Download

Is Global Warming Affecting Hurricanes?






Advertisement
/ 56 []
Download Presentation
Comments
hailey
From:
|  
(823) |   (0) |   (0)
Views: 80 | Added: 24-02-2012
Rate Presentation: 0 0
Description:
Is Global Warming Affecting Hurricanes?. Kerry Emanuel Massachusetts Institute of Technology. Program. Overview of hurricane risk Evidence connecting hurricane activity to tropical sea surface temperature The evidence for anthropogenic forcing of tropical ocean temperature The future.
Is Global Warming Affecting Hurricanes?

An Image/Link below is provided (as is) to

Download Policy: Content on the Website is provided to you AS IS for your information and personal use only and may not be sold or licensed nor shared on other sites. SlideServe reserves the right to change this policy at anytime. While downloading, If for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.











- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -




Slide 1

Is Global Warming Affecting Hurricanes?

Kerry Emanuel

Massachusetts Institute of Technology

Slide 2

Program

  • Overview of hurricane risk

  • Evidence connecting hurricane activity to tropical sea surface temperature

  • The evidence for anthropogenic forcing of tropical ocean temperature

  • The future

Slide 3

Hurricane Risk

  • Tropical cyclones account for the bulk of natural catastrophe U.S. insurance losses

  • Losses vary roughly as the cube of the maximum wind speed

  • Katrina caused > 1300 deaths and > $130 billion in damage

Slide 4

Total U.S. Hurricane Damage by Decade, in 1010 2004 U.S. Dollars

Source: Roger Pielke, Jr.

Slide 5

Population of Florida, 1790-2004

Slide 6

Total Adjusted Damage by Decade, in 1010 2004 U.S. Dollars

Source: Roger Pielke, Jr.

Slide 7

Total Number of Landfall Events, by Category, 1870-2004

Slide 8

U.S. Hurricane Damage, 1900-2004,Adjusted for Inflation, Wealth, and Population

Slide 9

Summary of U.S. Hurricane Damage Statistics:

  • >50% of all normalized damage caused by top 8 events, all category 3, 4 and 5

  • >90% of all damage caused by storms of category 3 and greater

  • Category 3,4 and 5 events are only 13% of total landfalling events; only 30 since 1870

  • Landfalling storm statistics are grossly inadequate for assessing hurricane risk

Slide 10

Part II: Evidence Connecting Hurricane Activity to Tropical Sea Surface Temperature

Slide 11

No Long-Term Trend in Global Frequency

Slide 12

Intensity Metric:The Power Dissipation Index

A measure of the total frictional dissipation of kinetic energy in the hurricane boundary layer over the lifetime of the storm

Slide 13

Power Dissipation Based on 3 Data Sets for the Western North Pacific(smoothed with a 1-3-4-3-1 filter)

Years included: 1949-2004

aircraft recon

Data Sources: NAVY/JTWC, Japan Meteorological Agency, UKMO/HADSST1, Jim Kossin, U. Wisconsin

Slide 14

North Atlantic PDI and Sea Surface Temperatures

(Smoothed with a 1-3-4-3-1 filter)

Years included: 1970-2006

Scaled Temperature

Power Dissipation Index (PDI)

Data Sources: NOAA/TPC, UKMO/HADSST1

Slide 15

Atlantic Sea Surface Temperatures and Storm Max PDI

(Smoothed with a 1-3-4-3-1 filter)

Years included: 1870-2006

Power Dissipation Index (PDI)

Scaled Temperature

Data Sources: NOAA/TPC, UKMO/HADSST1

Slide 16

Decadal Perspective:

Slide 17

What Environmental Factors Control Hurricane Power Dissipation?

  • Potential Intensity

  • Wind Shear

  • Low level environmental vorticity (“spin”)

Slide 18

Energy Production and Potential Intensity

Slide 19

Distribution of Entropy in Hurricane Inez, 1966

Source: Hawkins and Imbembo, 1976

Slide 20

Maximum Theoretical Wind Speed, Vpot

Net outgoing radiation

Sea Surface Temperature

Incoming solar radiation

Ocean mixed layer entrainment

Temperature at top of storm

Surface Trade Wind speed

Slide 21

Potential intensity and SST can be changed by:

  • Changing solar and infrared radiation

  • Changing ocean mixed layer entrainment

  • Changing mean surface wind speed

Also, Potential Intensity (but NOT SST) can be changed by changing the storm top temperature

Slide 22

Observed Potential Intensity

Slide 23

MDR Lower Stratospheric Temperature

Slide 24

Contributions to North Atlantic Potential Intensity

(Log of each contribution, minus long-term mean)

Slide 25

Contributions to North Atlantic Hurricane Power Dissipation:

(Log of each contribution, minus long-term mean)

Slide 26

Part III: What is Causing Changes in the Tropical Sea Surface Temperature?

