Implications of climate variability & change 1 WMO Expert Meeting on CAT Insurance & Weather Risk Management Markets December 7, 2007 Climate Variability

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

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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%





• For North Atlantic and North Pacific hurricanes:

For every degree Celsius of tropical SST increase, core rainfall rates will increase 6-18%





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




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




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

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• 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


• 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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Implications of climate variability & change 1 WMO Expert Meeting on CAT Insurance & Weather Risk Management Markets December 7, 2007 Climate Variability