Historical Essays On Meteorology Definition

Rise of interdisciplinary research on climate

Spencer Weart1

Center for History of Physics, American Institute of Physics, College Park, MD 20740

1E-mail: moc.liamg@1traews.

Author contributions: S.W. wrote the paper.

Edited by Susan Solomon, Massachusetts Institute of Technology, Cambridge, MA, and approved June 11, 2012 (received for review May 24, 2011)

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Proc Natl Acad Sci U S A. 2013 Feb 26; 110(Suppl 1): 3657–3664.

Published online 2012 Jul 9. doi:  10.1073/pnas.1107482109

This article has been cited by other articles in PMC.

Abstract

Until the middle of the 20th century, the discipline of climatology was a stagnant field preoccupied with regional statistics. It had little to do with meteorology, which itself was predominantly a craft that paid scant attention to physical theory. The Second World War and Cold War promoted a rapid growth of meteorology, which some practitioners increasingly combined with physical science in hopes of understanding global climate dynamics. However, the dozen or so scientific disciplines that had something to say about climate were largely isolated from one another. In the 1960s and 1970s, worries about climate change helped to push the diverse fields into contact. Scientists interested in climate change kept their identification with different disciplines but developed ways to communicate across the boundaries (for example, in large international projects). Around the turn of the 21st century, the Intergovernmental Panel on Climate Change institutionalized an unprecedented process of exchanges; its reports relied especially on computer modeling, which became a center of fully integrated interdisciplinary cooperation.

Keywords: history, global warming

At the middle of the 20th century, the professional study of climate was a scientific backwater (this article is based on my essay “Climatology as a profession,” online at http://www.aip.org/history/climate/climogy.htm, which contains additional documentation and links to related material). People who called themselves climatologists were mostly drudges who compiled statistics about weather conditions in regions of interest—the average temperatures, extremes of rainfall, and so forth. This information could have offered a broad global perspective, but most climatologists set the planet as a whole aside and attended to regional problems. The people who needed climate information were farmers planning their crops and engineers designing dams or bridges. This focus did not mean that climatologists overlooked unusual weather, because it was precisely the decade-long drought or extraordinary flood that most worried the farmer or civil engineer. However, people saw such catastrophes as just part of the normal situation, transient excursions within an overall state that looked permanent on the timescale of human society. The job of the climatologist was to remove uncertainties with statistics, fixing the probable size of a 100-year flood and so forth.

Most historians of science have painted a different picture, focusing their writings on a handful of scientists in other fields who speculated about climate. Since ancient times, many people wondered about gradual changes on a regional scale; starting in the mid-19th century, the discoveries of the Ice Ages and other great perturbations in the geological record raised questions about climate change on a global scale. The natural philosophers John Tyndall and James Croll, the physical chemist Svante Arrhenius, the geologist T. C. Chamberlin, the engineer G. S. Callendar, and others published innovative works. Given the broad range of their explanations, we could call these interdisciplinary contributions, although the term is anachronistic for most of the 19th century, because firm disciplinary boundaries were not established. In retrospect, this invaluable work laid the foundations for the present study of climate change. Many other scientists published speculations that are now justly forgotten. However, none of this information was of much interest to people engaged in the professional discipline of climatology as it stood in the mid-20th century: their concern was the climate of the present.

Typical was the situation at the US Weather Bureau, where an advisory group reported in 1953 that climatology was “exclusively a data collection and tabulation business” (ref. 1, p. 24). Not much money or administrative attention was committed to such work, and the intellectual prospects were not enticing. To the extent that workers had research plans, their aim was just to find better ways to synthesize piles of data. A climatologist was somebody who described climate, mainly at ground level, where the crops and structures were found. These climatologists’ products were highly appreciated by their customers (such studies continue to this day). Additionally, their tedious, painstaking style of scientific work would turn out to be indispensable for studies of climate change. However, scientists regarded the field (as one practitioner complained) as “the dullest branch of meteorology” (H. Lamb quoted in ref. 2, p. 90). Another expert remarked that, in the study of climates, “the scientific principles involved are barely mentioned … Whether they are right or wrong does not seem to be of any moment, because they are never used to calculate anything” (ref. 3, p. 113).

When climatologists did try to go beyond statistics to explanations, they would explain the temperature and precipitation of a region in geographical terms: the sunlight at that particular latitude, the prevailing winds as modified by mountain ranges or ocean currents, and the like. The explanations were chiefly qualitative, with more hand-waving than equations. This information was close to the field called physical geography, a matter of classifying climate zones, with less interest in their causes than their consequences. If, in the first half of the 20th century, you looked in a university for a climatologist, you would probably find one in the geography department, not in a department of atmospheric science or geophysics (hardly any of the latter departments existed anyway). The geographical way of explaining regional climates was an essentially static exercise loosely based on elementary physics. The physics itself was useless for telling farmers what they needed to know. Attempts to make physical models of the simplest regular features of the planet’s atmosphere (for example, the trade winds) failed to produce any plausible explanation for how the winds circulated, let alone for variations in the circulation.

This failure was hardly surprising, because meteorologists did not have an accurate picture of what they were trying to explain. Few measurements existed of the winds, moisture, and temperature above ground level, and even ground-level data were scanty for vast portions of the globe. Most textbooks of climatology accordingly stuck to listing descriptions of the normal climate in each geographical zone compiled by authors who, as one scientist complained, “know little, and care less, about mathematics and physical science” (ref. 4, p. xii).

Climatology could hardly be scientific when meteorology itself was more art than science. If the general circulation of the atmosphere was a mystery, how could anyone calculate the course of storm systems? People had a variety of techniques for making crude weather forecasts. For example, whereas climatologists tried to predict a season by looking at the record of previous years, meteorologists similarly tried to predict the next day’s weather by comparing the current weather map with similar maps in an atlas of weather from the past. More often, a forecaster just looked at the current situation and drew on his experience with a combination of simple calculations, rules of thumb, and personal intuition.

This craft had little to do with scientific advances. As one expert remarked ruefully as late as 1957, the accuracy of 24-h weather forecasts had scarcely improved over the preceding 30 or 40 years. A canny amateur with no academic credentials could predict rain at least as successfully as a PhD meteorologist, and indeed, most of the professionals in the US Weather Bureau lacked a college degree. Aside from a handful of professors in a few pioneering universities (mostly in European geophysical institutes), meteorology was scarcely seen as a field of science at all, let alone a science firmly based on physics. Meteorology, one academic practitioner complained to another in 1950, “is still suffering from the trade-school blues” (5).

Since the 19th century, the forecasters and statistical climatologists had gone their separate ways. Neither group had much to do with the few professional academics, trained in physics, who, from time to time, attempted to analyze weather patterns with equations. Much of this work led nowhere and is now forgotten, but some laid the groundwork for later progress. Historians of science have naturally focused on the pioneering efforts of Vilhelm Bjerknes, L. F. Richardson, and others who developed the primitive equations that today form the foundation of scientific meteorology. Based on fundamental physics, this work was by definition interdisciplinary. Through the first half of the 20th century, however, these efforts had little impact on most of the people whose careers were in the discipline of meteorology.

Some hoped that climate, averaging over the daily vagaries of weather, might be more amenable to scientific investigation. They tried to understand changes on a timescale of decades or centuries and searched for regular climate cycles. Although a few looked for possible physical causes, it was more common for a climatologist to avoid such speculation and carry out grinding numerical studies in hopes of pinning down recurrences and, perhaps, predicting them. Analysis of large sets of data turned up various plausible cycles, correlated perhaps with variations in the number of sunspots. These correlations invariably turned out to be spurious, further lowering the poor reputation of climate change studies.

The stagnant condition of climatology mirrored a deep belief that climate itself was basically changeless. The careers of climatologists—their usefulness to society—rested on the conviction that statistics of the past could reliably describe future conditions. Their textbooks defined climate as the long-term average of weather over time, an intrinsically static concept. As one practitioner later complained, “authoritative works on the climates of various regions were written without allusion to the possibility of change, sometimes without mention of the period to which the quoted observations referred” (ref. 6, p. 299). In part, this approach reflected a simple absence of data. There were hardly any accurate records of daily temperatures, seasonal rainfall, and the like that went back more than half of a century or so, even for the most civilized regions. The records were scantier still for less-developed countries and mere fragments for the three-quarters of the world covered by water and ice. It seemed reasonable to assume that the existing records did reflect the average weather over at least the past few thousand years. After all, historical records back to ancient times showed much the same mixtures of frosts and rains and the crops that went with them in a given region.

