Energy Flows and feedback
processes: A systems perspective
Blue slides will have corresponding
questions in the student handout
From last time
• Your prediction: If rising CO2 increases
temperature, how will this change
evaporation (and H2O) in the atmosphere?
How do you think earth’s temperature will
respond?
• Take a minute to jot down your ideas in the space below,
compare with your neighbor and revise as appropriate, and
then be prepared to share with the class.
Example of a system diagram related to atmospheric water
What do you know?
Have you ever learned how to create and use systems diagrams
(causal loop diagrams)? ____Yes
___No
If yes, how would you rate your understanding of creating and using
them?
Very poor
1
2
3
4
5
Expert
Systems Diagrams
Our goal today is to learn how to create and analyze systems diagrams,
with emphasis on Earth’s climate system as well as their generic
applicability.
Review slide
Earth’s Energy Balance is used here to develop and explain causal loop diagrams.
Connections (+ or - ??)**
put a + or – near the tip of the arrow to indicate whether the connection between
the two climate system variables is positive or negative.
Absorbed Sunlight
Earth’s Mean Temperature
Planetary albedo
Earth’s Mean Temperature
Emitted Infrared
Earth’s Mean Temperature
Water Vapor
Earth’s Mean Temperature
CO2
Earth’s Mean Temperature
Cloud cover
Earth’s Mean Temperature
System variables should be nouns (Earth’s Temperature rather than warming.)
** 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 - ??)*
put a + or – near the tip of the arrow to indicate whether the connection between
the two climate system variables is positive or negative.
Absorbed Sunlight
+ Earth’s Mean Temperature
Planetary albedo
-
Earth’s Mean Temperature
Emitted Infrared
-
Earth’s Mean Temperature
Water Vapor
+ Earth’s Mean Temperature
CO2
+ Earth’s Mean Temperature
Cloud cover
+ or - Earth’s Mean Temperature
use nouns
* 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.
A system diagram
What are the missing connections? + or -
A system diagram: identifying
feedback structure
See Appendix 1 for further discussion of water vapor feedback.
Slides on clouds and climate from Appendix 2
could be inserted here but would likely make
this lesson exceed a normal 50 minute session.
A Challenge
• Draw a systems 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.
• Your diagram should have the sun’s brightness as an
external driver to Earth’s temperature and Earth’s
Temperature connected with emitted longwave
(infrared*) radiation.
* Infrared radiation emitted from Earth or its atmosphere is also referred to as
longwave or terrestrial radiation.
A first Challenge: diagram structure
• Draw a systems 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.
What are the missing connections? + or –
and is the loop a positive or negative feedback loop
A first Challenge: completed diagram
• Draw a systems 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
(or balances) the runaway effects of positive feedback processes.
Ice albedo feedback process
As Earth’s temperature increases
from increased solar radiation 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.
Again solar output (or intensity) is an
external driver and will not be within
the loop structure.
A systems diagram capturing the
essence of the feedback process is
shown on the next slide.
Ice albedo feedback. Diagram Structure
What is the polarity (sign) of each connection?
1.
2.
3.
4.
5.
What are the polarities of each connection?
What is the sign (polarity) of this feedback loop?
1. +
+
2.
-
3. +
+
-
+
4.
5. +
Is this a Positive or Negative feedback loop?
1. +
2.
+
-
3. +
+
-
4.
5. +
-
+
+
What is the sign of
this feedback loop?
Positive
When the number of
negative connections
in a causal loop is
even then the loop is
positive, odd then the
loop is negative.
It is important to realize that the negative feedback loop between
Earth’s temperature and emitted terrestrial radiation is always
present. This limits limits/balances the positive feedback.
The terms positive and negative feedbacks have
no reference to the value (good or bad) of the
feedback. They are often referred to as
amplifying and balancing feedbacks.
Sometimes the results of positive feedbacks are
characterized as “spiraling out of control” or the
“snow ball effect”.
Two new connections
Are the connections positive or negative?
Earth’s surface temperature
CO2 solubility in oceans
? CO
2
solubility in oceans
? Atmospheric CO
2
Two new connections
Are the connections positive or negative?
Earth’s surface temperature
CO2 solubility in oceans
- CO
2
solubility in oceans
- Atmospheric CO
2
Complete the causal loop diagram below. Make sure to label
all connections as + or – and also determine whether the
whole loop is a positive or negative feedback loop.
