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This website examines the emergence and predominance of climate modelling as a culture of prediction. It shows that the interests in climate and the research directions to investigate climate have changed enormously during the twentieth century.

Authors

Matthias Heymann
Dania Achermann
Gabriel Henderson
Janet Martin-Nielsen

Editors

Greg A. Good
Matthias Heymann
Dania Achermann
Gabriel Henderson
Lance Burch

Web Design

Nathan Cromer

We are also grateful to

Danish Council for Independent Research

Material on this site is copyright ©2018 American Institute of Physics.

• Climate Science: A Culture of Predictions
• Introduction
• Brief Intro
• Trajectories
• Climate Projections
• Climatology or Climate Science
• Spider Charts
• Research Directions and Institutions
• Climatalogical Traditions
• Classical Climatology
• Modernizing Climatology
• Medical and Bioclimatology
• Historical Climatology
• Modern Climate Research
• Physics of the Atmosphere
• Climate Modeling
• Institutions of Climate Science
• Programs and Policies
• Climate Conferences
• Changes of Climate 1961
• SCEP 1970
• SMIC 1971
• World Climate Conference 1979
• Global Scale Research
• Regional Scale Research
• Climate Researchers
• Modernizers of Climatology
• Hermann Flohn
• Hubert Lamb
• Helmut Landsberg
• Hans W. Ahlmann
• Movers of Heuristic Climate Modeling
• Syukuro Manabe
• John Mason
• Movers of Predictive Climate Modeling
• William W. Kellogg
• Stephen H. Schneider
• James E. Hansen
• Bert Bolin

A web exhibition on history of climate modelling

This website examines the emergence and predominance of climate modelling as a culture of prediction. It shows that the interests in climate and the research directions to investigate climate have been diverse and changed enormously during the twentieth century.

From the 1970s on, climate modeling has played a major role in forging a scientific consensus about climatic change. One of its most important results have been climate projections. Based on simulations with complex Earth System Models such projections have become an iconic product of this thriving science. However, scientific consensus tends to hide the conflicts, complex negotiations and tangible interests behind the consensus itself. This exhibition attempts to show fundamental and contested changes in climate science by taking a look at a few crucial representatives of climate science and many relevant documents.

Changing research interest in climate

The history of climate research in the twentieth century experienced crucial changes. Its path has not been a linear one but paved with negotiations of the questions which types of knowledge are important, which epistemic standards are used to judge that knowledge, and which applications of that knowledge are regarded as useful and socially relevant.

This web exhibition shows the enormous breadth of diverse ideas, interests and research approaches in climate throughout the twentieth century. Climate research has included disciplines as diverse as geography and geology on one side and physics on the other side.

The priorities and focus, though, changed considerably, first, from a geography-oriented to a physics based approach, and second, from a heuristic to a predictive use of climate models. If we imagine the trajectories of all climate researchers depicted as a flow diagram, it resembles one, in which the flow of the majority of scientists changed sides (see figure below).

Focus in the first half of the 20th century still clearly was on the left side, geography-oriented climatology, whereas it moved in the second half of the century to the right side, to physics-oriented atmospheric and climate modeling.

Exemplary personalities and institutions in climate research

The exhibition deliberately focuses on few exemplary personalities and institutions to highlight the diversity of interests and values to which scientists subscribed and the tensions and conflicts to which diverging conceptions of climate research gave rise to.

This exhibition is based on work and results in the research project “Shaping Cultures of Prediction: Knowledge, Authority and the Construction of Climate Change” at Aarhus university in Denmark.

The figures below illustrate the diversity and the changes of interests in time. Each arrow roughly represents the scientific interest of individual researchers or institutions ranging between a "classical" geography based approach towards climate (left) and the physics and model-based approach (right) changing in time (downwards). From around the 1970s on, a further division in the use of climate models is represented: in either a heuristic or a predictive way.

Professional trajectories of climate researchers depicted as a flow diagram. Click on the graph to follow the introductory animation!

The range of interests in climate spans a large range, but the focus of interests (indicted by a large desity of arrows) would show a shift of focus in time towards the physics-based, modelling-oriented approach. The individual climate researchers featuring our work represent this diversity of positions and interests.

Change in interests over time of Hermann Flohn (shown in red).

Climate projections as message

Climate projections have become a major task of climate modeling. The interest in predicting future climate change is of relatively recent origin and emerged during the 1970s. Climate projections consist of enormously complex data collection, data processing and simulation efforts. As the vast amount of data resulting from simulations is difficult to understand, interpret and communicate, climate modelers have contributed two unique inventions: 1) the definition of a global mean temperature as an artificial parameter and 2) the depiction of global mean temperature change on a graph as a powerful graphical language (see also William W. Kellogg and James E. Hansen). Both inventions originated from the mid-1970s, but quickly became a part of the emerging scientific culture of climate prediction.

This is a selection of figures that show different projections of climate change into the future; a genealogy of climate projections:

Climate projections are important, because they provide relevant scientific information about climate change. They tell us that future climate will change. These projections are based on computer simulations with complex Earth-System Models. Most of them suggest that global mean temperature may rise several degrees in the decades to come. These projections have gained significant scientific and political authority and raised enormous attention.

Climate projections as a historical phenomenon

At the same time, climate projections raise further questions and invite to further analysis. While projections of climate change vary according to assumptions regarding future socio-economic developments, estimates about likely future warming remained more or less stable since about four decades.

This web-exhibition takes a different look at climate projections: it grasps them as a historical phenomenon. Climate projections have emerged at a certain point in time within specific historical contexts. They are based on specific scientific methods. They have been crafted by scientists of particular disciplines in specific ways, furnished with specific types of information. They respond to particular questions and interests...

Climatology in the nineteenth and early twentieth century was radically different from the climate science we know today. It was a geographical science applying a holistic, descriptive methodology focusing on the collection and analysis of comprehensive sets of observational data. Its major interests included the investigation of spatial variations of climates and local interactions between climate, life and human beings. Some scientists referred to this discipline as “classical climatology” in order to distinguish it from attempts of modernizing climatology around the mid-twentieth century or from the radically different characteristics of modern climate research in more recent decades.

The climate science we know today is, in contrast, a physical science, pursuing rather a physics of the atmosphere with a focus on quantitative mathematical understanding of atmospheric phenomena based on the laws of physics. It investigates causal relations and temporal variations of atmospheric phenomena, such as in the case of global climate change. Climate science, in addition, is not a coherent discipline, but comprises a large variety of research domains ranging from paleo-archeology (investigating climates of the distant past) to climate modeling (simulating projections of climate in the distant future).

These deep-reaching and fundamental differences should be captured by preserving a clear distinction between the terms “climatology” on the one side and “climate science” and “climate research” on the other side. These terms, however, tend to be confused and often used synonymously in many languages. In this exhibition we strictly keep this distinction and suggest the table below as a rough guideline. The relevance of this distinction becomes visible in labels such as the “World Climate Research Program,” which was not (and deliberately not called) a world climatology program. “Climate research” is a broad concept, of which climatology is still a (small) part that usually refers to the collection and analysis of observational data.

Climatology (mainly pre-1950)	Climate science (post-1950)
geographical science climate conceived as local and stable in time focus on descriptive approach data collection and analysis as main methodology	physical science climate conceived as global and changing in time focus on casual understanding mathematical modling as main methodology

Spider charts

The following spider chart emphasises this dynamics of the discipline and the changes of scientific interests in climate. It clearly shows the shift of focus towards a physical understanding of climate and the use of climate models as a heuristic or predictive tool. Click on the chart to find out more.

Graphic representation of interests in 1960s.

Graphic representation of interests in 1970s.

Definitions of the spider axes:

Climate modeling: This axis of the spider chart shows how strong a climate researcher was interested in developing and using climate models (for a short description of climate modelling click here).

Heuristic modeling: This axis of the spider chart shows how strongly a climate researcher was interested in heuristic modeling, which describes the use of climate models as a research tool to investigate and better understand the atmosphere (for a short description of heuristic modelling click here).

Predictive modeling: This axis of the spider chart shows how strongly a climate researcher was interested in predictive modeling, which describes the use of climate models as a predictive tool (for a short description of predictive modelling click here). The results of these calculations are often represented in charts like these.

Modernizing climatology: This axis of the spider chart shows how strong the interest was in "modernizing" climatology from the 1950s onwards (for a short description of attempts of modernizing climatology click here).

Classical climatology: This variable shows how strong the interest in the approach of the classical climatology was (for a short description of classical climatology click here).

