Classical climatology had been challenged and expanded since the early 20^th 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 19^th century and coined the name “aerology” for this new subdiscipline. With the introduction of new technologies such as radiosondes and aeroplanes, the amount of observational data from the higher 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 (Bergeron 1930). 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-20th 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” (Godske 1959). 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” (Landsberg 1957). 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 a geography-based and a physics-based discipline. After the war, he demanded the integration of the physical and geographical traditions into one coherent and powerful discipline which he called “modern climatology” (Flohn 1954).

“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.” (Helmut Landsberg 1957: 17.)

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.

“To put it simplified: The classical climatology views climate as the average condition of the atmosphere. The modern climatology, in contrast, views it as the normal, that is typical, cycles of the weather.” (Hermann Flohn 1954: 13.)

This illustration (Flohn 1950a: 147) shows 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.

Sources:

Bergeron, Tor 1930: Richtlinien einer dynamischen Klimatologie, Meteorologische Zeitschrift, pages 246-262.

Flohn, Hermann 1950a: Neue Anschauungen über die allgemeine Zirkulation der Atmosphäre und ihre klimatische Bedeutung. Erdkunde 4:3/4.

Flohn, Hermann 1950b: Scherhags ’Neue Methoden der Wetteranalyse und Wetterprognose’ und die Entwicklung der dreidimensionalen Synoptik, Meteorologische Rundschau 3:1-2, page 19.

Flohn, Hermann 1954: Witterung und Klima in Mitteleuropa, Stuttgart.

Godske, C.L. 1959: Information, Climatology, and Statistics, Geografiska Annaler 41:2-3, page 85.

Landsberg, Helmut 1957: Review of Climatology, 1951-1955, Meteorological Research Reviews 3:12 (July 1957), pages 1-43.