THE climate of our surroundings can be studied on a variety of different scales. The emphasis in recent years, for well known reasons, has been on the climate of the entire planet, but traditionally climatologists have tended to concern themselves with the climate of regions or countries. And on an even smaller scale, studies have been made of the climate inside a single building, or of the variations in temperature and humidity over a single field of corn.
Weather people, of course, are a very pernickety lot. Not for them the "polite meaningless words" of W. B. Yeats, nor the Gilbertian apophthegm:
The meaning doesn't matter if it's only idle chatter
Of a transcendental kind.
Meteorologists have devised long words to describe precisely the different categories into which they divide this kind of work.
The term microclimate, for example, is used to represent the climate of the atmosphere very close to the ground - the zone in which the smaller plants and animals live. The yield of a field of crops, or the extent to which insects thrive or die away, is often determined by the microclimatology of their immediate environment. Vegetation, indeed creates its own microclimate, and it varies quite remarkably over very short distances. As one eminent meteorologist put it: "What a lucky creature an insect is. It can go from a cool humid climate to a Mediterranean one merely by climbing a single blade of grass".
On a somewhat larger scale there is the mesoclimate, the climatic characteristics of an area anything from say 5 to 100 miles in diameter. The eteorological properties of valleys, or of large cities, fall into this category. The urban heat island, for instance, is an important mesoscale phenomenon, as is the effect of local mountains on rainfall or sunshine in a particular area.
When we look at the kind of weather conditions experienced over a very large region, a country, or even an entire continent, we have wandered into the realm of the macroclimate; we are concerned with the macroclimate when we speak of the "temperate zones" of the world, or of a "Mediterranean" or a "tropical" climate. And on the largest scale of all is the study of the global climate, where attention nowadays is focused on the possible consequences of man induced changes to the composition of our atmosphere.