Historical climatology: This axis visualizes the interest in studying climatic changes of the past (for a short description of historical climatology click here).

Regional/small scale: This label shows to what extent regional or small scales were the predominant geographical scales of interest in the investigation of climate (see also Regional/small scale research of climate).

Global/large scale: This label shows to what extent large or even global scales were the predominant geographical scales of interest in the investigation of climate (see also Global/large scale research of climate).

The term “classical climatology” describes a specific interest in climate from the mid-19th century to the early 20th century. Typically, scholars like Alexander von Humboldt or Julius von Hann are considered to have set the theoretical basis for this type of climate research (Heymann 2009). As Humboldt explained:

The term climate denotes in its most general sense all changes of the atmosphere which directly affect our organs.¹

And the Austrian Meteorologist Julius von Hann later specified in his Handbook of Climatology:

What we understand as climate is the totality of meteorological phenomena which describe the average state of the atmosphere over a specific location on earth.²

The focus of classical climatology was hence on collecting as many meteorological observation data as possible to investigate climatological problems. Statistical averages of meteorological data described the climates of different locations on earth. These data served the investigation of specific climatic phenomena (such as the Indian monsoon) and the construction of climate classifications. The climate was, according to the climatological paradigm, understood as a static (within human time scales) and a represented spatial concept. Climatology was a quantitative and descriptive discipline. Research programs in climatology included the exploration and description of climates on all regions on earth, an understanding of climatic phenomena based on local and regional geographical factors and the interactions between human activities and climate.

Well into the 1930s, climatology was conceived as a sub-discipline of geography. In Europe as well as the United States, climatologists were typically educated in geographical departments in order to develop maps of climate regimes. One prominent representative of classical climatology was Wladimir Köppen. He developed one of the first and most influential classification systems of terrestrial climates since 1884, which is still in use today. Countless new editions of climate classifications and climate maps were published during the late 19th and early 20th centuries. According to contemporaries, the colossal new edition of the “Handbook of Climatology,” edited by Köppen and his younger colleague Rudolf Geiger between 1930 and 1936, was deemed “the crowning achievement of the classical period of climatology."³

“Als Begrenzung des Gegenstands darf gelten, dass alles das an meteorologischem Wissen in das Buch gehört, was geographische Gesichtspunkte enthält, und nur so weit, als dieses der Fall ist. Es sind also nur solche Fakten zu behandeln, von deren geographischer Verbreitung man bereits eine Vorstellung hat […]. Auch die Klimate des freien Ozeans und die der höheren Luftschichten werden kürzer besprochen, sowohl weil das Material viel spärlicher ist, als auch weil dies nicht Räume ständigen Aufenthalts von Menschen sind.“⁴

This is a reproduction of the Wladimir Köppen’s climate charts from 1954.

References +

Classical climatology had been challenged and expanded since the early-twentieth century by a number of developments – first, the “discovery” of the third (vertical) dimension of the atmosphere, i.e. the investigation of higher layers of the atmosphere with the help of balloon ascents, which became increasingly important with the emergence of air traffic; second, the increasing physical understanding of atmospheric processes and its quantitative description by physical laws; third, increasing evidence of the globally connected atmospheric circulation, which proved the influence of large-scale processes on small scale atmospheric phenomena; fourth, evidence of climatic fluctuations within human time scales, which undermined the idea of a static climate.

Many climatologists contributed to expanding the traditional focus of classical climatology. Wladimir Köppen, for example, took an interest in the investigation of higher layers of the atmosphere since the late 19th century and coined the name “aerology” for this new sub-discipline. With the introduction of new technologies such as radiosondes and aeroplanes, the amount of observational data from the upper atmosphere grew exponentially. Such data helped to bring the whole atmosphere into focus and to identify the larger context of regional climatic phenomena and its relations. Similarly, the emergence of dynamic meteorology, for example the development of physical concepts and descriptions by Vilhelm Bjerknes and his Bergen School of meteorology, improved the dynamic understanding of weather and climate and its dependence on large scale circulation patterns.¹ In addition, a pronounced warming episode in the Nordic hemisphere, especially in the polar areas between about the 1920s and 1940s raised interest in climatic fluctuations within human timescales.

Around mid-century, leading climatologists advocated a modernization of climatology and urged to get beyond the purely descriptive approach of classical climatology. The traditional, purely empirical focus appeared “underdeveloped” and “unsystematic.”² Hubert Lamb in England, Helmut Landsberg in the USA and Hermann Flohn in Germany all attempted to modernize climatology in different ways and aimed for a more dynamic and theoretical perspective on the atmosphere. Landsberg demanded a “new climatology."³ He pursued what he called a “renaissance” of climatology by making it more useful for agriculture and industry. Lamb became a pioneer of historical climatology, the analysis of historical data about climatic fluctuations and its impacts on human societies. Flohn realized early a fragmentation of climatology into different directions: the traditional geography-oriented and a new physics-based climatology. He demanded the integration of the physical and geographical traditions into one coherent, more powerful discipline which he called “modern climatology."⁴

The climatic manifestations are intimately related to the general circulation of the atmosphere. Theories of the general circulation should be capable of explaining the climatic mean states.⁵

These new approaches were all conceived not as entirely new disciplines, but as extensions of the classical approach to align it with new knowledge of the atmosphere and make it more relevant for science and society. Climatologists such as Landsberg, Lamb and Flohn were very productive and successful in their individual efforts, but their larger ambitions failed. Physics-based mathematical modelling and numerical simulation of weather and climate soon prevailed. The geographical tradition and identity of climatology with its focus on observation and local difference and detail became increasingly marginalized. While Köppen’s climate classification persisted and his climate maps remained hanging on classroom walls for many decades, attention had moved on to other topics such as weather prediction and climate change and research fields such as climate modeling.

This is an illustration⁶ of a theory of the global circulation with the distribution of pressure on the surface of the earth (full line) and in higher altitudes (dashed line), and with the wind systems (arrow lines). This theory indicates the existence of the equatorial westerlies (dashed line) which were understood as being a cause of regional phenomena like the monsoon. The drawing visualises the “transition from surface to space” resulting in the modernisation efforts. It shows a dynamic, three-dimensional atmosphere and large-scale climate systems such as the westerlies, the trade wind and the Intertropical Convergence Zone.

An example of a high altitude weather map from the northern hemisphere by Richard Scherhag, showing the pressure changes in an altitude of 500 mb (5000 meter) and on the earth’s surface on the day of the 15th Feb. 1962. Such maps were a novel working tools in the 1930s because until then, only weather maps from the surface of the earth were provided (enclosure to: Scherhag, Richard 1962: Einführung in die Klimatologie, 2. Aufl. Braunschweig: Georg Westermann Verlag).

References +

The notion of “bioclimatology” or “medical climatology” entails the investigation of the influence of climate on living organism such as plants, animals and the human body. In the first half of the 20th century, when climatology generally expanded within meteorological services and at universities, bioclimatology was a growing field of research.¹ The goal was to investigate and understand the effect of different climates on the origin and distribution of diseases as well as their healing qualities.² Examples were problems such as the dispersal of pollens and its relation to the proliferation of species and ailments like hay fever. Not only meteorological services but also and spas and sanatoriums maintained bioclimatological research stations. In the early 20th century, the German chemist Carl Dorno (1865-1942) founded bioclimatology as a research discipline, because his daughter suffered from tuberculosis.³

Bioclimatology prospered particularly in Germany during the 1930s when, under Nazi rule, new research institutions in agricultural and bioclimatology were established.⁴ In this context, German climatologist Hermann Flohn started his professional career in a bioclimatological unit of the German Reichswetterdienst (Imperial Weather Service). Also Helmut Landsberg in his career had an interest in bioclimatology. As assistant of the German geophysicist Franz Linke (1878-1944) at the University of Frankfurt he served as an editor of the journal Bioklimatische Beiblätter, a supplement to the leading scientific journal Meteorologische Zeitschrift.⁵ Also later, after Landsberg had fled to the United States in 1934, he continued to publish in this bioclimatological supplement.⁶

As sub-disciplines of classical climatology, bioclimatology and medical climatology (along with further sub-disciplines such as urban climatology and agrometeorology) exemplify the climatological focus on the relation of climate and human culture and life. Interest in these disciplines peaked in the interwar period, whereas they lost attention significantly in the postwar era. Today, bioclimatological research includes the investigation of problems such as heat transfer in human and animal bodies, metabolic processes and the impact of climate on insect populations that transmit malaria, dengue fever and other diseases.⁷

Images of children being treated by heliotherapy in Swiss mountains. Source: Transactions of the American Climatological and Clinical Association, vol. 30. Philadelphia 1914.