In fact, history gave only the crudest indications. However, climatologists scarcely recognized their ignorance, relying explicitly or implicitly on old assumptions about the stability of nature. In other sciences like geology, experts found good reason to maintain that natural processes operated in a gradual and uniform fashion. Ordinary people also mostly believed that the natural world was self-regulating. If anything perturbed the atmosphere, natural forces would automatically compensate and restore a self-sustaining balance.

To be sure, at least one immense climate change was known and cried out for investigation—the Ice Ages. The stupendous advances and retreats of continental ice sheets were worth study, not because scientists thought it was relevant to modern civilization but because they hoped to snatch the brass ring of prestige by solving this notorious puzzle. Both professionals and amateurs advanced a variety of simple explanations. Most of these explanations amounted to no more than vague but plausible-sounding arguments presented in a few paragraphs. Each expert defended a personal theory, different from anyone else’s theory. The few scientists who attempted to write down equations and calculate actual numbers for the effects managed to prove little, except at best, that their ideas were not wildly astray by orders of magnitude.

The most acceptable explanations for the Ice Ages invoked geological upheavals to block ocean currents or raise a mountain range against prevailing winds. This theory was necessarily an interdisciplinary sort of theory. “It is impossible to separate the geological from the meteorological,” as one meteorologist remarked, “as the two are expressions of the results of the same forces” (N. Shaw in ref. 7, p. 258). However, the many pages that scientists wrote amounted only to elaborate hand-waving, unsatisfactory within either field. “I, for one,” said the respected climatologist Hubert H. Lamb, “must confess to having been bewildered and left quite pessimistic by some discussions of climatic variation” (ref. 6, p. 4). The very concept of theory became suspect in climate studies.

Theoretical models, whether of climate stability or Ice Age changes, were usually pursued as a minor sideline when they were not just ignored. To study the climate of the planet as a whole was far less useful and promising than to study climates region by region. There was little point in attempting global calculations when all of the premises were uncertain and key data were lacking. Given the enormous obstacles to reaching reliable results and the prevailing view that the global climate could not possibly change on a timescale that would matter except to far future generations, what ambitious scientist could want to devote years to the topic?

Meteorology and Geophysics (1940s to 1950s)

However, it is the nature of scientists never to cease trying to explain things. A few people worked to lift meteorology and climatology above the traditional statistical approach. H. E. Landsberg’s 1941 textbook Physical Climatology (8) and the 1944 Climatology textbook written by two other meteorologists (9) showed how familiar physical principles underlay the general features of global climate and provided a rallying point for those individuals who wanted to make the field truly scientific. Many saw such studies as an exercise in pure mathematics, deliberately remote from the fluctuations of actual weather. As one scientist recalled, in the 1940s, “academic meteorologists would sometimes go out of their way to disclaim any connection with forecasting—an activity of dubious scientific standing” (ref. 10, p. 277).

These textbooks came into use during the Second World War as meteorology professors trained thousands of meteorologists for the armed services. The training gave a big boost to the few universities where scientific meteorology already existed and led to additional expansion after the war. One example was the young geology student Reid Bryson, who was picked up by the Air Force and trained in weather forecasting. After the war, he got a PhD in meteorology and, finding himself unwelcome in the geography department at the University of Wisconsin, founded a one-man meteorology department there. In 1962, the National Science Foundation gave him funds to establish an important climate research center. Another example was Edward Lorenz, who had intended to be a mathematician but was diverted into meteorology during the war, when the Army Air Corps put him to work as a weather forecaster. Bryson and Lorenz were among “a new breed of young Turks” (or at least, that is how some of them saw themselves) who broke away from the tradition of climatology as a mere handmaiden to forecasting (ref. 11, p. 31; ref. 12, chap. 9).

Leading the movement was a group at the University of Chicago, where in 1942, Carl-Gustav Rossby had created a department of meteorology. Rossby was a Swede who had learned mathematical physics in Stockholm and spent 2 years at Vilhelm Bjerknes’s institute in Bergen, Norway. It was in Bergen that some of the key concepts of meteorology had been discovered, notably the weather front (first recognized during the first World War and named in accord with the concerns of the time) (13). With their improved understanding of weather patterns, Bjerknes’s group had come to think of climate not so much in geographical terms as a matter of latitudes and locations but in terms of typical weather systems. Additionally, if the pattern of weather systems in a region changed, did that not mean a change of climate? It was a new way of looking at things, a “dynamical climatology” as one of the Bergen group put it (14).

Rossby had come to the United States in 1925 to work in the Weather Bureau. Outstanding not only as a theorist but also as an entrepreneur and organizer, Rossby soon left the somnolent Bureau. In 1928, he created the nation’s first professional meteorology program at the Massachusetts Institute of Technology. After his move to Chicago, he did still more thanks to the ample wartime support for training military meteorologists. The department trained some 1,700 in 1-year courses. Rossby also helped coordinate new programs for graduate training of meteorologists at several other American universities (15, 16).

Support continued after the war, as the Cold War and the expanding economy—especially the rapid growth of civil aviation—raised the demand for meteorologists. The Chicago group flourished. It was the first group anywhere to systematically develop physical models of climate, sending out numerous students to carry on the approach elsewhere. Meteorology began to gain a reputation in the United States (as it already held in Europe) as a true scientific discipline, and climatology followed (17). As Rossby (18) remarked a few years later, basic questions of climate change, such as storage of heat in the oceans or the level of carbon dioxide gas in the atmosphere, “mean a completely new class of questions … In these investigations one is hardly interested in geographical distributions” (ref. 18, p. 16). Unlike the traditional regional climatologists, his group looked at the entire planet as a physical system.

War-trained young meteorologists also moved into the US Weather Bureau, where they found “the stuffiest outfit you’ve ever seen,” as a member of the research-oriented new generation later recalled: “deadly, deadly dull … a backward outfit” (19). An official report complained in 1953 that “the Bureau has displayed an arbitrary and sometimes negative attitude toward new developments in meteorology originating outside the Bureau” (ref. 1, p. 36). To be sure, inside the Bureau and still more outside it, meteorology was incorporating important new approaches such as weather radar, radiosondes to measure the upper atmosphere, and attention to the air mass analysis introduced by the Bergen school. Additionally, partly in response to the negative reports, conditions in the Bureau were improving rapidly. However, as for climatology at the Bureau, in 1957, another report described it as still nothing but a passive subsidiary to the main task of forecasting (20).

Stagnation was unacceptable to those individuals who recalled the invaluable contributions of meteorology to military operations during the war. The armed forces thought it no less important for their postwar global operations, even if the Cold War stayed cold. Additionally, if nuclear bombs exploded, meteorology would be especially vital for tracking the deadly fallout. The Navy and Air Force, in particular, continued to use many hundreds of meteorologists. Also, in keeping with the new respect for science that they had learned during the war, the armed forces supported many academic researchers whose studies might ultimately make forecasting better. As for climate, some of these researchers held out the fascinating prospect of changing it deliberately, perhaps as a weapon. The advances that meteorology was making to solid scientific understanding, combined with the lavish Cold War funding for all science, made for a rapid expansion and professionalization of climatology.

It helped that the entire area of geophysics, which included most of the fields relevant to climatology, was becoming stronger and better organized. Since early in the century, there had been a few institutions, notably university institutes in Germany, that embraced a wide enough range of studies to take the name geophysical. Already in 1919, an International Union of Geodesy and Geophysics was founded, with separate sections for the different fields such as terrestrial magnetism and oceanography (21). An American Geophysical Union was also created in 1919 as an affiliate of the US National Academy of Sciences (it would not become an independent corporation with an international membership until 1972). There followed a few other national societies and journals such as Zeitschrift für Geophysik. Several German universities created formal programs teaching Geophysik.

As a founder of the International Union remarked, it was not so much a union as a confederation (ref. 21, p. 286). The other early professional organizations likewise brought little cohesion. Through the 1920s and 1930s, very few institutions of any kind addressed geophysics in a broad sense. Most individuals who might be called geophysicists did their work within the confines of one or another single field, such as geology or meteorology. As for the scientific investigation of climate change, it appeared in a great variety of books and journals. I have investigated this work in a bibliography of over 2,000 items that I found significant for my study of the history of the science of climate change (22, 23). The only journals that stood out from the crowd in this period were Quarterly Journal and Memoirs of Britain’s Royal Meteorological Society, which together, published 18% of the pre-1940 journal articles that I referenced in my work. The runner-up was Journal of Geology, with 9%.

