How is that relevant to ships? It’s released to high in the atmosphere.

There are gasses and particles that can be released into the atmosphere that will reflect sunlight and warmth away from earth. In theory that could be done very quickly.

We’re not as powerful as we think we are.

We could cause a new ice age easily. Just fire off a few percent of the nukes, and we will revert to an ice age almost immediately.
Of course a side effect would be massive starvation.

Remember it used to be called global warming, because that’s what’s actually happening. But morons thought a cold winter day disproved global warming, so it was renamed climate change.
And yes we can reverse global warming, but obviously that won’t recreate polar or mountain ice, or lower sea levels quickly, but we can get the temperature down to stop it first, which will also curb the increase in natural disasters, then the restoring of sea levels and ice will take at least decades and probably centuries.