Projections of Future Tropical Cyclone Activity


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Projections of Future Tropical Cyclone Activity
Isaac Ginis

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Projections of Future Tropical Cyclone Activity

  1. 1. 1 Projections of Future Tropical Cyclone ActivityHurricane Katrina, Aug. 2005 Isaac Ginis GSO/URI Model simulation of Atlantic hurricane activity
  2. 2. The zero line is determined from the global mean temperature during the period from 1951 to 1980.The black line is the annual mean and the solid red line is the five-year mean.The green bars show uncertainty estimates.
  3. 3. There is strong relationship between SST and the hurricane activity (hurricane power) in the Atlantic basin. Increasing data uncertainty Hurricane power (PDI) is proportional to the time integral of the cube of the surface wind speeds accumulated across all storms overSource: Kerry Emanuel, J. Climate (2007). their entire life cycles.
  4. 4. Atlantic tropical storms (< 2 day duration) show a strong rising trend, butstorms of >2 day duration--adjusted for missing storms--do not show a trend.
  5. 5. United States landfalling hurricanes do not show any long-term trend since 1851
  6. 6. IPCC Projections of Future Changes in ClimateIPCC best estimatefor low scenario(B1) is 1.8°C (likelyrange is 1.1°C to2.9°C), and for highscenario (A1FI) is4.0°C (likely rangeis 2.4°C to 6.4°C).Broadly consistentwith span quotedfor SRES in TAR,but not directlycomparableSource: IPCC 4th Assessment Report.
  7. 7. Two future projections of Atlantic hurricane power Projection 1: Absolute SST • ~300% projected increase in Power Dissipation • Indirect attribution: CO2 Atlantic SST Hurricanes Projection 2: Relative SST • Projected change: sign uncertain, +/- 80% • Indirect attribution: CO2 Atlantic SST – Global SST Hurricanes • Supported by dynamical modelsSource: Vecchiet al. Science (2008)
  8. 8. Example of a regional model that reproduces the interannualvariability and trend of Atlantic hurricane counts (1980-2006) 18-km grid model nudged toward large-scale (wave 0-2) NCEP Reanalyses Source: Knutson et al., 2007, Bull. Amer. Meteor. Soc.
  9. 9. The 26.5oC “threshhold temperature” for Atlantic tropical stormformation: a climate dependentthreshhold, which may increase to~28.5oC by the late 21st century with climate warming. Note the decrease in overall number of storms in the warmer climate Source: Knutson et al., 2008, Nature Geoscience.
  10. 10. Example of a “double-downscaling” method used to explore frequencies and intensities of Atlantic hurricanes at high resolution Geophysical Fluid Dynamics Laboratory/NOAA
  11. 11. SUMMARY OF PROJECTED CHANGE Cat 4+5 frequency: 81% increase, or 10% per decade Estimated net impact of these changes on damage potential: +28%• Colored bars show changes for the18 model CMIP3 ensemble (27 seasons); dotsshow range of changes across 4 individual CMIP models (13 seasons).Source: Bender et al., Science, 2010.
  12. 12. Late 21st Century Climate Warming Projection-- Average of 18 CMIP3 Models (27 Simulated Hurricane Seasons) Source: Bender et al., Science, 2010
  13. 13. Author Team:Tom Knutson, Co-Chair Geophysical Fluid Dynamics Laboratory/NOAA, Princeton, USAJohn McBride, Co-Chair Center for Australian Weather and Climate Research, Melbourne, AustraliaJohnny Chan University of Hong Kong, Hong Kong, ChinaKerry Emanuel Massachusetts Institute of Technology, Cambridge, USAGreg Holland National Center for Atmospheric Research, Boulder, USAChris Landsea National Hurricane Center/NOAA, Miami, USAIsaac Held Geophysical Fluid Dynamics Laboratory/NOAA, USAJim Kossin National Climatic Data Center/NOAA, Madison, USAA.K. Srivastava India Meteorological Department, Pune, IndiaMasato Sugi Research Institute for Global Change/JAMSTEC, Yokohama, Japan
  14. 14. SUMMARY ASSESSMENT:Detection and Attribution:It remains uncertain whether past changes in anytropical cyclone activity (frequency, intensity, rainfall,etc.) exceed the variability expected through naturalcauses, after accounting for changes over time inobserving capabilities.
  15. 15. SUMMARY ASSESSMENT:Tropical Cyclone Projections: FrequencyIt is likely that the global frequency of tropical cycloneswill either decrease or remain essentially unchangeddue to greenhouse warming. We have very lowconfidence in projected changes in individual basins.Current models project changes ranging from -6 to -34% globally, and up to ± 50% or more in individualbasins by the late 21st century.“Likely”: >67% probability of occurrence, assessed using expert judgment
  16. 16. SUMMARY ASSESSMENT:Tropical Cyclone Projections: IntensitySome increase in mean tropical cyclone maximumwind speed is likely (+2 to +11% globally) withprojected 21st century warming, although increasesmay not occur in all tropical regions. The frequency ofthe most intense (rare/high-impact) storms will morelikely than not increase by a substantially largerpercentage in some basins. “More likely than not”: >50% probability of occurrence, assessed using expert judgment
  17. 17. SUMMARY ASSESSMENT:Tropical Cyclone Projections: RainfallTropical cyclone rainfall rates are likely to increase.The projected magnitude is on the order of +20%within 100 km of the tropical cyclone center.
  18. 18. SUMMARY ASSESSMENT:Tropical Cyclone Projections: Genesis,Tracks, Duration, and Surge Flooding• We have low confidence in projected changes ingenesis location, tracks, duration, or areas of impact.Existing model projections do not show dramaticlarge-scale changes in these features.• The vulnerability of coastal regions to storm surgeflooding is expected to increase with future sea levelrise and coastal development, although thisvulnerability will also depend on future stormcharacteristics.
  19. 19. Implications to Rhode Island• Continued sea level rise means that storm surges and waves ride on a higher base level, causing storm surge impacts such as coastal erosion, even from minor storms, to increase, possibly dramatically.• Increased hurricane rainfall rates and intensity would increase the risk of coastal and inland flood and wind damage in areas affected by landfalling hurricanes.