Extreme Events and Climate Variability

Issues:

Scientists are telling us that global warming means more extreme weather.

Every year we seem to experience weather extremes.

What is the origin of extreme events?

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A Major Issue for All Countries Is Global Warming and Its Regional Impacts

Seasonal Climate Impacts Depend on theSimultaneous Influences of:

Natural Climate Variability El Nino/La Nina Pacific Decadal Oscillation (PDO) Arctic Oscillation (weak impact in Tropics)

Climate Change

Atmospheric Noise

Extreme Events are Mostly Related to Circulation Changes, i.e. to Variability

The El Nino/Southern Oscillation (ENSO) is a major factor in global climate variability.

R e fe re n c e : N a th a n M a n tu a U n iv e rs ity o f W a sh in g to n

The Pacific DecadalOscillation (PDO)

Typical wintertime Sea Surface Temperature (colors), Sea Level Pressure (contours) and surface windstress

(arrows) anomaly patterns during warm and cool phases of PDO

Departure from N ormal (mm)E l N ino (J uly 1997-J une 1998)~

Rainfall Changes A ssoc iated w ith EN SO are theL arges t Sourc e of Variability in the T ropic s

E N S O A ls o Impac ts H ur ric ane A c tivity

L a N ina (J uly 1998-J une 1999)~

Societal Impacts from 1997/98 El Nino

1. Crop/S toc k Damage 2. E nergy Savings 3. Famine 4. F ires 5. F isheries Dis ruption 6. Health R isks 7. Human Fata lit ies

8. P es ts Inc reased 9. P roper ty Damage10. Tourism Dec reased11. Transportation P roblems12. Soc ial Dis ruptions13. W ildlife Fata lit ies14. Water R ationing

Climate P redic tion Center

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Major Weather-Related Natural Disasters (1999 La Nina)60 N

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Climate P redic tion Center

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S Storm s, Hail, TornadoesF Floods, LandslidesH Hurricanes, TyphoonsD Drought

Flood 55,360 $1.3BStorm s 16,863 $17.0BDroughts 404 - Cold Waves 409 $1.3B

VictimsInsured Losses

R egion al 1999 F lood s P ossib ly L ink ed to L a N ina

D a te E v e n t

A p ril 9 -1 6 M u d s lid e s & h e a v y ra in s C o lu m b ia : C a u c a , A rg e liaM a y 5 -1 5 H ig h w a te r in A m a z o n a s , P e ruA u g u s t 1 5 -2 2 F lo o d in g in e a s te rn Ve n e zu e laA u g 3 0 -S e p t 11 F lo o d in g in C o lu m b ia : A n tio q u ia , C o rd o b a , C h o c oS e p t 1 2 -2 9 P e rs is te n t ra in s , f lo o d s , m u d s lid e s in C o lu m b ia , H o n d u ra s , N ica ra g u a , G u a ta m a laD e c 1 2 -1 9 M ajo r f lo o d in g a n d m u d s lid e s in Ve n e z u e la (5 0 ,0 0 0 + v ic tim s )

Impacts of December 1999 Floods

in Venezuela

Typical winter Weather Anomalies and Atmosphere Circulation

Changes During El Nino & La Nina

Extended Pacific Jet Stream& Amplified Storm Track

LLow Pressure

PolarJet

StreamWarm

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E l N in o~

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Variable Pacific Jet Stream

BlockingHigh

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PolarJet

Stream

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L a N in a~

Jet Stream Shifts Associated with Clim ate Variability Produce Regional Changes In Extrem e Weather Events

L ocation s F or M a jo r Sto rm s (D a ys P e r W in te r S ea s on )

E xten s iv e Sto rm sD ec 9 7-M a r 9 8

M a ss iveIce Sto rm

Ja n 98

Stro ng “N orthe aste r”

Sto rm sJa n-F eb 9 8

To rnad o O utb re akF eb 9 8

F re qu en t Sto rm sN ov 9 7-M a r 9 8

Examples of C limate Control Over Weather Patterns.The Basis of Linking Climate and Weather

LA N ina 1998-1999~Above AverageSto rm s, H u rricane

Force W indsN ov 98 - Feb 99

A ctive H urricaneSeason

A ug-N ov 98

TornadoesJan 1999

N o M ajo r “N ortheaste rs”

Be low N orm alSto rm iness

D ec 98 -Feb 99

M a jor Ice Sto rmJan 99

M a jorSnow Sto rm

Jan 99

Extensive IceSto rm

D ec 98D rought

Spring 1999

Dim inishedHurricane

Threat

T h e P a c if ic D e c a d a l O sc illa tio n (P D O )

ty p ic a l w in te r tim e S e a S u r fa c e Tem p e ra tu re (c o lo rs ) ,S ea L ev e l P ressu re (co n to u rs) a n d su rfa ce w in d stress (a r ro w s) a n o m a ly p a tte rn s d u rin g w a rm a n d c o o l p h a ses o f P D O w a rm p h a se c o o l p h a se

R e fe re n c e : N a th a n M a n tu a U n iv e rs ity o f W a sh in g to n

Contributions to Surface Temperature Trend from 1950-1999

Tota l Trend Pacific Decadel O scilla tion

Arctic O scilla tion G lobal Warm ing

SUMMARY

Extremes result from:

- major climate anomalies (e.g. especially El Nino

and La Nina in Tropics)

- unusual atmospheric circulation patterns

(mostly related to climate variability)

- factors acting together for air temperature

(e.g. ENSO, PDO, AO, global warming)

The impacts of the warming trend on circulation

changes, i.e. also extremes, is still a research issue