Slide 27

Atlantic Sea Surface Temperatures andSurface Temperature

Aug-Oct Sea Surface Temperatures (at key latitudes)

Aug-Oct HADCRU NH Surface Temperature

Slide 28

What is Controlling Northern Hemisphere Surface Temperature?

Slide 29

Begin with Global Mean

Surface Temperature

Slide 30

Carbon Dioxide

Methane

Nitrous Oxide

Halocarbons

Total LLGHG

Greenhouse Gases and Associated Radiative Forcing have been Increasing

3

2.5

2

Radiative forcing (Watts/square meter)

1.5

1

0.5

0

1750

1800

1850

1900

1950

2000

Year

Slide 31

Natural Forcing have also

Varied with Time

Slide 32

Pelée

Agung

El Chichón

Pinatubo

Slide 33

Northern hemisphere surface temperature (and late summer-early fall tropical Atlantic sea surface temperature) represents a linear combination of global warming and aerosol cooling

Hypothesis about Why the Northern Hemisphere Differs from the Globe:

Mann and Emanuel 2006

Slide 34

Tropical Atlantic SST(blue), Global Mean Surface Temperature (red), Aerosol Forcing (aqua)

Global Mean Surface T

MDR SST

Aerosol forcing

Mann, M. E., and K. A. Emanuel, 2006. Atlantic hurricane trends linked to climate change. EOS, 87, 233-244.

Slide 35

Best Fit Linear Combination of Global Warming and Aerosol Forcing (red) versus Tropical Atlantic SST (blue)

MDR SST

Global mean T

+ aerosol forcing

Mann, M. E., and K. A. Emanuel, 2006. Atlantic hurricane trends linked to climate change. EOS, 87, 233-244.

Slide 36

Part IV: The Future

Slide 37

Projections of Tropical Cyclone Activity: Downscaling from Global Climate Models

Slide 38

Using Physics to Improve Hurricane Risk Assessment

  • Generate very large number of synthetic storm tracks consistent with the general circulation of the atmosphere in a given climate

  • Run a coupled ocean-atmosphere model of hurricane intensity along each track to generate wind fields

Slide 39

Example: 200 Synthetic Tracks

Slide 40

Cumulative Distribution of Storm Lifetime Peak Wind Speed, with Sample of 2946 Synthetic Tracks

Slide 41

Use Daily Output from Climate Models to Derive Wind Statistics, Thermodynamic State Needed by Synthetic Track Technique(but hold genesis PDF constant!)

Slide 42

Compare two simulations from IPCC set: 1. Last 20 years of 20th century simulations2. Years 2180-2200 of IPCC Scenario A1b (CO2 stabilized at 720 ppm)

Slide 43

Results Using 2000 Atlantic and 2000 North Pacific Tracks from 5 Models:

Percent Increase in Basin Power Dissipation

Slide 44

Results Using 2000 Atlantic and 2000 North Pacific Tracks from 5 Models:

Percent Increase in Landfall Power Dissipation

Slide 45

Summary

  • Atlantic TC frequency, intensity and duration are co-varying with tropical Atlantic SST

  • Changes in tropical cyclone power are driven by changing potential intensity, wind shear, and “spin” of the low-level winds

Slide 46

  • Changes in tropical North Atlantic sea temperature mirror changes in northern hemispheric temperature and are probably driven by a combination of cooling by volcanoes and air pollution, and warming by greenhouse gases

  • Long-term risk assessments must account for climate change

Slide 47

Scientific Basis of the “Natural Cycles” Story

The Atlantic Multi-Decadal Oscillation (AMO)

Slide 48

Power Spectrum of North Atlantic Hurricane Frequency, 1851-2005

Slide 49

The AMO is a Pattern of Sea

Surface Temperature

High-latitude North Atlantic

“Main development region”

S. B. Goldenberg et al., 2001. Science, 293, 474-479

Slide 50

Variation with time of amplitude of third rotated EOF of the non-ENSO residual 1856-1991 de-trended SST data

Slide 51

Same, but showing global distribution. From Enfield et al., 1999

Slide 52

Source: Hadley Centre Global Surface Temperature Data

Slide 53

A

De-trended Aug-Oct Northern Hemisphere Surface Temperature

(Hadley Centre Global Surface Temperature Data)

Variation with Time of the Strength of the AMO

(Goldenberg et al. 2001)

Slide 54

3000 Atlantic storms in the current climate

Slide 55

Boston

HURDAT: 28 events Method 2: 3000 events

Slide 56

U.S. Landfall Probability, by Category: Present Climate versus Warmed Climate


Copyright © 2014 SlideServe. All rights reserved | Powered By DigitalOfficePro