Study: Oceans are warm­ing fast

The Idaho Statesman (Sunday) - - NEWS - BY KENDRA PIERRE-LOUIS New York Times

Sci­en­tists say the world’s oceans are warm­ing far more quickly than pre­vi­ously thought, a find­ing with dire im­pli­ca­tions for cli­mate change be­cause al­most all the ex­cess heat ab­sorbed by the planet ends up stored in their wa­ters.

A new anal­y­sis, pub­lished Thurs­day in the jour­nal Sci­ence, found that the oceans are heat­ing 40 per­cent faster on av­er­age than a U.N. panel es­ti­mated five years ago. The re­searchers also con­cluded that ocean tem­per­a­tures have bro­ken records for sev­eral straight years.

“2018 is go­ing to be the warm­est year on record for the Earth’s oceans,” said Zeke Haus­fa­ther, an en­ergy sys­tems an­a­lyst at in­de­pen­dent cli­mate re­search group Berke­ley Earth and an au­thor of the study. “As 2017 was the warm­est year, and 2016 was the warm­est year.”

As the planet has warmed, the oceans have pro­vided a crit­i­cal buf­fer. They have slowed the ef­fects of cli­mate change by ab­sorb­ing 93 per­cent of the heat trapped by the green­house gases hu­mans pump into the at­mos­phere.

But the ris­ing wa­ter tem­per­a­tures are al­ready killing off ma­rine ecosys­tems, rais­ing sea lev­els and mak­ing hur­ri­canes more de­struc­tive.

As the oceans con­tinue to heat up, those ef­fects will be­come more cat­a­strophic, sci­en­tists say. Coral reefs, whose fish pro­vide key sources of pro­tein to mil­lions of peo­ple, will come un­der in­creas­ing stress; a fifth of them have al­ready died in the last three years. Rainier, more pow­er­ful storms like Hur­ri­cane Har­vey in 2017 and Hur­ri­cane Florence in 2018 will be­come more com­mon, and coast­lines around the world will flood more fre­quently.be­cause they play such a crit­i­cal role in global warm­ing, oceans are one of the most im­por­tant ar­eas of re­search for cli­mate sci­en­tists. Av­er­age ocean tem­per­a­tures are also a con­sis­tent way to track the ef­fects of green­house gas emis­sions be­cause they are not in­flu­enced much by short-term weather pat­terns, Haus­fa­ther said.

“Oceans are re­ally the best ther­mome­ter we have for changes in the Earth,” he said.

But, his­tor­i­cally, un­der­stand­ing ocean tem­per­a­tures has also been dif­fi­cult. An au­thor­i­ta­tive U.N. re­port, is­sued in 2014 by the In­ter­gov­ern­men­tal Panel on Cli­mate Change, pre­sented five dif­fer­ent es­ti­mates of ocean heat, but they all showed less warm­ing than the lev­els pro­jected by com­puter cli­mate mod­els – sug­gest­ing that ei­ther the ocean heat mea­sure­ments or the cli­mate mod­els were in­ac­cu­rate.

Since the early 2000s, sci­en­tists have mea­sured ocean heat us­ing a net­work of drift­ing floats called Argo, named af­ter Ja­son’s ship in Greek mythol­ogy. The floats mea­sure the tem­per­a­ture and salti­ness of the up­per 6,500 feet of the ocean and up­load the data via satel­lites.

Be­fore Argo, re­searchers re­lied on tem­per­a­ture sen­sors that ships low­ered into the ocean with a cop­per wire. The wire trans­ferred data from the sen­sor to the ship for record­ing un­til the wire broke and the sen­sor drifted away.

That method was sub­ject to un­cer­tain­ties, es­pe­cially around mea­sure­ment depth, that ham­per to­day’s sci­en­tists as they stitch to­gether 20th-cen­tury tem­per­a­ture data into a global his­tor­i­cal record.

In the new anal­y­sis, Haus­fa­ther and his col­leagues as­sessed three re­cent stud­ies that ac­counted for older in­stru­ment bi­ases. The re­sults con­verged at an es­ti­mate of ocean warm­ing that was higher than the IPCC pre­dicted and more in line with the cli­mate mod­els.

The re­searchers also re­viewed a fourth study that had used a novel method to es­ti­mate ocean tem­per­a­tures over time and had also found that the world’s oceans were heat­ing faster than the IPCC pre­dic­tion. But that study con­tained an er­ror that caused its au­thors to re­vise their es­ti­mates down­ward, sug­gest­ing that ocean warm­ing was less of a prob­lem than they orig­i­nally re­ported.

As it turned out, the down­ward re­vi­sion brought that study’s es­ti­mates much closer to the new con­sen­sus. “The cor­rec­tion made it agree a lot bet­ter with the other new ob­ser­va­tional records,” Haus­fa­ther said. “Pre­vi­ously it showed sig­nif­i­cantly more warm­ing than any­one, and that was po­ten­tially wor­ri­some be­cause it meant our ob­ser­va­tional es­ti­mates might be prob­lem­atic. Now their best es­ti­mate is pretty much dead-on with the other three re­cent stud­ies.”

The sci­en­tists who pub­lished the four stud­ies were not try­ing to make their re­sults align, Haus­fa­ther said.

OLIVIER DUGORNAY NYT

The French re­search ship Pourquoi Pas de­ploys a sen­sor as part of the Argo project to mon­i­tor ocean tem­per­a­tures.

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