1896 Arrhenius (1119300), страница 8
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In the most different partsof the world, too, we have found traces of a great ice a_o'e, asill the Caucasus, Asia Minor, Syria, the Himalayas, ffndia,Thian Shan, Altai, Atlas, on Mount Kenia and Kilimandjaro(both very near to the equator), in South Africa, Australia,New Zealand, Kerguelen, lralkland Islands, Patagonia andother parts of South America. '.[he geologists in generalare inclined to think that these glaciations were simultaneouson the whole earth*; and this most natural view wouldprobably have been generally accepted, if the theory of Croll,which demands a genial age on the Southern hemisphere at thesame time as an ice age on the Northern and vice versd, hadnot influenced opinion.
By measurements of the displacementof the snow-line we arrive at the result,-- and this is veryconcordant for diffbrent placesqthat the temperature at thattime must have been 4°-5 ° C. lower than at present. The lastglaciation must have taken place in rather recent times,geologically speaking, so that the human race certainly hadappeared at that period. Certain American geologists holdthe opinion that since the close of the ice age only some 7000to 10,000 years have elapsed, but this most probably is greatlyunderestimated.One may now ask, How much must the carbonic acid varyaccording to our figures, in order that the temperature shouldattain the same values as in the Tertiary and Ice ages respectively ? A simple calculation shows that the temperature inthe arctic regions would rise about 8 ° to 9° C., if thecarbonic acid increased to 2"5 or 8 times its present value.In order to get the temperature of" the ice age between the&0th and 50th parallels, the carbonic acid in the air shouldsink to 0"62 --0"55 of its present value (lowering of temperature4°-5 ° C.).
The demands of the geologists, that at the genialepochs the climate should be more uniform than now, accordsvery well with our theory. The geographical annual anddiurnal ~ranges of temperature would be partly smoothedaway, if the quantity of carbonic acid wasLaugmented. The• iNeumayr~.Erd#esc~ichte, p. 648 ~ Nathorst,L e. p. 992.~n the Air upon the Temperature of the Ground.269reverse would be the case ( a t least to a latitude of 50 ~ fromthe equator)~ if the carbonic acid diminished in umount.
Butin both these cases I incline to think that the secondaryaction (see p. 257) due to the regress or the progress of thesn0w-covering would play the most important r6]e. Thetheory demands also that~ roughly speaking, the whole earthshould have undergone about the same variations of tempera°ture, so that according to it genial or glacial epochs must haveoccurred simultaneously on the whole earth. Because of thegreater nebulosity of the Southern hemisphere, the variationsmust there have been a little less (about 15 per cent.) tha~lin the Northern hemisphere.
The ocean currents, to% mustthere, as at the present time, have effaced the differences intemperature at different latitudes to a greater extent than inthe Northern hemisphere. This effect also results fi'om thegreater nebulosity in the arctic zones than in the neighbourhood of the equator.There is now an important question which should beanswered, namely :--Is it probable that such great ~ariationsin the quantity of carbonic acid as our theory requires haveoccurred in relatively short geological times ? The answer tothis question is given by Prof.
HSgbom. As his memoir onthis question may not be accessible to most readers of thesepages, I have summed up and translated his utterances which~re of most importance to our subject * : - '~ Although it is not possible to obtain exact quantitativeexpressions for the reactions in nature by which carbonicacid is developed or consumed~ nevertheless there are somefactors~ of which one may get an approximately true estimate,and from which certain conclusions that throw light on thequestion may be drawn.
In the first place, it seems to beof importance to compare the quantity of carbonic acid nowpresent in the air with the quantities that are being transformed. If the former is insignificant in comparison withthe latter, then the probability for variations is wholly otherthan in the opposite case." On the supposition that the mean quantity of carbonicacid in the air reaches 0:03 vol.
per cent., this number repre,sents 0"04:5 per cent. by weight, or 0"342 millim, partialpressure~ or 0 466 gramme of carbonic acid for every cm~of the earth's surface. Reduced to carbon this quantitywould give a layer of about 1 millim, thickness over theearth's surface. The quantity of carbon that is fixed in theliving organic world can certainly not be estimated with the~' H6gbom,Saensk kerMsk Tidskri/t, Bd. ~i. p. 169 (189~)_Phil. Mug. S.