Beginning in the late 1940s, a more significant number of inclusive institutions appeared. Institutes of geophysics were created at American universities and under the Soviet Academy of Sciences along with funding organs like the Geophysics Research Directorate of the US Air Force. Another big boost came in 1957–1958, when the International Geophysical Year pulled together thousands of scientists from many nations. They interacted with one another in committees that planned and sometimes conducted interdisciplinary research projects involving a dozen different geophysics fields (24, 25). Most of these fields were relevant to climatology.

The annual meetings of the American Geophysical Union became a rendezvous for diverse fields, and for the same purpose, the Union began publishing Journal of Geophysical Research (expanded from the older and narrower Terrestrial Magnetism). However, for the scattered scientists engaged with climate change, the best meeting place was Tellus, a quarterly journal of geophysics that the Swedish Geophysical Society created in 1949. The journal’s importance is evident in the list of papers that found their way into the bibliography that I compiled in my research on climate change science. During the decades 1940–1960, Tellus published some 20% of these papers, more than any other journal. [The runners-up were the American interdisciplinary journal Science (15%), Journal of Meteorology (10%), and Quarterly Journal of the Royal Meteorological Society (5%). Journal of Geophysical Research accounted for only 3%, about equal to American Journal of Science and Journal of Geology.]

Judging from a sample, about two-thirds of these papers were written in the United States—a much higher fraction than in earlier years. This finding was partly because the rest of the civilized world spent the 1950s recovering from the war’s devastation. However, it was also because generous US government support for geophysical research, based on Second World War successes, did not falter, even when memories of the war faded. Global military and economic concerns of the Cold War put geophysics near the head of the line for research funds.

Fragmentation

In geophysics, as in all of the sciences of the 20th century, expansion raised a risk of additional fragmentation. Early in the century, so little had been known about anything in geophysics that the best scientists had broad knowledge of many aspects of the subject. For example, between the World Wars, Harald Sverdrup published research on the circulation of the atmosphere, the circulation of the oceans, glaciers, geomagnetism, and the tides, not to mention the ethnology of Siberian tribes. A few decades later, when knowledge had grown deeper and techniques had become more esoteric, hardly anyone could do significant work in more than one or two fields.

It was getting ever tougher for a scientist to become expert in a second field of knowledge. Few now attempted it, for the diversion of energy risked your career. “Entering a new field with a degree in another is not unlike Lewis and Clark walking into the camp of the [Native American] Mandans,” remarked J. A. Eddy, a solar physicist who took up climate studies in the 1970s (26). “You are not one of them … Your degree means nothing and your name is not recognized. You have to learn it all from scratch, earn their respect, and learn a lot on your own” (ref. 26, p. 4). Some of the most important discoveries came from people like Eddy, who did spend years in a foreign camp. Another example was Nick Shackleton, who after studying physics (essential for laboratory work measuring isotopes) and mathematics (necessary for analysis of time series) became part of a research group that analyzed pollen in a university botany department. The eventual result was landmark work on the timing and nature of the Ice Ages (27). Such combinations, however valuable, were uncommon.

The problem was particularly severe for climate studies. There had never been a community of people working on climate change. There were only individuals with one or other interest who might turn their attention to some aspect of the question, usually just for a year or so before returning to other topics. An astrophysicist studying changes in solar energy, a geochemist studying the movements of radioactive carbon, and a meteorologist studying the global circulation of winds had little knowledge and expertise in common. Even within each of these fields, specialization often separated people who might have had something to teach one another. They were unlikely to meet at a scientific conference, read the same journals, or even know of one another’s existence. Also, theorists did not interact regularly with people who worked out in the field. As one climate expert remarked, “lack of interest has all too often characterized the attitude of physical scientists to the masses of information produced by botanists examining pollen deposits and the data turned out by geologists, glaciologists, entomologists, and others. These types of literature have never been part of their regular diet” (ref. 28, p. 200).

The gaps between fields of expertise went along with divergence in matters as fundamental as the sorts of data that people acquired and used. The economic importance of weather forecasting meant that climatologists could draw on a century-old and worldwide network of weather stations. “Meteorologists use mainly standard observations made by technicians,” as an oceanographer recently remarked, “while the much smaller number of oceanographers usually make their own measurements from a small number of research ships,” often with instruments they had built for themselves (ref. 29, p. 623). The climatologist’s weather, constructed from a million numbers, was something entirely different from the oceanographer’s weather—a horizontal blast of sleet or a warm, relentless trade wind.

On top of social and perceptual gaps were technical divergences. As one expert remarked in 1961, the “fact that there are so many disciplines involved, as for instance meteorology, oceanography, geography, hydrology, geology and glaciology, plant ecology and vegetation history—to mention only some—has made it impossible to work … with common and well-established definitions and methods.” Scientists in different fields might use standards so different, he said, “that comparisons between the results have been hardly possible” (ref. 30, p. 467).

Recognizing the problem, meteorologists made significant efforts to recruit students from various fields of the physical sciences and initiate interdisciplinary work. Physics, chemistry, and mathematics played an increasing role in what was coming to be called the atmospheric sciences. A Journal of the Atmospheric Sciences had been founded already in 1944. As one example of how the process went still farther, in 1961, Chicago’s pioneering Department of Meteorology merged with the Department of Geology to form the Department of the Geophysical Sciences. However, up to this point, the discipline of meteorology itself had remained, to a large degree, divided. The climatologists who continued to gather empirical weather statistics and analyze them were intellectually remote from the academic theorists, who worked up mathematical models based on physical principles rather than observations. Both often looked down on practical forecasters, who in turn, had little faith in the professors’ abstractions. Among all three types of meteorologists, very few worked on questions of long-term climate change (ref. 12, pp. 1–2).

Confronting Climate Change (1960s to 1970s)

For studies of climate, fragmentation was becoming intolerable by the 1960s. More than half of a century of reliable temperature measurements were now in hand from around the world, and they showed that global temperatures had risen. Meanwhile, observations of the climbing level of carbon dioxide in the atmosphere brought a threat of serious future changes. Additionally, scholarly studies that extended the climate record far into the historical past were revealing large climate shifts. Most notable was evidence of a century or so of exceptional warmth in parts of medieval Europe and the North Atlantic. There had followed winters so harsh that early modern times could be called a Little Ice Age—at least in some regions. Records were spotty, at best, for the world outside the North Atlantic region, but for many places, evidence was emerging of anomalies, such as centuries of prolonged drought.

Painful experience drove the point home. One notorious case was the experience of firms that contracted to build dams in central Africa in the 1950s and consulted with climatologists about the largest floods that could be expected according to past statistics. The firms then began construction, only to suffer 50-year floods in each of the next 3 years (ref. 28, p.178). Such experiences pulled the props out from the traditional climatology. The laboriously compiled tables of past statistics were plainly not reliable guides to the future.

This unhappy fact was not easily accepted. As late as 1968, a textbook on Climatology and the World’s Climate said baldly, “The subject of climatic change is not given specific treatment in this book” (ref. 31, p. vii). Applied climatologists continued to base their projections of the future on their hoards of old statistics, simply for lack of anything better. Their work was, in fact, becoming increasingly useful. As the database grew and methods of analysis expanded, climatological studies brought a better understanding of how warm spells affected crops, what factors contributed to floods, and so forth (32). Nevertheless, during the 1960s, more and more scientists realized that climate predictions could not rely only on past observations but must use physical models and calculations. Traditionally, climate had been defined as the weather in a region averaged over a period. For example, in 1935, the International Meteorological Organization had adopted the years 1901–1930 as the climatic normal period. A moving 30-y span became accepted as a baseline for predictions of future climates. However, experts increasingly saw that this practice, however necessary to provide answers to pressing questions, could be misleading. The first three decades of the century turned out to have weather far from what was normal in later decades. Indeed, there might be no such thing as a set of decades that could define a normal climate. Climate was something that changed continually under the impact of physical forces.

The new thinking was displayed in full at a 1965 symposium held in Boulder, Colorado, on “Causes of Climate Change.” Although the meeting made little special impression at the time, in retrospect, it was a landmark. It deliberately brought together scientists from a fantastic variety of fields, experts in everything from volcanoes to sunspots. Presiding over the meeting was an oceanographer, Roger Revelle. Lectures and roundtable discussions were full of spirited debate as rival theories clashed, and Revelle needed all his exceptional leadership skills to keep the meeting on track. Convened mainly to discuss explanations of the Ice Ages, the conference featured a burst of new ideas about physical mechanisms that could bring surprisingly rapid climate shifts. In his formal summary of the discussions, the respected climatologist J. M. Mitchell reported that our “comparatively amicable interlude” of warmth might give way to another Ice Age sooner than had been supposed (33). This foreboding possibility required scientists to understand the causes of climate change, he said, and suggest how we might use technology to intervene (ref. 33, pp. iii–iv and 157).

