CAS ES 107 Chapter Notes - Chapter 2: Gaia Hypothesis, Daisyworld, Mechanical Equilibrium
7 Jun 2018
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Chapter 2: Daisyworld
-system→ entity composed of diverse but interrelated parts that function as a complex whole
-components→ individual parts of a system (reservoir of matter, of energy like temp)
-state→ of a system is the set of important attributes that characterize the system at a particular
time
-the components of a system interact in such a way that a change in the state of a system is
“sensed” throughout the system
-couplings→ the linking of one component with another
-positive coupling→ a change in one stimulus (increase or decrease) leads to a change in the
same direction (negative coupling is the opposite)
-these interactions or couplings create a feedback loop between components
-negative feedback loops→ diminish the effects of disturbance (an increase in body temp,
makes you turn down the controller on blanket, the blanket gives off less heat, so now your body
temp decreases)
-positive feedback loops→ amplify the effects of disturbances
****count the number of negative couplings to tell if the feedback is negative or positive
-Negative feedback loops= odd number of negative couplings
-positive feedback loops= no negative couplings or even number of them
Equilibrium
-stable equilibrium state→ modest disturbances from this state will be followed by system
responses that return this state to its equilibrium state, this is created by a negative feedback loop
-unstable equilibrium state→ the slightest disturbance from a comfortable state led to system
disturbances that carried the system further and further from that state, positive feedback loop
Perturbations and Forcings
-perturbation→ temporary disturbance (SO2 in our atmosphere following a volcanic eruption
but it is later naturally removed from the air)
-forcing→ a more persistent disturbance (the gradual increase of sunlight received by earth over
the years is affecting climate)
DaisyWorld
-the extent of daisy coverage on this planet affects the surface temp and the surface temp affects
the growth rate of daises, which in turn affects the daisy coverage of the planet
Response of Surface Temp to changes in daisy coverage
-dark surfaces absorb more, and therefore reflect less, of the incoming solar energy than light
surfaces
-albedo→ reflectivity of a surface, and is expressed as a decimal fraction of the total incoming
energy reflected from the surface
-the more daises, the more sunlight is reflected off their white petals, the less sunlight absorbed,
and finally the cooler the surface temp
-the daises must also have an optimum, or favorable, temp for growth
-if the temp is below the optimum value for daisy growth, the coupling is negative. If the temp is
above the optimum value, the coupling is positive
find more resources at oneclass.com
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Document Summary
System entity composed of diverse but interrelated parts that function as a complex whole. Components individual parts of a system (reservoir of matter, of energy like temp) State of a system is the set of important attributes that characterize the system at a particular time. The components of a system interact in such a way that a change in the state of a system is. Couplings the linking of one component with another. Positive coupling a change in one stimulus (increase or decrease) leads to a change in the same direction (negative coupling is the opposite) These interactions or couplings create a feedback loop between components. Negative feedback loops diminish the effects of disturbance (an increase in body temp, makes you turn down the controller on blanket, the blanket gives off less heat, so now your body temp decreases) Positive feedback loops amplify the effects of disturbances.
