1. Implications of climate variability & change 1 WMO Expert Meeting on CAT Insurance & Weather Risk Management Markets December 7, 2007 Climate Variability & Change Implications for CAT insurance & Weather Risk Management Markets Hurricanes & Storms A Presentation for the WMO Expert Meeting on CAT Insurance & Weather Risk Management Markets Sharon LeDuc, Deputy Director NOAA’s National Climatic Data Center December 7, 2007

2. 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

3. Implications of climate variability & change 3 WMO Expert Meeting on CAT Insurance & Weather Risk Management Markets December 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%

4. Implications of climate variability & change 4 WMO Expert Meeting on CAT Insurance & Weather Risk Management Markets December 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%

5. Implications of climate variability & change 5 WMO Expert Meeting on CAT Insurance & Weather Risk Management Markets December 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

6. Implications of climate variability & change 6 WMO Expert Meeting on CAT Insurance & Weather Risk Management Markets December 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

7. Implications of climate variability & change 7 WMO Expert Meeting on CAT Insurance & Weather Risk Management Markets December 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

8. 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 8

9. 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 9

10. Storms: Hurricanes - Data Adjustments are necessary to account for missing storms Sparser and less reliable observations earlier in 20 th 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

11. Implications of climate variability & change 11 WMO Expert Meeting on CAT Insurance & Weather Risk Management Markets December 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

12. 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 12