THE SCIENCE

The Monthly (Australia) - - CONTENTS - by Les­ley Hughes

Jean-Bap­tiste Joseph Fourier was a very busy man. The French math­e­ma­ti­cian and physi­cist was, at var­i­ous times, a baron, im­pris­oned for his po­lit­i­cal ac­tiv­i­ties in the French Rev­o­lu­tion, and a sci­en­tific ad­viser to Napoleon dur­ing his Egypt cam­paign. Best re­mem­bered to­day for his epony­mous math­e­mat­i­cal and phys­i­cal the­o­rems about vibrations and heat trans­fer, Fourier also found time to play a piv­otal role in our un­der­stand­ing of the Earth’s cli­mate. In 1822, Fourier’s quest for a uni­ver­sal the­ory of ter­res­trial tem­per­a­tures cul­mi­nated in his mag­num opus, Théorie an­a­ly­tique de la chaleur. The core of the book ex­pounded the re­la­tion­ship be­tween the Earth as a cooling body, the Sun as the heat source, and the atmosphere, de­light­fully de­scribed as the “di­aphanous” in­ter­me­di­ary, slow­ing the rate of heat loss from the Earth’s sur­face to space. Tan­gi­ble ev­i­dence for the mech­a­nism by which Fourier’s di­aphanous in­ter­me­di­ary might af­fect the Earth’s cli­mate came decades later. The per­son tra­di­tion­ally cred­ited with demon­strat­ing the heat-trap­ping po­ten­tial of dif­fer­ent at­mo­spheric gases was Ir­ish physi­cist John Tyn­dall. A su­perb ex­per­i­men­tal­ist, Tyn­dall de­vised a ma­chine to mea­sure the abil­ity of dif­fer­ent gases – ni­tro­gen, oxy­gen, wa­ter vapour, car­bon diox­ide, ozone, methane – to ab­sorb ra­di­ant heat. He pub­lished his work in 1859. With­out wish­ing to di­min­ish Tyn­dall’s great sci­en­tific break­throughs, we now know that he was pipped to this par­tic­u­lar post by three years. Eu­nice New­ton Foote was a sci­en­tist, in­ven­tor, painter and women’s rights cam­paigner from New York. In a se­ries of ele­gantly sim­ple ex­per­i­ments, Foote com­pared how glass jars filled with air, wa­ter vapour and car­bon diox­ide heated up when placed in the sun. “The high­est ef­fect of the sun’s rays I have found to be in car­bonic acid gas,” she wrote, us­ing the con­tem­po­rary term for car­bon diox­ide. With re­mark­able pre­science, she went on to spec­u­late that “An atmosphere of that gas would give to our earth a high tem­per­a­ture.” Foote’s work was pre­sented at a con­fer­ence of the Amer­i­can As­so­ci­a­tion for the Ad­vance­ment of Science in 1856. Since Foote was a mere woman and thus in­el­i­gi­ble to be a mem­ber of that au­gust body, a Pro­fes­sor Joseph Henry gave the pre­sen­ta­tion. He pref­aced it with the words “The sphere of woman em­braces not only the beau­ti­ful and the use­ful, but the true.” A nice if some­what pa­tro­n­is­ing ges­ture, though one can’t help but feel ag­grieved that it was not un­til the dis­cov­ery of the con­fer­ence tran­script in 2011 that Foote was fi­nally given her due. Cred­its for the next few sci­en­tific break­throughs in this story be­long to a trio of Swedes. In 1894, ge­ol­o­gist Arvid Hög­bom, seek­ing to un­der­stand the global car­bon cy­cle, es­ti­mated that in­dus­trial sources of CO2 emis­sions (mainly from coal burn­ing) were roughly equiv­a­lent to that which nat­u­ral sources ab­sorb and emit. In­spired by Hög­bom’s re­sults, the great chemist Svante Ar­rhe­nius quan­ti­fied the re­la­tion­ship be­tween at­mo­spheric CO2 