Royal Swedish Academy of Sciences

Arrhenius' 1896 Model of the Greenhouse Effect in Context

Author(s): Elisabeth Crawford
Source: Ambio, Vol. 26, No. 1, Arrhenius and the Greenhouse Gases (Feb., 1997), pp. 6-11
Published by: Allen Press on behalf of Royal Swedish Academy of Sciences
Stable URL: http://www.jstor.org/stable/4314543
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Elisabeth Crawford

Arrhenius' 1896 Model of the Greenhouse

Effect in Context

knew aboutresearchon heat-absorbinggases in the atmosphere

Arrhenius' 1896 model of the influence of carbonic acid and their influence on climate; and (ii) how he advanced such
(CO2) in the air on the temperature on the ground arose knowledge by his capacity to take advantage of data-in this
from debates concerning the causes of the Ice Ages in the case Samuel P. Langley's observationsof the radiationreceived
Stockholm Physics Society. The calculation of the on earth from the moon-that could be used in supportof his
absorption-coefficients of H20 and C02, which were the key ideas. Hopefully, this will enable us to better understandthe
to the construction of the model, was made possible model and the conclusions that have been drawn from it, both
through Arrhenius's use of Samuel P. Langley's measure- in Arrhenius's time and later. However, it is necessary to be
ments of heat emission in the lunar spectrum. The model
somewhat more explicit than Arrheniusto understandwhy he
enabled Arrhenius to show variations in mean temperature
in sectors from 70?N to 600S during four different seasons embarkedon this work.
given five different levels of C02. The immediate reactions
to the model concerned the question which Arrhenius had THE STOCKHOLMPHYSICSSOCIETY,C02 AND
attempted to answer, i.e., the causes of the Ice Ages. GLACIALEPOCHS
Since the 1970s Arrhenius's work has received much wider
attention due to the concern with global warming resulting In 1895, Arrheniuswas 36-years old, but he had already left
from the burning of fossil fuels. behind a career in physical chemistry. This career had started
rather inauspiciously with his doctoral thesis on the conduc-
tivity of electrolytes, which he defended at Uppsala Univer-
In early 1896, Svante Arrheniuspublishedtwo articles present- sity in 1884 at the age of 25. Controversywith his professors
ing the first model of the influence of carbonic acid (CO2) in and their uncomprehendingattitudestoward the novelty of the
the air on the temperatureon the ground. One appearedin the ideas presentedin the thesis led to its being awardeda very low
Supplementto the Proceedings of the Royal Swedish Academy grade. Basically, this put an end to Arrhenius'shopes for a ca-
of Sciences (1), the other in the Philosophical Magazine (2). As reerat UppsalaUniversity.To gain researchexperienceand also
he often did, Arrheniushad written similar articles in German to have access to laboratoryfacilities he spentthe next four years
and English, in orderto make his work known to the two major on the Europeancontinent,workingat what we would today call
scientific language groups of his time. The article in the Philo- postdoc level, but at the time his position in the laboratoriesof
sophical Magazine contained two distinct parts: the first pre- Wilhelm Ostwald in Leipzig, Ludwig Boltzmann in Graz, and
sentedcomputationsallowing Arrheniusto predictthe variations J. H. van't Hoff in Amsterdamwas much more diffuse. In 1887,
in temperature,which would result from variationsof C02; the at the age of 28 while at the Instituteof Physics at the Univer-
second discussed such variationsas the cause of climatic change sity of Wurzburg,he formulatedthe hypothesis of ionic disso-
in geological times, especially the Ice Ages. This second part ciation, the idea that electrolytes dissociate into their constitu-
contained a translationfrom Swedish of part of an article by ent ions, i.e. atoms or groups of atoms chargedwith positive or
Arvid Hogbom on the geological carboncycle. negative electricity, in very dilute solutions. In the next few
Arrhenius'sarticles did not conform to modem prescriptions years, his hypothesis maturedinto the theory of electrolytic dis-
for the presentationof the resultsof scientific work.The research sociation, which spawned importantnew investigations on so-
question "Is the mean temperatureon the lutions and became one of the corner-
groundin any way influencedby the pres- stones of the new physical chemistry.
ence of heat-absorbinggases in the atmo- In 1891, Arrhenius returned perma-
sphere?" and its status in the literature, nently to Sweden having been appointed
were glossed over in the first paragraph. teacher of physics at the Stockholm
He then moved on to the computations Hogskola(which laterbecame the Univer-
involved in constructingthe model. When sity of Stockholm). At the age of 32, he
he finally discussed the reasonsfor under- had secured his first stable employment.
taking this work they were stated only in Although his reputationattractedforeign
the vague termsof the "verylively discus- postgraduates who came to do work in
sions on the probable causes of the Ice physical chemistryat the Hogskola, in the
Ages" that had taken place in the Stock- early 1890s, he graduallywithdrew from
holm Physics Society. Much of this can be active researchin solution theory. In part,
explained by the haste with which the reasonsfor this withdrawalwere based
..... .. ... .. ..

