Documenting and detecting long-term precipitation trends: Where we are and what should be done

A brief review of problems and achievements in documenting precipitation changes during the period of instrumental measurements is presented. Concern is expressed that without appropriate studies in the coming period of a new generation of precipitation measurements, technological progress in instrumentation may adversely and inadvertently affect our capability for monitoring and detecting future changes in terrestrial precipitation. At the same time, only a new generation of instrumentation will be capable of resolving the problems of monitoring precipitation over oceans. Special attention is paid to validation of the increasing trend in terrestrial precipitation observed during the past hundred years at high latitudes of the northern hemisphere - a feature of global warming predicted by most climate models.