Causal Loop Diagrams Causal loop diagrams can be

Causal Loop Diagrams Causal loop diagrams can be very helpful for explaining the mechanism behind feedback loops and identifying whether the feedback loop structure is a positive or negative feedback loop.

Earth’s Energy Balance is used here to develop and explain causal loop diagrams.

Connections (+ or - ? ? )* Absorbed Sunlight Earth’s Mean Temperature Planetary albedo Earth’s Mean Temperature Emitted Infrared Earth’s Mean Temperature Cloud Cover Earth’s Mean Temperature Volcanic aerosol Earth’s Mean Temperature Water Vapor CO 2 use nouns Earth’s Mean Temperature * A connection is positive if when the first increases the second also increases, and a connection is negative (opposite) if when the first increases the second decreases

Connections (+ or - ? ? ) Absorbed Sunlight Planetary albedo Emitted Infrared Cloud Cover* Volcanic aerosol Water Vapor CO 2 use nouns + + or - Earth’s Mean Temperature - Earth’s Mean Temperature + Earth’s Mean Temperature * The effect of cloud cover is complicated because they reduce sunlight be day but provide warming at night. High thin ciro stratus clouds also influence the Earth system differently than low thick stratus clouds.

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.

Answer • 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 + Notice that the sun is not within the feedback loop structure. This negative feedback loop is always present in the Earth System and helps limit the runaway effects of positive feedback processes.

Ice albedo feedbck process Draw a causal loop diagram capturing the essence of the feedback process decribed below. As Earth’s temperature increases from an increase in solar output there will be less snow and ice cover globally. This decreases the planetary albedo causing even more sunlight to be absorbed by the climate system resulting in amplified warming.

What are the polarities of each connection? 1. 2. 3. 4. 5.

What are the polarities of each connection? 1. + + 2. - 3. + + - - 4. 5. + What is the sign of this feedback loop? +

What is the sign of this feedback loop? 1. + + 2. - 3. + + - - + 4. 5. + What is the sign of this feedback loop? +

Air Resistance

Connections (+ or - ? ? ) Size (area) of car Air resistance force Air temperature Air resistance force Speed of car Air resistance force Remember use nouns

Connections (+ or - ? ? ) Size (area) of car + - Air temperature Air resistance force** + Speed of car Remember use nouns **Warmer air is thinner air Air resistance force

Air resistance Net downward Force weight

Connections (+ or - ? ? ) Size of parachuet Air resistance force Altitude Air resistance force Jumper’s speed Air resistance force Remember use nouns

Connections (+ or - ? ? ) + Size of parachuet - Altitude Air resistance force + Air resistance force Jumper’s speed Note: our text uses For an opposite connection - Remember use nouns o

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, weight, and net downward force in your diagram.

Whenever the number of negative (opposite) connection is odd The loop is a negative feedback loop.