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The Netherlands approach for generating climate change scenarios Bart van den Hurk, KNMI and many others Exercise from last week Give an order of estimate of the climate sensitivity based on the observed CO 2 and T. Give arguments about the validity of this approach

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the netherlands approach for generating climate change scenarios

The Netherlands approach for generating climate change scenarios

Bart van den Hurk, KNMI

and many others

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

exercise from last week
Exercise from last week
  • Give an order of estimate of the climate sensitivity based on the observed CO2 and T. Give arguments about the validity of this approach

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

what are climate scenarios
What are climate scenarios?
  • No predictions but What if… projections

prob

T

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

what are climate scenarios4
What are climate scenarios?
  • No predictions but What if… projections
  • With the following characteristics:
    • Plausible: fair chance of actually occuring in the future (excluding very unlikely situations)
    • Internally consistent: mean and extreme precipitation, temperature etc can all occur in the same climate
    • Relevant: aimed at information needs for impact assessment or policy evaluation applications

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

model projections of future global climate
Model projections of future global climate
  • Models are imperfect
  • Future greenhouse gas concentrations are unknown
  • Coordinated effort:
    • define set of emission scenarios
    • calculate concentration evolution
    • use this to make projections with range of GCMs
  • AR4: Large (~25) nr of GCMs available for 1900 – 2200 (http://www-pcmdi.llnl.gov/)

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

projections mean precipitation 2050 1990 with the mpi model
Projections mean precipitation (2050/1990) with the MPI model

A2

A1B

+25%

Winter

Summer

-50%

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

projections mean precipitation 2050 1990 with the mpi model7
Projections mean precipitation (2050/1990) with the MPI model

A2

A1B

+25%

Winter

Mean change

Winter change  +5 – +10%

Summer change  -10 – -15%

Difference scenarios

A2 a bit stronger in winter

A1B a bit stronger in summer

Gradient

N-S gradient in winter

SE-NW gradient in summer

Resolution

Resolution very coarse

(>150 km)

Extremes

Only seasonal mean!

No info on extremes or

nr of wet days.

Summer

-50%

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

the production of the knmi 06 scenarios
The production of the KNMI’06 scenarios

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

the production of the knmi 06 scenarios9
The production of the KNMI’06 scenarios

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

global mean climate change scenarios
Global mean climate change scenarios
  • Start with projections with Global Circulation Models (GCM’s):
    • Multiple emission scenarios
    • Multiple models

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

but there s more than global mean temperature
But there’s more than global mean temperature

Sea level pressure difference

from 2 different GCMs

Van Ulden and Van Oldenborgh, 2006

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

g west in west europe for present day climate
G-west in West-Europe for present-day climate
  • Approx 10 AR4 GCM-runs

Observations

Models

Van Ulden et al, 2006

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

g west end of 21 st century with doubled co 2 levels
G-west end of 21st century with doubled CO2-levels
  • Changes relative to present climate

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

g west end of 21 st century with doubled co 2 levels14
G-west end of 21st century with doubled CO2-levels
  • Changes relative to present climate

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

the influence from the driving gcm
The influence from the driving GCM!
  • Change of precipitation annual cycle in Rhine area from multiple regional climate model simulations
  • Two different GCM’s

ECHAM4/OPYC (more Atlantic advection in winter, less in summer)

HadAM3H (small changes in circulation statistics)

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

winter temperature and wind direction
Winter temperature andwind direction

A2 scenario

Control

simulation

Observed

14 12 10 8 6 4 2 0 -2 -4 -6 -8 -10

  • Eastern winds give low winter temperatures

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

rationale of the scenarios
Rationale of the scenarios
  • The steering variables
    • 1. Global temperature

– 2. Strength of seasonal

mean west-circulation

(not for zsea)

Strength of west-circulation

month

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

the production of the knmi 06 scenarios18
The production of the KNMI’06 scenarios

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

regional climate change downscaling
Regional climate change: downscaling
  • GCM-grid box too coarse

Global model

Regional model

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

downscaling
Downscaling
  • Downscaling = local interpretation of GCM-scenario by using local added information
    • Orography, land/sea
    • Land use, …
  • 2 families of methods
    • Statistical
    • Dynamical

