Global Warming Science In The Age Of Napoleon: Joseph Fourier
If we think of Revolutionary and Napoleonic France, many things might come to mind: "Liberty, Equality, and Fraternity," Marie Antoinette and her unfortunate dietary recommendations for the poor; La Marseillaise, the Guillotine, the Terror; Napoleon's rise and coronation as Emperor; his great enemy, the British Royal Navy and its tragic hero, Admiral Horatio Nelson; great pitched battles fought with musket, cannon and saber, and of course the brutal retreat from Moscow, when 400,000 French and allied troops starved and froze to death in the Russian snows. The science of global warming, however, would not be likely to appear on most lists of such associations.
Yet there is a connection, in the person of Jean Baptiste Joseph Fourier. Born into a tailor's family of in 1768 in Auxerre, a hundred miles or so southeast of Paris, he was the twelfth of an eventual fifteen children. Orphaned at the age of ten, he was educated first by the music master at the cathedral school, and the great promise he showed there led to his admission, at twelve, to the local Royal Military School. It was there that the most constant passion of his life--the passion for mathematics--began to blossom.
At nineteen, Fourier undertook training to the priesthood, betraying an idealism that rivaled his ambitions to achieve immortality as a mathematician. In 1790, however, he left the abbey and returned to Auxerre, taking a teaching position at his old school. By 1793, his idealism had taken quite a different turn. Fourier joined the local Revolutionary committee, writing:
As the natural ideas of equality developed it was possible to conceive the sublime hope of establishing among us a free government exempt from kings and priests, and to free from this double yoke the long-usurped soil of Europe. I readily became enamoured of the cause, in my opinion the greatest and most beautiful which any nation has ever undertaken.
Revolutionary politics, however, were as dangerous as they were idealistic. The Terror, Robespierre's campaign of wholesale executions, seems to have prompted Fourier to attempt, unsuccessfully, to withdraw from the Committee. He was left no alternative but to attempt to ride the tiger of factional conflict. In this, "Citizen Fourier, a young man full of intelligence and zeal" was aided by an ability to "talk very well." Yet by the fall of 1795 he would be imprisoned twice, and would endure a real prospect of execution by guillotine. It would have been a tragedy more than personal, had factional politics removed a head later so productive of original and highly useful mathematics.
Fourier's "Napoleonic age."
Though politics produced hardship and terror for the young Fourier, it seems quite likely that they were also responsible for his 1794 nomination to the École Normale in Paris, where he was able to study under Laplace and Lagrange, two of Europe's leading scholars. This greatly advanced his scientific and mathematical researches, and in turn soon led to an appointment at the École Polytechnique, where he would gain renown as an outstanding lecturer. He remained there until 1798, when his next great adventure began, as he joined Napoleon's invasion of Egypt in the capacity of scientific advisor.
The invasion began well for the French, with quick victories leading to control of the Nile delta. But on August 1 the British fleet, commanded by Admiral Nelson, changed that. Though the larger French fleet was moored in a defensive line protected by reefs at Aboukir Bay, the British were able to find ways to attack their ships piecemeal. The spectacular explosion of the French flagship, the 120-gun L'Orient, provided the bloody affair a dramatic focus later painted for posterity by George Arnald. The Battle of the Nile was decisive: Nelson nearly annihilated the French fleet; British naval superiority was firmly established for the duration of the Napoleonic wars; and Napoleon--and with him, Jean Baptiste Joseph Fourier--was stranded in Africa.
The Destruction of l'Orient
Fourier In Charge
In Egypt Fourier's career took an administrative turn. While Napoleon took the Expeditionary Force off on a successful but ultimately pointless conquest of Syria, Fourier helped establish educational institutions, undertook archaeological explorations, and served as co-founder and secretary of the Cairo Institute. Returning to Paris in 1801, he briefly rejoined the faculty of the École Polytechnique. But his successes in Egypt must have caught Napoleon's eye. Bonaparte had returned in 1799 to engineer a coup d'état, resulting in his appointment as "First Consul." In 1801 he wrote:
. . . the Prefect of the Department of Isère having recently died, I would like to express my confidence in citizen Fourier by appointing him to this place.
