CLIMATE CHANGE AND GLOBAL DAMAGES FROM TROPICAL CYCLONES Robert Mendelsohn Kerry Emanuel Shun Chonabayashi Laura Bakkensen

Acknowledgements Funding by World Bank-United Nations Global Facility for Disaster Reduction & Recovery Report: –Natural Hazards, UnNatural Disasters: The Economics of Effective Prevention –Apurva Sanghi

Goal of this Study Predict how climate change will affect tropical cyclones Reflect underlying changes in vulnerability in future periods Estimate damage functions for tropical cyclones Measure how climate change affects future tropical cyclone damages

Current and 2100 Baseline Impacts of Extreme Weather Events

Current and Future Extreme Event Damages by Region

Current and Future Deaths by Extreme Event

Current and Future Deaths by Region

Past Climate Results IPCC 1996 estimates CC increases US tropical cyclone damages by about 0.02% of GDP and world damages by 0.002% of GWP Nordhaus 2010 estimates CC doubles US tropical cyclone damages (0.06% of GDP) Narita et al 2007 estimate CC doubles world tropical cyclone damages (0.006% GWP)

Emissions Trajectory Climate Scenario Tropical Cyclone Behavior Vulnerability Projection Damage Function Damage Estimate Integrated Assessment Model

IPCC Emissions Scenarios This study

Projected Warming: This study

Climate Models CNRM ECHAM GFDL MIROC

Tropical Cyclone Generator 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, taken from the global climate model Step 3: Run a detailed cyclone intensity model for each event, 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

500 Synthetic Tracks Coded by Minimum Pressure

Change in Tropical Cyclone Power by Ocean Basin

Tropical Cyclone Damage Function ConstantMinimum Pressure IncomePopulat. Density US607.5 (10.39) (9.96) (0.45) (1.53) Global15.17 (22.77) (6.44) (3.04)

Baseline Tropical Cyclone Damages Current Global Damages: $20 billion/yr (0.03% GWP) Future Baseline Damages: $55 billion/yr (0.01% GWP) Baseline increases by 2100 because of higher income but not as much as GWP Baseline assumes current climate

Current and Future Baseline Damages by Region

Estimate Climate Impacts Calculate future baseline damages (current climate) Calculate future damages with future climate Subtract baseline from future damages with future climate to get net climate impact

Climate Change Damages From Tropical Cyclones in 2100 Billion USD/yr/(%GWP) CNRMECHAMGFDLMIROC Minimum Pressure 80.1 (0.15%) 13.9 (0.03%) 78.8 (0.15%) 41.6 (0.08%)

Climate damages by region

Climate damage as percent of GDP by region

Climate change increases frequency of high damage storms

Limitations All steps of the integrated assessment are uncertain Possible interaction with sea level rise not yet taken into account Current analysis at national level- needs finer spatial resolution No explicit adaptation

Conclusions-1 Damages from tropical cyclones almost triple by 2100 from income growth Climate change likely to double these damages Largest CC impacts felt in US and then China Island nations will have largest CC impacts as a fraction of GDP

Conclusions-2 Damages concentrated in large infrequent storms- 10% worst storms will cause 93% of total damages with CC Protect against high winds with coastal building codes Hard structures (sea walls) are ineffective protection against infrequent storm surge Restricted land use at low points along vulnerable coast