The following, scary pictures are making it around the net at present:

And here separating the fresh water:

If we were to do similar with the air we breathe, say putting the earth’s atmosphere into a little ball that is throughout at normal standard pressure, looking at it would make you literally choke. But is this more than scaremongering? What do these pictures tell us? Let me first criticize this visual framing and then add a thought about how perhaps one may recover some justification for visualizing water resources like that.

The pictures are supposed to scare us about the scarcity of water and warn us not to poison that little drop we have. Here is a comment that is spot on (I especially like “This is the visual equivalent of that trick”, which made me create the phrase “visual framing”, perhaps because I am not sure about what framing really means):

If you want to make something sound big, you describe it in terms of area or length. If you want to make something sound small, you describe it in terms of volume. So, when someone tells you how many times all the X’s would stretch from the earth to the moon and back, they’re almost always trying to make X sound very abundant. In contrast, when someone tells you the dimensions of a swimming pool that would hold all the X’s, they’re usually trying to make X sound scarce.

This is the visual equivalent of that trick. We see the earth’s crust stretched over a huge sphere of other stuff (as in reality), but we see the water forming a 100%-water sphere, with nothing else inside it (unlike reality). As a result, the water looks woefully inadequate to give the earth what it needs. – John Cohen, via Metafilter