References +

Until the first half of the 20th century, mainly geologists and a few biologists studied climates and climate changes of the distant past, what was often referred to as paleoclimatology. This research rested upon studying fossils or geomorphological features like moraines and landscape peculiarities such as erratic blocks from which climatic features and information on the ice ages could be derived.¹ Around 1900, paleoclimatological studies in geology thrived, before it entered years of stagnation.²

From the mid-20th century onwards, a rising number of scientists from other disciplines such as physics, chemistry and biology discovered paleoclimatology as a field of study. They investigated tree rings, ice cores, ocean and lake sediments, fossilized pollen, moraines, or bones and used them as proxies to retrieve information about the climate in the distant past. Paleoclimatology evolved into a highly interdisciplinary field.

At that time, a few climatologists began to take a stronger interest in the history of climates and climatic changes. The idea of the static character of climate (at least within human time scales) of classical climatology had still prevailed in the first half of the twentieth century. Around 1940, evidence from meteorological records and glaciological investigations had accumulated that the northern Hemisphere, particularly the polar areas, experienced a significant warming episode between about the 1920s and 1940s. This early twentieth-century warming undermined the idea of static climates and raised many questions: How common were significant climatic changes within only a few decades? Which were its causes? And what impacts did they have on human societies?

English climatologist Hubert H. Lamb pioneered the systematic investigation of historical weather observation series as far back as possible and became one of the founders of historical climatology. He considered the study of past weather data and the reconstruction of past climatic changes as a key to the understanding weather and climate and the atmospheric processes governing it:

The aim of meteorology in this quest for the facts of the past is to identify the true nature of the weather events and the atmospheric circulation processes at work.³

Lamb collected, studied and evaluated a vast amount of old data series along with other information on weather to reconstruct regional variations and fluctuations of temperature, precipitation and other climatic features as far back as the 18th century. Lamb’s interest, however, was not limited to the reconstruction of past climates. He also engaged in the investigation of the relation of fluctuating climates and human societies culture and life. Lamb, thus, maintained a core interest and tradition in classical climatology: a comprehensive perspective on climate and its relation to human life.

Lamb’s historical climatology seemed an outdated specialty to his superior, director of the Britisch Meteorological Office, John Mason, since the mid-1960s. Lamb, consequently, left the MetOffice and founded the Climatic Research Unit at the University of Eastern Anglia in Norwich (UK) in 1971.⁴ Its first aim was to “establish further knowledge of the history of climate (in the recent and distant past)” and, hence, continue and expand historical climatology.⁵

About two decades later, historical climatology proved to be a most important discipline – although for different reasons than Lamb’s. Data about the past climates turned out to be crucial for the testing and validation of global climate models. Lamb, ironically, had always remained very skeptical and reluctant about mathematical modeling and numerical simulation. He deplored that climate modeling gained priority, whereas the interest in the relations of climate and human conditions, which remained paramount to him, largely passed into oblivion. Today, climate science and climate models rest to a large degree on data established in historical climatology.

References +

In the nineteenth and early twentieth-century, climatology was largely conceived as a climatological science and taught in geographical programs. At the same time, however, theoretical meteorologists and physicists attempted to describe atmospheric processes based on physical laws. This domain in meteorology generally came to be called “dynamic meteorology”. Due to the complexity of the atmosphere, its quantitative understanding and mathematical description proved enormously difficult.

A significant step forward was the work of Norwegian physicist Vilhelm Bjerknes. Bjerknes developed a foundational framework for the quantitative description of atmospheric processes, hoping to make meteorology an exact science of the atmosphere. In 1904, he published a famous paper laying out the basis for a solution to the problem of weather prediction. Seven non-linear partial differential equations with the seven main physical parameters—temperature, pressure, density, humidity, and wind velocity in three directions—describing the hydro- and thermodynamic properties of the atmosphere and in principle the state of the atmosphere at any point in time and space.

"Image of Vilhelm Bjerknes" courtesy of the Bjerknes family is licensed under CC BY-SA 4.0

These so-called “primitive equations” proved a revolutionary step. First, they bore the promise of a comprehensive physical understanding of the atmosphere and represented a boost for dynamic meteorology. Second, they represented an important push in reversing priorities in meteorology and climatology in the long term: a priority of physical theory in describing the atmosphere. Meteorology and climatology had primarily built on a strong empirical tradition of data collection, which many atmospheric scientists later considered rather obscure and dull. Third, climatology was a discipline strongly interested in the interactions of human and climate: in questions related to climate and agriculture, climate and human health, but also the impact of human action on local climates.

Climate scientist Willliam Welch Kellogg on climatology¹:

... the subject of climatology changed completely around the late 1960s and 1970s. It went from a subject which was just usually taught in the geography department and had to do with statistics of the weather to a physically-based theory of climate ... So, from a relatively-obscure and rather dull subject, climatology became a very exciting field of new research involving some of the best brains in the business and some of the fastest computers.

Bjerknes' “primitive equations,” however, proved to be far from primitive, because they had no analytical solution. Only with the help of complex numerical approximation the equations could be solved. These numerical approximations required such an enormous amount of computations that they were effectively feasible only with the help of computers. After World War II, when computers became more available, so-called numerical modeling and simulation experienced a very quick rise. An example was the development of numerical weather prediction (NWP) and climate modeling.

The main six “primitive equations” by Vilhelm Bjerknes in modern notation.

References +

Further Reading +

Basics of Climate Modeling

Approximation in Climate Modeling

Heuristic Climate Modeling

Predictive Climate Modeling

Early Pioneers of Climate Modeling

British Meteorological Office

Climate Research Unit

Max Planck Institute for Meteorology

Global Atmospheric Research Program

National Academy of Science

US National Climate Program

From 2 to 7 October 1961 the Rome Symposium “Changes of Climate” was organized by the United Nations Educational, Scientific and Cultural Organization (UNESCO) and the World Meteorological Organization (WMO). 115 scientists from 36 countries participated and 45 papers were given in nine different working sessions. The conference highlighted a strong global interest in climatic changes that had recently emerged (find full conference proceedings here¹). Climate was mostly conceived as stable within human timescales in the tradition of classical climatology. In the mid-twentieth century, this understanding had eroded.

The conference took place as part of UNESCO’s Arid Zone Program. After its foundation in 1945, UNESCO took a strong interest in problems related to natural resources and the protection of nature. The dramatic dustbowl in the Western United States during the 1930s and similar events in Australia and Southern Africa, drought related famine in India, and the French obsession with the desiccating effects of deforestation in North and West Africa made climatic problems of arid zones an international focus of interest. UNESCO wanted to contribute to better knowledge about arid zones and solutions to its climatic challenges.

Buried machinery in South Dakota, United States, during the Dust Bowl in 1936.¹ (Source: United States Department of Agriculture).

In 1949 UNESCO established the Arid Zone Program, which in 1956 evolved into the Arid Lands Major Project, one of UNESCO’s three so-called “Major Projects.” In this program, UNESCO sought to facilitate a comprehensive interdisciplinary approach to the problem of deserts and to produce an international community of arid zone researchers. The program comprised the collection and dissemination of information on Arid Zone hydrology and related fields – such as climatology, biology, ecology, geology, soil science and engineering – and the organization of international conferences on topics such as hydrology and underground water (Ankara 1952), renewable energy sources (New Delhi 1954) and climatology and microclimatology (Canberra 1956).

The Symposium “Changes on Climate” represented a major synthesizing event. ”The problem of climatic fluctuations is one of extreme complexity and one which relates to many disciplines,” stated the foreword of the proceedings. “The purpose of the symposium was to bring together scientists who have contributed to the subject from such fields as meteorology, oceanography, geomorphology, geography, hydrology, botany, geology and even archaeology, so as to obtain a coherent and comprehensive picture of present knowledge, theories and implications of climatic change” (UNESCO 1961, Foreword). Accordingly, the contributions to this conference covered a wide range of research domains.

The conference represented a striking example of the comprehensive approach and holistic ambitions that had characterized climatology in the nineteenth and early twentieth century. This ambition was soon to be abandoned and replaced with a focus on physical approaches and numerical modeling and simulation. Two conferences on problems of climatic change organized just a decade later, the Study of Critical Environmental Problems in 1970 and the Study on Man’s Impact on Climate, clearly made manifest fundamental changes in the study of climate.