This sort of thinking spread widely in the early 1970s. A spate of devastating droughts and other weather disasters showed that climate was grossly unreliable. With the alarming news came warnings that the near future might see still worse—whether drastic cooling or global warming—thanks to pollution of the atmosphere after the explosive growth of human population and industry. This view was an active and even aggressive view of climate in relation to humanity; it called for aggressive research. “The old descriptive climatology,” an authority remarked in 1975, “concerned mainly with statistics and verbal interpretation of them, is evolving into a new mathematical, or dynamic, climatology with predictive capability based on physical-mathematical processes rather than extrapolation of statistical measures” (ref. 34, p. 76).

This view required a new kind of research community, more closely linked to other fields and other kinds of science. This need was happening in all of the Earth sciences. The traditional observational geologist, out in the field with his high-laced engineer’s boots and rock hammer, had to make room for the investigator who saw rocks mainly in her laboratory, or perhaps only in pages of equations and calculations. Old-school geologists grumbled that the move to laboratory and theoretical geophysics took people away from a personal confrontation with nature in all its complexity and grandeur. The same filtering of experience was spreading in climate studies. Most scientists with something to contribute focused on technical problems peculiar to their own specialty. How do aerosols make clouds? How can you get a computer model to show the annual cycle of the seasons? What was the pattern of ancient glacial cycles? Those individuals who did attack broader questions head on seemed out of date. Some continued to propose simple hand-waving models with physical explanations for climate change (especially the Ice Ages). However, the different explanations were patently speculative, infected by special pleading and mostly incompatible with one another.

Scientists were more skeptical than ever of the traditional approach, in which each expert championed a favorite hypothesis about some particular cause for climate change—blaming every shift on variations in, say, dust from volcanoes or the Sun’s luminosity. It seemed likely that many factors contributed together. Meanwhile, the factors were interacting with one another. On top of these external influences, it seemed that some part of climate change was self-sustaining through feedbacks involving the atmosphere, ice sheets, and ocean circulation. “It is now generally accepted,” wrote one authority in 1969, “that most climatic changes … are to be attributed to a complex of causes” (ref. 35, p. 178).

The shortcomings of the old single-cause approach were especially visible to those individuals who tried to craft computer models of climate. A plausible model could not be constructed, let alone be checked against real-world data, without information about a great many different kinds of things. It became painfully clear that scientists in the various fields needed one another. Specialists began to interact more closely, drawing on one another’s findings or, equally valuable, challenging them. It was the stringent requirements of numerical computation more than anything else that forced the isolated communities of meteorology—empirical climatologists with their statistics, weather forecasters with their practical intuition, and academic scientists with their theories and equations—to communicate with one another in a common enterprise and, beyond communication, talk with other scientists of every stripe.

Means of Communication (1970s to 1980s)

The changes in meteorology and geophysics were typical of a movement in all of the sciences. For more than a century, many fields of science had narrowed their perspective to simplified cases, pursuing solutions as compact and elegant as Newton’s equations. Subjects as far afield as sociology were swayed by what some began to call physics envy. Only a few scientists insisted on looking instead at whole systems with all their complexities. This approach began to spread in various fields during the postwar years, and a growth spurt in the 1970s brought into prominence what was coming to be called holistic investigation. In biology, for example, different disciplines were talking to one another within the increasingly popular field of ecology. This discussion was timely, because scientists were increasingly concerned that biological communities were yet another feature that interacted intimately with the planet’s climate. Some specialists had long been aware of such interactions—most notably in oceanography, which was explicitly a union of physical oceanography and biological oceanography (if only because the researchers had to bunk alongside one another on their voyages). Now, all of geophysics was coming to be seen as part of a larger field, the Earth sciences.

In the fields relating to climate, as in other sciences, textbooks and review articles in ever-growing numbers summarized the recent findings of this or that specialty for the benefit of outsiders. More and more conferences were held with the aim of bringing together anywhere from a dozen to several hundred people from different but relevant fields. Most scientists, however, continued to call themselves oceanographers, computer scientists, or paleobotanists. Not many would identify themselves as primarily a climate change scientist. There was not even an accepted term to describe the nondiscipline. The typical landmarks for the creation of a discipline, such as departments at universities or a scientific society named for the subject, never came. The key elements for any profession—socialization and employment, which for scientists, usually meant training as a graduate student and employment as a professor—were largely carried out within traditional disciplines, like meteorology or oceanography, or more broadly defined fields, such as atmospheric sciences, in which climate change was included only as one among many elements.

In 1977, one landmark for the recognition and coalescence of a scientific discipline did come with the foundation of a dedicated journal, Climatic Change. However, unlike many new journals, this journal one did not, in fact, launch itself as the flagship of a new discipline. Its explicit policy was to publish papers that were mainly interdisciplinary, such as explorations of the consequences that global warming might have on ecosystems (36). The founding editor, S. H. Schneider, said later that he took up the task “to spite my institute director,” who had warned him that pursuing interdisciplinary work would hurt his career (37). Many scientists believed that solid research could be done only within the strict framework of a traditional discipline (ref. 37, pp. 75–76).

Most scientific papers on climate change itself continued to be published in journals dedicated to a particular established discipline, like the meteorologists’ Journal of the Atmospheric Sciences or the paleontologists’ Quaternary Research. However, key papers were also welcomed by the two great interdisciplinary scientific journals, Science and Nature, where specialists in every field would see them. In my bibliography for 1960–1980, Journal of the Atmospheric Sciences published 10% of all papers, and Quaternary Research published 7.5%. Science published 23% (if one includes a few news articles), and Nature published 10%. Tellus was down to 5%, equal to Journal of Geophysical Research, followed by Journal of Applied Meteorology at 4%. Quarterly Journal of the Royal Meteorological Society fell to 2.5%.

To a degree, climate science remained “a scientific backwater,” as one of its leading figures recalled decades later (38). “There is little question,” he claimed, “that the best science students traditionally went into physics, math and, more recently, computer science” (38). The study of climate was not a field where you could win a Nobel Prize or a lucrative patent. You were not likely to win great public fame or get great respect from scientists in fields where discoveries were more fundamental and more certain. In the mid 1970s, it would have been hard to find a hundred scientists with high ability and consistent dedication to solving the puzzles of climate change. Now, as before, many of the most important new findings on climate came from people whose main work lay in other fields, from air pollution to space science, and they took temporary detours from their main concerns.

Coordination and communication, nevertheless, improved as climate science was swept along by changes in the sciences as a whole. During the 1960s and 1970s, governments doubled and redoubled the budgets for every field of research, and geophysics got its share. Scientists concerned about climate change worked to get governmental and international agencies to organize their diverse research efforts through a central office or committee. It took decades of failures and false starts, but by the end of the 1970s, they managed to put together a number of ambitious climate programs. Although still lacking central coordination, each of the programs embraced a variety of fields. In particular, the United States established a National Oceanic and Atmospheric Administration that united oceanography with meteorology in a formal institutional sense, even if the usual bureaucratic barriers remained between divisions. Meanwhile, within the National Aeronautics and Space Administration, where designing satellites to observe the Earth from space gave a push to broader views, some worked deliberately to break down disciplinary boundaries and create an “Earth System Science” (39). Specialists in diverse fields with an interest in climate change found themselves meeting in the various committees and panels that reviewed and directed such programs. The process was officially capped in the mid-1980s by the creation of an International Geosphere–Biosphere Program, which coordinated work across so many disciplinary boundaries that some began to worry that there were now too many cooks in the kitchen.

The researchers in such programs no longer spoke of studying climates in the old sense of regional weather patterns but of the climate system of the whole planet, involving everything from minerals to microbes. This approach was fundamentally novel. Many things contributed to the approach but nothing so much as the computer studies that began producing plausible climate models during the 1970s. The models spoke eloquently of a global system in their basic concepts and showed it memorably in their computed maps of weather patterns (40).

For studying a system with features dispersed among many specialties, the solution was collaboration. This trend was strong in all of the sciences, because research problems spanned ever more complexities. Scientists with different types of expertise exchanged ideas and data or worked directly together for months if not years. Universities and other institutions, braced by ample funding, increasingly encouraged coalitions of research groups in a variety of fields. Specialists in the ionosphere, the Earth’s interior, ocean currents, and even biology found themselves sharing the same funding agencies, institutions, and perhaps, buildings. Sessions bringing together different specialists on one or another climate topic multiplied at meetings of the American Geophysical Union and similar organizations. It became increasingly common to hold entire workshops, meetings, or conferences devoted to a particular interdisciplinary topic.