Arrhenius completed this project, all of on his feeling thatphysical chemistrywas

which, from inceptionto publication,only a field in which the most productive re-
occupied him for a little over a year (De- search topics had alreadybeen exploited.
cember 1894 to January 1896). That he However, a more compelling reason was
still managedto constructthe first model his involvementin the interdisciplinaryre-
of the influence of CO2on climate, makes search effort known as cosmic physics.
it worth trying to understandhow he ar- This was an effort to bring the phenom-
rived at it. This can be done by placing the ena of the seas, atmosphere, and solid
work in context from: (i) what Arrhenius Arvid Hogbom 1857-1940. earth into the domain of the physical sci-

6 ? Royal Swedish Academy of Sciences 1997 Ambio Vol. 26 No. 1, Feb. 1997
 ..~~~~~~~~~~~~~~~~~~~~~~~~~
'.R ......

'a
4 i lu~*SI -.

Waitingto take off for the

NorthPole in the
summerof 1896.The ,

balloonists (Nlls Ekholm

fourthfromthe left Inthe . 4
last row)entertainthe
crew of the vessel
"Virgo"which had
broughtthem to
Spitsbergen.
"Hydrographer"
Arrheniusis seated on ;?'
the table Inthe frontrow.
Photo: RoyalSwedish
Academyof Sciences.

.:!14UE X o
..... Y}fl . ! ~~~~~~~~~~~~~~~~~~~~~~J

ences and to produce new theories taking into account the in- minutesof the Physics Society and the articlesaboutthe debates
terrelatednessof terrestrial,atmospheric,and cosmic events. The that Arrheniuswrote for the daily papers.Two different strands
task was facilitatedby the rapidaccumulationof data,often pro- of inquiryin the Society were involved, one concernedCO2and
duced throughnew means-balloon ascents and spectroscopy the otherclimatic change (3).
applied in astrophysics,for instance-concerning all aspects of Startingin 1892, Pettersson,Andree and Hogbom gave lec-
the earth and its atmosphereas well as the solar and lunar sys- turesto the Society presentingfresh dataon CO2on the ground,
tems. in the oceans and in the atmosphere.The lecturesHogbom gave
Cosmic physics was a productof the unique mix of persons to the Physics Society in 1893 and to the Swedish Society of
and institutions that made up the Stockholm scientific milieu Chemists in 1894 were the most important,because they be-
in the 1890s. At the center was the Stockholm Hogskola a pri- gan to transformthe problemof CO2from conjectureinto theory
vate, nondegreegrantinginstitutionconcentratingon science and (4). Hogbom had originally become interestedin CO2in the air
naturalhistory.It was here thatArrheniusbecame,first,a teacher as a geologist observing the formation and extension of lime-
of physics in 1891, then professor of physics in 1895 and, fi- stone (the chief source of CO2) across the globe. But he soon
nally, rector in 1896. One of Arrhenius'sfirst initiatives when expanded his inquiry to include all the components of the
he joined the Hogskolafacultywas to foundthe StockholmPhys- geochemical cycle in which CO2is developed and consumed.
ics Society. The purposeof the Society was to meet fortnightly His originalcontributionswere to make estimatesof the amount
to hear lectures and engage in discussion concerning the latest of CO2 supplied to the atmospherethroughdifferent processes
advances in physics, broadly defined to include fields such as (what is now referredto as the geochemical carbon cycle) and
meteorology, geophysics, astrophysics,and physical chemistry. to point to the bufferingeffects of the oceans. As for the short-
The Society met with immediate success. It soon drew to its term cycle, Hogbom listed six ways in which atmosphericCO2
meetings not only scientists from the Hogskola but also those is produced and three ways in which it is consumed. Among
from other institutions,for instance, the MeteorologicalOffice, the former, i.e. productionof C02, were volcanic exhalations,
the Swedish Geological Survey,and the Museumof NaturalHis- combustion and decay of organic bodies (especially burningof
tory. Among the core group,therewas Arrheniushimself as Sec- fossil fuels), and release of CO2dissolved in sea water because
retary of the Society, Otto Pettersson, Arvid Hogbom, and of increases in temperature.Among the latter, i.e. consump-
Vilhelm Bjerknes,who were all professorsat the Hogskola, Nils tion of C02, were the formationof carbonatesfrom silicates on
Ekholm from the MeteorologicalOffice, and S.A. Andree from weatheringand the absorptionof CO2in the sea.
the PatentOffice. In 1897, Andr6eundertookan ill-fatedattempt The main thrust of Hogbom's inquiry concerned the proc-
to reach the North Pole by balloon. Together they represented esses that may have caused variations in CO2 on a geological
disciplinesas diverseas physics, chemistry,mechanics,geology, time scale. He found that many of the processes making up the
and meteorology. carboncycle, for instance,combustionand decay of organicbod-
Cosmic physics in Stockholmwas never institutionalizedinto ies or decomposition of carbonates,are either of little signifi-
teaching programsor chairs, but was practiced in the Society cance or go on so rapidlythattheirvariationcan not be of much
as a purely intellectualactivity by persons who were, one might consequence. Volcanic eruptions representedfor him the one
say, on leave from their home disciplines. As Arrheniushim- source that does not flow regularlyand uniformly and can fur-
self indicatedin the article in The Philosophical Magazine, the thermorereach high levels of intensity. He concluded that even
discussions in the Physics Society stimulatedhim to construct a small increase or decrease of the supply must lead to remark-
the model. How this came about can be reconstructedfrom the able alterationsof the quantityof CO2in the air. He saw no hin-