and global tem­per­a­tures, not­ing that “any dou­bling of the per­cent­age of car­bon diox­ide in the air would raise the tem­per­a­ture of the earth’s sur­face by 4°”. But he went one step fur­ther, specif­i­cally ar­gu­ing that the burn­ing of fos­sil fu­els by hu­mans was sub­stan­tial enough to af­fect the Earth’s tem­per­a­ture: “The enor­mous com­bus­tion of coal by our in­dus­trial es­tab­lish­ments suf­fices to in­crease the per­cent­age of car­bon diox­ide in the air to a per­cep­ti­ble de­gree.” Ar­rhe­nius thought all this would hap­pen very slowly, per­haps over thou­sands of years, and would be a good thing. He spec­u­lated that by in­creas­ing CO2 in the atmosphere “we may hope to en­joy ages with more equable and bet­ter cli­mates, es­pe­cially as re­gards the colder re­gions of the earth, ages when the earth will bring forth much more abun­dant crops than at present, for the ben­e­fit of rapidly prop­a­gat­ing mankind”. Me­te­o­rol­o­gist Nils Gustaf Ekholm, Ar­rhe­nius’s great friend and col­league, went one op­ti­mistic step fur­ther, not­ing that hu­man con­trol of the atmosphere might even pre­vent the ar­rival of the next ice age. We can also credit Ekholm for pop­u­lar­is­ing the metaphor of the green­house. In 1901 he wrote that “the atmosphere may act like the glass of a green-house, let­ting through the light rays of the sun rel­a­tively eas­ily, and ab­sorb­ing a great part of the dark rays emit­ted from the ground, and it thereby may raise the mean tem­per­a­ture of the earth’s sur­face”. Ar­rhe­nius’s cal­cu­la­tions were hotly dis­puted – sound fa­mil­iar, any­one? – and over the next few decades be­came sub­sumed into a larger de­bate as to whether at­mo­spheric changes caused the ice ages. But let us fast for­ward to the 1930s, to the work of English steam en­gi­neer, in­ven­tor and am­a­teur cli­ma­tol­o­gist Guy Cal­len­dar. Cal­len­dar pain­stak­ingly com­piled mea­sure­ments of tem­per­a­tures around the globe from 1880 to 1935 and cor­re­lated th­ese with mea­sure­ments of at­mo­spheric CO2 – surely one of the nerdi­est hob­bies of all time. He cal­cu­lated that a 0.3 oC rise in global tem­per­a­tures over the pre­vi­ous 50 years was largely due to the in­creased at­mo­spheric CO2 from fos­sil-fuel burn­ing. Cal­len­dar’s hand-drawn graph of the cor­re­la­tion, pub­lished with lit­tle fan­fare in 1938 in the Quar­terly Jour­nal of the Royal Me­te­o­ro­log­i­cal So­ci­ety, looks like it was sketched on the back of the prover­bial en­ve­lope, be­ly­ing the metic­u­lous work be­hind it. Echo­ing the ear­lier

op­ti­mism of the Swedes, Cal­len­dar con­cluded that the warm­ing trends he graphed would be ben­e­fi­cial, de­lay­ing “the re­turn of the deadly glaciers”. In a pre­view of later at­ti­tudes, the “Cal­len­dar Ef­fect” was met with scep­ti­cism – most no­tably from Sir Ge­orge Simpson, then direc­tor of the Me­te­o­ro­log­i­cal Of­fice, Lon­don, who thought the cor­re­la­tion be­tween CO2 and tem­per­a­ture was merely a co­in­ci­dence. Simpson had pre­vi­ously aired his view that CO2 in the atmosphere has “no ap­pre­cia­ble ef­fect on the cli­mate” and made a point of de­scrib­ing Cal­len­dar as a “non-me­te­o­rol­o­gist”. Un­de­terred, Cal­len­dar doggedly con­tin­ued to pub­lish dur­ing the 1940s and 1950s. He even­tu­ally