Half-a-de­gree of warm­ing boosted ex­treme weather

Kuwait Times - - HEALTH & SCIENCE -

Half a de­gree Cel­sius of global warm­ing has been enough to in­crease heat waves and heavy rains in many re­gions of the planet, re­searchers re­ported Fri­day. Com­par­ing two 20-year pe­ri­ods — 1960-79 and 1991-2010 — be­tween which av­er­age global tem­per­a­tures jumped 0.5 C, sci­en­tists found that sev­eral kinds of ex­treme weather gained in du­ra­tion and in­ten­sity. The hottest sum­mer tem­per­a­tures in­creased by more than 1 C across a quar­ter of Earth’s land ar­eas, while the cold­est win­ter tem­per­a­tures warmed by more than 2.5 C.

The in­ten­sity of ex­treme pre­cip­i­ta­tion grew nearly 10 per­cent across a quar­ter of all land masses, and the du­ra­tion of hot spells-which can fuel dev­as­tat­ing for­est fires-length­ened by a week in half of land ar­eas. These changes were well out­side the bounds of nat­u­ral vari­abil­ity, ac­cord­ing to the study, pub­lished in the jour­nal Na­ture Cli­mate Change. “We have to rely on cli­mate mod­els to pre­dict the fu­ture,” said lead au­thor Carl-Friedrich Sch­leuss­ner, a re­searcher at the Pots­dam In­sti­tute of Cli­mate Im­pact Re­search.

“But given that we now have ob­ser­va­tional ev­i­dence of around 1 C warm­ing, we can also look at the real-life im­pacts this warm­ing has brought,” he said in a state­ment. In sci­ence, ob­served trends are gen­er­ally seen as more re­li­able than pro­jec­tions, which can vary sharply depend­ing on the as­sump­tions made. Changes in cli­mate-some­times de­fined as “av­er­age weather”-can only be de­tected across time pe­ri­ods mea­sured in decades or longer.

0.5 C does mat­ter

Global warm­ing caused mostly by the burn­ing of fos­sil fu­els be­gan slowly in the early 19th cen­tury with the on­set of in­dus­tri­al­iza­tion, but has ac­cel­er­ated rapidly over the last 50 or 60 years. The 196na­tion Paris Agree­ment, inked in the French cap­i­tal in 2015, vowed to cap the rise of the planet’s av­er­age sur­face tem­per­a­ture at “well un­der” 2 C, and to “pur­sue ef­forts” to block it at 1.5 C.

To in­form that ef­fort, the In­ter­gov­ern­men­tal Panel on Cli­mate Change (IPCC) — the UN’s top sci­ence ad­vi­sory group-will is­sue a re­port for pol­icy mak­ers in Septem­ber 2018 on the fea­si­bil­ity of the 1.5 C tar­get, and what im­pacts might be avoided if it is met. The new study-one of thou­sands that will be re­viewed by the IPCC-sug­gests even a half de­gree rise is sig­nif­i­cant. “With the warm­ing the world has al­ready ex­pe­ri­enced, we can see very clearly that a dif­fer­ence of 0.5 C re­ally does mat­ter,” said co-au­thor Erich Fis­cher, a sci­en­tist at ETH Zurich in Switzer­land. —AFP

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