The organisations assembling datasets

Most precipitation data have been collected by national weather services (NWSs) and national hydrological organisations, and by those collecting data for some specific project. But many of these records do not cover long enough periods, few spanning a century without some break or discontinuity. Until concerns about climate change arose recently this was an acceptable state of affairs. Now that we wish to understand and follow the climate changes that have occurred, are occurring and will occur in all climatic variables including precipitation, in the future, it has become necessary to look more closely at all these disparate data and to assemble them into some order covering the entire globe. None of these data were collected for this purpose, but for the simpler and more routine function of weather forecasting on a national scale or for water resources assessment on a local or regional scale. For climatic research, however, it is necessary to assemble all of these unrelated data into one integrated global dataset. Let us first take a look at the organisations involved in attempting this difficult task or in some way contributing to it.

The World Meteorological Organization (WMO)

The WMO is an intergovernmental organisation of 187 member states and territories which originated as the International Meteorological Organization, founded in 1873. Established in 1950, WMO became the specialised agency of the United Nations for weather and climate, operational hydrology and related geophysical sciences.