Weather Modification

A review is given of the current status of attempts to increase precipitation by artificial means. Major research efforts are being made on this problem, both in the United States and in foreign countries. A review of the evidence currently available tends to substantiate the conclusions of the President’s Advisory Committee on Weather Control for accepting the reality of precipitation increase resulting from cloud seeding in cold-cloud orographic cases. Some evidence is available to suggest that, in some cases, a precipitation decrease may have resulted from cloud seeding. New techniques are available for detection of silver iodide in precipitation. Some evidence exists for a carry-over effect from seeding with silver iodide, subsequent to termination of the seeding operation.