Ambio Vol. 26 No. 1, Feb. 1997 ? Royal Swedish Academy of Sciences 1997 7
drance to imagining that this quantity might in a certain geo-
logical period have been several times greateror considerably
less, thannow.
The other strand of inquiry concerned changes in climate.
Given the Society's membership,their interestin the glacial ep-
ochs that had given Scandinaviaits specific geology is not sur-
prising. In 1893, Nils Ekholm gave a lecture on the "astronomi-
cal, physical, and meteorological" conditions that could have
broughtabout the Ice Ages following the period of milder cli-
mate in tertiarytimes. The lecture gave rise to a lively debate
concerning contemporary theories explaining the Ice Ages.
James Croll's idea that changes in the earth's orbit, especially
its eccentricity,had broughtaboutthe Ice Ages did not find favor
among the discussants, nor did the opinion that they were due
to changes in the position of the poles on the earth's surface.
Among the geologists present,Gerardde Geer chose land eleva-
tion as an explanation for a drier and harsher climate. Arvid
Hogbomdid not thinkthatsuch a drasticgeological changecould
have occurred,for, if that was so, the Ice Ages could not have
been interruptedby milder periods.
Here the matterrested until Arrheniusgave a lecture in early
1895 in which he linked climatic change to long-term varia-
tions in CO2.This idea had come to him at the end of 1894, - ~~~~~~~~~~i.
probably after he heard Hogbom lecture at the Swedish Soci-
ety of Chemists. He proposed to calculate the changes in CO2
necessary to bring about periods of both milder (+8?C) and
harsherclimate (-5?C), i.e., the conditionswhich reignedbefore,
during and between the Ice Ages. His preliminarycalculations
showed that the requiredchanges in CO2were in the order of
50%. Hogbom, who was present,confirmedthat those changes
could have occurredin geological times. It remained,however,
to demonstratethis quantitatively.The constructionof the model
which enabledhim to do so occupiedhim for most of 1895. Writ- Arrhenius in his Stockholm laboratory 1908.
ing to a friend at the end of the year, he found it "unbelievable
thatso triflinga matterhas cost me a full year"(5). But his com-
plaints in letters to other friends about how difficult it was to
bringthe "carbonicacid matter"to an end showed how arduous peratureof the globe and the planets, Fourier established the
a process this had been. We shall now learn what was involved analogy between the heat-conservingcapacity of de Saussure's
from a conceptualand a practicalpoint of view. instrumentand thatof the atmosphere(7). Pouilletused this prin-
ciple when he workedout the first equationfor the thermalequi-
libriumof "light"and "dark"rays (8). However, none of these
THECONCEPTUALFOUNDATIONSOF THEMODEL three scientists likened heat conservationby the atmosphereto
The conceptualbasis for Arrhenius'model is set out in the first that occurringin a hotbed, hothouse or greenhouse.
paragraphof his article in the Philosophical Magazine. It con- Some time duringthe first three-quartersof the 19th century,
cerns the way the atmosphereretains the heat emanatingfrom someone turnedthe analogyestablishedby Fourierinto the meta-
the ground ("darkrays") in contrastwith that emanating from phor of the hothouse or hotbed, later to become the greenhouse
the sun ("light rays") which is let through.In his rapid review and attributedit to him (9). The introductionof this metaphor
of the history of researchon this problemhe cited three names: may not have been recorded in a publication, in any event, no
Fourier,Pouillet, and Tyndall. such early reference has been found; instead, it became part of
Joseph Fourier (1786-1830) and Claude-Servais-Mathias the lore passed down from one generation of scientists to an-
Pouillet (1790-1868), both French natural philosophers, are other. In his 1888 memoir on the temperatureof the moon,
rightly cited by Arrheniusas pioneers in the field. They were Langley took this version for granted,referringto de Saussure's
both concerned with the temperatureof the globe. Fourier es- having carried out his experiments "by the use of glass in a
tablished the distinction between the light heat (chaleur hotbed" (10). Since Arrhenius too used this latter term
lumineuse)received on the earthfrom the sun and the darkheat ("drivba.nk" in Swedish) (1 1), it is likely that he took Langley's
(chaleur obscure) reflected back into the atmosphere.He also version for a fact. The article in the Philosophical Magazine
pointed to the lesser facility with which dark heat passes contained the same version though by then the "hotbed"had
through the atmosphere, thus bringing about higher tempera- become the "hothouse."
turesthanwould otherwisehave been the case. In describingthis Not surprisinglyfor a physicist, Langley was more punctili-
phenomenon, Fourier drew on experiments conducted by ous about the correctness of the greenhouse metaphorfrom a
Horace-Benedictde Saussure (1740-1799), professor of natu- physics point of view than he was with its antecedents. "On
ral history in Geneva. De Saussure had constructedan instru- the faith of these two eminent names [Fourierand Pouillet],"
ment he called a "solar captor"consisting of a box with an in- he wrote, the notion that the processes whereby heat is trapped
terior covered with black cork in which were inserted layers by the atmosphereare the same as those occurringin a green-
of glass at equidistance.He used his instrumentin experiments house, "hasbeen received as a physical datum...where one well-
aroundMont Blanc to show thatthe temperatureunderthe glass conducted experiment ... would have shown that the action of
was much higher than on the outside, and that it remainedthe the terrestrialatmospherewas directly the reverse of that of the
same irrespectiveof the altitude (6). In his treatise on the tem- glass in a hotbed" (10). The experimentcalled for by Langley

