A Climate Modifier

A CLIMATE MODIFIER. P.Y FRED J. PACK, B. S. The subject of this discussion is a very old one, but, through the recent investigations of some of our great thinkers, a profound interest in it has been revived.It will be remembered that but a few years ago Prof. Chamberlin, of the University of Chicago, proposed the "Planetesimal Theory" of earth origin, in contradistinction to the time-honored "Nebular Theory" of LaPlace. It was through a long series of experiments and deductions concerning the properties of carbon dioxide that Prof. Chamberlin was led to his conclusions in regard to earth genesis. And today many of the greatest students of both the eastern and western continents are gravely studying this problem, with the hope that here lies the secret of many perplexing geological phenomena. We shall, however, confine our discussion chiefly to a consideration of the value of carbon dioxide as a climate modifier, and shall touch but incidentally upon the many other problems immediately associated. From geological researches, the fact is well established that climatic conditions have varied greatly in different periods of the earth's history. For instance, during parts of the Carboniferous, Tertiary, and other ages, the temperature was such that tropical plants and animals flourished in the arctic regions; then succeeding these seasons were periods of cold, when at least on two occasions great ice- sheets stretched far down into the temperate zones of today. Coincident with and corresponding to these were periods of similar nature on the southern continents, thus proving that the changes of temperature were such as to affect the entire earth. What is the cause of these remarkable changes of climate?

The ablest scholars of many generations tell us that as the carbon dioxide content of the atmosphere increases or decreases the temperature will correspondingly rise or fall. In other words, it serves the purpose of a blanket to the earth. It is now our pleasant task to discuss these points more fully, and verify the statements made. To even the boy in tne grades there is no difficulty in distinguishing between the great ferns of the tropics and the lichens of Greenland, and with little thought he is able to describe the nature of the climate in which each grows. Let an individual be taken to some equatorial region where vegetation grows in profusion. If every sense, save that of sight, be taken from him, he will recognize the general character of the climate of the country. Further, let all living vegetation be destroyed, and still the accumulations of leaves in the swamps and other favorable places will bear testimony to him that plant life once flourished there under tropical conditions. Even if these vegetable accumulations were buried deep in the earth, the evidence remains the same. So it is when we visit the regions of the far north. Even at the great latitude of Spitzbergen the remains of plant life tell us in unmistakable terms of the genial climate that once prevailed there. These occurrences are by no means exceptional, but are found distributed over very wide aseas. And what is the evidence from which we learn of the great ice- sheets that once swept from the polar regions far into the zones now temperate? Go, if you will, to some region of present glaciers, say the valleys of the Alps, or better the coasts of Greenland. There you will see the glaciers and glacial sheets at work, slowly but surely planing off the elevations and filling up the minor depressions. There are the morains at the termination of the ice, dumped helter-skelter upon whatever may chance to be there. The boulders and bed-rocks are scratched and furrowed, while the latter are also rounded into great sheep-backs, so named from their*appearance. Where the ice is confined to canyons, the latter are carved out to the broad U shape, so characteristic of ice worn regions, and in bold contrast to the narrow V shaped canyons of stream erosion. The morainic material is often piled in such places so that the natural drainage is dammed off, and lakes are formed. In fact the entire topography of the country is so strik-

A CLIMATE MODIFIER. 683 ingly different from that of places wholly worn by water, that the attention of even the most casual observer will be attracted thereby. Evidences similar to these are found over nearly all latitudes, higher than forty or fifty degrees; and when the ice- sheet had its greatest extent, the countries now the home of the highest civilization were covered with ice.This was the case with all of northern Europe and many places in the southern parts of that continent. At the same time North America was covered on the west coast to the 47th parallel, on the east coast to the 40th parallel, and in the central part to the 37th. In most sections of the world, too, we have found indications of this great ice age, as in Asia Minor, the Himalayas, South Africa, Australia, New Zealand, and many parts of South America. Geologists in general are inclined to think that these glaciations were simultaneous over the whole earth, and viewed from the standpoint of geology must have taken place in very recent times. It should be of special interest to readers of this article to know that we have full and indisputable evidence of the former existence of a glacier in Little Cottonwood canyon, Utah. No one can make an examination of the conditions there and come away other than profoundly impressed that it's existance was very, very recent. Evidences of glaciation are also to be seen in the High Plateau region, and at the head of Farmington canyon. The reader must not get the impression that there has been but one great change of climate in times past. Quite to the contrary, we are now coming to believe that these alternating periods of heat and cold have recurred time and time again. Prof. Chamberlin would have us believe that life of the warm temperate types prevailed in the arctic lands during the Middle Ordovisic, the Middle Siluric, the Middle Carbonic, the Middle Cretacic, and the Early Tertiary ages, and alternating with these were periods of cold, when perhaps glaciation stretched far into the temperate zones of today. (Journal oj Geology, Vol. VI, p. 619). But perhaps the most notable feature connected with the extension of life into the polar regions is the marvelous equality of temperature. It has been recently shown by White and Schuchert that during the Potomac epoch an almost identical fauna and flora flourished in the north of Greenland and in the eastern United

