How to Change the North American Climate
EVERY one knows how widely the climate of North America differs from that enjoyed by our neighbors in the more favored lands of Europe. While our autumns and springs have for a little time a decent gentleness of behavior which makes the tender allegories of those seasons seem not altogether ironical, the times between are quite generally mere brutal exhibitions of unreasoning temperatures. Just after the gentle month of June there comes a rush of tropical savage powers, as relentless as an old Saracen invasion; and while the autumn is painting all sorts of affectionate remembrances on our hills and valleys, there comes a horde of invaders from about the pole, as ruthless as Huns, slaying and scalping all the creatures of summer like barbarians as they are. Our land is a perfect war-path of the contending north and south, without defenses of seas or mountains, entirely open to both forces.
It may not seem to add much to our present satisfaction to know that the conditions were not always thus; that there was a period when we were more favored than Europe now is. This period was not long ago, for our tulip-trees and sassafrases and other forest plants have but yesterday in the geological chronology held their own in the long night of the poles, and flourished greatly in the long day of their summer. On the shores of Greenland, within twelve degrees of the pole, we have buried forests which are mush like those now flourishing on the banks of the Mississippi below the junction of the Ohio ; the plants are so like those that now make up the vegetation of the southern half of the United States that these forests about the pole must have looked even more like those now found in Kentucky and Missouri than those of New England of to-day. This is but one thread in a strong line of evidence leading us to the conviction that the temperature of the north pole is far more rigorous now than in the immediate past; that at a time possibly not more remote than the age of the earliest human remains which have been found, the icewrapped lands of the north were bathed in a temperate and little-varied air, and so flowed over by perpetual streams of heat that even the long night of its winter could not bring as bitter cold as comes each year to the shores of the Hudson and the Upper Ohio. In place of contending with the fleets of the icebergs, the overtopping glaciers that tear the mountains down and chain up the seas, a voyager of that age could have sailed through sombre forests and verdant mountains, and in the long summer’s day found his unbroken way from the southern lands to the pole.
It is difficult to conceive how great must have been the difference in the climate of North America when its north winds came over endless forests in place of the vast fields of polar snow and ice; when even in the depth of winter the wind at its start could have been hut little below the freezing-point in its bitterest season. Fancy the shores of Hudson’s Bay and Great Slave Lake with a climate like the north of England; the whole of that great land north of the Laurentian Hills and the Saskatchewan — now dead for nine months of the year, and only faintly stirred by the breath of a brief summer which is hut a spasm of life — with seasons which could have hardly been more rigorous than those of Ireland of to-day ! The north of Europe and of Asia must have been equally favored in that happily balanced time. Siberia could not have had its ever-frozen soil, on which vegetation clings as lichen on a rock, for the condition that brought forests to Northern Greenland could not have left any part of the northern continents under the strong bondage of cold.
Looking, amid the sulphuric air of a New England house furnace, out over a New England frozen earth and sky swept by a ruthless north wind as merciless as flame, we feel it impossible to be quite content with the order that sent us to this frozen heritage, where the fossil sunshine of the old coal banks makes poor amends for the vanished warmth of an earlier day. Some solace may, perhaps, be had from a study of the condition that made the differences between that day and this what they are. We may thereby see that the changes have been a part of great physical laws; that they are, moreover, results of the great forces that bring about the successions in the animate and inanimate world, and not the accidents of an unruled chance. It is perhaps easier to bear the inconveniences that come from a plan than to endure the results of mere vagrant forces. The causes which are at work in shaping the climatal conditions of North America are in a way remote, so that the reader will have to exercise some patience in following even in outline the workings of the great agents that determine the distribution of heat and cold over the surface of the earth. But there the no great mysteries about the matter, for the earth, however complex in details of structure, has in its general order the same simplicity which we find in the heavens.
When naturalists first became convinced that the earth had once borne vegetation of a luxuriant, kind, semitropical in its character, within the arctic circle, and especially when it was found that at other times the glaciers had marched far to the south, there was a very common desire to look to mighty convulsions, to wandering comets that turned the earth away in her course, bringing poles where the equator was before, or to general outbreaks of internal fire that warmed the earth’s surface from thousands of volcanic craters, to explain the perplexing changes. Slowly but with no backward course there has come the conviction that the even-minded earth has always in the past gone on much as at present, the changes of each day falling in with those of yesterday and to-morrow, and so building up revolutions from alterations which are each slight in themselves. This way of looking at the world has become the most important of the properties of our modern science, and is the slow-grown faith of a thousand years. Following its teachings the student of nature endeavors to find in the things at work about him today the key to the changes of the past, only accepting the intervention of forces which he does not see constantly at work when these permanent causes fail to explain the mystery he is exploring.
