Scales matter significantly in the investigation of climate. Classical climatology typically pursued a small scale, regional approach by studying climates in specific geographical locations. It’s 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/large scale research of climate). In their eyes, these approaches neglected local detail and, hence, the 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.