8 ? Royal Swedish Academy of Sciences 1997 Ambio Vol. 26 No. 1, Feb. 1997
was carriedout by R.W. Wood in 1907. It showed that glass- such an experiment.Instead,he looked for alreadyexisting data
houses retain heat through an absence of convection and which he found in Langley's measurementsof heat emission in
advection ratherthan through the absorption and re-emission the lunar spectrum.These data became the empirical basis for
of long-wave radiation(12). the model. Without them there is no doubt that his investiga-
tion would have foundered.
Neither Fouriernor Pouillet had discussed the reasons for the
heat-absorbingcapacity of the atmosphereexcept in the most SamuelP. Langley (1834-1906), an Americanastronomerand
general terms. To point to the role of CO2 and aqueous vapor physicist, specialist on infraredspectroscopy, had carried out
(H20) was the contributionof the British naturalphilosopher extensive observationsconcerningthe amountof heat received
John Tyndall (1820-1893). To Arrhenius it was thanks to on the earth from the full moon at the Allegheny Observatory
Tyndall that one had come to recognize "the enormous impor- duringthe years 1885 to 1887 (16). For this he used the bolom-
tance" of "the influence of the absorption of the atmosphere eter, an instrumenthe had developed to measurethe energy of
upon the climate" (13). In support of this statement he cites radiationas a function of wavelength. The bolometer was par-
Tyndall's best-selling book Heat a Mode of Motion based on ticularly well suited to measure the small quantities of "dark
Tyndall's lectures and demonstrationsat the Royal Institution heat"emitted by the moon that fell in the extreme infraredpart
(14). Through ingeniously designed experiments and under of the spectrum.Since the temperatureof the moon is similarto
strict laboratoryconditions, Tyndall had measuredthe heat ab- that of the earth, their emission spectrawould also be similar.
sorption by gases, among them CO2and H20. What caught Thus,Arrheniusfelt confidentaboutusing Langley's data.A fur-
Arrhenius's attention, however, was the discourse "On radia- ther simplificationwas introducedby assumingthatthe absorp-
tion through the earth's atmosphere." In this short piece, tion of H20 and CO2by the heat rays entering the earth from
Tyndall assigned to the "atoms"of aqueous vapor a capacity the moon when they traversedthe atmospherewas similarto that
15 times as large as those of oxygen and nitrogen to retain the
of the heat radiatedfrom the earthinto the atmosphere.
heat reflected from the earth, despite the fact that these "at- The key to Arrhenius'model was the absorptioncoefficients
oms" only constitute 0.5% of the atmosphere. Tyndall also for CO2(designated K) and H20 (W) that he calculated using
made the link with climate by pointing to field observations, Langley's data on the radiationof rays from the moon hitting
made among otherplaces in the Himalayas,which showed how the earthat angles of deviationrangingfrom 350 to 40?. He based
an absence of aqueous vapor caused enormous differences in these calculationson the principlethatthe quantitiesof CO2and
temperatureat different times of the day. H20 are proportionalto the pathof the ray which traversesthem
It is noteworthy that Arrhenius does not cite Tyndall's (termed"air mass" by Langley). Setting K and W at the value
Bakerian lecture in which he is much more explicit about the of 1 for a vertical ray, he could calculate how they increasedat
effect of H20 and CO2on climate. Given Arrhenius's interest differentangles of deviation;i.e. largerquantitiesof "airmass".
in explaining long-term variationsin climate it may have been He worked the absorptioncoefficients into an equation (3) that
because he did not know about it. Tyndall startedhis lecture relatedchangesin K andW to changesin temperature.The equa-
with a reference to the "observations and speculations of de tion also took into accountthe influence of clouds and the heat-
Saussure, Fourier, M. Pouillet, and Mr Hopkins, on the trans- moderatingeffects of snow and water.Working"backwards"as
mission of solar and terrestrialheat throughthe earth's atmos-it were, this enabled him to calculate the variationsin tempera-
phere." After having presented his laboratoryexperiments on ture that would accompany a given change in K and W. Pre-
the heat-absorptionby the gases and vapors of a large number sented schematically, the work of assembling the model thus
of elements and compounds, he extended these to climate. He came to representa three-stageprocess. Such a presentation,of
noted that "if, as the above experiments indicate, the chief in-
course, masks the Herculeanlabors that his work entailed, in-
fluence be exercised by the aqueous vapor, every variationof volving calculationsestimatedto have been between 10 000 and
this constituentmust produce a change of climate. Similar re- 100 000.
markswould apply to the carbonicacid diffused throughthe air, The three steps were as follows:
while an almost inappreciableadmixtureof any of the hydro- i. A first step involved workinghis calculationsof mean tem-
carbonvaporswould producegreateffects on the terrestrialrays peraturesat differentplaces aroundthe earth into the equation
and produce correspondingchanges of climate. It is, therefore,in order to arrive at the temperaturechange that would follow
not necessary to assume alterationsin the density and height of
from a variationfrom K = 1 to, e.g., K = 1.5. At this stage W
the atmosphereto account for different amounts of heat being was kept constant. Using available charts he calculated mean
preservedto the earth at different times; a slight change in its
temperaturesduring four seasons for every sector situatedbe-
variableconstituentswould suffice for this. Such changes in fact
tween two parallels differing by 10? and two meridiansdiffer-
may have produced all the mutations of climate which the re- ing by 20?.
searches of geologists reveal. However this may be, the facts ii. An intermediarystep took into account the fact that the
above cited remain;they constitutetrue causes, the extentalonewater vapor in the air increases with temperature.Hence, the
of the operationremainingdoubtful"(15). change in temperaturethat would follow from the change in
K would also influence humidity. To account for this he cal-
culated relative and absolute humidity in the same manner as
THE EMPIRICALBASIS OF THE MODEL that for temperature.He found that the influence of humidity
Arrhenius'researchquestion was: What precisely is this extent on temperaturewas relatively uniform aroundthe globe.
of the influence of H20 and CO2in the atmosphereon the tem- iii. A final step involved the presentationof his data in a ta-
peratureon the ground?Althoughin the next 30 years,Tyndall's ble (Table VII) which showed variationsin mean temperature
laboratorymeasurementswere extended and supplementedby in sectors from 70?N to 60?S duringfour different seasons, as-
directobservationsby KnutXngstriim,ErnstLecher,Josef Maria suming that K was respectively 0.67, 1.5, 2.0, 2.5 and 3 times
Perntner,and Wilhelm Rontgen among others, the question re- the present observed atmosphericlevel, that is 1.
mainedunanswered.As Arrheniuspointed out, it would be nec- The general rule which emerged from the table was that if
essary to carry out a laboratoryexperimentin which one mea- the quantity of CO2 increases in geometric progression, tem-
suredthe absorptionof the heat emanatingfrom a body at +15?C peraturewill increase nearly in arithmeticprogression.For ex-
(the average temperatureof the earth)by quantitiesof H20 and ample, if the quantityof CO2increases 1.5 times the mean in-
CO2in the proportionsin which these were presentin the atmos- crease in temperature(+3?C) would be the same as the mean
phere, but contemporaryresearchtechnology did not allow for fall in temperature(-3?C) broughtabout by a decrease in CO2

