Global Climate Change and Hurricanes:

the Science, the Controversy & the Risk

Judith A. Curry

Storm Deaths Locations AffectedGreat Hurricane of 1780 >22,000 Barbados, Martinique

Hurricane Mitch (1998) 11,000 – 18,000 Honduras, Nicaragua

Hurricane Fifi (1974) 8,000 – 10,000 Belize, Guatemala, Honduras

Hurricane Flora (1963) 7,186 – 8,000 Tobago, Hispaniola, Cuba

1930 Dominican Republic Hurricane 2,000 – 8,000 Hispaniola, Cuba

Pointe-a-Pitre Bay Hurricane (1776) >6,000 Martinique, Guadeloupe

San Ciriaco Hurricane (1899) 3,433 Puerto Rico

1932 Cuba Hurricane 3,033 Cuba, Bahamas

1934 Yucatan Hurricane 1,000 – 3,000 Belize, Guatemala,

El Salvador, Honduras

1931 Belize Hurricane 2,500 Belize, Guatemala

Hurricane Stan (2005) 1,620 Guatemala, El Salvador, Nicaragua, Honduras, Costa Rica

Deadliest Hurricanes to Hit Central America and the Caribbean

Hurricane Strength Distribution for Landfalling Storms in Central America and the Carribean

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5

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1951-1955 1956-1960 1961-1965 1966-1970 1971-1975 1976-1980 1981-1985 1986-1990 1991-1995 1996-2000 2001-2005

Year

Number of Systems

Tropical Storms/Depressions Cat 1&2 Cat 3, 4, 5

Atlantic Landfalling Storms Striking

Central America and the Caribbean

Are more hurricanes a harbinger of

the Caribbean’s future?

To assess the Caribbean’s risk from landfallinghurricanes in the coming decades, we must understand:

Impact of global warming on hurricane activity

Natural variability in the Atlantic Ocean

Nature of local risks

“Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global average sea level.”

“Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely [>90%] due to the observed increase in anthropogenic greenhouse gas concentrations.”

4th Assessment Report Summary for Policy Makers

WMO

UNEP

UNEP

INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE

Global surface temperature has increased 0.74oC since 1906

Warmest 12 years:1998,2005,2003,2002,2004,2006, 2001,1997,1995,1999,1990,2000

Meehl et al, 2004

Increased global temperatures since 1970 is attributed to greenhouse warming

WMO

UNEP

UNEP

IPCC AR4: Hurricanes Detection of Change

There is observational evidence for an increase of intense tropical cyclone activity in the North Atlantic since about 1970, correlated with increases of tropical sea surface temperatures

There are suggestions of increased intense tropical cyclone activity in other regions where concerns over data quality are greater

Multi-decadal variability and the quality of the tropical cyclone records prior to 1970 complicate the detection of long-term trends in tropical cyclone activity

Increased tropical cyclone activity since 1970,

correlated with increasing sea surface temperatures

surface aircraft satellite recon

North Atlantic Tropical Cyclones and SST11 year running mean

Global View of Tropical CyclonesW. Pacific Ocean

40%N. Atlantic Ocean

11%E. Pacific Ocean

17%

SW Pacific Ocean8%

S. Indian Ocean19%

N. Indian Ocean6%

Each year there are about 85-90 tropical cyclones globally

# of cat 4+5 hurricanes has doubled globally since 1970 Data quality questioned in the Indian Ocean, Pacific Ocean

Global tropical cyclone intensity Webster, Holland, Curry, Chang (2005) Science

Wall Street JournalFebruary 2, 2006

Cold Front

Debate Shatters Civility of Weather Science

Hurricanes Worsened by Global Warming?

