“Detonating nuclear weapons above ground sends radioactive materials as high as 50 miles into the atmosphere. Large particles fall to the ground near the explosion-site, but lighter particles and gases travel into the upper atmosphere. The particles that are swept up into the atmosphere and fall back down to Earth are called fallout. Fallout can circulate around the world for years until it gradually falls down to Earth or is brought back to the surface by precipitation. The path of the fallout depends on wind and weather patterns.” https://www.epa.gov/
When you detonate a fusion weapon can you accurately predict its collateral damage? I doubt it because we cannot accurately predict the weather. We can create models and endless data but in the end there will be unseen and unintended damage.
This causes wars