Unexpected Effects of Cloud Seeding with Silver Iodide

Recent analysis of measurements of precipitation and ice nucleus concentrations made during several cloud-seeding experiments in Australia show apparent effects of cloud seeding with silver iodide that last not only for many days but even for many months. If these effects are real, the sensitivity of conventional analyses of cloud-seeding experiments using target/control or seeded/unseeded comparisons will beconsiderably or even totally degraded. Consequently, cloud seeding may have been far more effective over a far wider area than has usually been considered possible. Some hypotheses of how such long-persisting effects could occur are discussed which suggest that a physical basis is at least possible.