A little observation, even with eye and. mind untrained, will show any one that the great machinery of the earth’s movements is all worked by the forces that come from the sun. Every stir in the air and sea, the sap in the trees and the blood in the animals, the falling rain and the rising mist, are made to move by the heat of the sun. These streams of power pour from the sun with nearly equal force in all directions; if they fell upon a plane surface the whole of it would receive equal shares, but on the earth, as is well known, its spherical form makes the distribution unequal: a square mile in the tropics receives far more than one in temperate latitudes; and within the arctic circles, where the surfaces look away from the sun and only see it askant, even for a part of the year, the amount of heat received is relatively small. If these volumes of power were like meteors, incapable of motion, they would heap up, and their effect would be practically ended where they fell; hut owing to the simple law that bodies generally expand in becoming heated, there is a great system of movements created which result in carrying away about one third of all the heat that falls within the tropics to be used in regions beyond their boundaries.1
The principal elements of the machinery used in the carriage of heat can be easily illustrated : in any common room in the winter time, where there is a heated stove in the centre and cold walls on the borders, a little smoke will show that there is a constant motion of the air. It rises to the ceiling with rapidity, then courses more slowly towards the sides of the room; cooled by its contacts there it falls down, courses along the floor, and returns again to the stove, and so pursues an endless circle. Or if we take a line of greenhouses with a flue along the centre of the floor, we can see what is for our purposes an even better analogy: the air runs from either wall to the central flue, thence to the roof, and back to the point of starting. This heated strip in the centre of the house fairly represents the equatorial warm belt, and the colder roof and sides the cold of the upper air and the polar regions. As every one knows, the winds can carry a considerable amount of heat or cold, and at first it would seem as if the air currents were the great carriers of heat on the earth’s surface; but though the winds are the most conspicuous agents of temperature distribution, it is not to them but to their products, the ocean currents, that we must look for the real work of carrying the solar force in the shape of heat from the over-favored tropics to the starving polar circles. We now know that the Gulf Stream is more potent in this work of warming than all the winds that sweep the earth. Left for their warmth to the winds alone, Europe would be uninhabitable by man, and a large part of North America would be the prey of lifeless cold. The tropics would have their temperature raised by several degrees, and the world would not be half as fit for life as it is at present. The way these rivers of the sea come to do their work may be easily understood by looking at any globe. The winds that come down to the equator from the poles, in the circuit, caused by the tropical heat, start from their polar bounds straight away to the equator. If the earth did not revolve, they would take the shortest road thereto and meet its line at right angles; but as each particle of air borne by the trade-wind goes away from the pole, it continually passes into a region having a greater movement than that it left, and in all its path to the equatorial line is always in this condition. The reader who has ever jumped upon a car in motion has felt his body try to lag behind, just as the particle of air lags behind at every step on its journey from the pole to the equator. He can represent this motion to his own mind by walking in his imagination from the centre of a great revolving disk to its periphery; it would, as is easily seen, be impossible to make this course a straight line, but it would come down on to the outer line, meeting it obliquely. It is this action that causes the trade-winds to come to the equator from the northeast and from the southeast rather than just along the meridian. This peculiarity may seem unimportant, but in fact it is one of the most important links in the great chain of connection which has made our earth a fit place for the development of life. Every one who has lived by the sea or any large lake knows how a strong wind can urge the surface water before it, and so can picture to himself how the trade-winds drive along the waters they blow over. If these streams came down in vertical lines from the poles they would meet each other so as to make dead water; but meeting obliquely, the result is to cause a current setting from east to west, and filling a broad space, some hundreds of miles across, beneath the equator. In the faroff day when the lands were small, this current may well have gone on in a steady way encircling the earth in its unbroken course; but from the time that the continents came up to bar its way it was no longer a girdle around the earth in which each particle swam continually in the same latitude, but it became a set of great whirlpools. If the reader has grasped the cause of the oblique movement of the air from the poles to the equator, he will find little difficulty in picturing to himself how the waters of this great equatorial current, moving towards the poles at the rate of three thousand miles a month, would behave when turned to the right and left by an equatorial barrier such as South America now interposes against their course. Their constant passage to regions having greater movement by virtue of the earth’s rotation led to the deflection of the tradewinds to the west as they came down to the equator; the reverse conditions affect the waters which are turned from the equator towards the poles. They are in this part of their course moving faster than the regions they are continually entering, and as a consequence they move more rapidly than the earth at each successive point at which they find themselves in their journey towards the poles, and so take paths leading to the northeast and to the southeast. The