How credible are hydrological projections in a changing world?
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Transcript of How credible are hydrological projections in a changing world?
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Thorsten Wagener1,2, Riddhi Singh1, Denis Hughes3, Evison Katsangawiri3 1Civil & Environmental Engineering, Penn State University, USA 2Soon: Civil Engineering, University of Bristol, UK 3Ins?tute of Water Research, Rhodes University, South Africa
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We need (climate) change impact projections at decision-making scales to guide adaptation
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What is an alterna?ve
scien?fic method?
Tradi?onal View: “Model simula?ons derive credibility by reproducing historical
observa?ons”
Wagener et al. (2010) Water Resources Research
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!
Trading-Space-for-Time
Can we transfer models and their projections in space and time?
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!
!
Historically Calibrated Model
How can we best use observations in a non-stationary world?
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Are model projections robust given that boundary conditions might be highly uncertain?
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What possible (though unlikely) events are not considered in our models?
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Can we estimate the uncertainty (confidence) in our projections?
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!
Olifants Basin, South Africa
What controls the uncertainty (confidence) in our projections?
What is our ‘margin of error’?
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How consistent with (equivalent to) the underlying system is our environmental model?
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Are expected and simulated dependencies (controls) identical under unobserved conditions?
1942 1989
Santa Cruz River near Tucson, Arizona
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So instead of asking whether our impact projections can be validated (they cannot) …
… we should ask whether they are T.R.U.E.! Transferable Robust Uncertain Equivalent
We need to rethink the scien?fic method from which we derive projec?on credibility in a non-‐sta?onary world!
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Wagener and Forest (In Review)