Bru­tal cold snap was freak of na­ture

Arc­tic blast a rar­ity that bucks warm­ing trend, anal­y­sis finds

The Dallas Morning News - - Focus On Weather - Seth Boren­stein,

WASH­ING­TON — Con­sider this cold com­fort: A quick study of the bru­tal Amer­i­can cold snap found that the Arc­tic blast wasn’t re­lated to global warm­ing but was a freak of na­ture.

Frigid weather like the two-week cold spell that be­gan around Christ­mas is 15 times rarer than it was a cen­tury ago, ac­cord­ing to a team of in­ter­na­tional sci­en­tists that does re­al­time analy­ses to see if ex­treme weather events are likely to have hap­pened be­cause of cli­mate change.

The cold snap that gripped the East Coast and Midwest was a rar­ity that bucks the warm­ing trend, said re­searcher Clau­dia Te­baldi of the Na­tional Cen­ter for At­mo­spheric Re­search and the pri­vate or­ga­ni­za­tion Cli­mate Cen­tral.

The same team had con­nected man­made global warm­ing to sev­eral weather events last year, in­clud­ing Hur­ri­cane Har­vey, which bat­tered the U.S. and the Caribbean, and French floods.

“It was very def­i­nitely strange, es­pe­cially now,” said study co-au­thor Gabriel Vec­chi of Prince­ton Univer­sity. A cen­tury ago “it wouldn’t have been that strange. Things like this are be­com­ing stranger.”

The study by World Weather At­tri­bu­tion an­a­lyzed weather records dat­ing to 1880 and found the cold that hit a swath of the U.S. from Maine to Min­nesota tends to hap­pen once ev­ery 250 years. In the early 1900s, it hap­pened about once ev­ery 17 years. Cli­mate change has made such cold spells less com­mon and less in­tense, the group said.

That find­ing agrees with ear­lier stud­ies, said Univer­sity of Ge­or­gia me­te­o­rol­ogy pro­fes­sor Mar­shall Shep­herd, who wasn’t part of the study.

“I think the pub­lic frenzy over the re­cent cold snap il­lus­trated that we are less ac­cli­mated to such events,” he said in an email.

The study, based on ob­ser­va­tions and statis­tics, did not find ev­i­dence for a pop­u­lar sci­en­tific the­ory that links melt­ing Arc­tic sea ice to blasts of cold air es­cap­ing the top of the world.

The the­ory, which is still de­bated by sci­en­tists but gain­ing cre­dence among many, is based on pres­sure changes and other fac­tors that cause the jet stream to plunge and weather sys­tems to get stuck. But the lat­est anal­y­sis didn’t find such ev­i­dence.

Three sci­en­tists whose stud­ies have con­nected Arc­tic warm­ing to changes in ex­treme events dis­agree. Be­cause such at­mo­spheric pres­sure changes hap­pen oc­ca­sion­ally, quick stud­ies that rely on av­er­ages miss ex­treme events like the re­cent cold spell, said James Over­land of the Na­tional Oceanic and At­mo­spheric Ad­min­is­tra­tion, who sup­ports the the­ory.

“Things like this are be­com­ing stranger.” Gabriel Vec­chi of Prince­ton Univer­sity, a co-au­thor of the study

Julie Ja­cob­son/the As­so­ci­ated Press

Fik,ifi­clmir­wlaik­lkrm­lifi the frozen har­bor of Lake Mon­tauk in New York on Sun­day. A quick study of the re­cent bru­tal cold snap found that cli­mate change wasn’t a fac­tor but that global warm­ing is mak­ing such frigid weather spells much rarer.

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