Complete the causal loop diagram below. Make sure to label
all connections as + or – and also determine whether the
whole loop is a positive or negative feedback loop.
+
+
+
-
The figure above shows 5 components of a systems diagram intended to show
the interconnections between key factors driving climate change policy.
• Take a minute to think about the possible connections between these
components and whether the connection are positive or negative.
• Pair up with a neighbor or two and exchange your ideas.
•
• Be prepared to share your ideas with the class.
As a start, think about whether the connections shown above are positive or
negative, and whether the loop structure is a positive or negative feedback
loop.
Then compare your answers with those of your nearest neighbors
and be prepared to share your results with the class.
How’d you do??
Add the connections shown above (CE and EA).
think about whether the connections shown above are positive or negative, and
whether the additional loop structure is a positive or negative feedback loop.
Compare your answers with those of your nearest neighbors and
be prepared to share your results with the class.
Two feedback loops shown above
ABCDA (outside perimeter)
ABCEA (right hand loop)
Finally, add the connections (BE and EB) shown above. Think about:
• How pressure on policy makers influences the media? + or • How the media influences pressure on policy makers? + or • Whether these are positive or negative connections, and whether the additional loop
structures are positive or negative feedback loops.
• In this diagram how many feedback loops are there?
Compare your answers with those of your nearest neighbors and be prepared to
share your results with the class.
Five loops
ABCDA (outside perimeter),
ABCEA (not shown with loop symbol-- perimeter of right side),
ABEA , BCEB , and BEB
All are positive in this example.
How would you rate your understanding of creating and
using systems diagrams now?
Very poor
1
2
3
4
5
Expert
What about today’s lesson has been most helpful?
What suggestions do you have for improvements in today’s lesson?
Assignment
Volcanic eruptions are a good example of a
natural climate forcing mechanism.
To prepare you for our module capstone project
on the possible effects of a modern day
catastrophic volcanic eruption, complete
Volcanic Eruptions Part A before coming to class
on _April 4 2015(the day of unit 6)______
A little background on volcanoes
How would a volcanic eruption alter Earth’s
mean surface temperature
Volcanic eruption
? Earth’s mean surface Temperature
Take a minute to jot down your ideas in the space below, compare with your
neighbor and revise as appropriate, and then be prepared to share with the class.
How would a volcanic eruption alter Earth’s
mean surface temperature
Volcanic eruption
- Earth’s mean surface Temperature
Figure suggests that solar cooling is greater than increased greenhouse trapping.
See 1883 Krakatoa eruption
And 1991 Mt Pinatubo Eruption
Both indicated by vertical lines
What: Large eruption event
Approximately 10 km3 (tephra)
10 Gtonnes magma (~ 5 km3)
20 Mtonnes SO2 (USGS)
Eruption: June 12 – 16 , 1991
The abundance of sulfate aerosols created from
SO2 and water vapor evolve over time.
Other reading related to System Diagrams
• Systems Diagrams: Understanding How Factors Affect One Another. By
Ruth hall http://www.mindtools.com/pages/article/newTMC_04.htm
• Guidelines for Drawing Causal Loop Diagrams By: Daniel H. Kim The
Systems Thinker, Vol 3, No 1, pp5-6 (Feb 1992).
http://www.cs.toronto.edu/~sme/SystemsThinking/GuidelinesforDrawing
CausalLoopDiagrams.pdf
• Folk Tales, Foreign Policy, and the Value of Systems Thinking By Karl
North | January 30, 2014
Appendix 1
Water vapor feedback
In your own words describe the feedback loop a b c d e a.
In your own words describe the feedback loop a b c d e a.
Possible Answer: As Earth’s temperature increases, increased evaporation
(not shown) increases atmospheric water vapor. This increases the
atmospheric emissivity, resulting in more longwave radiation going downward
from Earth’s atmosphere to its surface. This results in increased surface
heating and subsequently a higher surface temperature than would be
expected without this positive feedback process.
What is the meaning of loop a b c f g d e a?
What is the meaning of loop a b c f g d e a ?
Possible answer: this captures the idea that as the atmosphere warms it
also radiates more energy to the surface.
i.e. The downward flux of longwave radiation from the atmosphere to Earth’s
surface is proportional to the product of atmospheric emissivity and the fourth
power of atmospheric temperature.
Loop a b c d e a captures the increase in emissivity
Loop a b c f g d e a capture the increase in atmospheric temperature.
