1. Generalized diagram of the Earth system

2. Systems Notation = system component = positive coupling
= negative coupling

3. Positive Coupling Car’s gas pedal Car’s speed Amount of food
eaten
Body weight
A change in one component leads to a change of the same
direction in the linked component

4. Positive Coupling Atmospheric CO2 Greenhouse effect
An increase in atmospheric CO2 causes
a corresponding increase in the greenhouse
effect, and thus in Earth’s surface temperature
Conversely, a decrease in atmospheric CO2
causes a decrease in the greenhouse effect

5. Negative Coupling Car’s break Car’s speed system Body weight Exercise
A change in one component leads to a change of the opposite
direction in the linked component

6. Negative Coupling Earth’s Earth’s albedo surface (reflectivity)
temperature
An increase in Earth’s albedo causes a
corresponding decrease in the Earth’s surface
temperature by reflecting more sunlight back to
space
Or, a decrease in albedo causes an increase in
surface temperature

7. Increasing carbon dioxide: forcing (long term)

8. Volcanic eruption: perturbation (short term)

9. positive coupling
childrens’
noise
parents’
anger
negative coupling

10. Negative Feedback Loops:
Electric Blankets
person A’s
body
temperature
person A’s
blanket
temperature
person B’s
blanket
temperature
person B’s
body
temperature

11. A Positive Feedback Loop: Mixed-up Electric Blankets
person A’s
body
temperature
person A’s
blanket
temperature
person B’s
blanket
temperature
person B’s
body
temperature

13. A simplified climate system:
Daisyworld
Average Temperature = 30 oC
No clouds, no ocean
Soil = light gray (absorbs some light)
Life = white daisies (reflects all light)
Sun = like Earth’s
Daisy growth = changes with temperature

14. Albedo: measure of reflectivity of a surface, expressed as a % of reflected insolation to incoming insolation.
(Christopherson, Elemental Geosystems, 2004)

16. albedo=0.75
albedo = 0.5

18. Systems diagram explicitly including albedo

19. Response of average surface temperature to daisy coverage
Systems diagram

20. completely covered planet

21. Equilibrium States: Graphical Determination
Overlay the two graphs (this is the graphical way of setting them equal to each other).
The points where they meet are equilibrium points.
Draw a systems diagram to determine whether each one is stable or unstable.

22. The Faint Young Sun Problem
More H2O
Kasting et al., Scientific American (1988)

23. Response of average surface temperature to daisy coverage
Systems diagram

24. External Forcing: the response of Daisy World
Assume that the external forcing is an increase in solar luminosity
The effect of temperature on daisy coverage should not change (this depends on the physiology of daisies)
The effect of daisy coverage on temperature should change: for the same daisy coverage, higher temperature