1. Problems using downscaled scenarios
in studies of climate effects.
Lars Bakken
- The EACC project
Our first trials (and errors)*
More scenarios?
Better scenarios?
Simple wheather manipulations?
Wheather generators? *

2. COUP Snow cover Water stress Soil moisture Soil erosion Plant growth
Soil biology
C- and N model
Trace gas model
Frost/thaw
Driving data
Soil temp.
Water transport

3. The scenarios:
Dynamic downscaling (HIRHAM) based on:
- AOGCM ECHAM4/OPYC3 with the GSDIO integration
- IPCC IS92a scenario
The control period: :
Obs80-99 = Observed wheather
Scen80-99= Simulated weather
The future wheather:
Scen30-49= simulated wheather

4. Snow depth
Frost depth
And soil frost
is somewhat more shallow
Much less snow
in a warmer climate

5. Colder soils in a warmer climate?
More frequent freeze/thaw events in a warmer climate?
Number of ”frost spells” in the soil:

6. The summer is more problematic:
The Scenarios are wet and cold!

7. And the Scenarios have a peculiar distribution of rain:

8. The cool and wet summers delayed the phenological development
The high and frequent precipitation resulted in moist grains
=> Much delayed grain harvest!

9. The high Scenario-precipitation in July-August resulted in
much too high drainage and surface runoff
High erosion!

10. High erosion
in summer
High early-spring
erosion due to snow
melt on frozen soil

11. Quo vadis?
Don Quijote & Sancho Panza (Daumier)

12. Several scenarios => More uncertainty
Longer scenarios => Better statistics
But the climate models will gradually become better…
- Simulations driven by climate scenarios tend to be anecdotic
the simulations are not causally transparent
general respons patterns cannot be ”extracted”
The difference between two scenarios are multidimensional
The simulated ecological processes are nonlinear
To understand the reasons for contrasting results is difficult

13. Alternative 1: Simple manipulations of observed wheather
Additive for temperature (seasonal og whole year)
Multiplicative for prcipiation
Or stochastic
Factorial model experiments => interactions detected
Winter temperature: ∆T winter=
Summer temperature: ∆Tsummer =
Winter precipitation : KPwinter =
Summer precipitation: KPsummer =
All combinations: 81 simulations

14. Wheather generators
Based on existing weather
=> reliable weather ”quality” ?
Parameterized by contrasting climate scenarios
plausible combinations ?
Many or long time periods simulated
=> Statistics will be OK