result is that practically no large part of the Atlantic equatorial stream escapes out of its basin, and each of the several oceans has its circulation kept to itself to a very great extent. When these vast whirlpool currents sweep away from the equator on their stately northward march, they take with them the temperature acquired in several months’ exposure to the heat of a tropical sun. Waters which perhaps a year before were at the temperature of melting ice start again for the pole at the temperature of from eighty to eightyfive degrees Fahrenheit, moving in the case of the Gulf Stream with the speed of nearly five miles an hour. The momentum of its impact against the shore which turned it from its course deepens the tide of warm water in the Gulf Stream to a thousand feet or more; but generally these streams of warm water become shallower at each stage of their progress to the north, until they are but a few hundred feet deep. Although the streams lose a good deal of their heat on their road towards the pole, they still retain enough at their crossing of the arctic circle to make them inconceivably powerful in their effect on the temperature of the high northern regions. Mr. James Croll, in his admirable studies on this subject, has clearly shown that tlio Gulf Stream, or the Atlantic whirlpool, carries nearly as much heat into the arctic circle as is cast into that region by the rays of the sun. As shown by that distinguished physicist, the difference of the mean temperature of the equator and poles, now only eighty degrees Fahrenheit, would be as much as two hundred degrees Fahrenheit were there no ocean streams; the equator would then have a temperature of one hundred and thirty-five degrees above, and the poles eighty degrees below zero, the equator being fifty-five degrees warmer than, at present, the poles eighty-three degrees colder. To annihilate the ocean currents would be to extinguish the organic life over a considerable district beneath the equator, and in all the territory beyond about forty-five degrees of latitude. The atmospheric contention which would arise from this wide difference between the poles and the equator would make the small part of the earth where organic life could find a foot-hold a perfect battle-ground of the elements; so that even in the strip of twenty or thirty degrees of width where the temperature conditions would seem to permit life, it is questionable whether any considerable development of this life would Ifr possible.
When we have once come to see that not only are the ocean currents powerful instruments of climatic correction, but that the very existence of organic life depends on their work, we are willing to look to the accidents of their course for the causes of great climatic changes. It is easily seen that if by geographical changes these ocean currents were excluded from their ancient tracts, or admitted to new fields, the world’s climate could be greatly bettered. If, for example, the relatively shallow water between Iceland and Scandinavia were to be changed to dry land, so as to shut out the Gulf Stream from the Arctic Ocean, there is not the smallest doubt that the climate of Europe would suffer somewhat the same change as has come of late to North America. In place of a rather mild northern sea, the waters which lave the arctic shores of that continent and Northern Asia would be visited by an even deeper cold than now makes desolate the shores of the northernmost lands of our own continent, while Southern and Western Europe would receive more heat and moisture than now fall to their lot. If the reader will take a globe or a good world-map in hand, he will see that our greater and more easily conceived climatal variations can occur through very simple geographical modifications, He will see that while the arctic circle is wide open to the Atlantic, the Pacific shores draw close their lines in the north, giving but a narrow and a shallow strait to unite the Arctic and the Pacific waters, He will see that the Pacific gulf stream, the Kara Sivo of the Japanese, possessing a current probably much greater in power than our Atlantic Gulf Stream, sweeps off the coast of Asia, and pours its waters into the great bay formed by the converging shores of Asia and America. Into this bay and along its shores the heat is discharged in great volume, but much of it finds its way back into tropical waters, unexpended. Perhaps not a hundredth part of it drifts through the difficult passage of Behring Strait into the polar sea. Yet even this slender thread of tropical water keeps a somewhat open sea in this section in the depth of the sunless winter. If the vast lowlying districts of Eastern Siberia and Western Alaska were sunk beneath the sea, even to the. depth of a few hundred feet, a trifling change in the great mechanism of the continents, it would open wide the road of this vast ocean stream straightway to the pole. The immediiate result of this change is in good part told us by the effects of the Atlantic Gulf Stream. The temperature of the internretic region is now lifted at least as much as thirty degrees by the action of the Gulf Stream. An equal effect would he exercised bv the Japanese current when the great gates were thrown wide open by the recurring geological changes. Thirty degrees is the least rise in the annual temperature of the region about the pole that would come from the action of this great Japanese current if it could make its way to the north as freely as does the Gulf Stream. Whenever the Alaskan gates to the pole are unbarred, the whole of the ice-cap of the circumpolar regions must at once melt away; all the plants of the northern continents, now kept in narrow bounds by the arctic cold, would begin their march towards the pole. The plants of the Ohio Valley would soon come again on to the Greenland shores. The Gulf Stream and the Pacific stream would bring not only their life-sustaining heat, but at the same time a great store of the seeds of the plants which would be candidates for the new places in the awakened lands. The Gulf Stream is every day taking a great quantity of seeds to the northern shores of Europe and America; trees stuck full of acorns and nuts by the busy woodpeckers