Causal Loop Diagrams

Exponential growth of a bank account. The two positive connections between Bank balance and interest added for a positive feedback loop.

Causal Loop Diagrams

Earth’s Energy Balance. More absorbed sunlight increases Earth’s temperature. A warmer Earth sends off more heat radiation (a.k.a. longwave, infrared, or terrestrial) to space keeping our planet from getting too hot.Earth’s albedo is the fraction of sunlight reflected back into space without being absorbed.

Connections (+ or - ??)

Absorbed Sunlight Earth’s Mean Temperature

Emitted Infrared Earth’s Mean Temperature

Cloud Cover

Volcanic aerosol

Earth’s Mean TemperatureCO2

Remember use nouns

Earth’s Mean TemperatureWater Vapor

Planetary albedo Earth’s Mean Temperature

snow Cover Planetary albedo

Planetary albedo

Planetary albedo

Knowing the “sense” of connections between two system components is essential to understanding overall system behavior.

If when the first increases the second also increases the connection is positive.

If when the first increases the second also decreases the connection is negative.

Connections (+ or - ??) AnswersAbsorbed Sunlight Earth’s Mean Temperature

Emitted Infrared Earth’s Mean Temperature

Earth’s Mean TemperatureCloud Cover

Earth’s Mean TemperatureVolcanic aerosol

Earth’s Mean TemperatureCO2

Remember use nouns

Earth’s Mean TemperatureWater Vapor

Planetary albedo Earth’s Mean Temperature

+

-

+

+

-

-

-

+ or

snow Cover Planetary albedo+

Example

• Draw a causal loop diagram to describe the following:

• The sun becomes brighter causing Earth to warm. As the Earth warms it gives off more longwave radiation until it settles into a new equilibrium temperature.

Example

• Draw a causal loop diagram to describe the following:

• The sun becomes brighter causing Earth to warm to a new equilibrium temperature.

sunlightEarth’s mean Temperature

Emitted infrared energy+

-

-+

Air Resistance

Connections (+ or - ??)Size (area) of car Air resistance force

Air temperature Air resistance force

Speed of car

Remember use nouns

Air resistance force

weight

Air resistance

Net downward Force

Connections (+ or - ??)Size of parachuet Air resistance force

Altitude Air resistance force

Jumper’s speed

Remember use nouns

Air resistance force

Size of parachuet

Net downward forceAltitude

Jumper’s speed

Net downward force

Net downward force

Draw a causal loop diagram to describe the following:

As the sky diver falls she travels faster and faster until reaching a terminal velocity. Include diver’s speed, air resistance and net downward force in your diagram.

Gas pedal depression car’s speed

MPH above speed limit car’s speed

Home Heating

Home Heating

Home Heating