References +

Two very unusual conferences played a significant role in making the problem of climate change visible: the Study of Critical Environmental Problems (SCEP) in 1970 and the Study of Man’s Impact on the Climate (SMIC) in 1971. These conferences were major events that helped put problems of climate change in focus as a potentially significant environmental problem. They were initiated and organized by Carroll Louis Wilson, professor of management at the Massachusetts Institute of Technology (MIT) with an extraordinary personality. Wilson was a man of action and an outstanding organizer. Born in 1910, he had made a remarkable career as an administrator, businessman and university professor with excellent contacts and ties to the worlds of politics and business.

The SCEP for the first time highlighted potential changes of climate as an important environmental issue. It was a study conference lasting over the entire month of July, 1970. The approximately seventy participants came from universities, corporations, laboratories, and federal agencies in the United States. These participants embraced a panoply of disciplines: meteorology, atmospheric chemistry, oceanography, biology, ecology, physics, engineering, economics, the social sciences, and law. They discussed and synthesized the state of knowledge on four topics: 1) Climatic Effects, 2) Ecological Effects, 3) Monitoring and 4) Implications of Change. William Kellogg chaired the work group on Climatic Effects.

“A thorough understanding and reliable prediction of the influence of atmospheric pollutants on climate requires the mathematical simulation of atmosphere-ocean systems, including the pollutants.”¹

The study report emphasized that participants “acted as individuals, not as representatives of the agencies or organizations with which they were affiliated” (SCEP 1970, p. xiv). This autonomy helped to relieve the participants from consideration of official narratives and duties. Likewise, it allowed Carroll Wilson to shape the event and its major product, the SCEP report, according to his ambitions. The SCEP report was published very quickly in October 1970. It provided a comprehensive assessment of environmental problems. The report suggested the adoption of the principle of precaution and included calls for “corrective action.” A language of concern set the tone from the outset. The conference was concluded with a press conference. In addition, a comprehensive volume of SCEP background papers was published in spring 1971.²

“This is a collection that most meteorologists should read, especially those concerned with environmental problems.”³

References +

Should preventive or remedial action be necessary, it will almost certainly require effective cooperation among the nations of the world. SMIC was developed to assist in that process by providing an international scientific consensus on what we know and do not know and how to fill the gaps.¹

Immediately after the successful SCEP Conference in 1970, its organizer Carroll Wilson and his closest collaborators decided to hold a second, international conference of the same type with a sole focus on climate problems, the Study of Man’s Impact on Climate (SMIC). Wilson wanted to inspire international cooperation, reach an international consensus and address an international audience. SMIC took place for a period of three weeks from 28 June to 16 July 1971 at the conference center Wijk close to Stockholm, and was hosted by the Swedish Royal Academy of Sciences. The study conference was financed for the most part by the U.S. National Science Foundation. This time, 30 scientists from 14 countries participated, among them notable experts such as Belgian Jacques van Miegham, one of the principal architects of the International Geophysical Year, Mikhail Ivanovich Budyko, leading climatologist from the Soviet Union, Hermann Flohn, the leading climatologist in Germany, and Syokuro Manabe, one of the outstanding climate modeling pioneers in the United States.

The SMIC Report was published quickly and distributed widely. It served the scientific preparation of the 1972 UN Conference on the Human Environment in Stockholm, which was a milestone in the development of international environmental politics. The Report sought “to be definitive and authoritative in assessing the status of our present knowledge and in recommending the needed programs.” Over 300 pages it provided a comprehensive account of the state of knowledge about climate. It emphasized the urgency of responses to the risk of warming due to rising carbon dioxide concentrations. Its recommendations included the improvement of models (with detailed suggestions) and its “expanded use” for modeling experiments including the long-term prediction of climate change.² The SMIC meeting also revealed the contested character of much of the available climate knowledge. William Kellogg, one of its organizers, attempted to overcome an “apparent impasse in the assembled group between two opposing schools of thought: the climate 'coolers' and the climate 'warmers'.”³ This attempt failed, however.

In spite of disagreement whether a future warming or a future cooling was to be expected, the SCEP and SMIC reports exemplified an intellectual and ideological sea change from an era defined by military and geopolitical reasoning and logic in the early Cold War, to an era that was strongly influenced by environmental concern (Hare 1972). Climate was reinterpreted as a condition of the human environment that could change and demanded urgent attention. Furthermore, SCEP and SMIC were important social experiences for many of the participants and presaged changes in the culture of climate science.

It is now quite clear that climatology in particular, and physical geography in general, is going to be remade as a result of the innovations of the environmental movement ... The volumes under review here are essential documents in the rethinking process now under way.⁴

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On 12-23 February 1979 the World Climate Conference, A Conference of Experts on Climate and Mankind, took place in Geneva. The World Meteorological Organization (WMO) had taken increased interest in issues related to climate and climate change since the early 1970s and organized or sponsored a number of smaller meetings. On its 29th session the Executive Committee of the WMO decided to convene the World Climate Conference “(a) To review knowledge of climatic change and variability, due both to natural and anthropogenic causes; and (b) To assess possible future climatic changes and variability and their implications for human activities” (WMO 1979, p. vii; the full proceedings of the conference can be found here).¹

During the 1970s, concerns increased that the emission and rising concentration of carbon dioxide in the atmosphere may cause future climate change. The World Climate Conference represented a visible and politically influential response to these concerns. Robert M. White, Chairman of the Conference, provided in his opening keynote a broad overview on diverse problems related to climate ranging from pressures on agriculture and food production and deadly famines due to climatic fluctuations to the problem of global climate change. “If natural climate disasters had not been enough to motivate governments and the scientific community to action, the ominous possibilities for man-induced climatic changes would have triggered our presence here,” he concluded.²

In the first week of the World Climate Conference invited speakers presented “comprehensive and authoritative Overview Papers covering current knowledge of climate and the interactions between climate variability and change and human society” to an audience of 350 participants from all parts of the world. In the second week, invited experts assessed the present understanding of climate and its interactions with mankind and formulated general recommendations for international action. Major topics comprised climate data, applications of knowledge of climate, studies of the impact of climate on human activities and research on climate change and variability. These themes were the major components of the planned World Climate Research Program.

Another topic, however, was looming as a major issue of interest in many of the discussions. The Conference noted that there was an additional issue of special importance that pervades all the above-mentioned components: The problem of possible human influences on climate. As one major outcome, the conference published a “Declaration of the World Climate Conference.³” The declaration included “An Appeal to Nations” (see box) and emphasized the political challenge posed by carbon dioxide emissions and global climate change.

An Appeal to Nations scanned excerpt.

The “Declaration of the World Climate Conference” concluded: “It is possible that some effects on a regional and global scale may be detectable before the end of this century and become significant before the middle of the next century. This time scale is similar to that required to redirect, if necessary, the operation of many aspects of the world economy, including agriculture and the production of energy.”

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The observation of winds in the atmosphere raised the question of large-scale movements of air masses. In the 18th century, George Hadley, an English lawyer and amateur meteorologist, proposed a tropical atmospheric circulation with warm air rising near the equator, flowing poleward at 10–15 kilometers above the surface and descending in the subtropics.¹ This so-called "Hadley cell" could explain the trade winds. Interest in global circulation phenomena continued, but its systematic use to understand climatic phenomena only began in the 20th century.

Comparison of modern diagram² and recreation of original sketch of a Hadley cell.

Classical climatology took an opposite approach and attempted to understand climatic phenomena from a local perspective through local investigation (see also Regional scale research). When higher layers of the atmosphere became a matter of intensive investigation in the early 20th century, the climatological bottom-up approach from the local to the global became challenged. Large scale circulation patterns had a tremendous impact on climatic phenomena such as tropical rain belts, subtropical deserts and the monsoon. Climatologists such as Hermann Flohn, who made significant contributions to the understanding of the monsoon, attempted to modernize climatology and integrate local and large-scale approaches in climatology (see modernizing climatology).

Climate modeling took from its very beginning a larger scale approach, and could not deal adequately with small-scale phenomena. Climate models are based on differential equations, which in principle describe the state of the atmosphere at every point in time and space. The solution of these equations, however, required an averaging of the state of the atmosphere in large grid cells covering the surface of the earth. These grid cells usually have a side length of several hundred kilometers. Smaller scale phenomena such as cloud formation and precipitation, hence, cannot be modeled in a realistic manner.

It is ironic that we cannot represent the effects of the small-scale processes by making direct use of the well-known equations that govern them.³

With the dissemination of general circulation models (and a raising awareness of global environmental problems) from the 1970s onwards, the attention increasingly moved away from local and regional detail to the global character of climate. A typical example of this globalization is the construction of the artificial parameter “global mean temperature” by James Hansen and others as a lead parameter to assess and predict global climate change (see Climate Projections). Coarse grid resolution and simplifications in climate models reinforced a reductionist approach which blurred regional and local characteristics (such as local topography etc.).