Though for Fourier this must have seemed like an exile to the provinces, one did not say "no" to the Emperor-to-be, however much Napoleon might still use such Republican forms of address as "citizen." Moreover, Fourier's elevation to Baron and Chevalier of the Legion of Honor could hardly have seemed a disadvantage.
Grenoble, the capital of the Department of Isère, presented a very strong contrast to Egypt. Fourier had experienced the heat and aridity of Cairo, where rain is extremely unusual between April and October, and the temperature will often reach 35 C (95 F) or higher. In Grenoble, he would rarely feel temperatures much above 21 C (70 F), though on occasion 30 C (86 F) was possible. Better yet, each month in Grenoble could normally be expected to provide at least a few welcome days of rain.
Surrounded by mountains, Grenoble is often called "the capital of the Alps." It is not too surprising, then, that in between supervising such projects as draining marshes or building highways, writing his portions of the famous Description of Egypt (strategically edited by Napoleon before its publication in 1810), or creating the highly original 1807 paper known in English as On The Propagation Of Heat In Solid Bodies, Fourier at some point encountered the work of a Swiss Alpinist and scientist named Horace-Benedict de Saussure.
Saussure had died in Geneva in 1799, but Fourier recognized his ingenuity as a scientific observer: Saussure had been much concerned with all sorts of measurements concerning his beloved mountains, from temperature to humidity to the exact color of the Alpine sky. He had carried instruments to the highest peaks and had invented or improved many types of apparatus. Among these was the heliothermometer, which Fourier would later describe as:
. . . a vessel covered with one or more plates of glass, very transparent, and placed at some distance one above the other. The interior of the vessel is furnished with a thick covering of black cork, proper for receiving and preserving heat. The heated air is contained in all parts, both in the interior of the vessel and in the spaces between the plates. Thermometers placed in the vessel itself and in the intervals above, mark the degree of heat in each space.
Every theoretician needs experimentalists to provide solid data, and Fourier appreciated the "capital experiment" carried out by "the celebrated traveler, M. de Saussure."
Though the Grenoble years were busy ones, they offered, for a time, relative tranquillity. Yet the political troubles of the wider world would revisit Fourier soon enough. On June 23, 1812--coincidentally, just five days after the upstart government of the United States declared war on Great Britain--Napoleon commenced his invasion of Russia. By November, his Grande Armée had been smashed, and along with it, his reputation as an invincible general. By the end of October, 1813, Napoleon had fought and lost the battle of Leipzieg. At stake had been control of his German territories. Despite the military brilliance the Emperor displayed during the Six Days' Campaign in February of 1814, he was forced back upon Paris and abdicated the Imperial throne on April 6.
Exiled to the Italian island of Elba, the defeated Emperor should have passed through Grenoble en route from Paris; but Fourier, not wishing to see Bonaparte, sent word that this would be too dangerous for his old patron. The maneuver was successful, and Fourier presumably heaved a sigh of relief. It would be less than eleven months, however, until Napoleon would return to Paris from exile, marching once more through Isère. This time Fourier, who had spoken against Bonaparte in support of the restored Monarchy, considered it wiser to flee.
Perhaps Fourier's old gift, the ability to "talk very well," came into play once again, for despite these incidents, Napoleon briefly appointed Fourier Prefect of the Rhone, and later granted him a pension of 6,000 francs. Unfortunately for Fourier, it was to have been payable from July 1, 1815--a week after Napoleon's second and final abdication, following the battle of Waterloo--and Fourier never received any payments.
Fourier returned to Paris and was elected to the Académie des Sciences in 1817, becoming Secretary of that body in 1822--the year following Napoleon's death at St. Helena. Fourier's remaining years were marked by nothing worse than scientific controversies, and he died in 1830 of unspecified causes--possibly as the consequence of a fall.
What Fourier Said--And Why It Matters
So, what did Fourier contribute to the foundations of the science of global warming? His greatest intellectual contribution was undoubtedly mathematical. Cajori's A History of Mathematics (1913) stated that Fourier's Analytic Theory of Heat
. . .marks an epoch in the history of both pure and applied mathematics. It is the source of all modern methods in mathematical physics involving the integration of partial differential equations in problems where the boundary values are fixed.