Ambio Vol. 26 No. 1, Feb. 1997 ? Royal Swedish Academy of Sciences 1997 9
from 1 to 0.67. The table showed that the effect would be dif-
ferent for differentparts of the globe dependingon the amount
of CO2in the air. Thus, in the 0.67 scenario the maximum ef-
fect would be on 400 and 50?N whereas in the 3.0 one, they
would be north of the 70th parallel. Furthermore,the table in-
dicated that the influence was greaterin the summerthan in the
winter.An increasein CO2would also diminishtemperaturedif-
ferences between day and night, but this was not shown in the
table.
Arrhenius'final results are impressive both as an innovative
exercise in model-buildingand as a first approximationof the
influence of CO2on climate. This should not make one forget,
however, that they hardly rested on solid empirical ground.
= 11 - l *1 II 1' 1 ES~~~~~~~~11
Arrheniusdid not heed Langley's warning that his investiga-
tion had yielded "no conclusion which we are absolutely sure
of." But Langley's data were the only data available to him.
Later, both Langley's data and the use that Arrhenius had
made of them were the subject of severe criticisms by Knut
Angstrom,associate professorin physics at Uppsala University
and an expert on measurementsof the solar spectrum(17, 18).
Furthermore,Langley's data only allowed for calculationsby
interpolationof the temperatureeffects of the 0.67 and 1.5 lev-
els of CO2 in Arrhenius'stable. The three levels above 1.5 were
extrapolatedas were those below 0.67. The latter (0.62-0.55)
giving a temperaturedecreaseof 4-50C were used by Arrhenius
in discussions, both in the articlein the Philosophical Magazine _~~~~~
and in the Physics Society, to argue that an Ice Age brought ..:::. . .

