We are not sure we can, but we have always wanted to do so! In the past, people rang bells or fired cannons to prevent lightning or cause rain — producing sound and fury but nothing in the way of success.
The scientific era of weather modification took hold in the 1940s and ’50s with the advent of cloud-seeding experiments. In cloud seeding, airplanes drop particles of dry ice or silver iodide into clouds with temperatures below freezing. These particles are very effective in generating ice particles, with the hope of increasing the amount of rainfall or snowfall.
However, progress in cloud seeding has been slow as the processes are poorly understood. Not only that, these experiments aren’t reproducible in the sense that we can never really know if a seeded cloud would not have precipitated on its own, without assistance.
Farmers have long sought a way to suppress hail. One hailstorm can destroy a year’s crops in a few minutes. Cloud seeding during the early stages of cumulonimbus development is thought to encourage a reduction in hail damage by keeping hailstone sizes small, but again, the results have been mixed.
Another active area of weather modification has been fog dispersal. Fog can shut down an airport for hours, causing delays with negative economic impact. Like clouds, fog can be seeded with materials that cause the water droplets in fog to turn into ice, which then precipitates out, dispersing the fog. While a practice at many airports worldwide, it is impractical to apply over large regions.
Humans have changed the atmosphere in many ways. These changes usually come about as unintended byproducts of modern civilization. So far, humans have been more effective at modifying weather and climate by mistake than by design.