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

4

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

5

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

6

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

7

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

8

NOAA/CPC

El Niño

Normal

Geophysical Fluid Dynamics Laboratory

Projected ENSO changes (CMIP3/AR4)

9

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

10

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

11

Wittenberg (GRL 2009)

Geophysical Fluid Dynamics Laboratory

The most extreme ENSO epochs

12

Wittenberg et al.(in prep.)

Geophysical Fluid Dynamics Laboratory

Initial conditions for “perfect” reforecasts

13

Wittenberg et al.(in prep.)

Geophysical Fluid Dynamics Laboratory

40 “perfect” reforecasts – best possible skill

14

Wittenberg et al.(in prep.)

Geophysical Fluid Dynamics Laboratory

1860: Spread of 100yr NINO3 SST spectra

15

286 ppmv

Wittenberg (2009)

Geophysical Fluid Dynamics Laboratory

1990: Stronger annual cycle & ENSO

16

353 ppmv

Wittenberg (2009)

Geophysical Fluid Dynamics Laboratory

2xCO2: A perfect climate for ENSO?

17

572 ppmv

Wittenberg (2009)

Geophysical Fluid Dynamics Laboratory

4xCO2: Stronger annual cycle, weaker ENSO

18

1144 ppmv

Wittenberg (2009)

Geophysical Fluid Dynamics Laboratory

Competing changes in ENSO feedbacks

19

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

20

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