1. Possible Causes of Climate Change  Plate Tectonics and Mountain Building Theory of plate tectonics Ridge and subduction Mountain interaction with airflow and ocean currents  Variation on the Earth’s Orbit Milankovitch Theory ○ Eccentricity ○ Precession ○ Obliquity

6. Possible Causes of Climate Change  Plate Tectonics and Mountain Building Theory of plate tectonics Ridge and subduction Mountain interaction with airflow and ocean currents  Variation on the Earth’s Orbit Milankovitch Theory ○ Eccentricity ○ Precession ○ Obliquity

7. Eccentricity

8. Evolution of Earth’s eccentricity. Data taken from Berger and Loutre (1991) Comparison of Antarctic temperature reconstructed from Vostok ice core deuterium measurements, with the Earth’s eccentricity cycle. Vostok temperature data was taken from Peteet et al. (1999)

9. Precession

10. Evolution of precession angle relative to the Northern Hemisphere Summer Solstice, and the associated July insolation at 65N. Data taken from Berger and Loutre (1991)

11. Obliquity

12. Evolution of the Earth’s obliquity. Data taken from Berger and Loutre (1991) Evolution of Mars’ obliquity. Data taken from Laskar et al. (2004)

13. Possible Causes of Climate Change  External Causes Change in incoming radiation Change in composition of the atmosphere Change in Earth’s surface  Feedback Mechanisms Infrared radiation (-) Snow-albedo feedback (+) Water vapor-greenhouse gas feedback (+?) Cloud feedback (+ or - ?)

15. What is feedback?  Feedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same event / phenomenon in the present or future.  Feedback is used in many applications, and here are a some examples: 1. Biology 2. Engineering 3. Computing systems 4. Social Sciences 5. Climate Science

16. Stefan-Boltzmann (Infrared Radiation) Feedback: Negative

17. Snow Albedo Feedback Mechanism: Positive

18. Water Vapor Feedback Mechanism: Thought to be positive by climate models and most climatologists

19. Cloud Feedback Mechanism: Sign of feedback basically unknown