Perhaps most important, every scientist read Science and Nature, which competed with one another for outstanding papers in all fields, including those papers connected with climate change. Both of these weekly journal/magazines also published expert reviews and commentaries, and Science published staff-written news articles, keeping everyone up to date on selected developments outside their own field. Of the papers in my bibliography for 1981–2000, Nature and Science tied with 25% each, including commentary and news articles, followed by Journal of Geophysical Research with 15% and Climatic Change with 7%. Tellus fell below 1%. The journal EOS: Transactions of the American Geophysical Union, publishing a mixture of short scientific reviews and news articles, came in at 4%. A variety of new review journals titled Advances in… and Reviews of… collectively contributed another 4%.

Climate science was now mainstream, with new developments covered thoroughly not only in Science and Nature but the popular press and in the 2000s, on the internet. The number of scientific papers in the field soared exponentially: as a fraction of all scientific publications, papers on climate change doubled every 5 years from the 1980s into the 2000s (41).

An especially powerful mechanism for cooperation was the formation of projects to address particular interdisciplinary topics. For example, specialists in computer modeling got together with paleontologists to test whether the models were robust enough to simulate a climate different from the present one. The Cooperative Holocene Mapping Project (COHMAP) was conceived in the late 1970s at the University of Wisconsin, where Reid Bryson had established a group that reconstructed past climates from fossil pollen and the like. COHMAP expanded through the 1980s, recruiting a variety of domestic and foreign collaborators. Some of them would devote most of their research careers to the project. Typical of such projects, all of the collaborators would convene from time to time in large assemblies. However, a few leaders would also gather in smaller meetings, “often hosted in home settings where conversations were unhurried and brainstorming was lively” (ref. 42, p. 107). Computer models confronted paleontological data in a continual dialogue, each discrepancy forcing one side, the other, or both to go back and do better. (Ultimately, the modelers produced a good simulation of the climate maps that the paleontologists developed for a warm period 8,000 y ago.)

COHMAP was only one example of many interdisciplinary projects driven by the demands of modelers, who sought empirical data on a scale to match the floods of numbers gushing from their computers. Large modeling groups in the United States, Great Britain, Germany, and elsewhere, pursuing empirical data to validate and correct their work, inspired costly projects in specialties ranging from satellite instrumentation to oceanography to forestry. Traditional climatology, with its vast archives of data, helped with its own major projects of analysis and synthesis.

Cooperation and Integration (1990s to 2000s)

Projects with multiple contributors were becoming common in all of the sciences, a consequence of the increasing specialization within each discipline plus increasing value in making connections between disciplines. Versatile scientists like Sverdrup—or as another example, Bert Bolin, who had mastered fields ranging from the mathematics of atmospheric circulation to the geochemistry of carbon dioxide—were a vanishing breed. Nearly all of the papers written before 1940 in my bibliography were published under a single name; only a few were the work of two authors. However, of papers written in the 1980s, less than one-half had one author. Many of the rest had more than two authors, and a paper listing, say, seven authors was no longer extraordinary. Large projects were represented by, for example, a 1989 paper with 20 authors from 13 different institutions in seven countries (43). The trend continued through the 1990s, and single author papers became increasingly rare.

None of this cooperation entirely solved the problem of fragmentation. Into the 21st century, there remained entire communities of experts (for example, water resource managers) who still treated climate as something that fluctuated only within the unchanging boundaries described by historical statistics (44). Additionally, the more the research enterprise grew, the more scientists would need to specialize. Moreover, the imperatives of administration would always maintain boundaries between academic disciplines and between the government agencies and organizations that supported them. However, by now, everyone was keenly aware of the dangers of fragmentation and strove for better coordination. For many kinds of research, climatologists, geochemists, meteorologists, botanists, and so forth added to their disciplinary category a second form of identification—an all-embracing name reflecting a new social orientation and holistic approach—environmental scientist. They were borrowing the luster of a word that had come to stand for a widely admired attitude, with concerns embracing the Earth as a whole (15, 24).

Meanwhile, some scientists altered even their primary professional identification. By the end of the century, the issue of climate change had become important and prestigious enough to stand on its own. Certain scientists who once might have called themselves, say, meteorologists or oceanographers were now designated climate scientists (38). There was still no specific professional organization or other institutional framework to support climate science as an independent discipline. However, this lack of independence did not matter much in the new order of holistic interdisciplinary work.

The internet helped bring people closer together. As soon as you heard about a paper in any journal on any subject, you could now find it online with ease, sometimes months before its formal publication. E-mail made it far easier to argue out ideas and exchange data, with as many people listening to the conversation as you liked. A few climate scientists went on to maintain blogs (notably realclimate.org), encouraging a still more universal interchange.

Still, the most important mechanism was the one that had sustained scientific communities for centuries—you went to meetings and talked with people. As one scientist described the system, “Most successful scientists develop networks of ‘trusted’ sources—people you know and get along with, but who are specialists in different areas … and who you can just call up and ask for the bottom line. They can point you directly to the key papers related to your question or give you the unofficial buzz about some new high profile paper” (45).

For climate scientists, the process of meetings and discussion went a long step farther when the world’s governments demanded a formal advisory procedure. The resulting Intergovernmental Panel on Climate Change (IPCC) was not really a single panel but a nexus of uncounted international workshops, exchanges of draft reports, and arguments among individuals all devoted to producing a single authoritative assessment roughly every 6 years. From the 1990s on, the process engaged every significant climate scientist in the world (and many of the insignificant ones). At the time of its 2007 assessment, the IPCC process had grown to include 157 authors plus some 600 reviewers in the geophysical sciences, giving a rough measure of the size of the scientific community on which the world’s policy-makers now depended for crucial advice (46).

In some fields, the IPCC process became the central locus for arguments and conclusions. This process went farthest among computer modelers, whose efforts increasingly focused on cooperative projects to produce results for the IPCC assessments. When climate modelers studied the details of each factor that went into their calculations and sought large sets of data to check the validity of their results, they had to interact with every specialty that had anything to say about climate change. Every group felt an intense pressure to come up with answers, which were demanded by the world’s governments and their own rising anxieties about the future. In countless grueling exchanges of ideas and data, the experts in each field hammered out agreements on precisely what they could or could not say with confidence about each scientific question. Their projections of future climate and the IPCC reports in general were, thus, the output of a great engine of interdisciplinary research. In the world of science, this social mechanism was altogether unprecedented in its size, scope, complexity, and efficiency—as well as its importance for future policy.

Footnotes

The author declares no conflict of interest.

This paper results from the Arthur M. Sackler Colloquium of the National Academy of Sciences, “Fostering Advances in Interdisciplinary Climate Science,” held March 31–April 2, 2011, at the AAAS Auditorium in Washington, DC. The complete program and audio files of most presentations are available on the NAS Web site at www.nasonline.org/climate-science.html.

This article is a PNAS Direct Submission.

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Articles from Proceedings of the National Academy of Sciences of the United States of America are provided here courtesy of National Academy of Sciences

This article is about the study of weather. For the science of measurement, see Metrology. For the study of meteors, see Meteoritics.

For other uses of the root word "meteor", see Meteor (disambiguation). For the work by Aristotle, see Meteorology (Aristotle).

Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw modest progress in the field after weather observation networks were formed across broad regions. Prior attempts at prediction of weather depended on historical data. It wasn't until after the elucidation of the laws of physics and, more particularly, the development of the computer, allowing for the automated solution of a great many equations that model the weather, in the latter half of the 20th century that significant breakthroughs in weather forecasting were achieved.

Meteorological phenomena are observable weather events that are explained by the science of meteorology. Meteorological phenomena are described and quantified by the variables of Earth's atmosphere: temperature, air pressure, water vapour, mass flow, and the variations and interactions of those variables, and how they change over time. Different spatial scales are used to describe and predict weather on local, regional, and global levels.

Meteorology, climatology, atmospheric physics, and atmospheric chemistry are sub-disciplines of the atmospheric sciences. Meteorology and hydrology compose the interdisciplinary field of hydrometeorology. The interactions between Earth's atmosphere and its oceans are part of a coupled ocean-atmosphere system. Meteorology has application in many diverse fields such as the military, energy production, transport, agriculture, and construction.

