Estimating Hurricane Risk and Damages in Current and Future
Climate
Estimating Hurricane Risk and Damages in Current and Future
Climate
Kerry EmanuelLorenz Center, MIT
Program
Brief overview of hurricanes
What have hurricanes been like in the past, and how will they be affected by global warming?
How should we assess hurricane risk?
Brief Overview of Tropical Cyclones
The View from Space
Igor, 2010
Annual Cycle of Tropical Cyclones
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec NH Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun SH
a
a
Northern Hemisphere
(NH)
Southern Hemisphere
(SH)Nu
mb
er
of
Ev
en
ts p
er
Mo
nth
Hurricane Risks:
Wind
Storm Surge
Rain
Basic Hurricane Economics
Windstorms Account for Bulk of Insured Losses Worldwide
Total US Damages by Natural Hazard, 1980-2012
Source: NOAA
Source: Roger Pielke, Jr.
Total U.S. Hurricane Damage by Decade, in 1010 2004 U.S. Dollars
Population of Florida, 1790-2004
Source: Roger Pielke, Jr.
Total Adjusted Damage by Decade, in 1010 2004 U.S. Dollars
U.S. Hurricane Damage, 1900-2004,Adjusted for Inflation, Wealth, and Population
Total Number of Landfall Events, by Category, 1870-2004
Limitations of a strictly statistical approach to hurricane risk assessment
>50% of all normalized U.S. hurricane damage caused by top 8 events, all category 3, 4 and 5>90% of all damage caused by storms of category 3 and greaterCategory 3,4 and 5 events are only 13% of total landfalling events; only 30 since 1870 Landfalling storm statistics are inadequate for assessing hurricane risk
Overcoming Limits of a History-Based Statistical Approach
barrier beach
backbarrier marshlagoon
barrier beach
backbarrier marshlagoon
a)
b)
Source: Jeff Donnelly, WHOI
upland
upland
flood tidal delta
terminal lobes
overwash fan
overwash fan
Method 1: Paleotempestology
Method 2: Risk Assessment by Direct Numerical Simulation of Hurricanes:
The Problem
The hurricane eyewall is a front, attaining scales of ~ 1 km or less
At the same time, the storm’s circulation extends to ~1000 km and is embedded in much larger scale flows
The computational nodes of global models are typically spaced 100 km apart
Histograms of Tropical Cyclone Intensity as
Simulated by a Global Model with 50 km grid
point spacing. (Courtesy Isaac Held, GFDL)
Category 3
Global models do not simulate the storms that
cause destruction
ObservedModeled
Numerical convergence in an axisymmetric, nonhydrostatic model (Rotunno and Emanuel, 1987)
How to deal with this?
Option 1: Brute force and obstinacy
How to deal with this?Option 1: Brute force and obstinacy
Option 2: Applied math and modest resources
Time-dependent, axisymmetric model phrased in R space
Hydrostatic and gradient balance above PBL
Moist adiabatic lapse rates on M surfaces above PBL
Boundary layer quasi-equilibrium convection
Deformation-based radial diffusion
Coupled to simple 1-D ocean model
Environmental wind shear effects parameterized
21
2M rV fr 21
2fR M 2 sinf
How Can We Use This Model to Help Assess Hurricane Risk in Current and Future Climates?
Risk Assessment Approach:
Step 1: Seed each ocean basin with a very large number of weak, randomly located cyclones
Step 2: Cyclones are assumed to move with the large scale atmospheric flow in which they are embedded, plus a correction for the earth’s rotation and sphericity
Step 3: Run the CHIPS model for each cyclone, and note how many achieve at least tropical storm strength
Step 4: Using the small fraction of surviving events, determine storm statistics
Details: Emanuel et al., Bull. Amer. Meteor. Soc, 2008
Comparison of Random Seeding Genesis Locations with Observations
Cumulative Distribution of Storm Lifetime Peak Wind Speed, with Sample of 1755 Synthetic Tracks
90% confidence bounds
Return Periods
Sample Storm Wind Swath
Accumulated Rainfall (mm)
Storm Surge Simulation
SLOSH mesh~ 103 m
ADCIRC mesh~ 102 m
Battery
ADCIRC model(Luettich et al. 1992)
SLOSH model(Jelesnianski et al. 1992)
ADCIRC mesh~ 10 m
(Colle et al. 2008)
Taking Climate Change Into Account
Captures effects of regional climate phenomena (e.g. ENSO, AMM)
Modeling Center Institute ID Model Name Average Horizontal Resolution
National Center for Atmospheric Research
NCAR CCSM4 1.25o X 0.94o
NOAA Geophysical Fluid Dynamics Laboratory
GFDL CM3 2.5 o X 2.0 o
Met Office Hadley Center MOHC HADGEM2-ES 1.875 o X 1.25 o
Max Planck Institute for Meteorology
MPI MPI-ESM-MR 1.875 o X 1.865 o
Atmosphere and Ocean Research Institute (The
University of Tokyo), National Institute for
Environmental Studies, and Japan Agency for
Marine-Earth Science and Technology
MIROC MIROC5 1.41 o X 1.40 o
Meteorological Research Institute
MRI MRI-CGCM3 2.81 o X 2.79 o
CMIP5 Models
Return Periods based on GFDL Model
Return Periods of Storm Total Rainfall at New HavenGFDL Model
GCM flood height return level, Battery, Manhattan
(assuming SLR of 1 m for the future climate )
Black: Current climate (1981-2000)Blue: A1B future climate (2081-2100)Red: A1B future climate (2081-2100) with R0 increased by 10% and Rm increased by 21%
Lin et al. (2012)
Human Adaptation: Century Time Scales
Current and Future Probability Density of U.S. Damages, MIROC
Model
Current and Future Damage Probability, MIROC Model
A Black Swan: Dubai
Aerts, C. J. H. J., W. J. W. Botzen, K. Emanuel, N. Lin, H. de Moel, and E. O. Michel-Kerjan, 2014: Evaluating flood resilience strategies for coastal megacities. Science, 344, 473-475.
Benefit-Cost Ratios
From: American Climate Prospectus Economic Risks in the United States
Sea level rise alone
Sea level rise + changing storms
Summary
History is too short and imperfect to estimate hurricane risk
Better estimates can be made from paleotempestology and downscaling hurricane activity from climatological or global model output
Hurricanes clearly vary with climate and there is a risk that hurricane threats will increase over this century
Spares
What is a Hurricane?
Formal definition: A tropical cyclone with 1-min average winds at 10 m altitude in excess of 32 m/s (64 knots or 74 MPH) occurring over the North Atlantic or eastern North Pacific
A tropical cyclone is a rapidly rotating storm system between 100 and 1000 km in diameter and characterized by low surface pressure, strong winds, and a spiral arrangement of thunderstorms. The rotational character of the storm is a consequence of conservation of angular momentum imparted by the Earth’s rotation as air flows inward toward the rotation axis.
What is a Tropical Cyclone?
The word Hurricane is derived from the Mayan word Huracan and the Taino and Carib word
Hunraken, a terrible God of Evil, and brought to the West by Spanish explorers
Blow, winds, and crack your cheeks! rage! blow! You cataracts and hurricanoes, spout Till you have drench’d our steeples, drown’d the cocks!
-- King Lear
ADCIRC Mesh
Heat Engine Theory Predicts Maximum Hurricane Winds
MPH
Black Swans
Peak Surge at each point
along Florida west coast