5. Vol. 41. No. 251. ATrll 1896.U270Prof. S. Arrhenius on the Influence of Carbonic Acidsame degree of exactness ; but it is evident that the numbersthat might express this quantity ought to be of the sameorder of magnitude, so that the carbon in the air can neitherbe conceived of as very great nor as very little, in comparison with the quantity of carbon occurring in organisms.With regard to the great rapidity with which the transformation in organic nature proceeds, the disposable quantity ofcarbonic acid is not so excessive that changes caused byclimatological or other reasons in the velocity and value ofthat transibrmation might be not able to cause displacementsof the equilibrium." The following calculation is also very instructive for theappreciation of the relation between the quantity of carbonicacid in the air and the quantities that are transformed.The world's present production of coal reaches in roundnumbers 500 millions of tons per annum, or 1 ton per kin.
~of the earth's surface. Transformed into carbonic acid, thisquantity would correspond to about a thousandth part ofthe carbonic acid in the atmosphere. It represents a layer oflimestone of 0"003 millim, thickness over the whole globe,or 1"5 kin? in cubic measure. This quantity of carbonicacid, which is supplied to the atmosphere chiefly by modernindustry, may be regarded as completely compensating thequantity of carbonic acid that is consumed in the formationof limestone (or other mineral carbonates) by the weatheringor decomposition of silicates.
From the determination of theamounts of dissolved substances, especially carbonates, in anumber of rivers in different countries and climates~ and ofthe quantity of water flowing in these rivers and of theirdrainage-surface compared with the land-surface of the globe,it is estimated that the quantities of dissoh'ed carbonates thatare supplied to the ocean m the course of a year reach atmost the bulk of 3 km?As it is also proved that therivers the drainage regions of which consist of silicatesconvey very unimportant quantities of carbonates comparedwith those that flow through limestone regions, it is permissible to draw the conclusion, which is also strengthenedby other reasons, that only an insignificant part of these 3 kin.
3of carbonates is formed directly by decomposition of silicates.In other words, only an unimportant part of this quantity ofcarbonate of lime can be derived from the process of weathering in a year. Even though the number given were onaccount of inexact or uncertain assumptions erroneous to theextent of 50 per cent. or more, the comparison instituted is ofvery great interest, as it proves that the most important ofall the processes by means of which carbonic acid has beenin the Air upon the Temperature of the Ground.271removed from the atmosphere in all times, namely thechemical weathering of siliceous minerals, is of ~he sameorder of magnitude as a process of contrary effect, which iscaused by the industrial development of our time, and whichmust he conceived of as being of a temporary nature." In comparison with the quantity of carbonic acid whichis fixed in limestone (and other carbonates), the carbonic acidof the air vanishes.
With regard to the thickness of sedimentar~- formations and the great part of them that is formedby limestone and other carbonates, it seems not improbablethat the total quantity of carbonates would cover the wholeearth's surface to a height of hundreds of metres. If weassume 100 metres,--a number that may be inexact in a highdegree, but probably is underestimated,--we find that about25,000 times as much carbonic acid is fixed to lime in thesedimentary formations as exists free in the air. Everymolecule of carbonic acid in this mass of limestone has~however, existed in and passed through the atmosphere inthe course of time.
Although we neglect all other factorswhich may have influenced the quantit'y of carbonic acid inthe air, this number lends but very slight probability to thehypothesis, that this quantity should in former geologicalepochs have changed within limits which do not differ muchfl'om the present amount. As the process of weatheringhas consmned quantities of carbonic acid many thousandtimes greater than the amount now disposable in the air,and as this process from different geographical, climatological and other causes has in all likelihood proceeded withvery different intensity at different epochs, the probabilityof important variations in the quantity of carbonic acidseems to be very great, even if we take into account the compensating processes which, as we shall see in what follows~are called fbrth as soon as, for one reason or another,the production or consumption of carbonic acid tends todisplace the equilibrium to any considerable degree.
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