(note: finding supporting links for the following excerpt was extremely challenging to locate, so we offer what little the United Nations World Meteorological Organization has available from their site)
Physics and Chemistry of Clouds and Weather Modification Research Programme
In 1975, the Seventh World Meteorological Congress adopted a Weather Modification Programme. Since then WMO has been recognized as the international body with the necessary scientific and technical expertise to respond to requests concerning weather modification. The name of the programme was later changed to include the physics and chemistry of clouds.
The focal point of the programme is the WMO Executive Council Panel of Experts/ Commission for Atmospheric Sciences (CAS) Working Group on Physics and Chemistry of Clouds and Weather Modification Research.
The Panel/Working Group keeps under review relevant research and provides advice to the WMO Executive Council, CAS and other bodies on urgent problems related to physics and chemistry of clouds and weather modification research.
The main objective of the Programme on Physics and Chemistry of Clouds and Weather Modification Research is to provide guidance to Members on the rationale underlying all aspects of weather modification and on the promotion of research of the physics and chemistry of clouds and of their applications to all fields of atmospheric sciences.
Research focuses upon the physics and chemistry of clouds with reference to weather prediction, weather modification and atmospheric composition and pollution. Research into the role of clouds in chemical transportation of pollutants, as well as their precipitation processes is also featured in the programme.
Between 1979-1981 field studies of a WMO-managed Precipitation Enhancement Project (PEP) were conducted, which contributed significantly to the development of an international consensus on precipitation enhancement. The 34 reports published regarding PEP are sought-after references for the scientific basis upon which activities and decisions concerning weather modification are based today.
In order to advise WMO Member countries, a Statement on the Status of Weather Modification (PDF) as well as Guidelines for Advice and Assistance Related to the Planning of Weather Modification Activities have been issued and are regularly under review.
WMO also organizes and conducts at approximately four-year intervals Scientific Conferences on Weather Modification (2007 conference) that are recognized as significant dates in the international calendar of weather modification events.
The promotion of research on physics and chemistry of clouds is the focal point of activities in the programme.
Current activities also center around guiding Member countries on all aspects of weather modification. In addition, WMO compiles information from Members on their activities and publishes an annual Register of National Weather Modification Projects, the only publication of its kind containing such information.