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U.S. NEWS Tuesday 14 November 2017

Harvey’s ‘Biblical’ rainfall is getting more likely

BY SETH BORENSTEIN said the study confirms
AP Science Writer what scientists have al-
WASHINGTON (AP) — The ready thought: “that the
chances of a hurricane most extreme rainfall
flooding parts of Texas, like events will become more
Harvey did, have soared likely as the planet warms.”
sixfold in just 25 years be- “These results highlight
cause of global warming the importance of finding
and will likely triple once ways to incorporate our
again before the end of understanding of climate
the century, a new study change in long-term ur-
says. ban planning, storm water
Study author Kerry Emanu- management and in flood
el, a meteorology profes- mapping,” Vecchi said in
sor and hurricane expert an email.
at the Massachusetts Insti- To do the study Emanuel
tute of Technology, found had to use some innova-
that what was once an tive modeling techniques.
extremely rare event — 20 Global climate models
inches of rain over a large used for future warming
area of Texas — could soon studies aren’t detailed
be almost common. enough to simulate hur- In this Tuesday, Aug. 29, 2017 file photo, water from Addicks Reservoir flows into neighborhoods
From 1981 to 2000, the ricanes. Hurricane mod- as floodwaters from Tropical Storm Harvey rise in Houston. The chances of a hurricane drenching
Texas, like Harvey did, have soared six fold in just a quarter century with global warming and will
probability of 20 inches els don’t say anything likely triple once again before the end of the century, says a new study published Monday, Nov.
of rain happening some- about the larger climate. 12, 2017, in the Proceedings of the National Academy of Sciences.
where over a large chunk So Emanuel combined the (AP Photo/David J. Phillip)
of Texas was 1 in 100 or models and then created
even less, Emanuel said. thousands and thousands
Now it’s 6 in 100 and by of fictional storm “seed-
2081, those odds will be 18 lings” to see what would
in 100, he said. happen.
“The changes in probabili- Emanuel’s calculations
ties are because of global used the 20-inch (half a me-
warming,” Emanuel said. ter) rainfall total because
The study was released that was the initial figure
Monday in the Proceed- discussed as the storm was
ings of the National Acad- dying down.
emy of Sciences. Later measurements
Texas state climatologist showed that Harvey’s rain
John Nielsen-Gammon said was far heavier — and far
he was struck by the poten- rarer — than initially report-
tial for much higher rainfall ed.
that Emanuel’s simulations After Emanuel had started
predict for the future and his work, records showed
how important it is for the Harvey’s Houston-wide
design of critical structures rainfall ended up closer to
like dams and nuclear 33 inches (84 centimeters).
facilities.“If the worst-case And in individual areas pit
precipitation scenario is peaked at 60 inches (1.5
getting worse, as Kerry’s meters).
study and other evidence Emanuel called those num-
implies, that safety margin bers “biblical.”
is shrinking,” Nielsen-Gam- “By the standards of the
mon said in an email, high- average climate during
lighting Emanuel’s results 1981-2000, Harvey’s rainfall
that also show the worst- in Houston was ‘biblical’ in
case storms becoming the sense that it likely oc-
wetter and more common. curred around once since
Gabriel Vecchi, a climate the Old Testament was
scientist at Princeton who written,” Emanuel’s study
wasn’t part of the study, said.q