Hur­ri­canes with rain like Har­vey more likely

Honolulu Star-Advertiser - - NATION - By Seth Boren­stein

WASHINGTON >> The chances of a hur­ri­cane flood­ing parts of Texas, like Har­vey did, have soared six­fold in just 25 years be­cause of global warm­ing and will likely triple once again be­fore the end of the cen­tury, a new study says. Study au­thor Kerry Emanuel, a me­te­o­rol­ogy pro­fes­sor and hur­ri­cane ex­pert at the Mas­sachusetts In­sti­tute of Tech­nol­ogy, found that what was once an ex­tremely rare event — 20 inches of rain over a large area of Texas — could soon be al­most com­mon. From 1981 to 2000 the prob­a­bil­ity of 20 inches of rain hap­pen­ing some­where over a large chunk of Texas was 1-in-100 or even less, Emanuel said. Now it’s 6-in100, and by 2081 those odds will be 18-in-100, he said. “The changes in prob­a­bil­i­ties are be­cause of global warm­ing,” Emanuel said. The study was re­leased Mon­day in the Pro­ceed­ings of the Na­tional Academy of Sciences.

Emanuel said he hur­ried the study to help Hous­ton of­fi­cials think about what con­di­tions they should con­sider when they re­build. Texas state cli­ma­tol­o­gist John Nielsen-Gam­mon said he was struck by the po­ten­tial for much higher rain­fall that Emanuel’s sim­u­la­tions pre­dict for the fu­ture and how im­por­tant it is for the de­sign of crit­i­cal struc­tures like dams and nu­clear fa­cil­i­ties.

“If the worst-case pre­cip­i­ta­tion sce­nario is get­ting worse, as Kerry’s study and other ev­i­dence im­plies, that safety mar­gin is shrink­ing,” Nielsen-Gam­mon said in an email, high­light­ing Emanuel’s re­sults that also show the worst-case storms be­com­ing wet­ter and more com­mon.

Gabriel Vec­chi, a cli­mate sci­en­tist at Prince­ton who wasn’t part of the study, said the study con­firms what scientists have al­ready thought: “that the most ex­treme rain­fall events will be­come more likely as the planet warms.” To do the study, Emanuel had to use some in­no­va­tive mod­el­ing tech­niques. Global cli­mate mod­els used for fu­ture warm­ing stud­ies aren’t de­tailed enough to sim­u­late hur­ri­canes. Hur­ri­cane mod­els don’t say any­thing about the larger cli­mate.

Emanuel com­bined the mod­els and then cre­ated thou­sands and thou­sands of fic­tional storm “seedlings” to see what would hap­pen.

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