Global surface temperature diagram depicting temperature anomalies.⁴

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Scales matter significantly in the investigation of climate. Classical climatology typically pursued a small scale, regional approach by studying climates in specific geographical locations. Its very methodological starting point is the local climate and its understanding, from which broader regional characteristics and patterns, like in Köppen’s climate maps (see classical climatology), were constructed. Classical climatology can be characterized by a bottom-up approach, which perceived detailed local information as the basis for generating knowledge about relations on the larger scale. This methodological approach also involved a comparably strong focus on local factors as an explanation for climatic features. In the early 20th century this approach was successfully pursued in climatological sub-disciplines such as microclimatology, bioclimatology and urban climatology.

The bottom-up research strategy in climatology was increasingly challenged since the early 20th century by new insights about large scale processes in the atmosphere such as a better understanding of the general circulation of the atmosphere and the importance of jet streams in high layers of the atmosphere, which have an influence on weather and climate at the surface of the earth. Many climatologists such as Hermann Flohn in Germany saw the importance of these dynamic, large scale processes and attempted to include them in their climatological reasoning (see modernizing climatology). Still, most climatologists kept to their observation-based, bottom-up methodology.

Some climatologists such as Hubert Lamb expressed reluctance to accept ambitious approaches in numerical modeling, which prioritized theoretical reasoning based on physical laws and approximations on large geographical scales (see also global scale research). In their eyes, these approaches neglected local detail and, hence, much of the complexity of climatic phenomena. After about 1950, these views increasingly represented a minority position, because the focus of research shifted towards computer-based numerical simulation and a more global view on climate.

Hermann Flohn was academically raised in a tradition he later called “classical climatology.” He studied geography, meteorology, geophysics and geology in Frankfurt a.M. and Innsbruck, and received his PhD in geomorphology in 1934. After his graduation, Hermann Flohn first specialized in medical climatology. He became an assistant at the Hygienisches Institut of the University of Marburg/Lahn. A few months later he became an intern at the Reichsamt für Wetterdienst in Berlin and soon officially took charge of its medical climatology section. At the age of 25 he was promoted head of the bioclimatological research station in Bad Elster, a small town at the Czech border. When World War II broke out in 1939 Flohn was called up to work at the weather service of the German Air Force, where he was mainly in charge of weather forecasting.

After the war, Flohn was detained and imprisoned for one year before he was classified as a “Mitläufer” (follower) of the NSDAP, sentenced to 1000 Reichsmark (or 30 days of work) and thereafter politically cleared. Right after, in 1946, Flohn joined the Central Bureau for Weather Service in the U.S. controlled zone in Bad Kissingen, an initially small successor of the once powerful Reichsamt für Wetterdienst. A few years later, from 1952 until 1961, he made a career in the newly founded Deutscher Wetterdienst (German Weather Service), in which he became head of the research department.

The monsoon, a regional climate phenomenon in the tropics and in East Asia became one of his main fields of interest. On the one hand, he investigated this wind as a “singularity” in the weather pattern; on the other hand, he increasingly put it also in the context of larger scales atmospheric circulations.

In summer 1949, Flohn accompanied his mentor Ludwig Weickmann for a research trip to the United States. It was the beginning of extensive travel activity by Flohn. At the Weather Service, Flohn gathered a group of young first class theoreticians around him including Friedrich (Fritz) Wippermann (1922-2005) and Karl Heinz Hinkelmann (1915-1986) and established a research group on numerical weather prediction. Flohn eventually left the Service in 1961 to become full professor and director of the newly established Institute of Meteorology at the University of Bonn.

With his advancing career, Flohn developed a particular interest in human induced climate change. He was often invited conferences and symposia on climate change in Europe and the United States as an expert. His expertise and engagement led him to also become an advisor, like his Swedish colleague Bert Bolin, when in 1974 the Max-Planck-Society decided to set up an Institute of Meteorology in Hamburg. Flohn was a strong supporter of the physical-mathematical approach towards climate as applied with computer models. But he also stuck to his conviction that climate is too complex to be understood, interpreted and predicted solely by such mathematical means.

In 1977, Hermann Flohn retired as professor in Bonn, but continued working and publishing in academia. At the same time, he strengthened his position as mediator between his scientific community and other disciplines as well as the public. He wrote for various journals and newspapers, where he warned of the danger of human-induced global warming.

“As a climatologist, I must confess, that to me this approach seems the most fascinating and rewarding one. It promises to be the base of a complete understanding of our present climate […].”

Flohn on numerical weather prediction 1965 (Flohn, Hermann 1965: Research Aspects of Long-Range Forecasting. In: WMO-IUGG symposium on research and development aspects of long-range forecasting, Boulder, Colorado. WMO Technical Note 66, page 4.)

Hubert Horace Lamb was a leading British climatologist and pioneer of historical climatology. He was born on 22 September 1913 in Bedford, UK, and died on 28 June 1997. Lamb studied geography during the 1930s at Trinity College, University of Cambridge, and shared a life-long interest in history. In 1936 he joined the UK’s national weather service, the British Meteorological Office (shortly often referred to as Met Office). During the war years he served at the Irish Meteorological Service on aviation forecasts.

After World War II, he joined the Met Office's climatology section in Harrow, in northwest London. In the basement of the Harrow office Lamb discovered archives of past weather observations in the world, which was perhaps the richest collection of its kind developed as a byproduct of Britain’s colonial and exploratory history. With this discovery Lamb grasped the opportunity to pursue his interests in history and explore the climates of the past. He was one of the first to propose that climate could change within human experience and opposed the long-held orthodox view in classical climatology that climate could be treated as constant within timescales of decades.

His life-long research focus became the question about the relationships between climate and human history. Lamb constructed monthly barometric pressure maps as far back in time and covering as much of the world as possible. He became fascinated by the timing, extent and causes of past climatic variations and explored its social and cultural impacts. Based on the investigation of past climatic data, Lamb developed theories about the Medieval Warm Period and the Little Ice Age. Lamb expanded his research program in historical climatology systematically. The reconstruction of past climates drew from results of many disciplines such as archaeology, history, paleobotany, glaciology, geology, geophysics, oceanography and others. Lamb was convinced that only such multi-disciplinary approach provided comprehensive knowledge about climatic changes.

The Met Office generously supported Lamb’s research efforts for more than a decade. When in 1965 British cloud physicist John Mason was appointed director of the Met Office, however, Lamb’s situation changed drastically. Mason transformed the culture at the Met Office deeply and focused operations systematically on numerical simulation, whereas other fields of activity were strongly reduced or closed. Lamb lost his scientific staff and financial support for his research in historical climatology.

Lamb strongly disagreed with Mason’s research strategy and criticized numerical simulation approaches. Raised in the empirical tradition of classical climatology, he put great emphasis on the collection of empirical information and was convinced that understanding the climate and its changes required a detailed analysis of past climates. In a paper in the journal Nature in 1969 he argued: “The computer models of atmospheric behavior and other climatic areas may be unrealistic, and may therefore proceed too far and too fast on faulty basic assumptions. Such developments should be preceded by acquiring fuller and firmer factual knowledge.”¹

Numerical modelling, Lamb believed, reduced climate to a purely physical phenomenon with no associations to culture, geography, or human history – a reductionist approach that he found misguided at best and harmful at worst. A numerical, interpretation of climate, Lamb worried, negated other ways of knowing – ways which might prove crucial to a full understanding of climate.

Lamb’s ongoing conflict with Mason eventually convinced him to leave the Meteorological Office in 1971 after 36 years of service. Solomon Zuckerman, chief science advisor to the British government commented aptly that “Lamb does not fit in very well to the Meteorological Office, which is predominantly manned by people trained in the physical sciences.”² In 1972, Lamb founded the Climatic Research Unit (CRU) at the School of Environmental Sciences, University of East Anglia in Norwich, with the help of Sir Graham Sutton, former director of the Meteorological Office and a supporter of Lamb’s research and Lord Solly Zuckerman, who served as an adviser to the University.

As director of CRU until his retirement in 1978, Lamb expanded his research program in historical climatology, even though CRU repeatedly suffered from funding problems. Initial sponsors included British Petroleum, the Nuffield Foundation and Royal Dutch Shell. Later the Rockefeller Foundation, the U.S. Department of Energy and the British Wolfson Foundation provided important contributions. Notably, the British Natural Environment Research Council refused to fund the Climatic Research Unit. Lamb complained repeatedly that throughout the 1970s numerical approaches received vastly more funding than historical climatology.

