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“Extreme” rain follows global warming

Aug. 7, 2008
Courtesy Science
and World Science staff

Heavy rain is coming more of­ten as glob­al warm­ing con­tin­ues—an in­crease that is out­strip­ping sci­en­tists’ pre­dic­tions, ac­cord­ing to a stu­dy. 

The find­ings imply that warm­ing-induced changes in the glob­al wa­ter cy­cle could have more dras­tic im­pacts than ev­er im­ag­ined, its au­thors said.

Heavy rain is oc­cur­ring more of­ten as glob­al warm­ing con­tin­ues—and the in­crease is out­strip­ping sci­en­tists’ es­ti­mates based on sim­ula­t­ions, ac­cord­ing to a stu­dy. (Image cour­tesy NA­SA)
The find­ings “re­veal a dis­tinct link be­tween rain­fall ex­tremes and tem­per­a­ture, with heavy rain events in­creas­ing dur­ing warm per­i­ods,” wrote the au­thors, Rich­ard P. Al­lan of the Uni­ver­s­ity of Read­ing, U.K. and Bri­an J. So­den of the Uni­ver­s­ity of Mi­ami, Fla. 

The re­port is to ap­pear in the Aug. 8 is­sue of the re­search jour­nal Sci­ence.

Al­lan and So­den used sat­el­lite ob­serva­t­ions and com­pu­ter sim­ula­t­ions to study the rela­t­ion­ship be­tween trop­i­cal rain­fall and changes in Earth’s sur­face tem­per­a­ture and at­mos­pher­ic mois­ture. 

The ob­serva­t­ions point to a di­rect link be­tween warm­er cli­mate and an in­crease in ex­treme pre­cipita­t­ion based on both sat­el­lite da­ta and sim­ula­t­ions, they wrote. But the ob­served in­crease in ex­treme rain­fall is larg­er than the in­creases pre­dicted by sim­ula­t­ions, sug­gest­ing the pre­dic­tions are too low, they added.

The pair warned that it’s cru­cial to find out the cause for this dis­crep­an­cy as soon as pos­si­ble in or­der to un­der­stand glob­al warm­ing and its ef­fects on the wa­ter cy­cle. In past stu­dies, sci­ent­ists have also sug­gested global warm­ing may wors­en the im­pact of hurri­canes and wild­fires.

* * *

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Heavy rain is occurring more often as global warming continues—and the increase is outstripping scientists’ estimates based on simulations, according to a study. The findings imply that warming-induced changes in the global water cycle could have more drastic impacts than ever imagined, its authors said. The findings “reveal a distinct link between rainfall extremes and temperature, with heavy rain events increasing during warm periods,” wrote the authors, Richard P. Allan of the University of Reading, U.K. and Brian J. Soden of the University of Miami, Fla. The report is to appear in the Aug. 8 issue of the research journal Science. Allan and Soden used satellite observations and model simulations to study the relationship between tropical rainfall and changes in Earth’s surface temperature and atmospheric moisture. The observations reveal a direct link between warmer climate and an increase in extreme precipitation events from both satellite data and model simulations, they wrote. But the observed increase in extreme rainfall is larger than the increases predicted by simulations, suggesting the predictions are too low, they added. The pair warned that it’s crucial to find out the cause for this discrepancy as soon as possible in order to understand global warming and its effects on the water cycle.