In other words, Fourier was vitally important in the further development of calculus as a tool to study diverse problems in physics. Today the series bearing his name is important in fields as different as data analysis, biosciences, and acoustics, in addition to the problems in the propagation of heat to which he originally applied it.
While the Analytic Theory of 1822 is often considered to be his masterwork, a less mathematical summary can be found in his 1824 paper, General Remarks on the Temperature of the Terrestrial Globe and the Planetary Spaces. (The English translation used here is the 1837 version by Ebenezer Burgess.) In it, Fourier sets forth several ideas that would prove fruitful or prescient.
Firstly, by attempting to catalog and evaluate all factors affecting the Earth's temperature, he in effect provides an early example of a planetary energy budget. Like most first attempts, it was not entirely successful. There was too much as yet unknown--a fact that did not escape Fourier, although he could not anticipate precisely what all of those unknowns might eventually turn out to be.
Among the most dramatic would be the discovery of radioactive decay, which provides the Earth the "interior fire" mentioned by Fourier, and the scientific acceptance of a much older Earth than traditionally calculated. Either would unseat Fourier's analysis of the Earth's interior heat. We may infer something about Fourier's knowledge of the age of the Earth from these remarks:
. . . we conclude that, from the Greek school at Alexandria, till the present time, the temperature of the surface has not diminished, on this account, the three hundredth part of a degree. Here again we find that stability which the great phenomena of the universe every where present.
Secondly, and as discussed above, he provided a highly specific model for the application of sophisticated mathematics to the study of the propagation of heat, using precisely measured physical data, such as those provided by the temperature measurements of Saussure.
Thirdly, he recognized the crucial fact that "luminous heat"--solar radiation--acted differently than "non-luminous heat"--infrared radiation:
The heat of the sun, coming in the form of light, possesses the property of penetrating transparent solids or liquids, and loses this property entirely, when by communication with terrestrial bodies, it is turned into heat radiating without light.
Further, this difference, demonstrated in Saussure's heliothermometer, "explains the elevation of temperature caused by transparent bodies."
Fourthly, he describes experimental and theoretical agreement with reference to the concept of an energy equilibrium, and asserts its applicability at terrestrial scales. In the heliothermometer, he says,
. . . the temperature rises till the heat flowing in, shall exactly equal that which is dissipated. . . When this effect is examined by the calculus, results are obtained in exact accordance with those of observation. It is necessary to consider attentively this order of facts, and the results of the calculus when we would ascertain the influence of the atmosphere and waters upon the thermometrical state of our globe.
Fifthly, it is remarkable--though perhaps slightly cryptic--that Fourier provides an early opinion that human agency can materially affect global, or at least, regional temperature:
The establishment and progress of human society, and the action of natural powers, may, in extensive regions, produce remarkable changes in the state of the surface, the distribution of the waters, and the great movements of the air. Such effects, in the course of some centuries, must produce variation in the mean temperature for such places; for the analytical expressions contain coefficients which are related to the state of the surface, and have a great influence on the temperature.
Prophetic, too, was Fourier's insistence on the mutual dependence of theory and experiment:
Perhaps other properties of radiating heat will be discovered, or causes which modify the temperatures of the globe. But all the principal laws of the motion of heat are known. This theory, which rests upon immutable foundations, constitutes a new branch of mathematical science. It is composed, at present, of differential equations of the motion of heat in solids and liquids, and of the integrals of these first equations, and theorems relative to the equilibrium of radiating heat.
These theories will be hereafter much farther extended, and nothing will contribute more to bring them to perfection than numerous series of exact experiments; for mathematical analysis can deduce from general and simple phenomena, the expressions of the laws of nature; but the application of these laws to very complicated effects, requires a long course of accurate observations.
These observations, and the extensions of the theory to which Fourier contributed, are still continuing to this day. Although this work still continues, we can--by looking back to pioneers such as the able Baron--appreciate the degree to which our certainty regarding factors affecting "the thermometrical state of our globe" has grown. Perhaps we may even gain some helpful perspective on one of the great scientific and political controversies of our day, the question of anthropogenic climate change.
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