La actual Mega-Sequía en Chile Central: Llegó el futuro?

René D. Garreaud + grupo de Sequía CR2Department of Geophysics, Universidad de ChileCenter for Climate and Resilience Research, CR2

IV Congreso Nacional de Oceanografía Fìsica y MeteorologíaPUCV 1u-Noviembre-2015

La megasequía 2010-2015

• Moderada (20-40% déficit anual)• Larga (5-6 años) e ininterrumpida• Extensa (30-40°S)• Cálida (+0.5 – 1°C)• Alta demanda hídrica

Recurrencia en el siglo XX• 2-3 casos similares en centro-norte• 2-3 casos similares en centro-norte• <1 caso en centro-sur• También es inusual en reconstrucción Paleo

Impactos:• Hidrología sfc y subterranea• Vegetación natural• Regimen de incendios• Sociales y economicos

La Megasequía 2010-2015

% con respectoa climatología

+40%

+20%

0

Norte Chico Centro Centro-sur

Período de retorno del año más seco durante la MS (años)

7 15 >30

Recurrencia de eventos secos (>30%) de 4 o mas años

4-6 2-3 1?

-20%

-40%

1967-1970 2010-2014

Valparaiso

La Serena% con respectoa climatología

Grandes sequías contemporáneas

+40%

+20%

Concepción

Valdivia

0

-20%

-40%

Una mirada al pasado

Reconstrucción dendroclimática (1000-2000 años d.C.) de la precipitación en Chile central

Sequía y calor

Promedio anual de la temperatura máxima en Santiago (DMC)

Impactos en Hidrología

(a) Promedio (b) Anomalía MS

Copiapo

La Serena

Desierto

Índice de Vegetación Mejorada (EVI)Julio-Agosto-Septiembre

(b) Anomalía Megaseqia

0 – 55 – 1010 – 1515 – 3030 – 50

La Serena

Talca

Santiago

Salamanca

Nieve

Veg

etac

ión

+50

- 5Seq

ued

adFuente de datos: NASA (producto MODIS MOD13A3)

Mapas producidos por David Lopez, CEAZA

DéficitPluviométrico(2010-2014)

DéficitPluviométrico(2010-2014)

La Megasequía 2010-2015

Gastos en Camiones Aljibes

(Mill$)

Gastos en Camiones Aljibes

(Mill$)

Seq

ued

ad

Apariciones en prensa escrita

(2014)

Apariciones en prensa escrita

(2014)

Seq

ued

ad

Deterioro vegetación

Agosto 2010-2015

Deterioro vegetación

Agosto 2010-2015

Incendios forestales de

magnitud

Incendios forestales de

magnitud

Transportede sedimentos

en invierno

Transportede sedimentos

en invierno

2008

2013

©GdG

No

dat

a

La Megasequía 2010-2015:Una lección para el futuro

www.cr2.cl/megasequia

Next Decade

100%

90%

80%

0%

10%

20%

Rai

nfa

ll an

om

aly

wrt

19

70

-20

00 R

ainfall d

eficit wrt

19

70????

Precipitación en Chile CentralEl desafío de la próxima década

1995 2005 2015 2025 2080

Far Future

RCP8.5

Mega

Drought

Recent

Past

80%

70%

20%

30%

Mid Future

RCP8.5

Rai

nfa

ll an

om

aly

19

70

-20

00

????

100%

90%

80%

0%

10%

20%

Rai

nfa

ll an

om

aly

wrt

19

70

-20

00 R

ainfall d

eficit wrt

19

70

Next Decade

Precipitación en Chile CentralEl desafío de la próxima década

1995 2005 2015 2025 2080

Far Future

RCP8.5

Mega

Drought

Recent

Past

80%

70%

20%

30%

Mid Future

RCP8.5

Rai

nfa

ll an

om

aly

19

70

-20

00

Rainfall (GCPC) Z500 (NNR) SST (NCEP-OI)

Drought Composite

Large-scale context for central Chile droughts

Cold

1967,68,64,73,76,85,96,87,03,07

-50 0 +50 m -1 0 +1°C-60 0 +60 mm/month

ColdHigh

Warm

Large-scale context for central Chile droughts

Cen

tral

Chi

le w

inte

r ra

infa

ll an

omal

y

La Niña El Niño

r ≈ 0.6

MJJAS Niño3.4 index [°C]

Cen

tral

Chi

le w

inte

r ra

infa

ll an

omal

y

Large-scale context for central Chile droughts

Cen

tral

Ch

ile R

ain

fall

An

om

aly

r ≈ -0.6

Cen

tral

Ch

ile R

ain

fall

An

om

aly

Z500 difference

Drought compositeMean Z500 anomalies (contours)

Std Z500 anomalies (colors)

Large-scale context for central Chile droughts

Reduced variability downstream of anomalous ridge

Enhaned variability downstream of anomalous trough

Rainfall Z500 SST

DroughtComposite

The 2010-2015 drought in Central Chile

ColdHigh

Warm

1967,68,64,73,76,85,96,87,03,07

2010-2014Average

-50 0 +50 m -1 0 +1°C-60 0 +60 mm/month

High

Warm

Cen

tral

Chi

le w

inte

r ra

infa

ll an

omal

y

La Niña El Niño

The 2010-2015 drought in Central Chile

2010

2014

2013

2012

2011

2009

MJJAS Niño3.4 index [°C]

Cen

tral

Chi

le w

inte

r ra

infa

ll an

omal

y

+

2015????

