How, why, what, when? - Start | BECC Christine Achberger Created Date: 4/19/2017 4:14:29 PM ...
Transcript of How, why, what, when? - Start | BECC Christine Achberger Created Date: 4/19/2017 4:14:29 PM ...
IPCC (AR4 WG 1 Chapter 1 page 113 Fig. 1.4).
K.M.A. Gabriel, W.R. Endlicher / Environmental Pollution 159 (2011) 2044e2050
Mortality rates for Berlin, 1994
"The most that can be expected from any model is that it can supply a useful approximation to reality: All models are wrong; some models are useful".
George Box
Downscaling algorithms
• Bias Correction• Historical modification
What is the first-guess future climate?
Modelled historical
Observed historical
Climate Change
Downscaled scenario
Historical ModificationModelled scenario
Bias-correction methods
• Advantages:– Better physical consistency.
• Disadvantages: – One time-series/climate model run.
• Example methods:– Bias-corrected RCM– Empirical-statistical downscaling.
Historical modification.• Advantages:
– Unmodelled parameters/time-periods.– Integrate information from models.
• Disadvantages:– Uncertain assumptions– Loose physical coherence
• Examples:– Weather-generators, delta-change– Analogue-resampling
One time-series containsClimate Change signal from 20 GCM runs!
Global Temp from CCSM3 SRESa1b run1.
Historical modification example.
When downscaling, think:
• What do you want to know?• How realistic must inputs be?• What data are available?