Something I haven't seen discussed here is the answer to your title when taken as the whole question; a not insignificant amount of water is "lost" to space every second in the form of H2 leaving our atmosphere. Said H2 can't be combined into watermolecules anymore, at least not on earth. Some molecules get enough kinetic energy (temperature) to simply shoot out of our orbit, others get taken away by solar winds.
Ancorarius t1_jabu3w7 wrote
Reply to Water on Earth is not Constant. Why ? by ItsDivyamGupta
Something I haven't seen discussed here is the answer to your title when taken as the whole question; a not insignificant amount of water is "lost" to space every second in the form of H2 leaving our atmosphere. Said H2 can't be combined into watermolecules anymore, at least not on earth. Some molecules get enough kinetic energy (temperature) to simply shoot out of our orbit, others get taken away by solar winds.