Transcript Causal Loop Diagrams

Homeostasis
• Walter Cannon 1932 “The Wisdom of the
Body”
• Jame Lovelock ~1969 Gaia hypothesis (Lovelock,
J.E.; Margulis, L. (1974). "Atmospheric homeostasis by and for the biosphere- The
Gaia hypothesis". Tellus 26 (1): 2–10.
• Draw a causal lop diagram describing a self
regulating component of the human body.
Example
• Draw a causal loop diagram to describe the
following:
• The sun becomes brighter causing Earth to
warm to a new equilibrium temperature.
sunlight
+
Earth’s mean Temperature
-
-
Emitted infrared energy
+
Coffee System
The hotter the coffee is
The faster it cools
Tc-TR
Cooling
Rate
+
Tc
The higher the cooling rate
The colder the coffee
TR
Cooling
Rate
-
Tc-TR
Coffee System
The hotter the coffee is
The faster it cools
The higher the cooling rate
The colder the coffee
Tc-TR
Tc
+-=-
TR
Cooling
Rate
Negative connection
The higher the cooling rate
The colder the coffee
Cooling
Rate
Tc
TR
-
Tc-TR
Positive connection
The hotter the coffee is
The faster it cools
Tc
Tc-TR
TR
+
Cooling
Rate
Negative feedback loop
The hotter the coffee is
The faster it cools
The higher the cooling rate
The colder the coffee
Tc-TR
Tc
+-=-
TR
Cooling
Rate
Cools with a characteristic time constant, t~10 minutes
Homeostasis is internal balance
Equilibrium
Stable equilibrium (negative feedback)
Unstable equilibrium (positive feedback)
• ,
Perturbations
Small changes that disturb a system
from its equilibrium state.
Hot Plate
Hot Plate
A simple Earth
TE
Heating rate
A simple Earth
Albedo
Absorbed
solar
TE
Heating rate
Complete the system diagram
• Daisy World simulation
Daisy World
Daisy coverage
Daisies
Ts
Albedo
Daisies
Ts
Daisy World
Daisies
Daisy coverage
Ts
Ts
Daisies
Daisy coverage
Daisy World
Ts
Ts
P1
P2
Daisies
P1
Daisies
Ts
Daisies
P2
albedo
albedo
Daisy World Model