AGU published research paper, “Evidence for a ‘Medieval Warm Period’ in a 1,100 year tree-ring reconstruction of past austral summer temperatures in New Zealand”. Looks like it had world wide effect.
http://ruby.fgcu.edu/courses/twimberley/EnviroPhilo/CookPalmer.pdf

Sequoias endured 500 years of fiery drought during the Medieval Warm Period, tree rings show
http://newswatch.nationalgeographic.com/2010/03/18/sequoias_endured_500_years_fire_and_drought/

Woods Hole Oceanographic Institution Examines 2,000 years of sediment records for temperature reconstruction
“A new 2,000-year-long reconstruction of sea surface temperatures (SST) from the Indo-Pacific warm pool (IPWP) suggests that temperatures in the region may have been as warm during the Medieval Warm Period as they are today.”
“Water temperature during the late Medieval Warm Period, between about A.D. 1000 to 1250, was within error of modern annual sea surface temperatures. (Oppo, Rosenthal, Linsley; 2009)”

http://www.whoi.edu/page.do?pid=7545&tid=282&cid=59106&ct=162

Found another interesting page about sediment record analysis at Woods Hole, covering the Medieval Warm Period and the Little Ice Age
http://www.whoi.edu/oceanus/viewArticle.do?id=3842

“Events warmer than today occurred about 500 and 1,000 years ago, during the Medieval Warm Period, and it was even warmer than that prior to about 2,500 years ago.”
“Because the Sargasso Sea has a rather uniform temperature and salinity distribution near the surface, it seems that these events must have had widespread climatic significance. The Sargasso Sea data indicate that the Medieval Warm Period may have actually been two events separated by 500 years, perhaps explaining why its timing and extent have been so controversial. Second, it is evident that the climate system has been warming for a few hundred years, and that it warmed even more from 1,700 years ago to 1,000 years ago.”

This graph of the Sargasso Sea Surface Temperature, reconstructed from sediment cores, shows what they are talking about
http://www.whoi.edu/oceanus/viewImage.do?id=8722&aid=3842

There is a ton of data on reconstructed temperatures around the world from the Medieval Warm Period at the Woods Hole web page. Go there and search for ‘Medieval Warm Period’

http://www.whoi.edu/search.do?q=Medieval+Warm+Period&g=ext&search=Search&type=search

Paper offering high resolution temperature proxy data from an Alaskan lake over the past 6,000 yrs, derived from midge analysis on the sediments. Shows temperatures there were higher in the past 3,000 yrs than today
“Although the Moose Lake TJuly record displays an increasing trend over the past 150 years, the TJuly values in several warm intervals of the past 6000 years were comparable to or exceeded early 20th-century values. For example, the TJuly values during the MCA were generally higher than the early 20th-century values (Fig. 4C). ”
http://www.life.illinois.edu/hu/publications/Clegg_et_al_2010.pdf

Evidence for the existence of the medieval warm period in China
“Abstract
The collected documentary records of the cultivation of citrus trees andBoehmeria nivea (a perennial herb) have been used to produce distribution maps of these plants for the eighth, twelfth and thirteenth centuries A.D. The northern boundary of citrus andBoehmeria nivea cultivation in the thirteenth century lay to the north of the modern distribution. During the last 1000 years, the thirteenth-century boundary was the northernmost. This indicates that this was the warmest time in that period. On the basis of knowledge of the climatic conditions required for planting these species, it can be estimated that the annual mean temperature in south Henan Province in the thirteenth century was 0.9–1.0°C higher than at present. A new set of data for the latest snowfall date in Hangzhou from A.D. 1131 to 1264 indicates that this cannot be considered a cold period, as previously believed.”
http://www.springerlink.com/content/gh98230822m7g01l/

Greenland recently incurred record high temperatures and ice loss by melting, adding to concerns that anthropogenic warming is impacting the Greenland ice sheet and in turn accelerating global sea-level rise. Yet, it remains imprecisely known for Greenland how much warming is caused by increasing atmospheric greenhouse gases versus natural variability. To address this need, we reconstruct Greenland surface snow temperature variability over the past 4000 years at the GISP2 site (near the Summit of the Greenland ice sheet; hereafter referred to as Greenland temperature) with a new method that utilises argon and nitrogen isotopic ratios from occluded air bubbles. The estimated average Greenland snow temperature over the past 4000 years was −30.7°C with a standard deviation of 1.0°C and exhibited a long-term decrease of roughly 1.5°C, which is consistent with earlier studies. The current decadal average surface temperature (2001–2010) at the GISP2 site is −29.9°C. The record indicates that warmer temperatures were the norm in the earlier part of the past 4000 years, including century-long intervals nearly 1°C warmer than the present decade (2001–2010). Therefore, we conclude that the current decadal mean temperature in Greenland has not exceeded the envelope of natural variability over the past 4000 years, a period that seems to include part of the Holocene Thermal Maximum. Notwithstanding this conclusion, climate models project that if anthropogenic greenhouse gas emissions continue, the Greenland temperature would exceed the natural variability of the past 4000 years sometime before the year 2100.
http://www.agu.org/pubs/crossref/2011/2011GL049444.shtml

Chris Shaker

Seriously though, the heating and cooling of the Earth is a cyclical event. Science has proven that the planet has heated and cooled numerous times; causing droughts, floods, submersion of land masses, exposure of land masses, periods where there was no ice, and periods where the planet was half frozen. None of which was caused by humans. These changes often came rapidly and have caused indigenous people to migrate or change their lifestyles to compensate for the weather changes. In some extreme cases, it has resulted in the deaths of certain groups of people who were unable to adapt or relocate in time.

I remember reading an article in 2005 where scientists found an area near the Arctic where melting ice had revealed grass that had been flash frozen over 25,000 years ago. Some scientists also argue that we are over-due for another ice age, and that such an event can occur with little to no warning, and could likely happen at any time. Taking into consideration the recent lack of sun spot activity and that the winter of 2009-2010 resulted in record low temperatures for much of North America, Europe and Asia, I wouldn’t be surprised if the next ice age happens sooner than later.

It seems clear that this is the case in Europe. How well can it be demonstrated elsewhere? I am aware of that book about the 1500 year cycle, but I’ve read so much about temperature proxies that I’d like to step back from them and look at something I can relate to (what the heck do I know about marine sediment and tree rings — nothing) — hence, glaciers.