Possible Effects of Possible Effects of Global Warming on Global - - PowerPoint PPT Presentation

Possible Effects of Possible Effects of Global Warming on Global Warming on Global Warming on Global Warming on Tropical Cyclone Tropical Cyclone Activity Activity

Johnny Chan

Guy Carpenter Asia Guy Carpenter Asia-

• Pacific Climate Impact Centre

Pacific Climate Impact Centre School of Energy and Environment School of Energy and Environment City University of Hong Kong City University of Hong Kong

Outline Outline

• Background

Background

• Relationship between global warming and

Relationship between global warming and frequency of intense tropical cyclone frequency of intense tropical cyclone

• ccurrence
• ccurrence

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

• Variations of tropical cyclone

Variations of tropical cyclone characteristics in the western North characteristics in the western North Pacific Pacific

• Summary

Summary

Background Background

• Global warming leads to

Global warming leads to

– –

an increase in the temperature near the earth’s an increase in the temperature near the earth’s surface (land and ocean) surface (land and ocean)

– –

an increase in the amount of water vapour in the an increase in the amount of water vapour in the atmosphere due to an increase in ocean temperature atmosphere due to an increase in ocean temperature and a higher atmospheric temperature capable of and a higher atmospheric temperature capable of

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

and a higher atmospheric temperature capable of and a higher atmospheric temperature capable of holding more water vapour holding more water vapour

• No study has definitively demonstrated that the

No study has definitively demonstrated that the dynamic factors are modified by global warming dynamic factors are modified by global warming (although some have suggested an increase in (although some have suggested an increase in vertical wind shear). vertical wind shear).

Background Background

• Due to global warming, the thermodynamic

Due to global warming, the thermodynamic factors have become more favourable for factors have become more favourable for tropical cyclone formation and development. tropical cyclone formation and development.

• To determine whether global warming has an

To determine whether global warming has an impact on the frequency of occurrence of impact on the frequency of occurrence of

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

impact on the frequency of occurrence of impact on the frequency of occurrence of tropical cyclones or of intense cyclones, we tropical cyclones or of intense cyclones, we need to examine whether the thermodynamic need to examine whether the thermodynamic factors are related to the variations on such factors are related to the variations on such frequencies. frequencies.

• A good proxy of the thermodynamic factors is

A good proxy of the thermodynamic factors is the Maximum Potential Intensity (MPI) the Maximum Potential Intensity (MPI)

• MPI = f(ocean temperature, outflow temperature, net

amount of energy available for convection)

• Because MPI gives the maximum possible intensity, a

higher value of MPI summed over the ocean basin and

• ver a season should imply a more thermodynamically

Background Background

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

energetic atmosphere, and more TCs could reach higher intensities

∴ ∴ ∴ ∴ a season with a higher value of MPI should have more intense TCs if the dominant control is thermodynamic

Atlantic

3 4 5 6

r of Cat45

62 64 66 68

PI Cat45 NCEP MPI

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong 1 2 3 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

Year Number o

54 56 58 60

MP

Western North Pacific

6 8 10 12

t45

68 70 72 74

PI

Jul-Nov Cat45 NCEP MPI

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

2 4 6

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year Cat4

60 62 64 66

MP

21 21-

• year running correlations with NCat45

year running correlations with NCat45

Ocean Basin Ocean Basin Period Period Correlation Correlation (best track) (best track) Correlation Correlation (Kossin et al. 2007) (Kossin et al. 2007) Atlantic 1960-2007 0.45 1970-2007 0.59 1980-2007 0.63 1979-2006 0.61 0.61 Western North Pacific 1960-2007

• 0.01

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

1970-2007

• 0.06

1980-2007

• 0.08

1981-2006

• 0.13
• 0.36

Eastern North Pacific 1960-2007 0.29 1970-2007 0.35 1980-2007 0.34 South Indian Ocean 1981-2007 0.35 South Pacific 1981-2007 0.03

21-year running correlations of MPI with NCat45

0.2 0.4 0.6 0.8

21 21-year running correlations with NCat45 year running correlations with NCat45

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

• 0.6
• 0.4
• 0.2

0.0 0.2 1980 1985 1990 1995 2000 2005 Atlantic WNP ENP

Summary Summary

• Thermodynamic control on the frequency

Thermodynamic control on the frequency

• f intense TCs is important
• f intense TCs is important only
• nly in the

in the Atlantic Atlantic

• Estimating the effect of global warming on

Estimating the effect of global warming on

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

• Estimating the effect of global warming on

Estimating the effect of global warming on the frequency of intense TCs therefore the frequency of intense TCs therefore must also assess such an effect on the must also assess such an effect on the dynamic processes. dynamic processes.