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

statistical downscaling
Statistical downscaling
  • Ingredients:
    • Local observed time series of weather variable (e.g. precipitation)
    • Archive of large scale circulation-indicators (e.g. air pressure, temperature/wind in higher atmosphere, gradients of humidity, pressure, …)
    • Correlation-equation
    • Large scale circulation-indicators from a GCM projection to be downscaled

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

statistical downscaling22
Statistical downscaling

I from GCM’s + a and b from local calibration  local P

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

dynamical downscaling regional climate model rcm
Dynamical downscaling: Regional Climate Model (RCM)
  • High resolution GCM (50 – 20 km)
    • better resolving land-sea, orography, atm.gradients
  • Lateral boundary conditions from reanalysis (present-day climate conditions) or GCM runs (scenario runs)
    • multi-level
    • temporal frequency dependent on domain
  • Inner domain free evolving

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

analysis of ar4 gcms precipitation and temperature
Analysis of AR4 GCMs: precipitation and temperature
  • Local downscaling:
    • Daily values rather than seasonal means
    • (Soft) extremes
    • Number of rain days
  • 10 PRUDENCE RCM’s
    • 8x HadAM3H (fairly dry in summer, modest SST, strong circ in summer, less in winter)
    • 2x ECHAM4 (very wet in winter and dry in summer, strong circ, stronger effect SST)
    • Problem: no GCM run representative for circ  0
    • “Escape”:
      • KNMI RCM remains fairly wet in summer (can be used for G- en W-scenario)
      • in winter the RCM runs cover the GCM-variability reasonable

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

analysis of ar4 gcms precipitation and temperature25
Analysis of AR4 GCMs: precipitation and temperature
  • Downscaling with RCM’s
    • Relationship local variables – steering variables

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

analysis of ar4 gcms precipitation and temperature26
Analysis of AR4 GCMs: precipitation and temperature
  • Downscaling with RCM’s
    • Relationship local variables – steering variables
    • Circulation-dependent and –independent regression-coefficient xcirc en xT
    • Apply regression in scenarios:

var = xT Tglob + xcirc circ

    • Weigh RCM’s per scenario to enhance differences

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

result change in 2050 relative to 1990
Result: change in 2050 relative to 1990

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

result change in 2050 relative to 199028
Result: change in 2050 relative to 1990

mean temperature

yearly coldest day

With circulation change the coldest

temperature changes more than mean

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

result change in 2050 relative to 199029
Result: change in 2050 relative to 1990

Nr of wet days strongly dependent on

circulation change

wet day frequency

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

result change in 2050 relative to 199030
Result: change in 2050 relative to 1990

Wet day mean precipitation dependent on

global temperature rise

mean precipitation

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

result change in 2050 relative to 199031
Result: change in 2050 relative to 1990

Extreme precipitation is more likely in a

wetter climate

daily precipitation exceeded 1/10yrs

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

result change in 2050 relative to 199032
Result: change in 2050 relative to 1990

annual maximum daily mean wind

Windscenarios hardly show a significant change

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

result change in 2050 relative to 199033
Result: change in 2050 relative to 1990

Sea level scenario’s after 2050 show acceleration:

For 2100 the range is between 35 and 85 cm

sea level rise

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

general picture
General picture
  • Extreme temperature change is stronger than mean, especially when circulation also changes
  • When circulation changes number of precipitation days is strongly reduced in summer, causing a reduction of mean summertime precipitation
  • In winter mean precipitation increases (dependent on circulation)
  • Extreme precipitation increases both in summer and winter
  • Sea level rise is slightly smaller than in TAR
  • 1/yr Wind slightly increases (but not significantly)

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

tailored climate scenarios
Tailored climate scenarios
  • Specific use in many applications (e.g. water management) requires “tailoring”
  • Examples
    • High resolution time series of precipitation
    • Ground water tables in the Netherlands
    • Long (>100 yr) time series
    • Dynamical downscaling in Rhine basin
    • Closure of Maasland barrier

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

the production of the knmi 06 scenarios36
The production of the KNMI’06 scenarios

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

generation of high resolution time series
Generation of high resolution time series
  • Climate scenarios provide general key numbers (change of mean, change of 1/10yr return value)
  • Change an existing (obs) time series of precipitation
    • linearly (using only mean change)
    • non-linearly (changing also shape of distribution and # wet days)