The word "meteorology" is from Greekμετέωροςmetéōros "lofty; high (in the sky)" (from μεταmeta "above" and ἀείρωaeiro "I lift up") and -λογία-logia "-(o)logy", i.e. "the study of things in the air".

History[edit]

Main article: Timeline of meteorology

The ability to predict rains and floods based on annual cycles was evidently used by humans at least from the time of agricultural settlement if not earlier. Early approaches to predicting weather were based on astrology and were practiced by priests. Cuneiform inscriptions on Babylonian tablets included associations between thunder and rain. The Chaldeans differentiated the 22° and 46° halos.[1]

Ancient IndianUpanishads contain mentions of clouds and seasons.[2] The Samaveda mentions sacrifices to be performed when certain phenomena were noticed.[1]Varāhamihira's classical work Brihatsamhita, written about 500 AD,[2] provides evidence of weather observation.

In 350 BC, Aristotle wrote Meteorology.[3] Aristotle is considered the founder of meteorology.[4] One of the most impressive achievements described in the Meteorology is the description of what is now known as the hydrologic cycle.[5]

The book De Mundo (composed before 250 BC or between 350 and 200 BC) noted[6]

If the flashing body is set on fire and rushes violently to the Earth it is called a thunderbolt; if it is only half of fire, but violent also and massive, it is called a meteor; if it is entirely free from fire, it is called a smoking bolt. They are all called 'swooping bolts' because they swoop down upon the Earth. Lightning is sometimes smoky, and is then called 'smoldering lightning"; sometimes it darts quickly along, and is then said to be vivid. At other times, it travels in crooked lines, and is called forked lightning. When it swoops down upon some object it is called 'swooping lightning'.

The Greek scientist Theophrastus compiled a book on weather forecasting, called the Book of Signs. The work of Theophrastus remained a dominant influence in the study of weather and in weather forecasting for nearly 2,000 years.[7] In 25 AD, Pomponius Mela, a geographer for the Roman Empire, formalized the climatic zone system.[8] According to Toufic Fahd, around the 9th century, Al-Dinawari wrote the Kitab al-Nabat (Book of Plants), in which he deals with the application of meteorology to agriculture during the Muslim Agricultural Revolution. He describes the meteorological character of the sky, the planets and constellations, the sun and moon, the lunar phases indicating seasons and rain, the anwa (heavenly bodies of rain), and atmospheric phenomena such as winds, thunder, lightning, snow, floods, valleys, rivers, lakes.[9][10][verification needed]

Early attempts at predicting weather were often related to prophesy and divining and sometimes based on astrological ideas. Admiral FitzRoy tried to separate scientific approaches from prophetic ones.[11]

Research of visual atmospheric phenomena[edit]

See also: Rainbow and Twilight

Ptolemy wrote on the atmospheric refraction of light in the context of astronomical observations.[12] In 1021, Alhazen showed that atmospheric refraction is also responsible for twilight; he estimated that twilight begins when the sun is 19 degrees below the horizon, and also used a geometric determination based on this to estimate the maximum possible height of the Earth's atmosphere as 52,000 passim (about 49 miles, or 79 km).[13]

St. Albert the Great was the first to propose that each drop of falling rain had the form of a small sphere, and that this form meant that the rainbow was produced by light interacting with each raindrop.[14]Roger Bacon was the first to calculate the angular size of the rainbow. He stated that a rainbow summit can not appear higher than 42 degrees above the horizon.[15] In the late 13th century and early 14th century, Kamāl al-Dīn al-Fārisī and Theodoric of Freiberg were the first to give the correct explanations for the primary rainbow phenomenon. Theoderic went further and also explained the secondary rainbow.[16] In 1716, Edmund Halley suggested that aurorae are caused by "magnetic effluvia" moving along the Earth's magnetic field lines.

Instruments and classification scales[edit]

See also: Beaufort Scale, Celsius, and Fahrenheit

In 1441, King Sejong's son, Prince Munjong, invented the first standardized rain gauge.[17] These were sent throughout the Joseon Dynasty of Korea as an official tool to assess land taxes based upon a farmer's potential harvest. In 1450, Leone Battista Alberti developed a swinging-plate anemometer, and was known as the first anemometer.[18] In 1607, Galileo Galilei constructed a thermoscope. In 1611, Johannes Kepler wrote the first scientific treatise on snow crystals: "Strena Seu de Nive Sexangula (A New Year's Gift of Hexagonal Snow)".[19] In 1643, Evangelista Torricelli invented the mercury barometer.[18] In 1662, Sir Christopher Wren invented the mechanical, self-emptying, tipping bucket rain gauge. In 1714, Gabriel Fahrenheit created a reliable scale for measuring temperature with a mercury-type thermometer.[20] In 1742, Anders Celsius, a Swedish astronomer, proposed the "centigrade" temperature scale, the predecessor of the current Celsius scale.[21] In 1783, the first hair hygrometer was demonstrated by Horace-Bénédict de Saussure. In 1802–1803, Luke Howard wrote On the Modification of Clouds, in which he assigns cloud typesLatin names.[22] In 1806, Francis Beaufort introduced his system for classifying wind speeds.[23] Near the end of the 19th century the first cloud atlases were published, including the International Cloud Atlas, which has remained in print ever since. The April 1960 launch of the first successful weather satellite, TIROS-1, marked the beginning of the age where weather information became available globally.

Atmospheric composition research[edit]

In 1648, Blaise Pascal rediscovered that atmospheric pressure decreases with height, and deduced that there is a vacuum above the atmosphere.[24] In 1738, Daniel Bernoulli published Hydrodynamics, initiating the Kinetic theory of gases and established the basic laws for the theory of gases.[25] In 1761, Joseph Black discovered that ice absorbs heat without changing its temperature when melting. In 1772, Black's student Daniel Rutherford discovered nitrogen, which he called phlogisticated air, and together they developed the phlogiston theory.[26] In 1777, Antoine Lavoisier discovered oxygen and developed an explanation for combustion.[27] In 1783, in Lavoisier's essay "Reflexions sur le phlogistique",[28] he deprecates the phlogiston theory and proposes a caloric theory.[29][30] In 1804, Sir John Leslie observed that a matte black surface radiates heat more effectively than a polished surface, suggesting the importance of black body radiation. In 1808, John Dalton defended caloric theory in A New System of Chemistry and described how it combines with matter, especially gases; he proposed that the heat capacity of gases varies inversely with atomic weight. In 1824, Sadi Carnot analyzed the efficiency of steam engines using caloric theory; he developed the notion of a reversible process and, in postulating that no such thing exists in nature, laid the foundation for the second law of thermodynamics.

Research into cyclones and air flow[edit]

Main articles: Coriolis effect and Prevailing winds

In 1494, Christopher Columbus experienced a tropical cyclone, which led to the first written European account of a hurricane.[31] In 1686, Edmund Halley presented a systematic study of the trade winds and monsoons and identified solar heating as the cause of atmospheric motions.[32] In 1735, an ideal explanation of global circulation through study of the trade winds was written by George Hadley.[33] In 1743, when Benjamin Franklin was prevented from seeing a lunar eclipse by a hurricane, he decided that cyclones move in a contrary manner to the winds at their periphery.[34] Understanding the kinematics of how exactly the rotation of the Earth affects airflow was partial at first. Gaspard-Gustave Coriolis published a paper in 1835 on the energy yield of machines with rotating parts, such as waterwheels.[35] In 1856, William Ferrel proposed the existence of a circulation cell in the mid-latitudes, and the air within deflected by the Coriolis force resulting in the prevailing westerly winds.[36] Late in the 19th century, the motion of air masses along isobars was understood to be the result of the large-scale interaction of the pressure gradient force and the deflecting force. By 1912, this deflecting force was named the Coriolis effect.[37] Just after World War I, a group of meteorologists in Norway led by Vilhelm Bjerknes developed the Norwegian cyclone model that explains the generation, intensification and ultimate decay (the life cycle) of mid-latitude cyclones, and introduced the idea of fronts, that is, sharply defined boundaries between air masses.[38] The group included Carl-Gustaf Rossby (who was the first to explain the large scale atmospheric flow in terms of fluid dynamics), Tor Bergeron (who first determined how rain forms) and Jacob Bjerknes.

