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

Earths Energy Balance. More absorbed sunlight increases Earths 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. Earths albedo is the fraction of sunlight reflected back into space without being absorbed.

Connections (+ or - ??) Absorbed SunlightEarths Mean Temperature Emitted Infrared Earths Mean Temperature Cloud Cover Volcanic aerosol Earths Mean Temperature CO2 Remember use nouns Earths Mean Temperature Water Vapor Planetary albedoEarths Mean Temperature snow Cover 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 - ??) Answers Absorbed SunlightEarths Mean Temperature Emitted Infrared Earths Mean Temperature Cloud Cover Earths Mean Temperature Volcanic aerosol Earths Mean Temperature CO2 Remember use nouns Earths Mean Temperature Water Vapor Planetary albedoEarths 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. sunlight Earths mean Temperature Emitted infrared energy

Example Draw a causal loop diagram to describe the following: The sun becomes brighter causing Earth to warm. As Earths surface warms it increases evaporation from the surface and adds water to the atmosphere which adds to the greenhouse effect.

Air Resistance

Connections (+ or - ??) Size (area) of carAir 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 parachuetAir resistance force AltitudeAir resistance force Jumpers speed Remember use nouns Air resistance force Size of parachuet Net downward forceAltitude Jumpers speed 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 divers speed, air resistance and net downward force in your diagram.

Draw a causal loop diagram showing how a thermostat works.

Gas pedal depression cars speed MPH above speed limit cars speed

Home Heating