and other seed-garnering animals are carried by the winter storms into the great rivers, and by them carried on into the Gulf of Mexico; in time they are borne, along with other seeds of plants, in great plenty, even as far as Iceland and Scandinavia, and to the shores of Greenland. Thus this current is through the ages continually making an offering of life to the frozen fields of the north. Wherever the changes are such as to make these germs welcome, they plant the life of the Mississippi borders in these far northern regions. Generally they fall on sterile soil, but the times come now and then when they meet climates suited to them, and take their place as makers of the forests. It may be to this that we owe the curious relations between the old forests of Europe and those of the Mississippi alley. With the coming of the Pacific stream to the arctic sea, we should have a climate in North America and Northern Asia exceedingly different from the present conditions in those, countries. The climate of Southern Ireland would probably be the nearest approach to that which these countries would then enjoy: there would be no winter of killing frosts, or summer of burning beats; the lifting of the arctic temperature by thirty degrees would lower the equatorial heat by about five degrees in the mean annual, so that the tropics would profit by the change as well as the northern regions. The rainfall of the arctic regions and of all Lhe high latitudes of the north would be considerably increased, for it depends largely on the mean temperature of any district. The rain-fall of northern North America and Northern Siberia is at the present time not Over twenty inches, while that of the intertropical belt is probably over ninety inches in a year. It is not too much to say that the life-sustaining power of the lands north of forty decrees of latitude would be doubled by the breaking down of the barrier which cuts off the Japanese current from the pole. When we compare the fitness of the world for the uses of man, we are convinced that this trifling change, would give us in effect a new earth, making the evils of equatorial heat far less than they are at present, and nearly doubling the area of the earth which is thoroughly habitable. To the student of nature the conditions of the moment are always made more bearable by the visions of the past and the hopes of the future. Beyond the most dismal accidents of to-day he can see the sunshine of the days that are gone or are to come, and feel that this clouding of the sun is but the fate of his individual moment of all time. If he is ground under the wheels of the vast machinery, it is much comfort to know that it is no car of Juggernaut dragged aimlessly by a mob of blind contending forces, but an engine, that lifts life from darkness to light. This comfort we can get if we study the history of the little bar of land which shuts the world out from its best conditions, plunging half of its surface into a hopeless war with the evils of heat and cold.
Geology has not yet gone so far as to find the perfect clew to the movements of the continents; but it has fixed some points with an approximation to certainty. Among these are some which will serve to show us how the successive admission and exclusion of the Pacific stream are connected with the general machinery of our earth. It is a well-established fact that during the last glacial period the whole northern region was more or less depressed beneath the sea. Near New York the depression did not exceed twenty or thirty feet, but it increased to seventy or more at Boston, and so steadily became more anti more important, until in Greenland the depression of the land certainly exceeded two thousand feet. It must not be supposed that during the time when the ice-cap lay about the pole this great depression which attended it was accompanied by an equal invasion of the sea over the surface of the lands; on the contrary, the ice made a new continental line, doubtless much further out to sea than the present shores of those regions. This could be proved by many things, but it is not necessary to discuss the evidence here. When the time came for the disappearance of this vast ice-sheet of the glacial time, the lands did not quickly recover from their sunken position, and so the sea ranged far over their surfaces, entering deeply into basins like Lake Champlain, for instance, and probably covering a large part of Labrador by its waves. As it is certain that the depression extended along the Pacific shores, the melting ice would have left the gates to the pole wide open to the warm streams of the tropical waters, which now are barred out by the land of the peninsulas of Asia and of America. There would have been a considerable interval of time, even in a geological sense, while the rapidly rising lands were as yet submerged, when the current of warm water would have moved steadily on to tho polar regions, so that the best climate the arctic circle ever saw must have followed immediately on the course of the retreating glacial streams. The time was probably short during which the Japanese, current had a complete access to the pole, but something of its effects probably held down to the period of human history. Whoever will read the evidences of an extensive occupation of Greenland seven centuries ago, or will compare the climatal conditions of Iceland now and a thousand years back, will be convinced that there has been some refrigerating agent at work throughout that region. There is none more likely than this gradual lifting of the Pacific harrier between the tropics and the pole, diminishing that current which now is but a slender thread. It is with no small satisfaction that we see this work ended, and that there is little chance that the polar forces are to be any more favored in their battles than they are at present. The entire closing of Behring Strait would be quite without further effect. The damage is done, at that point, and the Gulf Stream of the Atlantic flows over deep seas that are not likely to be limited by barriers to its steady way. Any other changes that these hidden forces of the deeper earth have in store for us must be beneficent in their results rather than hurtful.
