climate variability & change implications for cat insurance & weather risk management...
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Implications of climate variability & change1
WMO Expert Meeting on CAT Insurance & Weather
Risk Management MarketsDecember 7, 2007
Climate Variability & ChangeImplications for CAT insurance &
Weather Risk Management MarketsHurricanes & Storms
A Presentation for the WMO Expert Meeting on CAT Insurance & Weather Risk Management Markets
Sharon LeDuc, Deputy DirectorNOAA’s National Climatic Data Center
December 7, 2007
Storms: Hurricanes - Observed
• Increases in extreme wave heights along the East Coast are evident during the
hurricane season
• Increasing hurricane intensity is likely a contributing factor in this increase
2
Implications of climate variability & change3
WMO Expert Meeting on CAT Insurance & Weather
Risk Management MarketsDecember 7, 2007
Storms: Hurricanes - Projections
• For North Atlantic and North Pacific hurricanes:
For every degree Celsius of tropical SST increase, the surface wind speeds of the strongest hurricanes will increase 2-10%
Implications of climate variability & change4
WMO Expert Meeting on CAT Insurance & Weather
Risk Management MarketsDecember 7, 2007
Storms: Hurricanes - Projections
• For North Atlantic and North Pacific hurricanes:
For every degree Celsius of tropical SST increase, core rainfall rates will increase 6-18%
Implications of climate variability & change5
WMO Expert Meeting on CAT Insurance & Weather
Risk Management MarketsDecember 7, 2007
Storms: Hurricanes - Projections
N. Atlantic and N. Pacific hurricanes
• Frequency changes are too uncertain for confident projections
• Wind shear and SSTs play opposing roles
• Spatial distribution of hurricanes will likely change
Implications of climate variability & change6
WMO Expert Meeting on CAT Insurance & Weather
Risk Management MarketsDecember 7, 2007
Storms: Non-tropical - Observed
• It is very likely that there has been a northward shift in the tracks of strong storms in N. Pacific and N. Atlantic over the past 50 years
• In the North Pacific, the strongest storms are becoming even
stronger
• Data are insufficient to draw conclusions about changes in storm strength in the N. Atlantic
Implications of climate variability & change7
WMO Expert Meeting on CAT Insurance & Weather
Risk Management MarketsDecember 7, 2007
Storms: Non-tropical - Projections
• Human influences on changes in sea-level pressure are evident in the NH - affects the location and intensity of storms
• In the future, strong non-tropical storms are likely to be:
• more frequent • with stronger winds • and more extreme wave
heights
Precipitation Extremes
• Intense precipitation (heaviest 1%) increased 20% over the past century - total precipitation increased by 7%
• Overall, precipitation will likely be less frequent but more intense • 1-in-20 yr precipitation - projected to
occur 1-in-8 years by 2100 over much of eastern N. America
(mid-range emission scenario)
Extreme precipitation episodes (heavy downpours) became more frequent and intense in recent decades over most of North America
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Drought
• No trend in North American droughts in the last century
• But regional tendencies toward more severe droughts (southwestern U.S., parts of Canada, Alaska, Mexico)
• Droughts projected to become more severe in many locations (due to higher temperature &
evaporation potential & more sporadic rainfall)
likely that increasing temperatures (& associated increasing evaporation potential) already contribute to droughts making them longer & more intense
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Storms: Hurricanes - Data• Adjustments are necessary to account for
missing storms
• Sparser and less reliable observations earlier in 20th century
• For the Atlantic:• Data reliable back to 1945• Prior to 1900, data are too unreliable to
draw definitive conclusions
• Estimates of intensity, less reliable than frequency in historical record:
• Major hurricanes increased in intensity in the 1940s
• Observations improve with aircraft reconnaissance
10
Implications of climate variability & change11
WMO Expert Meeting on CAT Insurance & Weather
Risk Management MarketsDecember 7, 2007
Storms: Hurricanes - Observed
• No evidence of trend in U.S. landfalling hurricanes
• Frequency of Atlantic tropical storms, hurricanes & major hurricanes increased:
• substantial since 1970• likely substantial since 1950• less confidence in data prior to 1900
Storms: Hurricanes - Observed
• The increase in Atlantic hurricane frequency is associated with increasing sea surface temperatures (SSTs) in the hurricane formation region
• Human activities have had a discernable impact on SSTs in the hurricane formation region
• Hurricane destructive potential has increased since 1970, also in association with warmer SSTs
balance of evidence suggests human activity has caused a discernable increase in hurricane frequency in the N. Atlantic
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