Oceans are warm­ing faster

The Free Press Journal - - WORLD -

Heat trapped by green­house gases is rais­ing ocean tem­per­a­tures faster than pre­vi­ously thought, ac­cord­ing to a new re­search which shows that ear­lier claims of a slow­down or "hia­tus" in global warm­ing over the past 15 years were un­founded.

Ocean heat­ing is crit­i­cal marker of cli­mate change be­cause an es­ti­mated 93 per cent of the ex­cess so­lar en­ergy trapped by green­house gases ac­cu­mu­lates in the world's oceans.

Un­like sur­face tem­per­a­tures, ocean tem­per­a­tures are not af­fected by year-to-year vari­a­tions caused by cli­mate events like El Nino or vol­canic erup­tions.

"If you want to see where global warm­ing is hap­pen­ing, look in our oceans," said Zeke Haus­fa­ther, a grad­u­ate stu­dent at the Uni­ver­sity of Cal­i­for­nia (UC) Berke­ley, in the US. "Ocean heat­ing is a very im­por­tant in­di­ca­tor of cli­mate change, and we have ro­bust ev­i­dence it is warm­ing more rapidly than we thought," said Haus­fa­ther.

The new anal­y­sis, pub­lished in the jour­nal Science, shows trends in ocean heat con­tent match those pre­dicted by lead­ing cli­mate change mod­els, and over­all ocean warm­ing is ac­cel­er­at­ing.

As­sum­ing a "busi­ness-asusual" sce­nario in which no ef­fort has been made to re­duce green­house gas emis­sions, the Cou­pled Model In­ter­com­par­i­son Project 5 (CMIP5) mod­els pre­dict the tem­per­a­ture of the top 2,000 me­tres of the world's oceans will rise 0.78 de­grees Cel­sius by the end of the cen­tury.

The ther­mal ex­pan­sion caused by this bump in tem­per­a­ture would raise sea lev­els 30 cms on top of the al­ready sig­nif­i­cant sea level rise caused by melt­ing glaciers and ice sheets. Warmer oceans also con­trib­ute to stronger storms, hur­ri­canes and ex­treme pre­cip­i­ta­tion.

"While 2018 will be the fourth warm­est year on record on the sur­face, it will most cer­tainly be the warm­est year on record in the oceans, as was 2017 and 2016 be­fore that," Haus­fa­ther said.

Un­like sur­face tem­per­a­tures, ocean tem­per­a­tures are not af­fected by year-to-year vari­a­tions caused by cli­mate events like El Nino or vol­canic erup­tions.

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