It has been established that certain aspects of the weather, specifically cloud microphysical and precipitation processes, can be intentionally modified under various circumstances.
Beneficial effects, those in which favorable benefit/cost ratios are realized without producing any detrimental environmental impacts, can be achieved within each of the major categories of cloud modification using existing treatment (cloud seeding) methodologies. The magnitudes and temporal/spatial scales of seeding effects vary between and within those major categories.
It has also been established that unintentional anthropogenic effects (those caused by human activity) on weather do occur, and are commonly referred to as inadvertent weather modification.
These inadvertent effects can be manifested by modifications to air quality, temperatures, and precipitation patterns and intensities. The precipitation effects can be positive or negative.
Increasing demands are being placed upon existing fresh water supplies throughout the world. These increasing demands lead to greater sensitivity to drought and to even moderate precipitation shortfalls.
Recent investigations indicate negative impacts of air pollution on precipitation downwind of some industrialized areas and areas that practice open burning of vegetation.
Concerns about water supplies are producing increasing interest in the application of cloud seeding for precipitation augmentation.
Hail damage to crops and property and fog-induced problems continue to produce interest in their mitigation.