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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
0
5
10
15
20
25
30
35
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
JkljlJlkjljLhjljk
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
0
2
4
6
8
10
12
14
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?
0
2
4
6
8
10
12
14
16
18
1900 1920 1940 1960 1980 2000
Landfalling tropical cyclones striking the Caribbean and Central America
0 %
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
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