1 Robert S. Webb, Roger S. Pulwarty, Kristen Averyt Defining and Expressing Uncertainty Or, how not...
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Transcript of 1 Robert S. Webb, Roger S. Pulwarty, Kristen Averyt Defining and Expressing Uncertainty Or, how not...
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Robert S. Webb, Roger S. Pulwarty, Kristen Averyt
Robert S. Webb, Roger S. Pulwarty, Kristen Averyt
Defining and Expressing Uncertainty
Or, how not to do the wrong thing more precisely
Defining and Expressing Uncertainty
Or, how not to do the wrong thing more precisely
"In this world nothing can be said to be certain, except death and taxes." - Benjamin Franklin
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Desire for scientific certainty and unanimity among "experts" a barrier decisions to
mitigate or adapt to climate change
Desire for scientific certainty and unanimity among "experts" a barrier decisions to
mitigate or adapt to climate change
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Uncertainty in climate predictionsUncertainty in climate predictions
Uncertainty - a fundamental characteristic of weather, seasonal climate, and hydrological prediction, and no forecast is complete without a description of its uncertainty
Uncertainty - an overarching term that refers to the condition whereby the state of a system cannot be known unambiguously. Probability is one way of expressing uncertainty.
Probabilistic forecasts convey uncertainty in the prediction. The converse are deterministic forecasts, which provide single predictions of the future state of a system, with no information regarding uncertainty
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• “….The most important questions of life are, for the most part, really only problems of probability”(Laplace, Théorie Analytique des Probabilités, 1812)
• "The research community should be focused on delivering a "coherent" product without major disagreements, to the user communities if it seeks to have the information acceptable and used wisely" (Changnon, 1994)
• "Incorporating" or "building in" forecast information into a decision-making process does not automatically result from an explicit demonstration of “value” (Stewart, 1994)
• Value is a complex, user-dependent function (Murphy, 1994)
Uncertainty, managing risk, hedging strategiesUncertainty, managing risk, hedging strategies
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Epistemology: Are we asking the right question?
Risk: odds known Technical uncertainty: odds unknown, but
main parameters may be known Ignorance: don’t know what we don’t know Indeterminacy: causal chains/networks are
open (physical outcomes depend on social and institutional behavior)
Disagreement: divergence over observation, framing and interpretation of issues.
Epistemology: Are we asking the right question?
Risk: odds known Technical uncertainty: odds unknown, but
main parameters may be known Ignorance: don’t know what we don’t know Indeterminacy: causal chains/networks are
open (physical outcomes depend on social and institutional behavior)
Disagreement: divergence over observation, framing and interpretation of issues.
Types of uncertainty
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Different types and sources of uncertainty characterizations
Different types and sources of uncertainty characterizations
Morgan and Henrion Funtowicz and Ravetz
(1990) (1985)
1. Empirical quantities 1. Technical uncertainties
2. The functional form of models 2. Methodological3. Disagreements among experts 3. Epistemological
Morgan and Henrion Funtowicz and Ravetz
(1990) (1985)
1. Empirical quantities 1. Technical uncertainties
2. The functional form of models 2. Methodological3. Disagreements among experts 3. Epistemological
Decision analysis vs Decision-making
Decision Event vs Decision Process
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Sources of uncertaintySources of uncertainty
ObservationsInstrumental errorSpatial/temporal sampling
Methodology/TechnicalVariable quantities are uncertain because their
value varies, seemingly stochasticallyUncertainty in model parameters based on expert
judgment or on empirical estimates of a parameter's value
Uncertainty in model functional formsUncertainty in reduced model forms are based
on comparisons of full-form with reduced-form model results
Behavior/EnvironmentalPersonal/societal interactions and feedbacks
ObservationsInstrumental errorSpatial/temporal sampling
Methodology/TechnicalVariable quantities are uncertain because their
value varies, seemingly stochasticallyUncertainty in model parameters based on expert
judgment or on empirical estimates of a parameter's value
Uncertainty in model functional formsUncertainty in reduced model forms are based
on comparisons of full-form with reduced-form model results
Behavior/EnvironmentalPersonal/societal interactions and feedbacks
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Minimizing uncertainty:Minimizing uncertainty:
Where is the uncertainty? Where is the uncertainty?
