Climatology has developed considerably since the days when it was essentially a climate 'book-keeping' activity, and its status as a credible scientific pursuit was called into question. Despite its centrality to such things as the IPCC process, for some, the nature, scope and methodology of climatology still remain poorly defined. The purpose of this editorial essay, therefore, is to briefly outline for the wider scientific community, the scientific nature and scope of climatology. A secondary aim is to define how and by whom climatology is practised by deriving some simple diagnostics concerning the nature and scope of the subject from papers published in the International Journal of Climatology over the period 1981-2000.
The subject matter of climatology is climate, which is not simply the statistical assemblage of the weather at a location or for a region. Rather it 'is the thermodynamic/hydrodynamic status of the global boundary conditions that determine the concurrent array of weather patterns' (Bryson, 1997, p451). This reverses the abstract notion that climate is 'average weather' and suggests that weather is constrained by climate within a 'season's allowable array' (Bryson, 1997). For example, tropical cyclone formation and maintenance is very much constrained by sea surface temperature conditions. Such a definition of climate matches the common usage of the word; for instance, economic, social or political climate is often heard in daily conversations. Used in this way, climate describes the conditions under which 'things' are possible.
Climatology is not only concerned with the analysis of climate patterns and statistics (e.g. temperature, precipitation, atmospheric moisture, atmospheric circulation and disturbances) but also with seasonal to inter-annual climate variability, decadal to millennial climate fluctuations, long-term changes in mean and variability characteristics, climate extremes and seasonality (Glantz, 2003). Climatology also addresses its subject matter on many spatial scales, from the micro through the meso and synoptic to the hemispheric and global. Further, climatology works within a general systems' paradigm. At the heart of this is climate system theory. This states that climate is the manifestation of the interaction among the major climate system components of the atmosphere of hydrosphere, cryosphere, biosphere and land surface and external forcings such as solar variability and long term earth-sun geometry relationships. It also recognises that humans are an integral component of the climate system through their ability to alter levels of atmospheric trace gases. A major goal of climatology is to understand the flow of energy and matter and the feedbacks and non-linear interactions between the main components of the climate system and their associated climate outcomes.
Science is said to be: 'concerned either with a connected body of demonstrated truths or with observed facts systematically classified and more or less colligated by being brought under general laws, and which includes trustworthy methods for the discovery of new truth within its own domain' (http://dictionary.oed.com/cgi/entry/50044035).
Clearly, climatology falls within this definition. Some of the demonstrated truths that underpin climatology as a science include:
(1) climate is non-stationary (2) climate varies over a number of temporal and spatial scales (3) major modes of atmospheric circulation exist which may produce climate teleconnections (4) climate is the long-term manifestation of the interaction between the atmosphere and the earth's surface and of processes arising from other causes that are internal and external to the climate system