What to do about fogging in rear window?

[DopeScope]

So the last two weeks I've noticed that my rear window (behind the seats, in front of the engine) has been fogging up. From what I've read it's a double pane glass so it most likely means I have a leak of some sort.

Is there anything I can do short of replacing the window? Anything that will help make the fog go away? It seems to be worse at night than during the day. It was perfectly fine before 2 weeks ago. Not sure if it's the warmer weather we're getting in Sacramento or what it might be.

Thanks.

 

[SFNSXguy]

Could be a engine water leak. Better look at expansion tank.

 

[rbirling]

Which surface is fogging? Inside the car, inside the engine compartment, or between the panes?

 

[silver2002]

My guess: water sprayed up on engine from last wash [especially spraying right rear tire].

Does it show up a few minutes after you start the engine and go away in 5 minutes or less?

 

[DopeScope]

Which surface is fogging? Inside the car, inside the engine compartment, or between the panes?

Sorry, I guess I should have specified. It's between the panes.

It's a PITA since there's no way (that I know of) to get rid of it, especially when I'm driving. Sometimes it'll just go away and sometimes it gets worse. Seems to get worse at night, probably cause of the cooler temperatures causing condensation or something.