about by a change in CO2 was entirely plausible. Conversely,

he arguedthatthe doubling and even the triplingof CO2showed
that periods of warmerclimate (increasesof 8 to 9?C) had pre-
ceded the Ice Ages. Why then were the figures relating to the
higher, but not to the lower levels of C02, featuredin the table?
We do not know the reasons for this but we can surmise that it Portrait
of Arrhenius.
has reinforcedthe impressionthatArrheniuswas primarilycon-
cernedwith global warmingnot global cooling.

his idea Of C02-inducedclimatic change beyond the Physics So-

IMMEDIATE
AND LONG-TERMREACTIONS ciety and outside Sweden. In September 1895, he gave a lec-
TO THEMODEL ture on his work to the VersammlungDeutscherNaturforscher
Arrheniushad been inspiredto undertakewhat he referredto as und Artzte,best known as the Naturforscherversammlung, whose
"these tedious calculations"by the debates in the Physics Soci- annualmeetings,runningthe gamutof scientificdisciplines,were
ety concerning the causes of the Ice Ages. It was normal then wokhdcnice
important :i.hti for German
gatheringplaces and foreign
.agnrlsne ml scientists.
hne
thatthe first results should be presentedat Society meetings. On The
inC 1895 meeting, held in Lilbeck, is bestrigaotgooia
known in physics for
two occasions, in May and October 1895, he gave lectures in the _wrruniaivl:ufcett
epic confrontation
clmai chne(0.Hwve,we thattook place between the "energeticists"
.ertrndt h oi
which he kept the members informedabout the progress of his led anWilhelm
by
in~~~~..aril in thOstwald and the "kineticists"
saejunli_89 led by
epitdotta Ludwig
work and reiteratedhis thesis aboutvariationsin CO2as a cause Boltzmann,a battle decisively won by the latter.Anotherocca-
of climatic change and especially of the Ice Ages. His model sion to make his ideas known was a popularlecturethathe gave
not only providedhim with evidence in favor of this thesis, but at the Stockholm Hogskola in February1896 and published in
also with ammunitionagainst competing theories. He took par- the Swedish culturalreview Nordisk tidskrift(11). He reached
ticularpleasurein being able to refute Croll's argumentthat the his largest internationalaudience though, throughthe article he
Ice ages had been caused by changes in the earth's orbit. Here, sonsai
wrote for
forbelievngi htschaeceswrsn.prtonah
the Philosophical Magazine. Here he seems to have
he could point to his model to show that Croll's theory, which been motivatedchiefly by his desire to refuteCroll's hypothesis,
demandeda clementage on the SouthernHemisphereat the same which, as he wrote, "still seems to enjoy a certain favor with
time as an Ice Age on the NorthernHemisphere,and vice versa, English geologists" (19).
was wholly untenable. T'heonly recordedimmediatereaction to Arrhenius'sarticle,
He seems to have had more difficulty in convincing mem- which came from Thomas Chamberlin,an American geologist
bers of the society that he was right in assigning such an im- at the University of Chicago, concernedCO2 as the cause of the
portantrole to changes in CO2.Even in the discussion in May Ice Ages. In an article published in the Journal of Geology in
1895 Hogbom, who had earlier supportedthe idea of CO2 as 1897, Chamberlinrecountedthat he had had the same idea but
the cause of geological climatic change now sided with those had not wantedto express in publicly.Arrhenius'and Hogbom's
who thought this cause lay in changes in the position of the
poles on the earth's surface.After one or two more discussions,
equally inconclusive, the Society turned its attention to other
questions. This was normal given that the Society was a fo-
rum for debate not sustained research. Still, it had played an
invaluablerole in stimulatingArrhenius'work.
Both local and cosmopolitan publics were important to
Arrheniusin makinghis ideas known. In 1895 and 1896, he took