Western North Pacific Western North Pacific Tropical Cyclones Tropical Cyclones

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Tropical Cyclones Tropical Cyclones

Number and Intensity Number and Intensity

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Annual number of TSs and Cat45 TCs over the WNP

30 35 40 8 10 12 14 TS 10-yr filtered TS Cat45 10-yr filtered Cat45

Annual Number of TCs and Intense TCs in the WNP Annual Number of TCs and Intense TCs in the WNP

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

15 20 25 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2 4 6

Webster et al.’s (2005) Webster et al.’s (2005) Science Science paper paper

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

1975-89 1990-2004 Number 75 115

• No. of Category 4 and 5 Typhoons
• No. of Category 4 and 5 Typhoons

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Percentage 32 42

1960-74 1975-89 1990-2004 Number 105 75 115

• No. of Category 4 and 5 Typhoons
• No. of Category 4 and 5 Typhoons

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Percentage 37 32 42

ACE ACE vs.. vs.. VORT VORT, , SHEAR SHEAR and and MSE MSE

0.5 1.0 1.5 2.0 2.5 3.0 ACE VORT EOF1 SHEAR EOF1 MSE EOF2

Science, 311, 1713b, Tellus 2007

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

• 2.5
• 2.0
• 1.5
• 1.0
• 0.5

0.0 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

0.58 0.72 0.67

Wavelet Analysis of Intense Typhoon Occurrence Frequency Wavelet Analysis of Intense Typhoon Occurrence Frequency

2-7 yr

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

16-32 yr Period A1 Period B Period A2

Period A1 Period A2

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Ocean Ocean Temperature Temperature Anomalies Anomalies

Period B

Vertical Wind Shear Vertical Wind Shear

Period A1 minus Period B Period A2 minus Period B

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Period A1 Period A2

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Frequency of Frequency of Occurrence of Intense Occurrence of Intense Typhoons Typhoons

Period B

Period A1 minus Period B Period A2 minus Period B

Difference in the Frequency of Occurrence of Intense Typhoons Difference in the Frequency of Occurrence of Intense Typhoons

Proceedings, Royal Society A (2008) Proceedings, Royal Society A (2008)

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Blue shading: 95% Green shading: 90%

Track and Landfall Variations Track and Landfall Variations

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

• No. of TCs Making Landfall in Japan and Korea Every 5
• No. of TCs Making Landfall in Japan and Korea Every 5-year period (1970

year period (1970-2004) 2004)

• No. of Tropical Cyclones Making Landfall in Japan and Korea

20 25 30

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

5 10 15 1970-74 1975-79 1980-84 1985-89 1990-94 1995-99 2000-04 Year Number

• No. of Typhoons Making Landfall in East China Every 5
• No. of Typhoons Making Landfall in East China Every 5-year period (1960

year period (1960-2005) 2005)

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

• No. of Typhoons Making Landfall in South China Every 5
• No. of Typhoons Making Landfall in South China Every 5-year period (1960

year period (1960-2005) 2005)

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Variations of Landfall in Each Area at Various Oscillation Periods Variations of Landfall in Each Area at Various Oscillation Periods

STC

• 3
• 2
• 1

1 2 3 4

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

Year S t a n d a r d i z e d a n

• m

a l i e s

• 1.5
• 1
• 0.5

0.5 1 1.5 2

S t a n d a r d i z e d a n

• m

a l i e s

• riginal

2-8 yr 8-16 y r 16-32 y r

standardized anomalies standardized anomalies

MTC

1 2 3 4

d i z e d a n

• m

a l i e s

0.5 1 1.5 2

S t a n d a r d i z

• riginal

2-8 yr 8-16 yr 16-32 yr

standardize zed anomalies

South China, Philippines and Vietnam

East China

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

• 3
• 2
• 1

1945 1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

Year S t a n d a r d i z e d

• 1.5
• 1
• 0.5

a r d i z e d a n

• m

a l i e s

ized anomalies standardized anomalies standardized standardized anomalies

Japan/Korea

currence anomalies TC occurrence

1977-88 1964-76 Pattern 1 Pattern 2

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

Patterns of TC occu ce anomalies

1989-97 Pattern 3

Summary Summary

• No significant trend in any of the TC

No significant trend in any of the TC characteristics (number, intensity, track characteristics (number, intensity, track types, landfall locations) can be identified. types, landfall locations) can be identified. In other words, TC activity in the western In other words, TC activity in the western North Pacific North Pacific does not does not follow the trend in follow the trend in

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

the global increase in atmospheric or sea the global increase in atmospheric or sea- surface temperature. surface temperature.

• Instead, all such characteristics go

Instead, all such characteristics go through large interannual and interdecadal through large interannual and interdecadal variations. variations.

Summary Summary

• Such variations are very much related and

Such variations are very much related and apparently caused by similar variations in the apparently caused by similar variations in the planetary planetary-scale atmospheric and oceanographic scale atmospheric and oceanographic features that also features that also do not do not have the same trend as have the same trend as the global increase in air temperature the global increase in air temperature

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

the global increase in air temperature the global increase in air temperature

• Unless the temporal variations of such features

Unless the temporal variations of such features become linear, these TC characteristics are not become linear, these TC characteristics are not expected to vary linearly with time. expected to vary linearly with time.

Summary Summary

• Even if the observed global warming

Even if the observed global warming has an effect, it is probably in the has an effect, it is probably in the noise level relative to the large noise level relative to the large interdecadal variations and therefore interdecadal variations and therefore

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Guy Carpenter Asia-Pacific Climate Impact Centre, School of Energy and Environment, City University of Hong Kong

interdecadal variations and therefore interdecadal variations and therefore is not detectable. is not detectable.