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Helmut Erich Landsberg was born in Frankfurt, Germany. As a doctoral student at Frankfurt University during the late 1920s, he was heavily involved in efforts to apply geophysical knowledge to practical problems in agriculture and aviation. After completing his doctorate in 1930 in seismology, he continued to work under the auspices of one of his advisers, meteorologist Franz Linke, who would eventually help him immigrate to the United States in 1934 after the rise of the Nazi Party. His first academic position was located at Pennsylvania State College, where he applied his seismological knowledge to practical problems. During these early years in the United States, he was not heavily involved in climatological research. But with America’s entry into World War II in 1941, he sought to put climatology to work. He worked with the Army Air Force to make bombing more precise, and his superiors praised his efforts as being uniquely integral to the success of bombing campaigns on the Pacific Front.

During the war, Landsberg began to think critically about the place of climatology in American society. Given that climatology had always been subservient to its mother discipline of meteorology, he worried that climatology would fall into old patterns once hostilities ended. Imagining a so-called “climatological renaissance” as early as 1943, he began to argue that the study of climate would be integral to maintaining a stable society in peacetime. This ambition persisted for the remainder of the war, and afterward he used his expertise and connections to implement his vision. One would be hard-pressed to argue that climatology was seen generally as a useful discipline, and even Landsberg himself acknowledged often that attaining his goals would mean overcoming many intellectual and institutional barriers. Nonetheless, during the 1950s and 1960s, his efforts contributed to a growing awareness among America’s elites that climatology would be a useful discipline.

While Landsberg was clearly invested in maximizing the usefulness of climatology to human society, he wore multiple disciplinary hats – bioclimatologist, urban climatologist, microclimatologist. Omnipresent within the global climatological community, he gained recognition for being one of the most inspiring climatologists of the 20th century. While serving as director of the U.S. Weather Bureau’s Office of Climatology between 1955 and 1966, he argued often that studying the physics of the atmosphere would prove valuable in the long-term. Not only would the mathematization of the atmosphere provide the tools to predict future climate states, he believed that the momentum would usher in a world in which climatology would be seen as invaluable to human ambitions to provide sufficient levels of food, shelter, and stability.

While he always harbored a grand vision of climatology, Landsberg observed with great consternation the popularization of climate in contemporary affairs. Abhorring what he saw as the uptake of climate into popular culture and politics, he could not help but grow wary of claims about future climate-induced disaster. Contrary to claims that climate was becoming increasingly unstable during the 1970s, he instead argued that population growth combined with an unwillingness to consider climate in everyday decision making made the vagaries of climate appear more disruptive. “Some, who are not particularly familiar with the peculiarly complex mechanisms of the atmosphere have come forth with prophesies of impending climatic catastrophes,” he commented in 1976. While he acknowledged what appeared to be vacillations in climate parameters, things like temperature and precipitation, it seemed premature to equate such vacillations with long-term changes or to equate such changes as being the result of human activities.¹

While Landsberg had spent decades arguing for the value of climate understanding to human affairs, it seemed by the 1970s and early 1980s that genuine understanding had become secondary to the politics of alarm that swept across the country. Always envisioning climatology as a reticent discipline, he never felt comfortable in a society where climate change had become wrapped up into other salient issues that spilled out on the pages of national newspapers, including topics like anthropogenic global climate change and claims of an impending nuclear winter. While in retirement, it seemed integral to isolate climate from what he saw as the vulgarities of politics and popular culture, and he never found a solution that suited his style as a scientist. If there ever was a time when his own style contrasted with the ferment of the times, it was toward the end of his life. He passed away in December 1985 while attending a meeting of the World Meteorological Organization, a moment of passing that marked definitively the sunset of climate as a sensational topic of media intrigue and popular political debate. For him, this was not the vision set forth two decades earlier. As he articulated in light of the inauguration of John F. Kennedy,

Climatology is not a glamorous field. It does not produce what the newspaper jargon applied to science calls ‘exciting discoveries’ or ‘spectacular breakthroughs.’ Improved knowledge in this field will, however, assure better living for mankind... These ‘bread and butter’ goals may not fire the imagination nor kindle much enthusiasm but they will help us to the necessities of life.²

This quote, perhaps more than any other, illuminates the essence of Helmut Landsberg’s scientific life.

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Hans Jakob Konrad Wilhelmsson Ahlmann was a Swedish glaciologist and one of the leading figures in this discipline. He became known for his studies of glaciers and the discovery that they were retreating in the first half of the twentieth century due to a warming in the Northern hemisphere. Ahlmann was born on 14 November 1889. He studied geography at Stockholm University, where he also served as associate professor between 1915 and 1920 and professor of geography from 1929 to 1950. In 1950, Ahlmann was appointed Swedish ambassador in Oslo, where he served until 1956. Ahlmann died in 1974.

Ahlmann was a man of many talents and interests, both literary and artistic, and with a broad ranging interest in geography, stretching from fieldwork in Libya to a major study of the modern Stockholm region. In 1918, he started investigating the Horung massif glaciers in Jotunheimen in southern Norway. He was interested in the physiography of glaciers, their size and form and changes in time due to meteorological factors.

He made this interest a systematic life-long occupation, studying further glaciers at two expeditions to Spitsbergen in 1931 and 1934, an expedition to the Vatnajökull glacier in Iceland in 1936 and an expedition to northeast Greenland to study the Fröya glacier in 1939. Ahlmann wanted to combine the tradition of scientific expeditions with stringent methodology and a strong focus on precision in quantitative field measurements. Historian Sverker Sörlin called his style of fieldwork a “culture of precision.”¹

Ahlmann wanted to understand the processes of growth and retreat of glaciers by meteorological factors. He could show that glacier regimes depend more upon temperatures than upon precipitation. He became particularly famous and garnered much public attention during the 1940s and 50s for making an opposite inference: his observation of shrinking glaciers and understanding of the ablation processes led him to postulate a significant polar warming, which he called an “embetterment of climate.”²

In May 1947, Hans Ahlmann travelled to the United States from Sweden to lecture on polar warming. In a lecture to the Geophysical Institute of the University California in Los Angeles, he reported that Arctic temperatures had risen by five degrees Celsius in recent decades. Ahlmann concluded that a melting of the ice sheets in Greenland and Antarctica, in case the warming was global in nature, would have catastrophic consequences. This lecture and its horrifying conclusions received coverage in leading public media such as the New York Times. In June 1947, Ahlmann was invited to a meeting at the Pentagon. The U.S. military authorities took great interest in Ahlmann’s conclusions, because a polar melting threatened U.S. national security interests. This episode helped to strongly increase the focus on research efforts in arctic regions of the United States.

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One of the leading pioneers in the first generation of climate modelers was Japanese meteorologist Syukuro Manabe. Manabe was born on 21 September 1931. He received a PhD in Meteorology from the University of Tokyo in 1958. In 1959 he moved to the United States and joined the General Circulation Research Laboratory, which was led by Joseph Smagorinsky and initially located in Washington D.C. In 1963, the Laboratory was renamed the Geophysical Fluid Dynamics Laboratory and in 1968 moved to Princeton University.

Manabe had experiences in weather prediction research in Japan and was an excellent theoretical meteorologist. Smagorinsky hired him to contribute to General Circulation Model (GCM) development. Building on the work of early pioneers of climate modeling such as Jule Charney and Norman Phillips, Manabe and Smagorinsky adopted a cautious heuristic modeling research strategy. According to climate modeling historian Paul N. Edwards, they pursued a “long-range view of the circulation modeling effort” and their “research strategy used GCMs to diagnose what remained poorly understood or poorly modeled.”¹ “Strict attention to developing physical theory and numerical methods before seeking verisimilitude became a hallmark of the GFDL modeling approach.”²

Manabe, like his Japanese fellow climate modeler Akio Arakawa at the University of California, made very significant contributions to climate modeling by investigating and representing atmospheric processes, which had not yet been considered in GCMs. Manabe explored radiative transfer, convection and the thermal equilibrium in different heights of the atmosphere with a one-dimensional model representing the vertical dimension of the atmosphere. Arakawa, in contrast, was interested in accounting for the effects of clouds on climate. Many of these processes occurred on much smaller spatial scales than GCM could resolve. Hence, artificial schemes approximating these so-called sub-scale processes had to be developed for GCMs. These approximations are called “parameterizations” and have remained indispensable until today, even though they are major sources of model uncertainty (further details of the scientific work of Manabe and Arakawa are given in Weart 2017a³ and 2017b⁴).