10 i Royal Swedish Academy of Sciences 1997 Ambio Vol. 26 No. 1, Feb. 1997
times requisite to produce the effects assigned to them" (21). his work which is most often cited today, i.e., the link he made
He also pointed out that Hogbom had only considered the dif- between industry'sburningof fossil fuels and global warming.
ferent mechanisms that may have caused changes in CO2 but This link may have been largely fortuitousin that it depended
had not suggested how these could be measuredquantitatively. on the paucity of data concerningother sources of atmospheric
Chamberlin's criticism was astute but his suggestion was CO2.Two other featuresof his work were much more remark-
hardlyrealistic,for at the time it was not possible to obtainsuch able: one was linking Hogbom's work on the carbon cycle to
measurementsthroughdirect observation.This was evident in climatic change-Hogbom's work being in itself a major
Chamberlin'sown work, also limited to mechanismsratherthan achievement for which he has only very recently received re-
measurements.The only source of CO2supplied to the atmos- newed credit (25)-and the other was constructing a model
phere that could be measuredwas in fact that provided by the which for the first time made possible predictionsof both glo-
burningof fossil fuels. In his article, Hogbom had pointed out bal warmingand cooling.
that the CO2producedby the 500 million tons of coal annually
burntby modernindustryrepresentedabouta 1000thpartof CO2
in the atmosphere(4). He found, however, thatthis quantitywas
offset by the CO2 consumed in the formation of limestone References and Notes
throughweathering. 1. Arrhenius,S. 1896. Uber den Einfluss des atmospharischenKohlensaurengehaltsauf
die Temperaturder Erdoberflache.Bihang till Kungl. Svenska Vetenskapsakademiens
In his popularlecture at the Hogskola, Arrheniuswent a step handlingar22, No. 1, 1-102.
furtherand ventureda predictionof how long it would take for 2. Arrhenius,S. 1896. On the influence of carbonic acid in the air upon the temperature
on the ground.The Philosophical Magazine41, 237-276.
fossil-fuel burningalone to double the amountof CO2in the at- 3. Crawford,E. 1996. Arrhenius:From Ionic Theoryto the GreenhouseEffect. Science
mosphere.In an addendumto the publishedlecturehe presented HistoryPublications,Canton,MA.
4. Hogbom, A. 1895. Om sannolikheten for sekulara forandringar i atmosfarens
calculations of the buffering effects of the oceans, which kolsyrehalt.Svenskkemisktidskrift5, 169-176 (partiallyreproducedin Arrhenius,Note
2, 269-273). (In Swedish).
Hogbom had consideredbut had not quantified.These showed 5. SvanteArrheniusto GustafTammann,December24, 1895, ArrheniusCollection,Center
that if six partsof CO2are addedto the atmosphere,five will be for History of Science, Royal Swedish Academy of Sciences, Stockholm.
6. Sigrist, R. 1993. Le capteur solaire de Horace-B&ndict de Saussure: Genese d'une
absorbedby the oceans. In view of this, a doubling of CO2that science empirique.Geneve, EditionsPass&Present.
would have taken 3000 years if the earthwas a single land-mass 7. Fourier, J. 1824. Memoire sur les temperaturesdu globe terrestre et des espaces
planetaires.Mim. Acad. R. Sci. Inst. Fr. 7, 569-604. Also publishedas Fourier,J. 1824.
would occur in 500 years. During this latter period, tempera- Remarquesgeneralessur les temperaturesdu globe terrestreet des espaces planetaires.
tures would increase by 3-40C. Arrheniussaw nothing adverse Ann. Chi. Phys. 27, 136-167.
8. Pouillet, C. 1837. Memoire sur la chaleur solaire, sur les pouvoirs rayonnants et
in such a development.It will "allow our descendants,"he said, absorbantsde l'air atmospherique,et sur la temperaturede l'espace. C. R. Aca. Sci. 7,
24-65.
"even if they only be those of a distant future, to live under a 9. According to the Oxford English Dictonary (OED), a "hothouse,"a term whose first
warmer sky and in a less harsh environment than we were appearancein printhas been traced to 1749, is "a structurekept artificiallyheated to
cultivate flowers," a "hotbed"(1626) a "bedof earthcovered by glass," and a "green-
granted"(l1). Such a view is consonant with the ideology of house" (1664) a "glass-housein which delicate flowers are raised."Also accordingto
"optimisticevolutionism"embracedby Arrheniusand many of the OED, the first referenceto the "so-called greenhouseeffect of the atmosphere"is
from 1937.
his contemporaries(22). 10. Langley, S. 1889. The temperatureof the moon. Mem. Nat. Acad. Sci. 4, PartII, 107-
Arrhenius'sreferences to coal burningas a source of atmo- 212 (citationon 110).
11. Arrhenius, S. 1896. Naturens varmehushallning.Nordisk tidskrift 14, 121-130. (In
sphericCO2repeatedand revised upwards(but withoutthe pre- Swedish).
