system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why don't we just spend billions (or trillions) to desalinate ocean water? Wouldn't this battle rising oceans AND water shortages?
gpt
Well, no, it wouldn't battle rising oceans.

It would take care of a water shortage, and it is used in areas that have both money and a chronic shortage of fresh water -- Dubai is a great example.

But for the areas that don't have a chronic shortage, like California, it's not a great investment. Why? Because droughts end, and when they do, you've got billions and billions of dollars tied up in desalinization that can't economically compete with free water from the sky.

The other issue, for places like California, is that almost all of the water usage is away from the ocean, which means the *extremely* energy costly maneuver of sending water uphill.