Observation networks and weather forecasting[edit]

See also: History of surface weather analysis

In the late 16th century and first half of the 17th century a range of meteorological instruments were invented - the thermometer, barometer, hydrometer, as well as wind and rain gauges. In the 1650s natural philosophers started using these instruments to systematically record weather observations. Scientific academies established weather diaries and organised observational networks.[39] In 1654, Ferdinando II de Medici established the first weather observing network, that consisted of meteorological stations in Florence, Cutigliano, Vallombrosa, Bologna, Parma, Milan, Innsbruck, Osnabrück, Paris and Warsaw. The collected data were sent to Florence at regular time intervals.[40] In the 1660s Robert Hooke of the Royal Society of London sponsored networks of weather observers. Hippocrates' treatise Airs, Waters, and Places had linked weather to disease. Thus early meteorologists attempted to correlate weather patterns with epidemic outbreaks, and the climate with public health.[39]

During the Age of Enlightenment meteorology tried to rationalise traditional weather lore, including astrological meteorology. But there were also attempts to establish a theoretical understanding of weather phenomena. Edmond Halley and George Hadley tried to explain trade winds. They reasoned that the rising mass of heated equator air is replaced by an inflow of cooler air from high latitudes. A flow of warm air at high altitude from equator to poles in turn established an early picture of circulation. Frustration with the lack of discipline among weather observers, and the poor quality of the instruments, led the early modern nation states to organise large observation networks. Thus by the end of the 18th century meteorologists had access to large quantities of reliable weather date.[39] In 1832, an electromagnetic telegraph was created by Baron Schilling.[41] The arrival of the electrical telegraph in 1837 afforded, for the first time, a practical method for quickly gathering surface weather observations from a wide area.[42]

This data could be used to produce maps of the state of the atmosphere for a region near the Earth's surface and to study how these states evolved through time. To make frequent weather forecasts based on these data required a reliable network of observations, but it was not until 1849 that the Smithsonian Institution began to establish an observation network across the United States under the leadership of Joseph Henry.[43] Similar observation networks were established in Europe at this time. The Reverend William Clement Ley was key in understanding of cirrus clouds and early understandings of Jet Streams.[44]Charles Kenneth Mackinnon Douglas, known as 'CKM' Douglas read Ley's papers after his death and carried on the early study of weather systems.[45] Nineteenth century researchers in meteorology were drawn from military or medical backgrounds, rather than trained as dedicated scientists.[46] In 1854, the United Kingdom government appointed Robert FitzRoy to the new office of Meteorological Statist to the Board of Trade with the task of gathering weather observations at sea. FitzRoy's office became the United Kingdom Meteorological Office in 1854, the second oldest national meteorological service in the world (the Central Institution for Meteorology and Geodynamics (ZAMG) in Austria was founded in 1851 and is the oldest weather service in the world). The first daily weather forecasts made by FitzRoy's Office were published in The Times newspaper in 1860. The following year a system was introduced of hoisting storm warning cones at principal ports when a gale was expected.

Over the next 50 years many countries established national meteorological services. The India Meteorological Department (1875) was established to follow tropical cyclone and monsoon.[47] The Finnish Meteorological Central Office (1881) was formed from part of Magnetic Observatory of Helsinki University.[48] Japan's Tokyo Meteorological Observatory, the forerunner of the Japan Meteorological Agency, began constructing surface weather maps in 1883.[49] The United States Weather Bureau (1890) was established under the United States Department of Agriculture. The Australian Bureau of Meteorology (1906) was established by a Meteorology Act to unify existing state meteorological services.[50][51]

Numerical weather prediction[edit]

Main article: Numerical weather prediction

In 1904, Norwegian scientist Vilhelm Bjerknes first argued in his paper Weather Forecasting as a Problem in Mechanics and Physics that it should be possible to forecast weather from calculations based upon natural laws.[52][53]

It was not until later in the 20th century that advances in the understanding of atmospheric physics led to the foundation of modern numerical weather prediction. In 1922, Lewis Fry Richardson published "Weather Prediction By Numerical Process",[54] after finding notes and derivations he worked on as an ambulance driver in World War I. He described how small terms in the prognostic fluid dynamics equations that govern atmospheric flow could be neglected, and a numerical calculation scheme that could be devised to allow predictions. Richardson envisioned a large auditorium of thousands of people performing the calculations. However, the sheer number of calculations required was too large to complete without electronic computers, and the size of the grid and time steps used in the calculations led to unrealistic results. Though numerical analysis later found that this was due to numerical instability.

Starting in the 1950s, numerical forecasts with computers became feasible.[55] The first weather forecasts derived this way used barotropic (single-vertical-level) models, and could successfully predict the large-scale movement of midlatitude Rossby waves, that is, the pattern of atmospheric lows and highs.[56] In 1959, the UK Meteorological Office received its first computer, a Ferranti Mercury. [57]

In the 1960s, the chaotic nature of the atmosphere was first observed and mathematically described by Edward Lorenz, founding the field of chaos theory.[58] These advances have led to the current use of ensemble forecasting in most major forecasting centers, to take into account uncertainty arising from the chaotic nature of the atmosphere.[59] Mathematical models used to predict the long term weather of the Earth (climate models), have been developed that have a resolution today that are as coarse as the older weather prediction models. These climate models are used to investigate long-term climate shifts, such as what effects might be caused by human emission of greenhouse gases.

Meteorologists[edit]

Further information: Weather forecasting

Meteorologists are scientists who study meteorology.[60] The American Meteorological Society published and continually updates an authoritative electronic Meteorology Glossary.[61] Meteorologists work in government agencies, private consulting and research services, industrial enterprises, utilities, radio and television stations, and in education. In the United States, meteorologists held about 9,400 jobs in 2009.[62]

Meteorologists are best known by the public for weather forecasting. Some radio and television weather forecasters are professional meteorologists, while others are reporters (weather specialist, weatherman, etc.) with no formal meteorological training. The American Meteorological Society and National Weather Association issue "Seals of Approval" to weather broadcasters who meet certain requirements.

Equipment[edit]

Main article: Meteorological instrumentation

Each science has its own unique sets of laboratory equipment. In the atmosphere, there are many things or qualities of the atmosphere that can be measured. Rain, which can be observed, or seen anywhere and anytime was one of the first atmospheric qualities measured historically. Also, two other accurately measured qualities are wind and humidity. Neither of these can be seen but can be felt. The devices to measure these three sprang up in the mid-15th century and were respectively the rain gauge, the anemometer, and the hygrometer. Many attempts had been made prior to the 15th century to construct adequate equipment to measure the many atmospheric variables. Many were faulty in some way or were simply not reliable. Even Aristotle noted this in some of his work as the difficulty to measure the air.

Sets of surface measurements are important data to meteorologists. They give a snapshot of a variety of weather conditions at one single location and are usually at a weather station, a ship or a weather buoy. The measurements taken at a weather station can include any number of atmospheric observables. Usually, temperature, pressure, wind measurements, and humidity are the variables that are measured by a thermometer, barometer, anemometer, and hygrometer, respectively.[63] Professional stations may also include air quality sensors (carbon monoxide, carbon dioxide, methane, ozone, dust, and smoke), ceilometer (cloud ceiling), falling precipitation sensor, flood sensor, lightning sensor, microphone (explosions, sonic booms, thunder), pyranometer/pyrheliometer/spectroradiometer (IR/Vis/UV photodiodes), rain gauge/snow gauge, scintillation counter (background radiation, fallout, radon), seismometer (earthquakes and tremors), transmissometer (visibility), and a GPS clock for data logging. Upper air data are of crucial importance for weather forecasting. The most widely used technique is launches of radiosondes. Supplementing the radiosondes a network of aircraft collection is organized by the World Meteorological Organization.

Remote sensing, as used in meteorology, is the concept of collecting data from remote weather events and subsequently producing weather information. The common types of remote sensing are Radar, Lidar, and satellites (or photogrammetry). Each collects data about the atmosphere from a remote location and, usually, stores the data where the instrument is located. Radar and Lidar are not passive because both use EM radiation to illuminate a specific portion of the atmosphere.[64] Weather satellites along with more general-purpose Earth-observing satellites circling the earth at various altitudes have become an indispensable tool for studying a wide range of phenomena from forest fires to El Niño.

Spatial scales[edit]

The study of the atmosphere can be divided into distinct areas that depend on both time and spatial scales. At one extreme of this scale is climatology. In the timescales of hours to days, meteorology separates into micro-, meso-, and synoptic scale meteorology. Respectively, the geospatial size of each of these three scales relates directly with the appropriate timescale.

Other subclassifications are used to describe the unique, local, or broad effects within those subclasses.