12. Jones, M.D.H. and Henderson-Sellers,A. 1990. Historyof the greenhouseeffect. Prog.
dictions he ventured in his Hogskola lecture) in his Lehrbuch Phys. Geol. 14, 6 and 8.
der kosmischenPhysik (1903) (23), and Worlds in the Making 13. Arrhenius,S. 1896. On the influence of carbonic acid in the air upon the temperature
on the ground.Philos. Mag. 41, p. 237.
(1908) (24), are probablywhat has earnedhim his presentrepu- 14. Tyndall,J. 1865. Heat a Mode of Motion. 2nd ed. London,Longmans,Green and Co.
tation as the first to have predictedthe effect of this particular 15. Tyndall, J. 1861. On the absorptionand radiationof heat by gases and vapours, and
on the physical connexion of radiation,absorption,and conduction. -The Bakerian
source of CO2on climate. This view overlooks the fact thatfos- Lecture.Philos. Mag. 22, 169-194 and 273-285 (citationon 277).
sil-fuel burningby industryfiguredin Hogbom's geological car- 16. Langley, S. 1889. The temperatureof the moon. Mem.Nat. Acad. Sci. 4,107-212.
17. Angstrom, K. 1900. Ueber die Bedeutung des Wasserdampfesund der Kohlensaure
bon cycle and the equally importantfact that Arrheniusgave bei der Absorptionder Erdatmosphare. Ann. Phys. 3, 720-732.
18. Arrhenius,S. 1901. Ueberdie Warmeabsorption durchKohlensaure.Ann.Phys. 4, 690-
Hogbom creditfor this. This neglect forms partof course of the 705.
general way thatHogbom's contributionhas been forgotten. 19. Arrhenius,S. 1896. On the influence of carbonic acid in the air upon the temperature
on the ground.Philos. Mag. 41, 274.
The image of Arrheniusas the "discoverer"of the greenhouse 20. Chamberlin,Thomas C. 1897. A group of hypotheses bearingon climatic changes. J.
effect would not have takenhold withoutthe recontextualization Geol. 5, 653-683 (citationon p. 681).
21. Chamberlin,Thomas C. 1899. An attemptto frame a workinghypothesis of the cause
that occurs when a scientific problemis takenout of its histori- of glacial periods on an atmosphericbasis. J. of Geol. 7, 545-584 (citationon 548).
cal context and placed in one thatreflects present-dayconcerns. 22. Arrhenius-Wold, A.-L. 1959. Arrhenius och utvecklingsoptimismem. In: Svante
Arrheniustill 100-drsminnetav hansfodelse (K. VetenskapsakademiensArsbok1959.
It is thus that interest in Arrhenius's model, which had been Bilaga), Stockholm,Almqvist & Wicksell, pp. 65-100. (In Swedish).
minimal during the first 50 years of the 20th century, was re- 23. Arrhenius,S. 1903 Lehrbuchder kosmischenPhysik. 2 vols. Leipzig, Hirzel.
24. Arrhenius,S. 1908. Worlds in the making: The Evolution of the Universe. Trans. H.
suscitatedin the 1970s as a result of the model being placed in Bom. New York and London,Harpers.
25. Bemer, R. A. 1995. A. G. Hogbom and the development of the concept of the
the new context of global warming. As often happens, the geochemical cycle. Am.J. Sci. 295, 491-495.
recontextualizationof a work has led to its reinterpretation.In 26. I am gratefulto Gustaf Arrheniusfor his careful review of the manuscriptof this arti-
cle and to the participantsin the ArrheniusCentennialWorkshopfor theirhelp in gain-
Arrhenius'scase, this has been importantin two ways: first,with ing new insights into Arrhenius'swork. I have also been enlightenedby discussions
respectto the meaningof the "greenhouseeffect," which to him with Guy Chouraquiand JacquesGrinevald.
was simply the warmingeffect of atmosphericgases which are
radiativelyactive and not the anthropomorphicinfluence on the
productionof such gases, and, second, with respect to his mo- Elisabeth Crawfordis a senior research fellow at the Centre
tives for undertakingthe work, which were an interestin find- National de la Recherche Scientifique and a member of the
ing the causes of the Ice Ages and not concern with the effect Institutd'Histoire des Sciences at the Universite Louis
Pasteur in Strasbourg, France. She is a graduate of the
of the industrialrevolution. University of Stockholm. She has published several books
in the history and sociology of science, among them The
Beginnings of the Nobel Institution: The Science Prizes
CONCLUSION 1901-1915, Cambridgeand Paris, 1984, Nationalism and
Internationalismin Science, 1880-1939, Cambridge, 1992;
The genesis of Arrhenius'work was in the traditionof glacial and Arrhenius: From Ionic Theory to the Greenhouse Effect,
climatic change, representedby Tyndall, Croll and Chamberlin, Canton, MA.,1996. Heraddress: Institutd'Histoire des
among others. In importantrespects, however, his work broke Sciences, 7 rue de l'Universite, F-67000 Strasbourg, France.
with this tradition.This breakdid not lie so much in the partof

Ambio Vol. 26 No. 1, Feb. 1997 ? Royal Swedish Academy of Sciences 1997 11