Hurricane Risk: Importance of Climate Time Scale and Uncertainty

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1 Hurricane Risk: Importance of Climate Time Scale and Uncertainty FCHLPM Workshop Peter S. Dailey, Ph.D. July 23-24, AIR WORLDWIDE CORPORATION 1

2 Agenda Importance of Understanding Climate Change, and Uncertainties in Climate Science and Models Climate Influences on Atlantic Hurricane Risk 2009 AIR WORLDWIDE CORPORATION 2

3 Earth s Climate Feedback System FEEDBACKS INVOLVING WATER VAPOR Source: FEEDBACKS INVOLVING CARBON DIOXIDE 2009 AIR WORLDWIDE CORPORATION 3

4 Climate Teleconnections: The Walker Circulation and the El Nino Southern Oscillation (ENSO) Source: AIR WORLDWIDE CORPORATION 4

5 Global Ocean Circulation Circulation Period of Oscillation ~ 1000 Years Topographic View of Earth s Land and Ocean Surfaces Source: AIR WORLDWIDE CORPORATION 5

6 IPCC Emissions Scenarios Tell Very Different Stories About the Future CO 2 concentration Temperature rise 2009 AIR WORLDWIDE CORPORATION 6

7 Contribution of Various Agents to Global Mean Atmospheric Temperatures Since the Mid-1700s 2009 AIR WORLDWIDE CORPORATION Source: 7

8 Qualitative Comparison of the State of Research on the Future Impact of Climate Change on Atmospheric Perils Tropical Cyclones Extratropical Cyclones Flood Severe Thunderstorm Wildfires F I F I F I Range of scientific opinion 2009 AIR WORLDWIDE CORPORATION 8

9 Climate Change Projections Point to Less Frequent, but More Intense Tropical Cyclones Decrease in Overall Frequency Increase in Most Intense Storms Increase in Precipitation Intensity With expected Climate Change (IPCC) More likely than no (>50%) Likely (>66%) Likely (>66%) Latest Research Confirms Trend Confirms Trend Confirms Trend The response to forcing is not uniform across the globe Regional differences within ocean basins exist How much of this variability translates into landfall activity is not known, thus this is an active area of research 2009 AIR WORLDWIDE CORPORATION 9

10 Important Global Climate Oscillations in the Middle and Tropical Latitudes PERIOD Atlantic Meridional Mode (AMM): Long-lived (multidecadal) mode of oscillation combining key ingredients for tropical cyclone development Pacific Decadal Oscillation (PDO): Long-lived El Nino-like pattern in the Pacific, most apparent in the North Pacific Quasi-Biennial Oscillation (QBO): Oscillation in the mean direction of stratospheric winds (west-east) Madden-Julian Oscillation (MDO): Short-lived oscillation in tropical precipitation, especially in the Indian and Pacific North Atlantic Oscillation (NAO): Short-term atmospheric oscillation related to surface pressure differences and behaving with complex periodicity (or aperiodicity) Decades Decade Years Months Weeks 2009 AIR WORLDWIDE CORPORATION 10

11 Model Predictability and Time Scale Weather Predictions Seasonal to Interannual Outlooks Model Predictability Weather Model Gap Climate Projections (e.g., IPCC) Climate Model Gap 2 Weeks 1 Year 10 Years 100 Years Time 2009 AIR WORLDWIDE CORPORATION 11

12 Key Climate Factors that Influence Atlantic Hurricane Activity Sea surface temperatures (hurricanes fuel ) Some consider cyclical, others trending, others a combination of both Persistent long-lived signal Wind shear conditions (hurricanes enemy ) Shear tears storms apart and prevents them from intensifying Atlantic wind shear is correlated with ENSO (La Nina = Low Shear) Steering currents (hurricanes chauffeur ) Mid-level wind flow directs storms across the Atlantic and potentially towards the North American coastline North Atlantic Oscillation (NAO) and the Atlantic Subtropical ( Bermuda ) High are climate measures which correlate to steering flow Unlike SSTs, these atmospheric climate signals are volatile and highly unpredictable on a seasonal timescale 2009 AIR WORLDWIDE CORPORATION 12