--Problem DomainProblem Domain
-science-science
-organizational-organizational
-community-community
-political-political
- adequate theory- adequate theory-multiple hypotheses-multiple hypotheses & congruent management & congruent management actions.actions.-tractability (complexity) -tractability (complexity) -confronting models w/data-confronting models w/data-independence/ rigor-independence/ rigor-novelty-novelty
Gunderson and others
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Managing Uncertainty:Managing Uncertainty:
Where is it? Where is it? --Problem DomainProblem Domain
-science-science
-organizational-organizational-community-community-cognitive-cognitive-political-political
- expressions of power- expressions of power- multiple equilibria- multiple equilibria
paths not takenpaths not taken- NONE are scale invariant - NONE are scale invariant - stability of institutions- stability of institutions
novelty of approachesnovelty of approaches-role of epistemic groupsrole of epistemic groups-perception of riskperception of risk-multiple discourses-multiple discourses-juggling domains-juggling domains
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Uncertainty in Weather vs. Climate
Uncertainty in Weather vs. Climate
Challenge....
What works for weather may not work for climate
“The entire [weather and climate] enterprise should take responsibility for providing products that effectively communicate forecast uncertainty information” NRC, 2006
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Climate & UncertaintyClimate & Uncertainty
Virtually certain
Extremely likely
Very likely
Likely
More likely than not
About as likely as not
Unlikely
Very unlikely
Extremely unlikely
Exceptionally unlikely
>99%
>95%
>90%
>66%
>50%
33–66%
<33%
<10%
<5%
<1%
IPCC AR4 WGI Terminology
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Climate & UncertaintyClimate & Uncertainty
FAR: IPCC (1990) Broad overview of climate change science, discussion of uncertainties and evidence for warming.
SAR: IPCC (1995) “The balance of evidence suggests a discernible human influence on global climate.”
TAR: IPCC (2001) “Most of the warming of the past 50 years is likely (>66%) to be attributable to human activities.”
AR4: IPCC (2007) “Warming is unequivocal, and most of the warming of the past 50 years is very likely (90%) due to increases in anthropogenic greenhouse gases.”
Did it work?
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Climate & UncertaintyClimate & UncertaintyGlobal Warming ‘very-likely’ Man-Made AP, Feb 1 2007
Science Panel calls global warming ‘unequivocal’
NY Times, Feb 2 2007
World urged to act on definitive report
Financial Times, Feb 2 2007
New tack on global warming: Report’s dire forecast seen as call to action
Chicago Tribune, Feb 4 2007
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Climate & UncertaintyClimate & Uncertainty
Virtually certain
Extremely likely
Very likely
Likely
More likely than not
About as likely as not
Unlikely
Very unlikely
Extremely unlikely
Exceptionally unlikely
>99%
>95%
>90%
>66%
>50%
33–66%
<33%
<10%
<5%
<1%
IPCC AR4 WGI Terminology
Very high confidence
High Confidence
Medium Confidence
Low confidence
Very low confidence
At least 9 out of 10
About 8 out of 10
About 5 out of 10
About 2 out of 10
Less than 1 out of 10
IPCC AR4 WGII Terminology
CCSP SAP 4.3
One size does not fit all!
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Regional Climate Assessments: Uncertainty Language
Regional Climate Assessments: Uncertainty Language
Quote & explain IPCC likelihood statements
Uses and explains IPCC terminology but scientists make own judgments
No uncertainty framework
“Modeling projections...indicate that by the 2080s the most probable amounts of change in NYC and its Watershed Region will be 7.5ºF to 8.0ºF....”
“Climate models project Colorado will warm 2.5ºF [1.5ºF to +3.5ºF by 2025....”
“...annual average temperatures across Pennsylvania are projected to increase by 2.5ºF....”
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Regional Climate Assessments: Uncertainty Language
Regional Climate Assessments: Uncertainty Language
Quotes & explains IPCC likelihood statements
Uses and explains IPCC terminology but scientists make own judgments
No uncertainty framework
“It is extremely likely (>95%) that global temperatures and temperatures over Chicago are expected to warm further over coming decades....”
