The World Meteorological Organization (WMO) is a specialized agency of the United Nations. By definition it is concerned with the atmosphere and atmospheric processes and, hence, with the human environment, for whatever definition of the human environment may be adopted, the atmosphere is clearly one of its essential elements. Many atmospheric processes are intimately, indeed inextricably, related to processes and phenomena the study of which falls within the compass of other geophysical disciplines — notably hydrology and oceanography. The WMO has therefore certain responsibilities in these fields also, and as a result its interest in the human environment is somewhat wider than its title may suggest.