By 1965 Manabe and his group had developed a three-dimensional global model with nine vertical levels. The model was still highly simplified, with no geography included, but was able to provide quite realistic simulation results of processes such as transfer of heat and moisture. A Committee of the National Academy of Sciences concluded in 1966 that the best models simulated atmospheres with gross features "that have some resemblance to observation."⁵ Manabe was also an early pioneer of attempts to include the role of oceans in climate models. In the late 1960s, together with oceanographer Kirk Bryan, he developed a first coupled model consisting of an atmospheric GCMs with a simple ocean model.

Simplified “geography” of Manabe’s coupled climate model. Manabe and Bryan made a globe by putting together three identical segments, each part land and part sea. The polar regions, hard to deal with mathematically, were cut off.⁶

While Manabe was a dedicated heuristic modeler who aimed at a physical understanding of the atmosphere and climate, he was also drawn into early attempts of climate prediction. In 1965, the U.S. Presidential Scientific Advisory Committee published a report on the state and problems of the environment (PSAC 1965). Joseph Smagorinsky was member of a working group that studied issues of climate for this report including rising carbon dioxide levels. Smagorinsky recalled in an interview that the committee meetings for the PSAC report prompted him to ask Manabe to add carbon dioxide to his radiation model in order to explore the impact of rising carbon dioxide levels.⁷

Syukuro Manabe and Richard Wetherald made the test and used their one-dimensional model to simulate what would happen if the level of carbon dioxide doubled. They came up with their famous result that global temperature—according to their model simulations—would rise roughly by 2°C, but added that this result was subject to great uncertainty.⁸ This result, though preliminary, simulated with a model and not validated by observation, became an important resource in the emerging climate change discourse. Oceanographer and climate researcher Wallace Broecker later recalled that it was this 1967 paper “that convinced me that this was a thing to worry about.”⁹

Title and abstract of Manabe’s and Wetherald’s famous paper providing a first model-based estimate of climate change in the case of doubled carbon dioxide content in the atmosphere (the relevant sentence in the abstract is highlighted)¹⁰. For a discussion of the article see here.

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Sir Basil John Mason, better known as John Mason, was an expert on cloud physics and powerful director of the British Meteorological Office from 1965 to 1983. He led the Met Office into the computer age and transformed it significantly “into a world centre for weather prediction.”¹ Born on 18 August 1923, Mason studied physics at Nottingham University and continued as lecturer in meteorology from 1947 and professor of cloud physics from 1961 at Imperial College London. In 1965, Mason was appointed director of the Met Office at the age of 42. During his long career he received numerous awards for his outstanding accomplishments. In 1979, he was knighted.

Mason was described as a “charismatic man”, who “possessed scientific vision, enthusiasm and an inspiring style of lecturing and advocacy that enabled him to recruit good scientists and raise the funds needed to achieve these ends, although his manifest self-belief and forthright manner upset some.”² Already in the early 1950s (in his late twenties), Mason built a scientific and a public lecturing career. He received a Rockefeller Travelling Fellowship for the United States (1951) and augmented his meager salary as lecturer by appearing frequently on radio and television programs and giving public lectures in the UK and abroad. He published about 70 papers and books on cloud physics between 1950 and 1965 and helped to establish cloud microphysics as a coherent discipline. Mason also served in the Executive Council of the World Meteorological Organization and was a strong supporter of the Global Atmospheric Research Program.

As new director of the Met Office, Mason immediately put his stamp on this venerable institution with some 3800 staff. One of his first major decisions, taken just weeks after assuming directorship, was to make numerical weather prediction operational – a decision that went against the advice of his senior staff and represented the beginning of a strong commitment to numerical methods and computer modeling at the office. One month after the beginning of Mason’s tenure (1 October 1965), on Monday, 2 November 1965, the Meteorological Office began issuing twice-daily numerical forecasts.

Met Office KDF9 Computer in 1966, Met Office Headquarters, Bracknell. Source: Met Office Archive

For Mason, the role of objectively implemented physical theory in meteorology and climate research was critical to the future of those disciplines. Numerical methods, he argued “are objective, logical, mathematical exercises based on a firm structure of physical theory,” whereas traditional weather forecasting and historical-based climate work depended heavily on individual experience.⁴

In subsequent years, the Office invested heavily in computer modeling, namely, numerical weather forecasting and, soon thereafter, numerical modeling of climate. Computers, Mason wrote in 1967, herald the end of “a long period of steady but unspectacular development in meteorology.” Numerical techniques, he continued, the Meteorological Office stood on “the threshold of a new era, with unprecedented opportunities for increasing our scientific understanding of the atmosphere.”⁵ On Mason’s demand, recruitment at the office was steered toward the natural sciences and, within a year of his appointment, only candidates with a first or second class honors degree in mathematics or physics could be considered for Scientific Officer positions at the Meteorological Office. For researchers at the Met Office pursuing different research interests and approaches, such as climatologist Hubert H. Lamb, no more support was granted.

Within a decade of his appointment, the Met Office had been extensively modernized and firmly based “on the most advanced numerical models in operational use,” as Mason wrote. Similarly, Mason approached the problem of climate. “By far the most promising approach to understanding the prediction of climatic change lies in the construction of physico-mathematical models of the global circulation of the atmosphere and oceans treated as a combined geophysical system,” Mason explained in an article in 1976.⁶

In spite of his enthusiasm for numerical approaches, Mason and his staff regarded climate simulation as a slowly developing research domain, in which at first an adequate understanding of atmospheric processes had to be gained. An application of the model for practical purposes was out of the question. Mason even rejected demands by the British government to come up with climate predictions for several years. “Our understanding of the mechanisms and causes of climatic trends and fluctuations is inadequate to allow their prediction,” he wrote in 1976.⁷ In contrast to scientists such as William W. Kellogg, Stephen H. Schneider and James E. Hansen in the USA, Mason did not share beliefs in risks of global warming. He remained cautious about the limitations of climate models and sought to protect the scientific authority of the MetOffice.

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William Welch Kellogg was a climate scientist who made very significant contributions to the emerging culture of climate prediction during the 1970s. He was one of the first scientists who demanded predictive modeling—the use of climate models for the simulation of future climate prediction—since the early 1970s. He was also one of the first climate scientists to to popularize the use and dissemination of a simple graphical representations of future climate projections. Such graphs helped to convey the risk of climate warming very effectively.

Kellogg was born in New York Mills, New York. He attended the Brooks School in North Andover, Massachusetts, and graduated from Yale in 1939 with a BA in physics. Kellogg continued graduate studies at U.C., Berkeley, with Jakob Bjerknes as teacher, whom he recalled as his “favorite professor at UCLA.”¹ These studies were interrupted by World War II, when he served in the Air Force's new meteorological program. As a pilot and weather officer, with a strong passion for flying, he collected some of the first data on the dynamics of thunderstorms by flying B-25s into the heart of the storms.

After the war, while working on a PhD from UCLA, he joined the RAND Corporation in Santa Monica, California. He completed his thesis “The Atmosphere Above 100 Kilometers” in 1949. At the RAND Corporation he became one of the leading experts and proponents of satellites for meteorological research. He developed many of the concepts still in use today. In 1964, he was invited to join the National Center for Atmospheric Research at Boulder, Colorado, as director of the Laboratory of Atmospheric Sciences. In this position he was involved in a range of research activities including air pollution and the chemistry of the atmosphere and the development of meteorological models of the higher atmosphere.

His serious interest in the investigation of climate started only in 1970s, when he became involved in the organization of the Study of Critical Environmental Problems (SCEP) in 1970, which was initiated and organized by MIT professor Carroll Wilson. In this one-month study, Kellogg led the Work Group Climatic Effects of Man’s Activities. One year later, Kellogg was one of the organizers of the international follow-up meeting entitled Study of Man's Impact on Climate (SMIC) held in Sweden in 1971. The investigation of climate became Kellogg’s main focus until his retirement in 1987.² While Kellogg was not an activist, he was concerned about the possibility of climate warming. As contributor to the SCEP and SMIC studies and as a consultant of the World Meteorological Organization, he was a very active lecturer and writer to public audiences, and became a strong supporter of using climate models for predictive purposes and projecting future climate in spite of model uncertainties.

