Weather Control
One big area where nanotechnology has been discussed is in the realm of weather control. We sort of already have a way of doing this by putting “seeds” into clouds to essentially cause rain to occur. Cloud seeding is not perfect and isn’t totally reliable, but with nanotechnology, we could likely fix this issue. Let’s say California is experiencing a 90-day drought without any rain. Nanotech could be used to cause rain in the area to prevent potential wildfires. While this is legitimately a great thing, weather manipulation could quite easily become a huge problem. We could cause rain but what if this also causes severe hurricanes or tornadoes, as well as major flooding issues? Just changing the temperature or humidity in the air could affect normal weather patterns which could cause global problems too!