Anyway, it's an over-reaction. It's boiling away the oceans to keep the enemy navy from reaching your shores, and destroying the atmosphere to keep the enemy bombers from flying over your cities. Why do it?
Because if the enemy does reach your shores, it will kill half your people and enslave the rest. And you have little chance of avoiding this outcome by other means.
And it's boiling away a part of the ocean/atmosphere you rarely use.
Consider that it would do no good to destroy subspace around enemy planets like Cardassia Prime or on the GQ side of the wormhole. The enemy will just bypass the disruption. There's no way to disrupt a large enough volume of space to prevent the enemy from reaching you, unless
you deploy Omega in your own
star system. It would be the only effective way to use it, but it's permanent. It's exactly like a scorched earth policy, but there's so rebuilding afterwards. You're destroying your civilization to spite the enemy.
Maybe if the United Earth leadership had been Russians, they might have considered it. It worked against Napoleon.