Presented by Andrew Wittenberg Geophysical Fluid Dynamics Laboratory 17 October 2012
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Transcript of Presented by Andrew Wittenberg Geophysical Fluid Dynamics Laboratory 17 October 2012
Geophysical Fluid Dynamics Laboratory
Presented byAndrew Wittenberg
Geophysical Fluid Dynamics Laboratory17 October 2012
Tropical Climate Change and ENSO
NOAAGOES-11
5 Oct 20111800 UTC
Geophysical Fluid Dynamics Laboratory
The Tropics: Firebox of the global circulation
2
ThompsonHigher Education
Geophysical Fluid Dynamics Laboratory
Projected surface temperature changes
3
Strongest warmingover land &
equatorial Pacific
More warmingin calm areas,
and wherewinds weaken
Feedbacks fromlow clouds &
ocean advection
Vecchi et al. (2008)Vecchi & Wittenberg
(2010)Collins et al. (2010)
Xie et al. (2010)
Geophysical Fluid Dynamics Laboratory
Projected water vapor changes
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Warming pumpswater vapor intothe atmosphere
Vecchi & Wittenberg (2010)
Collins et al. (2010)Xie et al. (2010)
Tropics today:~40 kg of water vapor
2050: +4 kg
Geophysical Fluid Dynamics Laboratory
Projected rainfall changes
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Broadly:“the wet get wetter,the dry get drier”.
Over tropicaloceans:
“the warmerget wetter”.
Held & Soden (2006)Vecchi & Wittenberg (2010)
DiNezio et al. (2010)Xie et al. (2010)
Geophysical Fluid Dynamics Laboratory
Projected tropospheric temperature changes
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Increasedstatic stabilityof atmosphere
Helps expandHadley Cell
Weakensconvective
mass fluxes &trade winds
Held & Soden (2006)Vecchi et al. (2006)
Frierson et al. (2007)Collins et al. (2010)
Geophysical Fluid Dynamics Laboratory
Projected upper-ocean temperature changes
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Tropical oceanmore stratified
Stronger,shallower, and
flatter equatorialthermocline
DiNezio et al.(JC 2009, EOS 2010)Collins et al. (2010)
Geophysical Fluid Dynamics Laboratory
Earth's dominant interannual climate fluctuation
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NOAA/CPC
El Niño
Normal
Geophysical Fluid Dynamics Laboratory
Projected ENSO changes (CMIP3/AR4)
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correl(SST trend of 1%/yr, SST.PC1 of PICTRL)10S-10N, 120E-80W
Yamaguchi & Noda (JMSJ 2006)
std(S
LP.P
C1
of
SR
ES.A
2 (
20
51
-21
00
))/
std(S
LP.P
C1
of
20
C3
M)
30
S-3
0N
, 3
0E-6
0W
van O
ldenborg
h e
t al. (
OS 2
00
5)
CM2.1
Weak/ambiguousnear-term
anthropogenicimpacts on ENSO
Intrinsicmodulation
Reviews:
Meehl et al.(IPCC-AR4 2007)
Guilyardi et al.(BAMS 2009)
Vecchi & Wittenberg (WIREs CC 2010)
Collins et al.(Nature Geosci. 2010)
Geophysical Fluid Dynamics Laboratory
Intrinsic modulation of ENSO: Observed
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Vecchi & Wittenberg(WIREs CC 2010)
Historical SSTA (ERSST.v3)
Palmyra corals(Cobb et al.,
Nature 2003)
Multiproxy reconstructions:Emile-Geay et al.(2011abc, subm.)
Geophysical Fluid Dynamics Laboratory
Intrinsic modulation of ENSO: Simulated
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Wittenberg (GRL 2009)
Geophysical Fluid Dynamics Laboratory
The most extreme ENSO epochs
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Wittenberg et al.(in prep.)
Geophysical Fluid Dynamics Laboratory
Initial conditions for “perfect” reforecasts
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Wittenberg et al.(in prep.)
Geophysical Fluid Dynamics Laboratory
40 “perfect” reforecasts – best possible skill
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Wittenberg et al.(in prep.)
Geophysical Fluid Dynamics Laboratory
1860: Spread of 100yr NINO3 SST spectra
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286 ppmv
Wittenberg (2009)
Geophysical Fluid Dynamics Laboratory
1990: Stronger annual cycle & ENSO
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353 ppmv
Wittenberg (2009)
Geophysical Fluid Dynamics Laboratory
2xCO2: A perfect climate for ENSO?
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572 ppmv
Wittenberg (2009)
Geophysical Fluid Dynamics Laboratory
4xCO2: Stronger annual cycle, weaker ENSO
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1144 ppmv
Wittenberg (2009)
Geophysical Fluid Dynamics Laboratory
Competing changes in ENSO feedbacks
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1. Amplifiers - stronger rainfall & wind stress responses to SSTAs - stronger thermocline, shallower mixed layer - weaker replenishment of surface waters from below
2. Dampers - stronger evaporative & cloud-shading responses - weaker upwelling -> surface less connected to thermocline - smaller dynamic warm pool -> less room for warming
3. Ambiguous effects - stronger intraseasonal wind variability
Guilyardi et al. (BAMS 2009); Vecchi & Wittenberg (WIREs CC 2010)Collins et al. (Nature Geosci. 2010); DiNezio et al. (JC 2009; EOS 2010; JC 2011 subm.)
Ongoing activities with CLIVAR Working Groups,D. Battisti, A. Atwood, M. Cane, C. Karamperidou, F.-F. Jin, J. Brown, F. Graham
Geophysical Fluid Dynamics Laboratory
Summary
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1. Projections of tropical climate change - tropics moisten, stratify, expand - circulation weakens; ocean thermocline shoals & flattens - SST: calm(er) get warmer; ocean advection changes - rainfall: wet get wetter; warmer get wetter - distinct from El Niño
2. Is ENSO changing? - diverse projections - competing feedbacks + optima + model biases -> uncertainty
3. Risk of intrinsic ENSO modulation - ENSO capable of wide swings in behavior on its own - interannual predictability only, except after a big event