Appendix 2
Clouds and climate
High thin cirrus clouds versus Low thick clouds, a short digression.
Three regions on Earth: I) clear skies II) low clouds III) high thin clouds
Red arrows represent ???? and green represent ????
High thin cirrus clouds versus Low thick clouds, a short digression.
Three regions on Earth: I) clear skies II) low clouds III) high thin clouds
Red arrows represent solar radiation and green represent terrestrial
radiation.
High thin cirrus clouds versus Low thick clouds, a short digression.
I. Is our reference with no radiative forcing.
II. Low clouds reflect sunlight but since the clouds are low they radiate longwave
radiation nearly as well as the surface, so the radiative forcing is dominated by
the increased reflection of sunlight and is negative.
III. High thin cirrus clouds do reflect some sunlight. Since they are much colder than
the surface, their presence drastically decreases the outgoing longwave radiation
and hence the radiative forcing is positive. That is, the greenhouse effect of high
thin clouds is more important than their reflection of sunlight.
• T/F Increasing clouds in the atmosphere will
always decrease Earth’s surface temperature.
• T/F All clouds influence Earth’s climate in the
same way.
What might be the radiative effect of smog on
the Los Angeles area?
Think for a minute on your own and then share
with your neighbors.
What might be the radiative effect of smog on
the Los Angeles area?
There is no right or wrong answer to this
question as the answer would be highly
dependent upon the composition, density, and
vertical extent of the smog layer.
Appendix 3. Possible systems
diagrams for:
Select one of the ideas below as a basis to create a complete yet simple
systems diagram……. In your own words, briefly explain your causal loop
structure.
1. Dieting: emotional health, caloric food intake, person’s weight , exercise.
2. Drug addiction: Self-esteem, Risk for drug use, drug use, emotional instability
(Can you think of an outside factor may initiate the original change in self esteem).
3. Forest Fires: Forest fires, activity to stop fires, forest fire fuel.
4. Career success: Interest in career, amount of time spent working, success on
projects
5. Crying wolf: boredom relief, crying wolf, attention gained.
6. Market place: Product Inventory, product price, consumption of product
7. Or one of your own.
Appendix 3.1
Dieting: emotional health, caloric food intake, person’s weight , exercise.
Both loops are positive suggesting that either weight gain or loss can be amplified. It
is interesting to speculate about modifications to this diagram that may capture key
aspects of anorexia or bulimia disorders.
Appendix 3.2
Drug addiction: Self esteem, Risk for drug use, drug use, emotional instability (Can
you think of an outside factor that may initiate the original degradation of self
esteem).
Granted this is an over simplistic view of the drug addition cycle. Outside factors
could be dis-functional relationships, outside demands for performance, or loss of
loved-one or long held job.
Appendix 3.3
Forest Fires: Forest fires, activity to stop fires, forest fire fuel.
Assumptions:
1) As Forest fires increase in number the tendency to fight fire increases
2) Fighting fires reduces then burning of underbrush and other fuels so fighting
fires increases the available forest fire fuel
3) When there is more fuel the chance of a forest fire start from lightning or human
activity increases.
Appendix 3.4
Career success: Interest in projects, time spent working on projects,
success on projects.
Assumptions:
1) Interest in projects inspires spending time working on projects
2) time spent working on projects promotes success on projects.
3) success on projects fuels interest in projects.
Appendix 3.5
Crying wolf: boredom relief, crying wolf, attention gained
Assumptions:
1) Crying wolf works at gaining attention
2) The attention gained helps relieve boredom
3) success at boredom relief promotes the desire to continue to cry wolf.
Karl North describes the full story and the balancing loop that dominates once the
“townspeople” lose trust in the boy. He extends this analogy in
“Folk Tales, Foreign Policy, and the Value of Systems Thinking”
Appendix 3.6
Market place: Product Inventory, product price, consumption of product
The connections
1) As product inventory increases, product price decreases
2) As product price increases, consumption of product decreases
3) As consumption of product increases, product inventory decreases.
A specific example of this structure related to hogs and pork is given in
http://cabiles-cano.wikispaces.com/Case+8+-+Building+%26+Simulating+a+Model+Using+Dynamo
Appendix 4
Other examples
Chemical weathering
T/F All loops in the systems diagram above are negative
Chemical weathering
True/False All loops in the systems diagram above are negative