Monte Carlo Experiment:5000 samples of 4 randomly chosen ENSO-neutral years

Central Chile Rainfall Anomaly

The 2

01

0-2

01

5 d

rou

ght in

Cen

tral Ch

ile

r≈

0.6

Central Chile Rainfall Anomaly

Z50

0 d

ifference

5800

5750

5700

5650

Subtropical box

NNRMMM

(hist+RC85)

Geo

po

ten

tial

hei

ght

[m]

The 2010-2015 drought in Central Chile

5300

5250

5200

5150

5000

5600

Midlatitude Box

MMM(hist+RC85)

NNR

Geo

po

ten

tial

hei

ght

[m]

Evidence for anthropogenic forcing

Climate simulation family

Attribution of the 2010-2015 mega drought

AMIP simulations: Global Circulation Model (GCM) forced by

• Observed SST

• Observed Sea Ice Distribution

• Observed or past Radiative Forcing (CO2, aerosols, O3,…)

Ensemble AMIP simulationsEnsemble AMIP simulations

• 10-30 “runs” of several decades long with slightly different initial conditions

• Ensemble mean reveals the SST forced response

• Ensemble spread reveals impact of internal variability (weather)

SST forcing includes natural variability (e.g., ENSO) but also anthropogenic impact

Ensemble mean with past radiative forcing excludes direct anthropogenic impact

Rainfall deficit

CAM4 (20) ECHAM5 (30)

May-September, 2010-2014

-50 0 +50 %

GPCP

Observations AMIP (Obs .SST, Obs. Rad.Forc.)

Z500 anomaly

-50 0 +50 m

NNR

SST variability + Obs. Rad. Forcing during 2010-2014 accounts about half of theobserved Z and P anomalies. Remaining anomaly can due to “bad luck”

(a) Nat-Hist forcing / Obs SST (b) Obs. Rad. Forcing / Obs. SST

Winter (MJJAS) rainfall anomaly 2010-2014LBNL CAM 5.1 AMIP simulations (50 runs)

-300 0 300 mm/year

-10% -20%

Obs RF / Obs SST (AMIP)

Rai

nfal

l ano

mal

y [%

]

2010-2014 Winter rainfall anomaly in Central Chile

Past RF Obs SST(AMIP) Obs RF / Coupled ocean

ECHAM5 (30)CAM4 (20)

CAM5 (50)

Rai

nfal

l ano

mal

y [%

]

CMIP5 (20 models)

CAM5 (50)

Observations@ 35S, 71W

The Next Decade Challenge

Next Decade

100%

90%

80%

0%

10%

20%

Rai

nfa

ll an

om

aly

wrt

19

70

-20

00 R

ainfall d

eficit wrt

19

70????

1995 2005 2015 2025 2080

Far Future

RCP8.5

Mega

Drought

Recent

Past

80%

70%

20%

30%

Mid Future

RCP8.5

Rai

nfa

ll an

om

aly

19

70

-20

00

????

The Next Decade Challenge

100%

90%

80%

0%

10%

20%

*

**

Rai

nfa

ll an

om

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wrt

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70

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ainfall d

eficit wrt

19

70

Next Decade

Unlikely

Unlikely

Likely

1995 2005 2015 2025 2080

Far Future

RCP8.5

Mega

Drought

Recent

Past

80%

70%

20%

30%

Mid Future

RCP8.5

MD Forcing

(*) Anthropogenic

(**) Natural (ENSO, PDO, Internal)

Rai

nfa

ll an

om

aly

19

70

-20

00

Very unlikely

Unlikely

Conclusions

• Current multi-year drought (MD) in central Chile is a very infrequent event in the historical record (100 years) and paleo-record (1000 years). It occurs during the warmest decade on record and much increased water demands.

• The uninterrupted sequence of 5 (6) dry years occurred during mostly ENSO-neutral conditions, a very unlikely situation.mostly ENSO-neutral conditions, a very unlikely situation.

• Roughly speaking, half of the current MD rainfall deficit can be attributed to concurrent SST state (cold-phase of PDO).

• Thus, anthropogenic climate change, mediated by circulation anomalies, is already influencing central Chile hydro-climate.

• So, we are not fully into the “future”, but this is how it will be…warm and dry.

Mea

n Q

N A

nn

ual

Pre

cip

itat

ion

[mm

/yea

r]

1900-10

1915-22

1926-42

1977-90

1991-2003

The error bars indicate the dispersion in the mean values when the initial or final year of each period is changed ±1 year

Warm PDO periodsCold PDO periods

The grey circles are 10-year synthetic PDO cold or warm periods

The blue circles are the composites using tree-rings reconstructions.

The 2010-2015 drought in Central Chile

Mean PDO Index

Mea

n Q

N A

nn

ual

Pre

cip

itat

ion

[mm

/yea

r]

1900-10

1942-57

1961-75

2007-2014

Long term mean

PDO Index

Year