It is quite obvious you need to put the water in a vacuum chamber, then heat it. Then you can safely store the dangerous gaseous steam in a bottle, then launch that bottle into space with a rocket. As we all know, rockets are both safe, and dangerous.
Once it is in space, space will be filled with a bottle of safely dangerous steam. Since space is already inherently dangerous, it doesn't really matter if we add a little more, so we won't really have to worry about it. Thus, Earth will be safe. Or at the very least, a little bit safer for the time being.