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H t t t d t Hot temperatures and storm surges: Modelling the change of g g g
climate extremesAndreas SterlAndreas Sterl
KNMI, De Bilt, Netherlands
• Climate system• Climate changeg• Climate modelling• Climate extremes
• Hot temperatures• North Sea storm surges
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
gHenk van den Brink, Gerrit Burgers, Henk Dijkstra, Reindert Haarsma,Wilco Hazeleger, Erik van Meijgaard, Camiel Severeijns, Hans de Vries
Climate – what’s that?
Climate = statistics of weatherClimate statistics of weather
Weather = state of atmosphereWeather = state of atmosphere at a particular time
“Climate is what you expect, weather is what you get”
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
The climate systemThe climate system
AR4 FAQ 1 2 Fi 1
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
AR4, FAQ 1.2, Fig. 1
How does the climate system How does the climate system work?
• short-wave radiation (sun) heats (tropics)
• atmosphere and ocean transport heat poleward (modulated by continents)poleward (modulated by continents)
l di ti i t l• long-wave radiation into space cools
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Radiative forcing
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
AR4, FAQ 1.1, Fig. 1
Greenhouse effect
Outgoing longwave radiation is Outgoing longwave radiation is absorbed in the atmosphere and radiated back to the surfaceradiated back to the surface.
without: T = 15°Cwithout: Tglob = -15 C observed: Tglob =
15°C+15°C
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Greenhouse gases
only 1 % of atmosphereH O 70 % < f db k ( 2 )• H2O 70 %
• CO2 15 %<= feedback (~2x)
• CH4 )• N2O ) 5 %2 )• Ozone, …)• (clouds 10 %) <= feedback (?)• (clouds 10 %) <= feedback (?)
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
(van Dorland, 1999, p. 17/18)
The past 159 yearsThe past 159 years
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Increasing
GHG COGHG concent
CO2
ra-tions CH4
N2O
SO4
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
(IPCC, 2001, Fig. SPM-2) ++++
Sim lationsSimulations<= multi model, all forcings multi model, all forcings
M lti d l t l f i
AR4, Fig. 9.5
Multi model, natural forcings =>
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Projectionsj
• Scenarios “How will the world change?”
• Scenarios => CO2 emissions and concentrationsconcentrations
CO• CO2 concentrations => climate
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Emission scenariosEmission scenarios
TAR, SPM Fig. 5
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
ESSENCEESSENCE
• ECHAM5/MPI-OMECHAM5/MPI OM
• observed GHG’s – SRES A1b
• 1950 – 2100
• 17 runs => good statistics
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Global mean temperature
blue: ESSENCEred: HadCRUT3+14.3
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Temperature trend
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Precipitationp
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
The N-year return value - 1
• value that on average occurs once per N years
( ) ⎪⎫⎪⎧ ⎤⎡ ⎞⎛ −− ξ
μx/1
years• obtained by fitting a GEV to annual maxima (x):
( )⎪⎭
⎪⎬⎫
⎪⎩
⎪⎨⎧
⎥⎦
⎤⎢⎣
⎡⎟⎠⎞
⎜⎝⎛ −
−σμxξ+=xG 1exp
(x):
⎪⎭⎪⎩ ⎦⎣ ⎠⎝
μ: locationμσ: scaleξ: shape
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
The N-year return value - 2⎫⎧ ξ/1
( )⎪⎭
⎪⎬⎫
⎪⎩
⎪⎨⎧
⎥⎦
⎤⎢⎣
⎡⎟⎠⎞
⎜⎝⎛ −
−− ξ
σμxξ+=xG
/1
1exp⎪⎭⎪⎩ ⎦⎣ ⎠⎝ σ
defined for 01 >μxξ+ ⎟⎞
⎜⎛ −defined for 01 >σ
ξ+ ⎟⎠
⎜⎝
=> bounded by xmax = μ-σ/ξ for ξ < 0
return time T(x) for level x is 1-1/T(x) percentile:
( ) ( )xG=xT−1
1
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
( )xG1
Example: NetherlandsExample: Netherlands
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
ΔΔμ
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
ΔΔσ
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
ΔTΔT100
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
TΔT100 / ΔTmean
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Model biasT100(ESS)-T100(ERA-40)
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Dutch Delta Committee:
What is the effect of global warming on
• maximum wind speed• maximum wind speed• wind directions• wave heights• storm surge levels?
ApproachApproach
• KNMI'06 scenarios• other literature• other literature• Essence + WAQUA
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
E WAQUAEssence + WAQUAEssenceEssence• ECHAM5/MPI-OMECHAM5/MPI OM• 17-member ensemble• 1950-2100, SRES A1b
WAQUA• storm surge model• storm surge model• Northwest European shelf• 8 km x 8 km• output every 10 minutesoutput every 10 minutes
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Will the wind change ?Will the wind change ?ERA-401971-20002071-2100
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Extreme windsExtreme winds
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
ESSENCE winds
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Uncertainty present-day water levelswater levels
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Future water levelsFuture water levels
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Other stationsOther stations
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
l iConclusions
large ensemble => good statistical basisbasistemperature extremes increase faster than the means faster than the means ...... and may reach dangerous levels within this centurywithin this centuryno change of surge heights along th D t h t b t the Dutch coast, but ...... sea level increases
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
Andreas Sterl, SEAMOCS, Malta, 17.03.2009
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