Medieval Warm Period

1. Medieval Warm Period Elizabeth Machado

2. What was the Medieval Warm Period? • The Medieval Warm Period (MWP) is the name given to the warm period observed in many parts of the world between 900 and 1200 AD. • Also known by Medieval Climate Optimum and Medieval Climatic Anomaly.

3. Temperature change during the MWP • The warmest part of the Medieval Warm Period was from about 950 until 1100 A.D. • There was also a slight cooling from 1040-1080 AD known as the Oort Minimum.

4. Hubert H. Lamb • Was a climatologist. • Developed early theories of Medieval Warm Period and the Little Ice Age. • 1965 published “The Early Medieval Warm Epoch and its Sequel”. • In this study he said that there is evidence for a warm climate followed by cooling that lasted a few centuries.

5. Causes • The sun is the driving force of climate change. • The warm climate overlaps with a time of high solar activity called the Medieval Maximum. • Also there was a decline in volcanic activity during this time. • Less terrestrial dust and sea spray in the MWP than in the Little Ice Age.

6. Conditions • With warmer temperatures, agriculture was possible at higher latitudes than is currently possible in many regions. • Bountiful harvests (such as grain) throughout Europe during this time. • Fig trees and olive trees grew in regions of Europe (northern Italy and parts of Germany) well north of their current range. • Geological evidence indicates that mountain glaciers throughout Europe retreated substantially at this time.

7. Conditions Continued • Central European vineyards have been found at elevations more than 200 m higher than today, indicating that summers were up to 1.5 °C warmer. • This indicates that there was little or no frost in the late spring, and summers that were relatively dry and sunny. • This is confirmed by estimates of seasonal temperature and rainfall compiled by Lamb, who estimated the mean temperature for July and August in central England from 1150 to 1300 at 16.3 °C compared with 15.8 °C for 1900–50. • Ice cores show that it was 1°C higher than today.

8. Conditions Continued • More land was devoted to agriculture. • Population in Europe increased by 50%. • Economies grew. • Vikings were able to navigate to Greenland because of less ice in the Atlantic. http://www.second-opinions.co.uk/images/viking-ship.jpg http://www.culturalgadfly.com/wp-content/uploads/2009/12/plow_medieval-300x264.gif

9. Settlers in Greenland • In Greenland, the Norse settlers, arriving around 1000 AD, maintained a settlement, raising dairy cattle and sheep. • Encouraged by the sight of pastures, grasses and dwarf woodlands of birch and willow resembling those at home.

10. How Do We Know Temperatures Were Warmer in Greenland? • The discovery early in the twentieth century of plant roots and Norse burial grounds in subsequently frozen soil suggests that temperatures were 2–4 °C higher than in the twentieth century. • Accounts told by people. http://upload.wikimedia.org/wikipedia/commons/thumb/1/17/Nicholas_Roerich%2C_Guests_from_Overseas.jpg/800px-Nicholas_Roerich%2C_Guests_from_Overseas.jpg

11. Was the MWP Global? • Evidence shows that South Africa had a warming from 900-1290 AD, which is the same time as the MWP. • East Africa was dryer than today. • China also experienced warm temperatures from 800-1400 AD and like Europe had a prosperous economy. • Pollen samples from different parts in the world show that there was a general warming in temperature during the Medieval Warm Period.

12. The end of the MWP • MWP was followed by the Little Ice Age (1280-1850). • Sea routes became tougher to navigate because of ice. • Difficult for the Norse to survive in Greenland.

13. Dr. Deming and his Study • Dr. Deming published an article in 1995 that looked at the borehole temperature data in North America. • He concluded that the warming is still within the range of estimated natural variability. • After this article he received an email from a climate researcher that said they had to get rid of the Medieval Warm Period.

14. “We Have to Get Rid of the MWP” • http://www.youtube.com/watch?v=u1rj00BoItw

15. What IPCC Said about MWP • “Current evidence does not support globally synchronous periods of anomalous cold or warmth over this time frame, and the conventional terms of 'Little Ice Age' and 'Medieval Warm Period' appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries".

16. Michael Mann’s Hockey Stick Graph

17. IPCC, hockey stick and MWP • Climate models used by the IPCC are inaccurate and incomplete. • The Medieval Warm Period and Little Ice Age almost disappeared, replaced by a largely benign, slight cooling trend that lasted until the 1900s.

18. What does the IPCC have to say about the graph now? • “Palaeoclimate science has made significant advances since the 1970s, when a primary focus was on the origin of the ice ages, the possibility of an imminent future ice age, and the first explorations of the so-called Little Ice Age and Medieval Warm Period. Even in the first IPCC assessment (IPCC, 1990), many climatic variations prior to the instrumental record were not that well known or understood. Fifteen years later, understanding is much improved, more quantitative and better integrated with respect to observations and modeling”. -IPCC

19. Actual Records Show… http://www.c3headlines.com/2010/06/2010-antarctica-peerreviewed-research-ice-core-data-confirms-medieval-period-warmer-than-present.html

20. What Does this Show? • This graph of ice cores from Dome C in Antarctica shows that the MWP was 1°C warmer than current temperatures. • It also shows that climate change is driven by natural forces and not caused by humans.

21. Conclusion • The Medieval Warm Period was 1°C warmer than today. • The IPCC, Michael Mann and others try to deny the existence of this time even though there is evidence that backs it up. • Climate change is driven by natural forces not by humans.