how credible are hydrological projections in a changing world?
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Professor Thorsten Wagener, Pennsylvania State University, USA How credible are hydrological projections in a changing world?TRANSCRIPT
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
!
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?
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?
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’?
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
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)