pretty much speaks for itself. For a considerable amount of time during the Medieval Warm Period, this large chunk of China was warmer than has yet to be experienced in modern times over a similarly-extended time span.
"After the AD 1310s, temperature decreased rapidly at a rate of 0.10°C per century; the mean temperatures of the four cold troughs were 0.6-0.9°C lower than the present, with the coldest value 1.1°C lower." This, of course, was the Little Ice Age, from which the world appears to still be in processes of recovering.
"Temperature has been rising rapidly during the twentieth century, especially for the period 1981-99, and the mean temperature is now 0.5°C higher than for 1951-80." Although such might well be true, Ge et al. report temperatures during the Medieval Warm Period that rose higher still, and for several 10- and 30-year time periods.
As new data such as these from central east China continue to come to the fore, it is our belief that scientific support for the revisionist climate history of Mann et al. will gradually erode and that this entire sorry episode will be looked back upon with both dismay and disbelief by those who follow us.
Sherwood, Keith and Craig Idso
References
Ge, Q., Zheng, J., Fang, X., Man, Z., Zhang, X., Zhang, P. and Wang, W.-C. 2003. Winter half-year temperature reconstruction for the middle and lower reaches of the Yellow River and Yangtze River, China, during the past 2000 years. The Holocene 13: 933-940.
Gong, G. and Chen, E. 1980. On the variation of the growing season and agriculture. Scientia Atmospherica Sinica 4: 24-29.
Houghton, J.T., Jenkins, G.J. and Ephraums, J.J. (Eds.). 1990. Climate Change: The IPCC Scientific Assessment. Cambridge University Press, Cambridge, UK.
Man, Z. 1990. Study on the cold/warm stages of Tang Dynasty and the characteristics of each cold/warm stage. Historical Geography 8: 1-15.
Man, Z. 2004. Climate Change in Historical Period of China. Shandong Education Press, Ji'nan, China, in press.
Mann, M., Amman, C., Bradley, R., Briffa, K., Jones, P., Osborn, T., Crowley, T., Hughes, M., Oppenheimer, M., Overpeck, J., Rutherford, S., Trenberth, K. and Wigley, T. 2003a. On past temperatures and anomalous late-20th century warmth. EOS, Transactions, American Geophysical Union 84: 256-257.
Mann, M., Amman, C., Bradley, R., Briffa, K., Jones, P., Osborn, T., Crowley, T., Hughes, M., Oppenheimer, M., Overpeck, J., Rutherford, S., Trenberth, K. and Wigley, T. 2003b. Response [to Soon et al. (2003b)]. EOS, Transactions, American Geophysical Union 84: 273, 276.
Mann, M.E., Bradley, R.S. and Hughes, M.K. 1998. Global-scale temperature patterns and climate forcing over the past six centuries. Nature 392: 779-787.
Mann, M.E., Bradley, R.S. and Hughes, M.K. 1999. Northern Hemisphere temperatures during the past millennium: Inferences, uncertainties, and limitations. Geophysical Research Letters 26: 759-762.
Mann, M.E. and Jones, P.D. 2003. Global surface temperatures over the past two millennia. Geophysical Research Letters 30: 10.1029/2003GL017814.
McIntyre, S. and McKitrick, R. 2003. Corrections to the Mann et al. (1998) proxy data base and Northern Hemispheric average temperature series. Energy and Environment 14: 751-771.
Sheng, F. 1990. A preliminary exploration of the warmth and coldness in Henan Province in the historical period. Historical Geography 7: 160-170.
Soon, W. and Baliunas, S. 2003. Proxy climatic and environmental changes of the past 1000 years. Climate Research 23: 89-110.
Soon, W., Baliunas, S., Idso, C.D., Idso, S.B. and Legates, D.R. 2003a. Reconstructing climatic and environmental changes of the past 1000 years: A reappraisal. Energy and Environment 14: 233-296.
Soon, W., Baliunas, S. and Legates, D. 2003b. Comment on "On past temperatures and anomalous late-20th century warmth. EOS, Transactions, American Geophysical Union 84: 473.
Wen, H. and Wen, H. 1996. Winter-Half-Year Cold/Warm Change in Historical Period of China. Science Press, Beijing, China.
Copyright © 2003. Center for the Study of Carbon Dioxide and Global Change
abob.libs.uga.edu |