Whoever looks upon man as a creature led up from the slavery of physical forces to something like a mastery over his conditions, and actual possession of his inheritance, will be inclined to ask whether there is hope for the bettering of the climate of the earth through man’s own exertions; whether it may not be possible to mend this matter of climate by the resources now or likely to be at the command of man. Is the amount of force that it would require to open an effective passage through the Alaskan peninsula so great that such a work is likely to be ever beyond the energies of our race? This is a difficult question to answer at the outset, but the enormous possibilities which it seems to open make it worth while to give it more than a passing consideration. Without troubling the reader with the reckoning, it may be said in general terms that the conditions are substantially these: an opening less than four hundred feet in depth, of which three hundred feet would be below the water-line, and one hundred miles wide cannot be expected to have a great effect on the arctic temperature. If through this opening there could be, a current made, moving at the rate of one half a mile per hour, the effect would be considerable, for it would discharge each day three hundred and twenty-six cubic miles of Pacific Ocean water into the arctic sea. If this water he assumed to have a heating power equal to that of the Gulf Stream, — it is doubtless somewhat greater, — then the effect would he somewhere about one twentieth of what is computed by Mr. Croll to he the influence of the Gulf Stream on the temperature of the interaretic region. A rough reckoning of the magnitude of this work makes it plain that to complete it would probably require more than all the power which has hitherto been given to the great, works of the world from the beginning of civilization. But it might be said that this is a bad measurement of the possibilities of human endeavor for the time to come. The resources of force available to man would not be seriously tasked in the extension of this channel over the area specified. Not counting the human force involved in the application of the power, there is little doubt that a part of the buried solar force stored in our coal seams would do all of the work necessary to open this gate to a good climate. If the world should ever make up its mind to use all of the life now wasted on things of even less immediate profit, on its armies and prisons, and give the means lavished thereon to the support of its millions of men in this work, there would doubtless be something more than it now finds to its credit at the end of each century. The reader will himself remark that perhaps not the least of the gains would be found in the chance of getting a place where all the refuse of mankind could be ground up to some good purpose. Who will dare to say that the prophetic soul that led our government to an otherwise inexplicable purchase in Alaska of a dominion of ice and darkness may not have foreseen for his restless countrymen the need of some such penal if not profitable undertaking? It would be a praiseworthy example and a source of much national relief if we could use our political and other tramps in this distant enterprise. The worthless life of the world could in no other way be so well built into its future hope. Even if we acknowledge that this is but an air-drawn scheme which can never be brought to ground, as, indeed, it seems to be,—if it should be shown that the work of making a way for the tropical waters is definitely beyond complete attainment, or that if done the forces of nature would block the channel up again, — it would not be complete proof that it was not worth while to undertake it. The time is perhaps near at hand when great deeds — deeds that may arouse the strength of generations—will have to he sought for the occupation of men. As the old Faust, his exuberance of youth spent with all youth’s spendthrift greed, comes at last to occupy his age in the great struggle to redeem the land from the sea, so man, whose history the poet meant, perhaps, to write in his poem, may well give his later years to a protest against the great wastes of our world, however imperfect the gain that his labor wins.
N. S. Shaler.
- This is the result of a general estimate based on temperatures of ocean streams, and cannot pretend to strict accuracy ; for such calculations data are yet wanting.↩