13 Climate Factors Exhibit Modes of Varying Predictability Climatological Factor Modes Mode Predictability Sea Surface Temperatures Warm/Cool High Wind Shear Conditions Moderate Steering Currents ENSO+/Neutral/ENSO- NAO+/Neutral/NAO- Low Saharan Air Layer Active/Inactive Low Other and Unknown???? 2009 AIR WORLDWIDE CORPORATION 13

14 NAO Phase Influences Hurricane Landfall Risk 2009 AIR WORLDWIDE CORPORATION 14

15 NAO Forecasts are Challenging Due to the Volatility of the Signal; but NAO and Steering are Key to Landfall North Atlantic Oscillation varies in response to atmospheric pressure distribution over the Atlantic Because atmospheric pressure is changing on short time scales, predictability of the NAO decays quickly Operational forecast models can only predict the NAO signal out a few weeks Climate (General Circulation) Models have been used to study the relationship between climate change and the NAO mechanism CPC MRF Ensemble NAO Forecast 2009 AIR WORLDWIDE CORPORATION 15

16 Forecasting SST Anomalies Beyond a Season is Highly Uncertain 90% Confidence Interval 2009 AIR WORLDWIDE CORPORATION 16

17 TCI Distributions for U.S. Hurricane Landfalls Based on SST Climate Condition 2009 AIR WORLDWIDE CORPORATION 17

18 TCI for U.S. Hurricane Landfalls Across the Intensity Spectrum (Warm Ocean Condition) 2009 AIR WORLDWIDE CORPORATION 18

19 Examination of Genesis Characteristics and Storm Response to Anomalous Ocean Climate HURRICANE INTENSIFICATION CLIMATOLOGY Probability of Hurricane Intensification COOL SST YEARS WARM SST YEARS 2009 AIR WORLDWIDE CORPORATION 19

20 Probabilistic Models Estimate the Impact of Climate Conditions that Persist for a Significant Number of Seasons U.S. Loss Producing Hurricanes U.S. Loss Producing Major Hurricanes Cindy Dennis Katrina Ophelia* Rita Wilma Dolly Gustav Ike Alex* Charley Frances Gaston Ivan Jeanne Dennis Katrina Rita Wilma Bertha Fran Bonnie Earl Georges Erin Opal Bret Floyd Irene Danny Lili Claudette Isabel Fran Opal Floyd Charley Frances Ivan AIR US Hurricane Model Standard Catalog AIR US Hurricane Model Warm SST Catalog Observed *Bypassing hurricane (no landfall but produces loss) 2009 AIR WORLDWIDE CORPORATION 20

21 Climate Change and Climate Volatility under Earth s Chaotic System of Feedbacks average conditions 2009 AIR WORLDWIDE CORPORATION 21

22 Is Hurricane Activity Becoming More Volatile in a Warming World? Atlantic Storm Counts (1970 to 2007) Storm Count Coefficient of Variation (COV) 2009 AIR WORLDWIDE CORPORATION 22

23 Volatility in Hurricane Tracks May Also React to a Changing Climate Current Atlantic Warm Period 2009 AIR WORLDWIDE CORPORATION 23

24 Summary Hurricane risk is significant and remains a critical component of overall P&C risk Climate is always changing Climate science and climate models are becoming more credible and sophisticated, but still there is much progress to be made Feedbacks and teleconnections inherent to the climate system are complex, but cannot be disregarded AIR has embarked on several new areas of climate impact research The current climate regime is, and always has been dynamic, and accounting for natural variability is critical to risk managers Future climate projections, while uncertain, may allow for insurers to plan for, and potentially mitigate against, anticipated changes in the longer-term climate Understanding and measuring uncertainty will be critical to the use of such information in any assessment of risk 2009 AIR WORLDWIDE CORPORATION 24