Weather is a decisive factor for agricultural production. Drought, hail, frost and other extreme weather events can cause major crop loss and economic damage. Due to the great dependence, man's desire for weather control and modification dates back to antiquity. Weather modification operations are intentional changes of weather and water conditions in cloud systems using technology such as cloud seeding. By causing small disturbance in the microphysical properties of the atmosphere, man can significantly alter the natural development of atmospheric processes. The most researched weather modification method is by cloud seeding, used to augment rainfall, suppress hail and lift fog. Cloud physiques can be changed by adding seeding materials like silver iodide. Fog seeding modification already became common practice in some larger transport airports. Also, methods for precipitation augmentation with ionizers have developed, that perform microphysical change in clouds with additional ionization (trace of natural) in liquid cloud water. At the same time methods for modification of global and space weather are developed as man tries to reduce negative effect of climate warming. Methods for the global weather modification are the SRM (Solar radiation management) and the ionosphere modification with ionospheric heaters. Despite the large amount of research, knowledge is still insufficient and each new project should be carried out only after a careful analysis of key variables, expected benefits, associated risks, optimal techniques, and effects. A number of ethical issues and challenges also arise, that require a study of the new social, ecological, economic and legal aspects of weather modification.
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