Notes: Climate on a geologic scale

Wasting class time?
Please get out a piece of paper and read the
board! 
Climate – on a geologic scale
First, try this:
Take the average of the following numbers:
100, 0
Take the average of
100,100,100,100,100,100,100,100,100,& 0
(that’s 9 sets of 100)
How does having more data
affect an average?
2014 global average temperature
58.24 oF
Three important inferences
Climate change has been a natural cycle
100,000 year cycles between glacial
maximum (ice age) and interglacial periods
(maximum warmth)
A change in global average of -3oC (about 5oF) can create an ice age
*Historically, the RATE has been slow
enough that species could evolve to keep up
with the changes.
CO levels in the geologic record
Response of ocean to increased radiation
as Milakovitch cycles brought Earth closer
to sun: warm ocean releases CO2
Milankovitch cycles create the 100,000
yr pattern
Obliquity (Axial tilt)
Eccentricity (orbit eliptical or circular)
Precession (wobble on axis)
Combination of these creates 100,000 year
cycle of warming and cooling
Earth’s orbit
around the sun
So where did this data come
from? (since historic records
have only been kept since 1880)
Studying geologic climate
Historic records exist 130 years (since 1880)
Inferred/Implied records
Fossil records
Tree rings – relative amounts of oxygen
isotopes (proxy methods)
Ice cores - paleothermometers
Tree rings – isotopes of Oxygen
Ice core sampling
Check for understanding
Which is surprising to climatologists – that the
climate changes or the current rate of
What is the name of the 100,000 year cycles of
warming and cooling?
How do climatologists study the ancient
atmosphere? (name 4 ways)
Why is a .7oC (1oF) change significant?
Climate and civilization
Human civilizations change when climate
20,000 ybp (years before present) ice age:
Bering strait freezes, people migrate to the
8,000-7,000 ybp – warming period
Mesopotamia flourishing, Jericho established
Mayan civilization – collapses suddenly
950 CE (common era – used to be called AD)
Leif Erikson – 950 CE sails to Greenland
Black Death in Europe – famine 13151317 – needed to import grain from China
Little Ice age – 1550-1850
Irish Potato Famine
Dust Bowl – 1930’s
Mild but persistent La
Nina conditions
coupled with changes
of sea surface
temperatures + poor
farming practices
Discuss with your neighbor:
How do humans depend on predictable
climate? (any examples in the news right
Explain how climate has changed over
geologic time on Earth.
CO levels currently
Mauna Loa Observatory - Hawaii
CO2 at beginning of Industrial revolution: 280 ppm
Current CO2 levels: 398ppm
(watch the movie – when is CO2 highest? Where???