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Regional Climate Assessments: Uncertainty Language
Regional Climate Assessments: Uncertainty Language
Quotes & explains IPCC likelihood statements
Uses and explains IPCC terminology but scientists make own judgments
No uncertainty framework
“also likely, though less certain, are increases in precipitation quantity (particularly in winter and spring), precipitation intensity, intensity of tropical and extratropical cyclones (though their frequency may decrease), and sea-level variability....”
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Regional Climate Assessments: Education
Regional Climate Assessments: Education
All had detailed explanations of
models, scenarios, downscaling, and
climate projections
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Moving ForwardMoving Forward
Do we need a best practices for regional climate assessments, including how best to develop the data (model results) that go into the them?
Can an uncertainty framework be developed that can be used in all regions by all sectors for all products?
Can we take the IPCC model and develop a model framework?
Can a typology approach work with different frameworks for different users?
Or should regions be left to their own devices?
Do we need a best practices for regional climate assessments, including how best to develop the data (model results) that go into the them?
Can an uncertainty framework be developed that can be used in all regions by all sectors for all products?
Can we take the IPCC model and develop a model framework?
Can a typology approach work with different frameworks for different users?
Or should regions be left to their own devices?
The need for climate information to inform decisions is immediate…and everyone is trying to fill that gap.
Different uncertainty frameworks are being used depending on the type of climate information, the intended use for planning, and the scale.
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Climate ScienceSociety:
Impact andresponse
Historical model of communicating uncertainty
Traditional Science and Policy InteractionsTraditional Science and Policy Interactions
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Participatory assessments:
Pathways for Communicating UncertaintyPathways for Communicating Uncertainty
Is the research compatible with existing
decision models?
Is the research accessible to policy/decision maker?
Are policymakers receptive to the
problem and to research?
Is the research relevant for decisions?
Analysis of usefulness for policy/decision making arena
Goals, Criticality, time frame, basis for decisions, usability, entry points, experience
Are the sources/providers of information credible
to the decision maker?
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1. Bring the delivery persons, research community etc, to an understanding of what has to be done to translate current information into usable information: assess this process
2. Interacting with actual and potential users to better understand the true informational needs, desired formats of information, timeliness of delivery etc.: How do people know what they’re missing?
3. Identify areas of agreement and divergence between scientists engaged in prediction/forecasting, the community that carries out research in impacts and human resources, and the community at large
1. Bring the delivery persons, research community etc, to an understanding of what has to be done to translate current information into usable information: assess this process
2. Interacting with actual and potential users to better understand the true informational needs, desired formats of information, timeliness of delivery etc.: How do people know what they’re missing?
3. Identify areas of agreement and divergence between scientists engaged in prediction/forecasting, the community that carries out research in impacts and human resources, and the community at large
Process for empowering decision making under uncertainty
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1. Classic decision analysis,2. Traditional scenario planning,3. Robust decision making,4. Real options, and5. Portfolio planning.
Decision Support Planning Methods: Incorporating Climate Change
Uncertainties into Water Planning
Decision Support Planning Methods: Incorporating Climate Change
Uncertainties into Water Planning
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• probability-based• systematically catalogs information and
mathematically evaluating and ranking decision alternatives against multiple, potentially conflicting, decision objectives
• illustrates the process with a decision tree or influence diagram
• handles uncertainty through the use of probabilities.• used to find a preferred plan with the best value
Decision Support Planning Methods: Incorporating Climate Change
Uncertainties into Water PlanningClassic decision analysis
Decision Support Planning Methods: Incorporating Climate Change
Uncertainties into Water PlanningClassic decision analysis
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• scenario-based • objective is development of a plan that best prepares
for a plausible range of uncertain circumstances• scenarios are developed through the identification of
critical uncertainties and driving forces • goal is to develop a range of future conditions that go
beyond extrapolation of current trends and represent surprising but plausible conditions
• scenarios are treated as equally likely to occur
Decision Support Planning Methods: Incorporating Climate Change
Uncertainties into Water PlanningTraditional scenario planning
Decision Support Planning Methods: Incorporating Climate Change
Uncertainties into Water PlanningTraditional scenario planning
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• combines features of both classic decision analysis and traditional scenario planning
• systematic way of developing a strategy to best adapt to a wide range of plausible future conditions
• uses existing or modified decision models to evaluate candidate strategies against large sets of quantitative scenarios that reflect future uncertainty.
