Past Climate Change
Learner Outcomes
At the end of this presentation you should be
able to describe the importance of the Younger
Dryas, Medieval Warming Period, and the Little
Ice Age.
Examples of Climate Change in the
Past
• Younger Dryas
• Medieval Warm Period
• Little Ice Age
Temperature Change
W. W. Norton. After McKenzie, 1998
Pleistocene
Younger Dryas
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10,000-8500 BC
Rapid cooling then rapid warming
Change in ocean circulation
North America melt water shut down Gulf
Stream
Younger Dryas
What is the Younger Dryas?
• Best preserved in a pollen record from northern Europe.
• During this event temperatures dropped abruptly 5-7oC
(within 50 years).
Medieval Warm Period
1100-1300 AD
• Vikings established
Greenland colony
Medieval Warm Period
Vikings
MWP
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800-1300 AD
Increased trade in Europe
Wine grapes grown in southern Britain
Japan experience MWP
Droughts in western US
Equatorial east Africa was drier
Vikings were busy: 800
Increased Trade
• Drift ice subsided
• Didn’t reappear until 1300s
• Increased settlement in areas where drift ice
had been
Knorr, the ship Vikings used to travel these
long distances.
Reason for Exploration
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Curiosity
More land
Banishment (Eric the Red was murderer)
Escape mean dictator (Norwegian King at
time, Harald Fairhair
Greenland Vegetation Resembled
Home
Ancient Norse Settlements
Greenland
• Trade necessary for Greenland survival
– Inadequate food supply
– Traded furs, wool, dairy products to obtain
vegetables, grains and timber
Greenland’s Viking Decline
• Early as 1130’s drift ice reappeared
• Cold weather, poor harvests, poor soil
management
• Decreasing meat supply
• (800) Early Vikings were 5’7”
• (1300) Late Vikings 5’ crippled, dwarflike,
twisted and diseased
Greenland Today: Seasonal Ice Melt
1992
Source: © 2005 ACIA
2002
2005
When was the Little Ice Age?
• An interval of cooling in the late
1500’s is known as the Little Ice
Age, which lasted through the
middle of the 19th century.
• This cooling was likely regional
rather than global in extent, and
may have been the result of
volcanic activity.
Skating on the Thames
Questions
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How do we define a glaciation?
How do ocean and air currents affect climate?
How do we measure glaciations?
What causes “short term” glaciations?
What causes “long term” glaciations?
Know when the Younger Dryas, Little Ice Age,
and Medieval Warming Trend occurred, possible
causes and their effects?
During the Younger Dryas
• A) Meltwater decreased the ocean conveyor
belt
• B) Rapid cooling occurred
• C) Rapid warming occurred
• D) all of the above