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Ever since I interviewed Kerry Emanuel at the onset of the 2018 #hurricane season, I've been showing some of the results of his team's downscaling approach that, combined with model simulations, can yield projected return periods for outlier cyclone events.

At my public outreach and educational presentations, I've shown how a hurricane like Irma at 180 MPH approaching Barbuda, a 1-in-800 year event, could have its return period reduced to 1-in-80 years by the end of this century. Similarly ...

A hurricane like María at 155 MPH approaching Puerto Rico, a 1-in-200 year event, could have a return period of 1-in-20 years by late this century.

I'm sure some of my followers that have seen my presentations in person recall me showing these slides.

Tonight, I'm sharing Dr. Emanuel's work (with his approval) on tropical cyclones that pass within 150 km of Marsh Harbour, downscaled from 7 #climate models and 2 climates: the late 20th century (1981-2000) and the late 21st century (2081-2100)...

This assumes Representative Concentration Pathway (RCP) 4.5 which a stabilization scenario, far from the "business as usual" (RCP8.5) incremental greenhouse gas emissions path. Dr. Emanuel's team simulated 2,000 tropical cyclones in each model for a total of 28,000.

The graph shows the estimated annual frequency of events whose max surface winds anywhere within 150 km of Marsh Harbour exceed the value on the bottom axis. Late 20th century is in blue, late 21st in red. Solid curves are multi-model means and shading measures scatter.

Using #Dorian's sustained winds of 160 knots (185 MPH), we find an annual frequency of 0.002 (about once in 500 years) at the end of the 20th century, and about 0.01 (once in 100 years) by 2081-2100.

Dr. Emanuel's paper can be found here: pnas.org/content/110/30…

Dorian undoubtedly was an extreme event, so much so that it would be considered a 1-in-500 year event as of a few years ago. But what happens when the return periods shorten to the point where resiliency is no longer achievable? How does Puerto Rico, for example...

possibly deal with a María once every 20 years? Is that even possible? #Abaco had Hurricane Floyd strike as a Category 4 hurricane 20 years ago next week. Anecdotally, the #Abacos just finished recovery from that landfall earlier this decade.

There are only so many resources developing countries can allot for resiliency, disaster mitigation and emergency preparedness. Unless the #ClimateCrisis is stopped - something that's very much in question - this yields a grim outlook for the fate of future societies.

10/10 fin
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