• used to identify major vulnerabilities within these strategies (unacceptable consequences).
• hedging options and alternative strategies are develop to address vulnerabilities
• Successive iterations lead to robust strategies
Decision Support Planning Methods: Incorporating Climate Change
Uncertainties into Water PlanningRobust decision making
Decision Support Planning Methods: Incorporating Climate Change
Uncertainties into Water PlanningRobust decision making
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• helps identify strategies that adjust over time and balance risks.
• determines sets of strategies that maximize value by using traditional discounted cash flow approaches.
• flexible investment strategies are sought that can be• risk-adjusted with time and deferred into the future• Uncertainties are handled through the use of
probabilities• Results are flexible in that they may incorporate
delaying and phasing of decision implementation
Decision Support Planning Methods: Incorporating Climate Change
Uncertainties into Water PlanningReal options
Decision Support Planning Methods: Incorporating Climate Change
Uncertainties into Water PlanningReal options
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• used in the financial world to select a portfolio containing a mix of assets or strategies that minimize exposure due to future scenarios
• uncertainty is handled through the use of probabilities and Monte Carlo simulations
• exposure to uncertainty is minimized through hedging• used extensively in the electric utility area
Decision Support Planning Methods: Incorporating Climate Change
Uncertainties into Water PlanningPortfolio planning
Decision Support Planning Methods: Incorporating Climate Change
Uncertainties into Water PlanningPortfolio planning
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___________________________________________________________________________
Approach Assumptions and actions
Development and From the risk expert to the public--finite and
delivery of a risk message uni-directional
Aimed at bringing public views into line with expert views
Assumes expert view has more validity for decision-making
Dialogue about risk Interactive exchange of risk information--continuous
Aimed at balancing the content of risk message
Assumes both views contribute to decision-making
Social processes Engage in a process that addresses concerns about risk
of risk communicationAimed at enhancing understanding among stakeholders (DECISIVE AND NON-DECISIVE). Assumes the process is as important as the product
_____________________________________________________________________________• Problem-definition and Framing: Mapping decision processes and information needs
across temporal and spatial scales
Approaches to risk communication and associated assumptions
Approaches to risk communication and associated assumptions
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Decisions are made every day under the cloud of uncertaintyDecisions are made every day under the cloud of uncertainty
3131
Backup SlidesBackup Slides
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Managing an Uncertain Future: Climate Change Adaptation Strategies for
California’s Water
Managing an Uncertain Future: Climate Change Adaptation Strategies for
California’s Water• array of adaptive water management
strategies must be implemented to better address the risk and uncertainty of changing climate patterns
• precipitation and runoff patterns are changing, increasing the uncertainty for water supply and quality, flood management, and ecosystem functions
• existing systems has some capacity to cope with climate variability, but extreme weather events resulting in increased droughts and floods will strain that capacity to meet future needs
• since some uncertainty will always exist, agencies need to perform sensitivity analyses of preliminary planning studies, and risk-based analyses for more advanced planning studies.
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2012 Central Valley Flood Protection Plan
Climate Change Scope DefinitionWork Group Summary Report
2012 Central Valley Flood Protection Plan
Climate Change Scope DefinitionWork Group Summary Report
• planning frameworks need to be flexible enough to incorporate uncertainties related to climate change in managing risks.
• planning approaches incorporating climate change probabilities, robust decision making, and adaptive management allow decisions to be more flexible and consider future advances in scientific understanding
• planning starts by identifying key system vulnerabilities and/or critical risk thresholds
• regional downscaled climate projections can be used to assess the likelihood of projected climate crossing system vulnerabilities or environmental thresholds
• as climate science, global modeling, and downscaling methods improve, better information can be used to assess if probability of occurrence of critical climate condition thresholds have change.
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Regional Climate Reports & Assessments
Regional Climate Reports & AssessmentsNOAA Near-Term Opportunities
Team: Assessing Assessments
R. Webb, C. McNutt, D. Easterling, N. Cyr, K. Averyt, D. Goodrich, D. Kluck, K. Broughton
– Provide guidance on the extent for downscaling as supported by the science
– Provide datasets in easy to use formats for the non-climate scientist
– Accurate portrayal of uncertainty (known unknowns)
– Create an online climate assessment and climate impact assessment toolkit