in­spired US geo­chemist Charles Keel­ing to es­tab­lish the Mauna Loa Ob­ser­va­tory in Hawaii in 1958, the first sci­en­tific es­tab­lish­ment ded­i­cated to mea­sur­ing at­mo­spheric gases. By 1961, Keel­ing had al­ready col­lected enough data to show that CO2 lev­els were ris­ing steadily, and he pro­duced the now-iconic “Keel­ing Curve”. Un­tram­melled op­ti­mism about the prospect of a world warmed by hu­man ac­tiv­i­ties fi­nally started to pall a lit­tle in the 1960s. The most prom­i­nent and vo­cal wor­rier was Paul Ehrlich, whose 1968 book The Pop­u­la­tion Bomb is bet­ter re­mem­bered for its dire Malthu­sian warn­ings about the per­ils of too many peo­ple. But Ehrlich also wrote that “the green­house ef­fect is be­ing en­hanced now by the greatly in­creased level of car­bon diox­ide … At the mo­ment we can­not pre­dict what the over­all cli­matic re­sults will be of our us­ing the atmosphere as a garbage dump.” By the mid 1970s, the term “global warm­ing” had be­gun to ap­pear in the sci­en­tific lit­er­a­ture (although some in the main­stream news me­dia were ex­press­ing con­cern that the op­po­site phe­nom­e­non was oc­cur­ring). And in the 1980s in­creas­ingly strong state­ments from in­ter­na­tional bod­ies such as the United Na­tions En­vi­ron­ment Pro­gramme pointed to pro­jec­tions of sig­nif­i­cant warm­ing over the next cen­tury. But the most news­wor­thy event came on a swel­ter­ing June day in 1988, when James Hansen, the direc­tor of the NASA God­dard In­sti­tute for Space Stud­ies, was in­vited by Se­na­tor Al Gore to tes­tify to the Se­nate Com­mit­tee on En­ergy and Nat­u­ral Re­sources. Hansen told the as­sem­bled law­mak­ers that he was 99 per cent cer­tain that the year’s record tem­per­a­tures were not the re­sult of nat­u­ral vari­a­tion. Global warm­ing, he said, “is al­ready hap­pen­ing now” and “it is time to stop waf­fling so much and say that the ev­i­dence is pretty strong that the green­house ef­fect is here”. (Sorry to be a pedant, but what he re­ally meant was the green­house ef­fect, see above. Apart from that, Jim was ab­so­lutely spot on!) Hansen’s tes­ti­mony sparked head­lines all over the world and is re­garded by many as a piv­otal mo­ment in rais­ing pub­lic aware­ness. So here we are, three decades since Hansen’s tes­ti­mony, and nearly 200 years since Fourier’s first bril­liant in­sights. The re­cently leaked draft of the In­ter­gov­ern­men­tal Panel on Cli­mate Change Spe­cial Re­port on 1.5 oC de­scribes “un­equiv­o­cal and sus­tained global warm­ing and sea level rise”, and sug­gests that hav­ing a two-thirds prob­a­bil­ity of hold­ing warm­ing to be­low 1.5 oC through­out this cen­tury is “al­ready out of reach”. Cal­len­dar’s “deadly glaciers” have cer­tainly been kept at bay – in­deed many have been oblit­er­ated com­pletely, with most of the rest re­ced­ing rapidly. The con­cen­tra­tion of CO2 in Fourier’s di­aphanous in­ter­me­di­ary recorded in July this year at Mauna Loa Ob­ser­va­tory was more than 40 per cent higher than pre-in­dus­trial con­cen­tra­tions. We are clos­ing in on 1 oC of warm­ing, and al­ready the be­nign world en­vis­aged by Ar­rhe­nius and friends has been bat­tered and burnt, flooded and fried. Some of us are slow learn­ers.

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