Type of motionHorizontal scale (meter)
Molecular mean free path10−3
Minute turbulent eddies10−2 - 10−1
Small eddies10−1 - 1
Dust devils1 - 10
Gusts10 - 102
Tornadoes102
Thunderclouds103
Fronts, squall lines104 - 105
Hurricanes105
Synoptic Cyclones106
Planetary waves107
Atmospheric tides107
Mean zonal wind107

Microscale[edit]

Main article: Microscale meteorology

Microscale meteorology is the study of atmospheric phenomena on a scale of about 1 kilometre (0.62 mi) or less. Individual thunderstorms, clouds, and local turbulence caused by buildings and other obstacles (such as individual hills) are modeled on this scale.[66]

Mesoscale[edit]

Main article: Mesoscale meteorology

Mesoscale meteorology is the study of atmospheric phenomena that has horizontal scales ranging from 1 km to 1000 km and a vertical scale that starts at the Earth's surface and includes the atmospheric boundary layer, troposphere, tropopause, and the lower section of the stratosphere. Mesoscale timescales last from less than a day to weeks. The events typically of interest are thunderstorms, squall lines, fronts, precipitation bands in tropical and extratropical cyclones, and topographically generated weather systems such as mountain waves and sea and land breezes.[67]

Synoptic scale[edit]

Main article: Synoptic scale meteorology

Synoptic scale meteorology predicts atmospheric changes at scales up to 1000 km and 105 sec (28 days), in time and space. At the synoptic scale, the Coriolis acceleration acting on moving air masses (outside of the tropics) plays a dominant role in predictions. The phenomena typically described by synoptic meteorology include events such as extratropical cyclones, baroclinic troughs and ridges, frontal zones, and to some extent jet streams. All of these are typically given on weather maps for a specific time. The minimum horizontal scale of synoptic phenomena is limited to the spacing between surface observation stations.[68]

Global scale[edit]

Global scale meteorology is the study of weather patterns related to the transport of heat from the tropics to the poles. Very large scale oscillations are of importance at this scale. These oscillations have time periods typically on the order of months, such as the Madden–Julian oscillation, or years, such as the El Niño–Southern Oscillation and the Pacific decadal oscillation. Global scale meteorology pushes into the range of climatology. The traditional definition of climate is pushed into larger timescales and with the understanding of the longer time scale global oscillations, their effect on climate and weather disturbances can be included in the synoptic and mesoscale timescales predictions.

Numerical Weather Prediction is a main focus in understanding air–sea interaction, tropical meteorology, atmospheric predictability, and tropospheric/stratospheric processes.[69] The Naval Research Laboratory in Monterey, California, developed a global atmospheric model called Navy Operational Global Atmospheric Prediction System (NOGAPS). NOGAPS is run operationally at Fleet Numerical Meteorology and Oceanography Center for the United States Military. Many other global atmospheric models are run by national meteorological agencies.

Some meteorological principles[edit]

Boundary layer meteorology[edit]

Boundary layer meteorology is the study of processes in the air layer directly above Earth's surface, known as the atmospheric boundary layer (ABL). The effects of the surface – heating, cooling, and friction – cause turbulent mixing within the air layer. Significant movement of heat, matter, or momentum on time scales of less than a day are caused by turbulent motions.[70] Boundary layer meteorology includes the study of all types of surface–atmosphere boundary, including ocean, lake, urban land and non-urban land for the study of meteorology.

Dynamic meteorology[edit]

Dynamic meteorology generally focuses on the fluid dynamics of the atmosphere. The idea of air parcel is used to define the smallest element of the atmosphere, while ignoring the discrete molecular and chemical nature of the atmosphere. An air parcel is defined as a point in the fluid continuum of the atmosphere. The fundamental laws of fluid dynamics, thermodynamics, and motion are used to study the atmosphere. The physical quantities that characterize the state of the atmosphere are temperature, density, pressure, etc. These variables have unique values in the continuum.[71]

Applications[edit]

Weather forecasting[edit]

Main article: Weather forecasting

Weather forecasting is the application of science and technology to predict the state of the atmosphere at a future time and given location. Humans have attempted to predict the weather informally for millennia and formally since at least the 19th century.[72][73] Weather forecasts are made by collecting quantitative data about the current state of the atmosphere and using scientific understanding of atmospheric processes to project how the atmosphere will evolve.[74]

Once an all-human endeavor based mainly upon changes in barometric pressure, current weather conditions, and sky condition,[75][76]forecast models are now used to determine future conditions. Human input is still required to pick the best possible forecast model to base the forecast upon, which involves pattern recognition skills, teleconnections, knowledge of model performance, and knowledge of model biases. The chaotic nature of the atmosphere, the massive computational power required to solve the equations that describe the atmosphere, error involved in measuring the initial conditions, and an incomplete understanding of atmospheric processes mean that forecasts become less accurate as the difference in current time and the time for which the forecast is being made (the range of the forecast) increases. The use of ensembles and model consensus help narrow the error and pick the most likely outcome.[77][78][79]

There are a variety of end uses to weather forecasts. Weather warnings are important forecasts because they are used to protect life and property.[80] Forecasts based on temperature and precipitation are important to agriculture,[81][82][83][84] and therefore to commodity traders within stock markets. Temperature forecasts are used by utility companies to estimate demand over coming days.[85][86][87] On an everyday basis, people use weather forecasts to determine what to wear. Since outdoor activities are severely curtailed by heavy rain, snow, and wind chill, forecasts can be used to plan activities around these events, and to plan ahead and survive them.

Aviation meteorology[edit]

Aviation meteorology deals with the impact of weather on air traffic management. It is important for air crews to understand the implications of weather on their flight plan as well as their aircraft, as noted by the Aeronautical Information Manual:[88]

The effects of ice on aircraft are cumulative—thrust is reduced, drag increases, lift lessens, and weight increases. The results are an increase in stall speed and a deterioration of aircraft performance. In extreme cases, 2 to 3 inches of ice can form on the leading edge of the airfoil in less than 5 minutes. It takes but 1/2 inch of ice to reduce the lifting power of some aircraft by 50 percent and increases the frictional drag by an equal percentage.[89]

Agricultural meteorology[edit]

Meteorologists, soil scientists, agricultural hydrologists, and agronomists are persons concerned with studying the effects of weather and climate on plant distribution, crop yield, water-use efficiency, phenology of plant and animal development, and the energy balance of managed and natural ecosystems. Conversely, they are interested in the role of vegetation on climate and weather.[90]

Hydrometeorology[edit]

Hydrometeorology is the branch of meteorology that deals with the hydrologic cycle, the water budget, and the rainfall statistics of storms.[91] A hydrometeorologist prepares and issues forecasts of accumulating (quantitative) precipitation, heavy rain, heavy snow, and highlights areas with the potential for flash flooding. Typically the range of knowledge that is required overlaps with climatology, mesoscale and synoptic meteorology, and other geosciences.[92]

The multidisciplinary nature of the branch can result in technical challenges, since tools and solutions from each of the individual disciplines involved may behave slightly differently, be optimized for different hard- and software platforms and use different data formats. There are some initiatives - such as the DRIHM project[93] - that are trying to address this issue.[94]

Nuclear meteorology[edit]

Nuclear meteorology investigates the distribution of radioactiveaerosols and gases in the atmosphere.[95]

Maritime meteorology[edit]

Maritime meteorology deals with air and wave forecasts for ships operating at sea. Organizations such as the Ocean Prediction Center, Honolulu National Weather Service forecast office, United Kingdom Met Office, and JMA prepare high seas forecasts for the world's oceans.

Military meteorology[edit]

Main article: Military meteorology

Military meteorology is the research and application of meteorology for military purposes. In the United States, the United States Navy's Commander, Naval Meteorology and Oceanography Command oversees meteorological efforts for the Navy and Marine Corps while the United States Air Force's Air Force Weather Agency is responsible for the Air Force and Army.

Environmental meteorology[edit]

Environmental meteorology mainly analyzes industrial pollution dispersion physically and chemically based on meteorological parameters such as temperature, humidity, wind, and various weather conditions.

Renewable energy[edit]

Meteorology applications in renewable energy includes basic research, "exploration", and potential mapping of wind power and solar radiation for wind and solar energy.

See also[edit]

A hemispherical cup anemometer
General Circulation of the Earth's Atmosphere: The westerlies and trade winds are part of the Earth's atmospheric circulation
Cloud classification by altitude of occurrence
This "Hyetographic or Rain Map of Europe" was also published in 1848 as part of "The Physical Atlas"
A meteorologist at the console of the IBM 7090 in the Joint Numerical Weather Prediction Unit. c. 1965
NOAA: Synoptic scale weather analysis.
Annual mean sea surface temperatures.
Forecast of surface pressures five days into the future for the north Pacific, North America, and north Atlantic Ocean

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