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Stephen Henry Schneider was a leading climate researcher. He played a significant role as a scientific activist and in the development and propagation of predictive modeling. Schneider was an engineering student at Columbia University when he started his first modeling experiment in 1970 at the Goddard Institute of Space Studies (GISS), where he also met James Hansen. In April 1971, William Kellogg invited Schneider to serve as a rapporteur at the Study of Man’s Impact on the Climate (SMIC), beginning in July 1971. In 1972, Schneider moved to the National Center of Atmospheric Research (NCAR) in Boulder, Colorado, to continue work on climate modeling and collaborate with William Kellogg and others. Schneider remained at NCAR until 1992 when he became professor at Stanford University, which remained his intellectual and professional home for the rest of his life.

Steve was as tough as nails.¹

Schneider was an enormously productive scientist. His interest also went far beyond process of climate and encompassed the impact of climates on the biosphere and on human societies. In 1977 he founded the influential journal Climatic Change to provide a broad platform for relevant scholarship from many disciplines. Schneider’s main scientific interest rested with climate models. He was excited about climate modeling which promised not only the opportunity of important scientific breakthroughs in the understanding of climate, but also a means to produce politically relevant future projections about climate change. Despite the imperfection of models, Schneider emphatically advocated predictive modeling.

Another outstanding characteristic of Schneider’s work was his strong engagement as popular writer and political activist. Already as a young postdoc at GISS he started to publish letters to the editor in the New York Times, which was not generally accepted and instigated a strong conflict with his director (Santer, Ehrlich 2010, p. 15). In 1976 Schneider published (with his wife, science writer Lynne E. Mesirow as co-author) a popular book about problems of climate variation and change and its relations to droughts and hunger (Schneider, Mesirow 1976). He expressed strong political concern about climate warming and emphasized the importance of climate models for climate prediction, even though these models involved significant uncertainties. One quote in this book neatly encapsulates Schneider’s scientific and political conviction:

Unfortunately, for the task of estimating the potential impact of human activities on climate the models are just about the only tools we have [italics in the original]. Should we ignore the predictions of uncertain models? … I think not – a political judgment, of course. … The real problem is: If we choose to wait for more certainty before actions are initiated, then can our models be improved in time to prevent an irreversible drift toward a future calamity? … This dilemma rests, metaphorically, in our need to gaze into a very dirty crystal ball; but the tough judgment to be made here is precisely how long we should clean the glass before acting on what we believe we see inside.²

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James Edward (Jim) Hansen is a leading climate researcher. He played a significant role in the emergence of predictive modeling. As an expert in solar radiation transfer in planetary atmospheres at the Goddard Institute of Space Studies of NASA, he began modelling radiative transfer in the Earth’s atmosphere in 1970. During the 1970s, Hansen became a leading climate modeling expert. In 1981 he and his collaborators published the first long term projections of climate based on model simulations in the journal Science (Hansen et al. 1981). Though this paper was very controversial, it set the stage for predictive modeling in the following years and decades.

Hansen was one of seven children of a tenant farmer in Iowa. He studied physics and astronomy at the University of Iowa, with the outstanding scientist, James van Allen. In 1967 he joined the Goddard Institute for Space Studies (GISS) in New York as a postdoctoral candidate and specialized in theoretical work on radiative transfer in planetary atmospheres. Around 1970, Hansen joined a weather prediction modeling project based on Arakawa’s general circulation model and started focusing on climate modeling in the following years.

Hansen developed ingenious modeling approaches by simplifying climate models for specific tasks. Many ambitious studies he pursued were based on a one-dimensional model, which only represented the vertical axis of the atmosphere. With this approach he could circumvent limits of computational power and apply the model for simulations of complex problems. He later explained his interests and ambitions in an interview with Spencer Weart:

“We’re taking the model and using it for climate applications. It’s hard to have enough time to work on the basic structure of the model and also use it”.

A one-dimensional model also served for the 1981 landmark paper in Science. In spite of a large amount of significant uncertainties, the authors developed trust in their model, because it reproduced past global mean temperature changes rather well. This achievement encouraged them to venture into simulating climate projections based on socio-economic assumptions regarding future CO2 emissions to the year 2100. In 1988 Hansen and his group—published for the first time—climate projections simulated with a three-dimensional climate model (Hansen et al. 1988).

Hansen became famous for his testimony before Congress in June 1988. In this summer the United States experienced an extraordinary heat wave. Hansen clearly expressed his conviction that climate warming was already happening:

Number one, the earth is warmer in 1988 than at any time in the history of instrumental measurements. Number two, the global warming is now large enough that we can ascribe with a high degree of confidence a cause and effect relationship to the greenhouse effect. And number three, our computer climate simulations indicate that the greenhouse effect is already large enough to begin to affect the probability of extreme events such as summer heat waves.

Hansen’s famous testimony before Congress on 23 June 1988 (Hansen 1988, p. 39).

This testimony brought him ample press coverage as well as significant criticism. It caused a steep rise of public attention to global warming. “Global warming has begun, Expert tells Senate,” titled the New York Times on its front page on June 24, 1988:

Hansen making headlines.

The general agreement between modeled and observed temperature trends strongly suggests that CO2 and volcanic aerosols are responsible for much of the global temperature variation in the past century. Key consequences are: (i) empirical evidence that much of the global climate variability on time scales of decades to centuries is deterministic and (ii) improved confidence in the ability of models to predict future CO2 climate effects.

Conclusions about simulations with a one-dimensional climate model (Hansen et al. 1981, p. 964).

Number one, the earth is warmer in 1988 than at any time in the history of instrumental measurements. Number two, the global warming is now large enough that we can ascribe with a high degree of confidence a cause and effect relationship to the greenhouse effect. And number three, our computer climate simulations indicate that the greenhouse effect is already large enough to begin to affect the probability of extreme events such as summer heat waves.

Testimony before Congress on June 23, 1988 (Hansen 1988, p. 39)

Bert Bolin was a leading Swedish climate researcher. Since the 1950s he took an interest in carbon dioxide and became a pioneer in the investigation of the carbon cycle. Bolin played an extraordinary role as a science diplomat and contributed significantly to forming international collaboration in atmospheric and climate research. He was one of the main organizers of the Global Atmospheric Research Program (GARP) in the 1960s and the Intergovernmental Panel on Climate Change (IPCC) in the 1980s. He served as chairman of the IPCC from 1988 to 1997. Bolin’s efforts were foundational for making climate warming a public and political issue.

Bolin was a student of Swedish meteorologist Carl-Gustaf Rossby at Stockholm University. During his doctorate he spent a year in 1950 at the Institute for Advanced Study in Princeton, New Jersey, where he worked with Jule Charney and others on the first computerized weather forecast. After Rossby’s sudden death in 1957 he succeeded him as director of the Meteorological Institute at the Stockholm University, where he became Professor of Meteorology in 1961. In 1959 Bolin made headlines in the New York Times, after he presented his research about the carbon cycle at the Annual Meeting of the U.S. National Academy of Science in Washington and predicted that the carbon dioxide content in the atmosphere may rise by 40 percent by the year 2000.¹ Bolin also took a strong interest in atmospheric pollution and acidification due to sulphur dioxide emissions.

In the 1980s, Bolin contributed to making climate change a political issue. He led a compre-hensive assessment supported by the United Nations Environment Program (UNEP) and the World Meteorological Organization (WMO), which formed a background for the International Conference on the Assessment of the Role of Carbon Dioxide and of other Greenhouse Gases in Climate Variations and Associated Impacts in Villach, Austria, in 1985. In this report the authors summarized the state of knowledge and emphasized that “the urgency of the problem is of decisive importance in the establishment of a policy for action.”² The Villach Conference was the catalyst for starting an international political process that led to the establishment of the IPCC in 1988. Bolin is best known for his efforts as chairman of the IPCC, which was awarded the Nobel Peace Prize in 2007 just before Bolin’s death.

...the CO2 problem, or rather the problem of a possibly changing climate due to emissions of greenhouse gases into the atmosphere ... is one of many important environmental problems that must be addressed but in a long-term perspective probably the most important one.”³

Projections of carbon emissions in 2050 based on a range of different investigations from the early 1980s (Source: Bolin et al. 1986a).

Scenarios for future atmospheric CO2 concentrations (Source: Bolin 1986b).

A comparison of results of recent assessments of the CO2 problem.

In their 1986 SCOPE report, Bolin and his co-authors summarized assessments of the CO2 problem from the early 1980s. All these assessments provided estimates for global warming for the case of doubled CO2 content in the atmosphere based on climate simulations with different models. The report showed that despite imperfections of climate models, their predictive use had become a commonplace part in the culture of climate science.⁴

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