13 Sep 2013 ... o Application of System Dynamics. • Sample ... Sterman J. Business dynamics:
systems thinking and modeling for a complex world. Boston, MA: ...
PARTICIPATORY SYSTEMS THINKING AND MODELLING FOR CLIMATE CHANGE GCCRP Climate Change Early Career Research Network 13 September 2013 EcoCentre, Nathan Campus
Russell RICHARDS Oz SAHIN Marcello SANO
Outline
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System Dynamics o
Feedback loops
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System behaviours
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Basics of System Dynamics
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Modelling steps
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Application of System Dynamics
Sample Case
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Two ways of thinking
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Mechanistic, and Systemic
MECHANISTIC VIEW • Universe is a machine • Analytic method leads to reductionism • Very effective when change is slow
CAUSE
EFFECT
• Management intervention for Cause-Effect •Mitigate the Effect (Fire-Fight) •Eliminate the Cause (Better not happen again) •Run Away (and hide) 4
SYSTEMIC VIEW • Focusing on principle of system, particularly interdependent relationships • The interactions between the parts of the system become more important than the parts themselves • Dealing with detail complexity and dynamic complexity • Seeing processes of change rather than snapshots
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Mechanistic Vs. Systemic View Mechanistic View (Open Loop) Goals Problem
Decision
Results
Situation
Systemic View (Feedback)
Actions
Delay
Goals
Delay
Delay
Delay Delay
“Side Effects”
Delay Delay
Environment Delay
Goals of Others Delay
Delay
“Side Effects”
Delay
Actions of Others
Delay
Sterman J. Business dynamics: systems thinking and modeling for a complex world. Boston, MA: Irwin McGraw-Hill, 2000.
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Complex Systems The complexities arise from interactions and interdependencies of a large number of elements Complex systems are dynamic and characterized by:
• • • •
feedbacks, changes over time, interdependencies, and chaotic and discontinuous non-linear relations of their elements.
A Model Is… They help us understand, explain, anticipate, and make decisions
“All models are wrong, some are useful.” -- George Box Sterman JD. All models are wrong: reflections on becoming a systems scientist. System Dynamics Review 2002;18(4):501531. Available at Sterman J. A sketpic's guide to computer models. In: Barney GO, editor. Managing a Nation: the Microcomputer Software Catalog. Boulder, CO: Westview Press; 1991. p. 209-229.
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Types of Model
Models
Hardware
Scale
Analogue
Conceptual
Mathematical
Probabilistic
Deterministic
Increasing abstraction
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We model interesting behaviors, not whole systems
We don’t model the whole system. Instead we model interesting (problematic) behaviorsover-time. The system we model contains only those elements of the whole system that are deemed necessary to give rise to the behaviors-over-time of interest.
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System Dynamics
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Methodology to study systems behavior It is used to show how the interaction between structures of the systems and their policies determine the system behavior
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Approach developed to study system behaviors taking into account complex structures of feedbacks and time delays
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System Dynamics Basics
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Computer simulation modeling for studying and managing complex feedback systems, such as business, engineering, and social systems
• •
Think in terms of cause-and-effect Focus on Feedback Loops o
situation when output from an event will influence the same event in the future Study
Grades More
More More
Parents’ Expectations
SD Modeling: Standard approach • • • •
Identify the problem Develop a dynamic hypothesis Create a basic causal loop diagram Convert the causal diagram to a Stock flow diagram
• •
Write the equations Estimate the parameters and initial conditions. o
using statistical methods, expert opinion, market research data or other relevant sources.
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Simulate the model and analyze results
Voinov (2009) . Systems Science and Modeling for Ecological Economics
A Four Pattern of System Behaviour System Behaviours 2,000
Person
1,500 1,000 500 0 0
6
12
18
24
30 36 Time (Year)
42
48
54
60
Population : S-shaped Population : Exponential growth Population : Oscillation Population : Goal seeking
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Exponential/Unconstrained Growth Positive feedback loops generate growth, amplify deviations, and reinforce change. dx/dt = ax, Where a = constant Solution: x = ceat 1: Lev el
Sy stem Lev el
1:
1000.00
x 1
Inf low
a
1:
500.00
1
Net increase rate
1 1 1:
0.00 0.00
3.00 Graph 1 (Untitled)
6.00 Time
9.00
12.00
7:00 PM Tue, Nov 14, 2000
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Goal Seeking/Constrained Growth Negative feedback loops seek balance, equilibrium, and stability.
Correctiv e Action
Sy stem Lev el
1: Sy stem Lev el 1 1:
200.00
1
1
1
1:
150.00
1
Discrepancy 1:
Rate of change
Goal
100.00 0.00
3.00 Graph 1 (Untitled)
6.00 Time
9.00
12.00
9:18 PM Tue, Nov 14, 2000
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S-shaped Growth No real quantity can grow (or decline) forever, eventually one or more constraints halt the growth.
Net Increase Rate
Sy stem Lev el
1: Sy stem Lev el 1:
1000.00 1
1 1:
500.00
Resource Adequacy Normal Growth Rate
1
Carry ing Capacity
1:
0.00
1 0.00
5.00 Graph 1 (Untitled)
10.00 Time
15.00
20.00
10:05 PM Tue, Nov 14, 2000
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Oscillation Time delays cause the state of system to constantly overshoots its goal or equilibrium state, reverses, then undershoots, and so on.
Correctiv e Action
Sy stem Lev el
1: Sy stem Lev el 1 1:
350.00
1
1:
200.00
1
Perception 1
Perception Delay
Discrepancy
1
Rate of change
1:
Goal
50.00 0.00
10.00 Graph 1 (Untitled)
20.00 Time
30.00
40.00
9:29 PM Tue, Nov 14, 2000
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Feedback Loop / Causal Loop Diagram • •
Shows how one variable affects another. Nodes represent variables and arrows (called causal links) represent relationship
•
Difficult to infer the behavior of a system only from its casual-loop
Node + Feedback Loop
Population
representation
Causal Link
time
Example: Filling a glass of water Am I filling the glass of water? + Desired Water Level
Tap Position
+
+ Water Flow
Perceived Gap Current Water Level
+
Or, is the level of water controlling my hand?
Stock and Flow Diagram
• •
Distinguishes between different types of variables Consists of three different types of elements: stocks, flows, and information
Information
Stock
Flow
Stock and Flow Diagram SFD allows to represent relations among variables in terms of equations.
For Example: Population = Initial(Population)+ ∫ (birth-death)dt
It becomes infeasible to solve as stocks and flows increase Use computer simulators
Many simulators are available, We used Vensim PLE by Ventana Systems, Inc. Simulation result is time-history of variables in terms of Graph/Table
Example 1 (Population and birth) + Births
Population
+
Births Population
Example 2 (Children and adults) + Births +
Children -
+
-
+
Children maturing
Adults
+
Children maturing
Births children
Adults
Applications of System Dynamics o
Energy and the environment
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Water balance and security modeling
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Corporate planning and policy design
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Economic behavior
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Public management and policy
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Biological and medical modeling
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Supply chain management
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And, many other fields
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Thank you… Any Questions?
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