Global Warming and our Changing World

Ok, I'm not referencing "The Arrival," but that does make sense.

Last night there was a lower-budget sci-fi movie on, and I was able to catch a few minutes of it. A priest having a crisis of faith was approached by devil-looking creatures and given the power to heal. At one point, one of the creatures revealed that he and his race were from a planet far, far away. Their plot was to slowly remove earth's atmosphere, siphoning it off for storage, transportation, and integration with their home world.

So... what if our atmosphere isn't chemically changing. What if it is eroding?

In all seriousness, I don't think that's the case, but the idea did strike me as thought-provoking.