States. Bearing upon this subject, but speaking of another age, Dana says: "The species living in the waters between the parallels of 30 degrees and 40 degrees were in part the same with, or closely related to, those that flourished between the parallels of 60 degrees and 80 degrees." We cannot conceive of a simple increase of solar heat, distributed as it is today, as accounting for this wonderful equalization of temperature. Under existing conditions, an increase of temperature at the poles certainly means a corresponding increase at the equator, but not so in times past. It appears that there must have been some equalizing factor. And this, eminent physicists, from the days of Tyndall to the present, encourage us to believe may be found in the critical item of carbon dioxide. It is now a little more than fifty years since Tyndall suggested that these periods of heat and cold might be dependent upon the amount of this gas in the air. He had demonstrated in his laboratory that carbon dioxide has the peculiar competence of retaining solar heat, while most of the other constituents of the atmosphere are insensible to it. But it appears that it was left to Arrhenius to demonstrate that with a given increase of this gas in the air there would be a correspondingly greater rise in temperature in the higher latitudes than near the equator. (London, Edinburgh and Dublin Philosophical Magazine, 5th series, Vol. 41, p. 266, 1896). This was a great step toward the solution of the problem, and now it is believed that the only requirement necessary to restore the genial climate of the Tertiary age is a simple increase of carbon dioxide. But let us approach this from another view point. Heat may be conveyed from one object to another in three different ways, conduction, convection, and radiation, in only the last of which we are interested here. To illustrate this method of heat transference, we shall use the following: I am now sitting beside a steam radiator. I place my hand upon it: it is uncomfortably warm. I hold my hand in the air a few inches from the heater, and experience no discomfort whatever, but the wall, two or more feet distant, is nearly as warm as the heater itself. How came the wall to be warmer than the air immediately surrounding the source of heat? Physicists tell us that the ether of the air acts as a carrier of the

A CLIMATE MODIFIER. 685 heat, and that while in this state it is imperceptible to the thermometer. It is not our purpose here to explain this phenomenon but simply to point out the fact that heat may be carried from one object to another without the temperature of the intervening space being appreciably raised. Just so does the earth receive its heat from the sun. We know that on high mountains even in equatorial lands the temperature may be so low that perpetual snow and ice prevail. So we see that space is not warm, but intensely cold, and were it not for the fact that some of the constituents of the atmosphere have the property of retaining heat once entrapped, the earth would be unfit for habitation. Travelers in desert regions are well aware of the fact that though they may suffer from the intense heat of the day, yet at night they will be compelled to draw their blankets close. In Sahara, where "the soil is fire and the wind is flame," the refrigeration at night is often painful to bear. The explanation of this sudden fall of temperature is simple. The air is parched and dry; there is nothing left in the atmosphere to prevent the heat from radiating back into space; even the carbon dioxide fails when left to this task alone; so, after the disappearance of the sun, the heat is rapidly lost and the temperature falls to this alarmingly low point This proves the value of moisture, or aqueous vapor, in the air, as a heat retainer. Tyndall says that "the removal, for a single summer night, of the aqueous vapor of the atmosphere that covers England would be attended by the destruction of every plant which a freezing temperature could kill." (Tyndall, Heat Considered as a Mode of Motion, p. 405. New York, 1863.) He has laid great stress upon the value of aqueous vapor in the atmosphere, in this connection; but others, notably Lecher, Pernter, Arrhenius, and Chamberlin are inclined to think that carbon dioxide plays a much more important part. The amount of water vapor in the air is dependent upon climatic conditions, while, as we shall now see, carbon dioxide is a producer of climate, and not a resultant of it. Fourrier maintained that the atmosphere acts like the glass of a hot house, while at present we are disposed to apply this likeness especially to carbon dioxide. The rays of heat accompanied by light from the sun are permitted to pass unimpaired through the glass of the conservatory, but when once in, they are

entrapped and cannot return. This property has given rise to the statement that glass is insensible to "light heat," but intercepts or absorbs "dark heat." This selective absorption is not exercised by the chief mass of the air, but in a high degree by carbon dioxide, which is present in the atmosphere in very small quantities. The chief bulk of the air is nitrogen and oxygen, which together equal about 99J per cent, and of the remaining part about .45 per cent is aqueous vapor, while not more than .03 per cent is carbon dioxide. If this apparently insignificant constituent of the atmosphere were reduced to carbon, it would form a layer not more than .04 of one inch thick over the earth's surface, and yet we are compelled to believe that if it were removed from the air, frigid conditions would immediately prevail. One may now ask, how much must the carbon dioxide vary in order that the temperature should attain the same values as in Tertiary and Glacial times, respectively? Arrhenius has shown that by a simple calculation, the temperature in the arctic regions would rise sufficiently to sustain life of the tropical and temperate kinds, if the carbon dioxide increased to 2.5 to 3 times its present value, and even when thus augmented it would represent but an inappreciably small portion of the atmosphere. In order to get the temperature of the ice-age, between the 40th and 50 parallels, the carbon dioxide in the air should decrease to .62 per cent to .55 per cent of it's present value. (London, Edinburgh, and Dublin Philosophical Magazine, 5th series, Vol. 41, p. 268, 1896). He adds: "The demands of the geologists, that at the genial epochs the climate should be more uniform than now, accords very well with the theory. The geographical, annual, and diurnal ranges of temperature would be partly smoothed away, if the quantity of carbonic acid was augmented." And again one may ask, is the critical item of carbon dioxide variable in any way,or is its percentage constant in the atmosphere? This much we can say, that to all our methods of measurement, it's value does not change, but we do know that it is being constantly supplied and removed. Perhaps the greatest source of supply is the exhalations from volcanoes and earth vents in general. It is mostly removed by the formation of carbonates from silicates in the process of rock weathering. It is also well known