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

non linear time series transformation
Non-linear time series transformation
  • Determination of extremes (via statistical downscaling)
    • From previous step: p50, p99, scaled to pn via assumed scaling of pdf
    • Observed time series transformed with pn
    • From transformed time series:
      • Return time of extremes
      • Nr of frost days
      • Length growing season…

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

generation of high resolution time series39
Generation of high resolution time series

non-linear transformation

introduces dry day

n-lin > obs

lin < obs

and different changes for different intensities

n-lin < obs

lin < obs

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

effect on groundwater table example
Effect on groundwater table (example)

non-linear transformation

has tendency to be wetter in wet episodes and drier in dry spells

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

change in ground water table the netherlands
Change in ground water table the Netherlands
  • Aim: first assessment of effect of W+ scenario on ground water table in various stages of the growing season
  • Tailoring:
    • production of location specific meteo (applied linearly in this example)
    • running high resolution ground water model

Lowest water

table during

growing season:

generally drier

Start of growing

season:

generally wetter

courtesy Timo Kroon,

Franziska Keller ea

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

long time series
Long time series
  • Extremes (1/x jr; x»1) have more impact than the mean climate
  • Length of time series is limited
    • Observations: < 150 jr
    • GCM’s: < 200 jr
    • RCM’s: < 50 jr
  • Estimation of extremes by:
    • Extrapolation of fitted Generalized Extreme Value (GEV) functions
    • Creation of long time series by resampling

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

fit of gev distribution
Fit of GEV-distribution
  • Assume that yearly maxima obey a given ditribution P(,) (for instance Gumbel)
  • Determine return time from ranked sequence
  • Fit GEV to ranked sequence
  • Extrapolate return times

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

resampling
Resampling
  • Use historical time series of combination of weather variables (P, T, u)
  • Select a random day
  • Search for analogues
  • Select a random analogue day
  • Take next day in historical time series
  • Preservation of temporal correlation

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

resampling45
Resampling

Simulated rainfall series

Historical rainfall series

date

value (mm)

Resampling with replacement

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

resampling46
Resampling

Historical rainfall series

date

value (mm)

Largest 4-day amount: 46 mm

Simulated rainfall series

Largest 4-day amount: 80 mm

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

dynamical downscaling using 1 rcm results for rhine discharge
Dynamical downscaling using 1 RCM: results for Rhine discharge

Control

J F M A M J J A S O N D

SWURVE project (Lenderink et al, 2003)

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

dynamical downscaling using 1 rcm results for rhine discharge48
Dynamical downscaling using 1 RCM: results for Rhine discharge

Annual cycle

increases

A2-scenario 2070-2100

Extreme value

analysis:

Shorter return period of peak discharge

J F M A M J J A S O N D

SWURVE project (Lenderink et al, 2003)

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

closure of maasland barrier costly
Closure of Maasland-barrier: costly!
  • Dependent on (simultaneous) high water level due to surge and Rhine discharge

Sea level at Hoek v Holland (m)

Rhine discharge ( 1000 m3/s)

H vd Brink ea

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

closure of maasland barrier costly50
Closure of Maasland-barrier: costly!
  • Dependent on (simultaneous) high water level due to surge and Rhine discharge

Sea level at Hoek v Holland (m)

Closure return time (years)

Rhine discharge ( 1000 m3/s)

Sea level rise (m)

H vd Brink ea

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

final remarks
Final remarks

Tailoring

Process of tailoring is important for application in practice. Close multi-disciplinary cooperation is required

Generic scenarios

Designed to span a wide range

of possible climate change,

suitable for many applications

Dry summers

Particularly dry summer conditions gain additional attention in Dutch climate adaptation policy

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

for next week
For next week
  • Think of an application interested in climate change information
  • Describe relevant meteorological variables & their statistical moments
  • Propose a procedure to create this specific climate change scenario

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios

more information
More information
  • Bart van den Hurk
    • hurkvd@knmi.nl
    • www.knmi.nl/~hurkvd
  • www.knmi.nl/climatescenarios

New climate scenarios for the Netherlands – www.knmi.nl/climatescenarios