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 (that’s 9 sets of 100)

How does having more data affect an average? 2014 global average temperature 58.24 oF

Observations?

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.

CO2 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 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 change? 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 changes 20,000 ybp (years before present) ice age: Bering strait freezes, people migrate to the Americas 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 1315-1317 – 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 now?) Explain how climate has changed over geologic time on Earth.

CO2 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??? Why???)