1 DEATH and DESTRUCTION from HURRICANES in the 21 st CENTURY Hugh Willoughby, FIU E&E National Tropical Weather Conference 9 April 2015

2 AGW ---Anthropogenic Global Warming

3

4 Using “Intrinsic Modal Functions,” Wu et al., 2011: Clim. Dyn.,

Why is AGW Credible? 0.7 o C warming since 1900 Atmospheric CO 2 increase to 400 ppm Melting ice and rising sea level (20 cm since 1900) are natural low-pass filters Well-established physical basis Consistent (sort of…) results as the models have improved Counterarguments: –Possible long-term >10 3 yr natural variability –Common intellectual heritage of models –Ad-hominem and economic arguments

Heat Engine Models of Hurricane Intenisty MPI is the lowest central pressure or strongest wind speed possible for given sea-surface and outflow temperatures.

Hurricane Intensity MPI corresponds to category 5 over most of the tropical seas during hurricane season. Most hurricanes don’t reach their MPI because of: –Vertical Shear of the surrounding winds –Hurricane-induced cooling of the sea –Eyewall replacement cycles –Lifecycle duration 7

8 Accumulated Cyclone Energy by Year ACE is the yearly sum of (Vmax) 2 from HURDAT

9 North Atlantic Tropical Cyclones North Atlantic TCs by Year How much of the apparent increase is due to incomplete observations in the past, and how much is due to climate change?

10 US Landfalls by Year

11 Normalized Hurricane Damage Pielke & Landsea (1998, 2008) Corrects for: –Inflation –Population increase –Greater personal wealth What would historical hurricanes cost with 2008 population and development? Constant at $11B per year, based upon updated data

Damage is NORMALIZED to 2008 by adjusting for inflation, population and individual wealth (Pielke et al. 2008) US Inflation-Adjusted and Normalized Damage

Deaths Respite Deaths Better Forecasts & Communications!

Year-to-Year Variations of Hurricane Numbers and Intensities: Apparent increase due to data issues before 1944 (or perhaps 1960 or 1974) El Niño—Warming of the equatorial Pacific that increases shear over the topical Atlantic every 3-5 years Atlantic Multi-Decadal Oscillation: –Warm phase---weaker shear, more hurricanes –Cool phase---stronger shear, fewer hurricanes Anthropogenic Global Warming –Stronger MPI, but…. –Probably more shear, too Chance---more about chance later

Hurricane Season (El Niño)

16 (La Niña)

17 Atlantic Multidecadal Oscillation

Cool-year mean = $5.6B Warm-year mean = $15.0B Explains 3.5 % or variance M-W p = 0.005

What do Global Climate Models Say about Hurricanes on a Warmer Globe?  Number of hurricanes should decrease because of greater shear  Strongest hurricanes should get stronger and rain more because of increased water vapor content  Effect should be strongest in the Western Atlantic  Neutral or weak in the Caribbean and Gulf  But we should not be able to detect it yet. (Bender et al. 2010)

20 Emanuel (2013), using a different downscaling

Pareto Distributions Power-law exceedance probability: “Fat Tails” and “Black Swans”

Role of Chance: A Pareto Model for Extreme US Damage Power-Law Cumulative distribution function Used to model “fat- tail” distributions. Fitted to the most damaging 10% of seasons I.e., one per decade Account for ⅔ of total normalized damage

AMO

25 The Earth is getting warmer Primarily because of human activity Warmer oceans should cause more-intense hurricanes But we don’t see credible signs, yet Detection is hard because of: El Niño & MDO Random extreme events (Pareto!) Damage is constant, when corrected for economic factors; whereas deaths have decrease dramatically because of better forecasts GCMs predict a measurable effect some time late in the 21 st Century Fewer hurricanes (perhaps), but more intense Scientific Conclusions

Thank you for your attention. Questions?