The future of precipitation chemistry measurements

The Earth s climate depends among other parameters (see later) on the chemical composition of the atmosphere. Thus, any variation in the composition raises the possibility of climatic change. First of all, the chemical composition regulates the radiation balance of the Earth-atmosphere system. However, since differences in radiation balance in various geographical regions control the atmospheric circulation, there is also a relationship between composition and dynamic processes. In this chapter we shall deal mainly with the effects of compositional variations on the radiation balance. Moreover, the significance of so-called feedback mechanisms will also be stressed. 

The history of the Earth dates back nearly 5 billion years. We have reliable information, however, concerning only the last 500 million years or so. This information has been obtained mostly from studies of minerals and oceanic sediments, as well as from studies of the forms of mountains and the ocean floor. The understanding of the climate of more recent eras was facilitated by the investigation 

1 Human activities can also influence the climate in other ways modification of the surface, energy production, etc. We shall limit our discussion, however, to the effects of air pollution in view of the scope of this book. 

Variation of, 80/l60 ratio ( )) as a function of time B. P. according to Dansgaard el al. (see SMIC. 1971). (By courtesy of Massachusetts Institute of Technology) 

In the Pleistocene era, wanner and cooler intervals alternated. There is some indication that each glaciation built up over a period of about 90 000 years and terminated in a shorter time of about 10000 years. The last ice age reached its 

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