Fifty years of dither­ing on cli­mate change

Lesotho Times - - Leader - Stefan rahm­storf

In novem­ber 1965, US Pres­i­dent Lyn­don B John­son was pre­sented with the firstever govern­ment re­port warn­ing of the dan­gers that could re­sult from burn­ing large amounts of fos­sil fu­els.

Fifty years is a long time in pol­i­tics, so it is re­mark­able how lit­tle has been done since then to ad­dress the threat posed by car­ry­ing on with busi­ness as usual.

In re­mark­ably pre­scient lan­guage, John­son’s sci­en­tific ad­vi­sory com­mit­tee warned that re­leas­ing car­bon-diox­ide into the at­mos­phere would lead to higher global tem­per­a­tures, caus­ing ice caps to melt and sea lev­els to rise rapidly.

“Man is un­wit­tingly con­duct­ing a vast geo­phys­i­cal ex­per­i­ment,” warned the sci­en­tists. “Within a few gen­er­a­tions he is burn­ing the fos­sil fu­els that slowly ac­cu­mu­lated in the earth over the past 500 mil­lion years…the cli­matic changes that may be pro­duced by the in­creased CO2 con­tent could be dele­te­ri­ous from the point of view of hu­man be­ings.”

The com­mit­tee’s fore­sight is not sur­pris­ing; the ex­is­tence of the green­house ef­fect had been known to sci­ence since the French physi­cist Joseph Fourier sug­gested in 1824 that the earth’s at­mos­phere was act­ing as an in­su­la­tor, trap­ping heat that would oth­er­wise es­cape.

And in 1859, the Ir­ish physi­cist John Tyn­dall car­ried out lab­o­ra­tory ex­per­i­ments that demon­strated the warm­ing power of CO2, lead­ing the Swedish physi­cist and no­bel Lau­re­ate Svante Ar­rhe­nius to pre­dict that burn­ing coal would warm the earth — which he saw as a po­ten­tially pos­i­tive de­vel­op­ment.

John­son’s ad­vis­ers were not so Pollyanna-ish.

Their re­port ac­cu­rately pre­dicted that the amount of CO2 in the at­mos­phere would in­crease by close to 25 per­cent over the course of the twen­ti­eth cen­tury (the ac­tual num­ber was 26 per­cent ).

To­day, the at­mo­spheric con­cen­tra­tion of CO2 is 40 per­cent higher than it was at the be­gin­ning of the In­dus­trial Rev­o­lu­tion — by far the high­est it has been dur­ing the past 1 mil­lion years, as we know from drilling into the Antarc­tic ice.

Fur­ther­more, John­son’s sci­en­tific com­mit­tee re­but­ted ob­jec­tions that con­tinue to be used to­day by those who deny the dan­gers of cli­mate change, in­clud­ing the claim that nat­u­ral pro­cesses might be be­hind the rise in CO2 lev­els. By show­ing that only about half of the CO2 pro­duced by burn­ing fos­sil fu­els re­mains in the at­mos­phere, the com­mit­tee proved that the earth acts not as a source of green­house gases, but as a sink, soak­ing up half of our emis­sions.

What John­son’s ad­vis­ers could not do was of­fer spe­cific pre­dic­tions for how much the rise in at­mo­spheric CO2 would af­fect global tem­per­a­ture; they said they would first need bet­ter mod­els and more pow­er­ful com­put­ers.

Those cal­cu­la­tions formed the ba­sis of the next land­mark re­port, the 1979 “Car­bon Diox­ide and Cli­mate: A Sci­en­tific As­sess­ment,” pre­pared by the U.S. na­tional Academy of Sci­ences. Widely known as the Char­ney Re­port — af­ter its lead au­thor, Jule Char­ney of MIT — it is a model of care­ful sci­en­tific de­lib­er­a­tion.

Char­ney’s re­port es­ti­mated that dou­bling the amount of CO2 in the at­mos­phere would warm the earth by about 3° Cel­sius — a num­ber that is well con- firmed to­day. It also pre­dicted that the heat ca­pac­ity of the oceans would de­lay warm­ing by sev­eral decades. Both find­ings are con­sis­tent with the global warm­ing ob­served since the re­port’s pub­li­ca­tion.

“We have tried but have been un­able to find any over­looked or un­der­es­ti­mated phys­i­cal ef­fects that could re­duce the cur­rently es­ti­mated global warm­ing … to neg­li­gi­ble pro­por­tions,” the re­port con­cluded. Since then, the sci­en­tific ev­i­dence has only got­ten stronger; to­day, the ba­sic find­ings laid out in th­ese two early re­ports are sup­ported by more than 97 per­cent of cli­mate sci­en­tists.

And yet, de­spite 50 years of grow­ing sci­en­tific con­sen­sus, the warm­ing of the earth con­tin­ues un­abated. Well­funded lobby groups have sowed doubt among the pub­lic and suc­cess­fully down­played the ur­gency of the threat.

Mean­while, geopol­i­tics has im­peded the de­vel­op­ment of an ef­fec­tive global re­sponse. The in­ter­na­tional cli­mate ne­go­ti­a­tions that are ex­pected to cul­mi­nate in an agree­ment at the United na­tions Cli­mate Change Con­fer­ence in Paris in novem­ber and De­cem­ber have been ham­pered by the re­quire­ment of con­sen­sus among the 195 coun­tries par­tic­i­pat­ing.

If ac­tion is not taken, bil­lions of peo­ple will suf­fer the con­se­quences of drought, crop fail­ure, and ex­treme weather. Even­tu­ally, ris­ing sea lev­els will flood large coastal cities and de­stroy en­tire is­land states. The hottest years since record-keep­ing be­gan in the nine­teenth cen­tury were 2005, 2010, and 2014, and last year’s record will al­most cer­tainly be bro­ken again this year.

It is time that world lead­ers put an end to 50 years of dither­ing. They must seize the op­por­tu­nity in Paris, set aside their short-term in­ter­ests, and fi­nally act de­ci­sively to avert a loom­ing plan­e­tary catas­tro­phe.

Man is un­wit­tingly con­duct­ing a vast geo­phys­i­cal ex­per­i­ment,” warned the sci­en­tists. “Within a few gen­er­a­tions he is burn­ing the fos­sil fu­els that slowly ac­cu­mu­lated in the earth over the past 500 mil­lion years…the cli­matic changes that may be pro­duced by the in­creased CO2 con­tent could be dele­te­ri­ous from the point of view of hu­man be­ings

l Stefan Rahm­storf is pro­fes­sor of physics of the oceans at Pots­dam Univer­sity, vis­it­ing pro­fes­so­rial fel­low at the Univer­sity of New South Wales in Syd­ney, and depart­ment head at the Pots­dam In­sti­tute for Cli­mate Im­pact Re­search. — marketwatch.com

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