Spats are so tempestuous, sides are barely talking

Charge of “brain fossilization”

Tropical cyclone genesis/intensification factors

Sea water temperature > 26.5oC. Major hurricanes >28.5oC

Small vertical shear (minimal variation of wind with height)

Moist mid-troposphere & convective instability

Pre-existing weather disturbance

Not too close to the equator These factors change both with natural climate variability (e.g., El Nino) and global warming

Global trends in the tropics since 1970

Sea surface temperature Wind shear

0.5oC (1oF) increase no trend

Hoyos et al. 2006

WMO

UNEP

UNEP

IPCC AR4: Hurricanes Projections of Future Change

It is likely [>66%] that future tropical cyclones will become more intense, with larger peak wind speeds and more heavy precipitation associated with ongoing increases of tropical SSTs

The apparent increase in the proportion of very intense storms since 1970 in some regions is much larger than simulated by current models for that period

Hurricane intensity change scaled for a 0.5oC SST increase:

Webster et al. obs: +6.0%

Climate models: Knutsen/Tuleya (2004): +2.0% Oouchi et al. (2006): +2.1%

Potential intensity theory: Emanuel +2.7% Holland +5.3%

3-legged stool analogy: Observations, theory, and climate models agree that hurricane intensity should increase; they disagree on the magnitude of the increase. The stool stands.

TC intensity - SST link

Since 1995, there has been a shift in the intensitydistribution towards more major hurricanes

0 %

5 %

1 0 %

1 5 %

2 0 %

2 5 %

3 0 %

3 5 %

4 0 %

4 5 %

5 0 %

1 9 7 0 - 1 9 8 2 1 9 8 3 - 1 9 9 4 1 9 9 5 - 2 0 0 6

T S

C a t 1

C a t 2

C a t 3

C a t 4

C a t 5

Intensity Distribution of North Atlantic Tropical Cyclones

What does the future hold for hurricaneactivity in the North Atlantic?

Combined impacts of greenhouse warming and natural variability

The uncertain climate futureClimate Model Projections

Scenario simulations indicate 1.8-4.0oC temperature increase by 2100

WMO UNEP

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For a 2.5oC temperature increase:

• up to 30% increase in number of N. Atlantic tropical cyclones (no increase or slight decrease in global numbers)

• 10% increase in tropical cyclone intensity

• 30% increase in the number of major hurricanes

Climate model projections of future hurricane activity

Relationship between # of Atlantic storms and

sea-surface temperature

Obs: 1oF increase in SST --> +5 storms/yearModel: 1oF increase in SST --> +1 storm /year

Since 1995, there has been 40-50% greater activity than the previous peak period ca. 1950

North Atlantic Ocean

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1850 1870 1890 1910 1930 1950 1970 1990 2010

Number of Storms

Named Storms Hurricanes Cat. 4&5

11 year centered running mean

Atlantic Multidecadal Oscillation (AMO)

# of Tropical Cyclones:

• Avg for last 50 yrs: 10

• Avg last decade: 14

• Avg ca. 2025: 15-20 category 4+5 3-4

Projections for the average number of NATL tropical cyclones for 2025

(0.5oC warming)

The combination of greenhouse warming and natural variabilitywill produce unprecedented tropical cyclone activity in the coming decades

What does the increase in North Atlantichurricane activity mean for the Caribbean?

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1900 1920 1940 1960 1980 2000

Landfalling tropical cyclones striking the Caribbean and Central America

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5 %

1 0 %

1 5 %

2 0 %

2 5 %

Mexico

Mexico(Yucatan)

Belize

HondurasNicaragua

Cuba

Jamaica/Caymans

Haiti

Dominican Republic

Bahamas

Puerto Rico

Lesser Antilles

Venezuela / T&T

1900-2006 1900-1969 1970-2006

Hurricane Landfall Location

SST Changes: Gulf of Mexico and Caribbean

Warmest decade

UNEP

Summary: Projection for next two decades

The number of North Atlantic tropical cyclones most likely will increase in coming decades and intensity is expected to continue to increase

The number of Caribbean landfalls will most likely continue to increase