There is 2 ways you can try to remove them...use a SSR with a 1 cut like XMT 1..PB's SSSR 1...with a orange pad....work it a few times....
another product I have used and worked great on glass etching is Weinmans glass polish...it's used to polish glass stove tops...and works great....get at wal mart....it also leaves a slick surface that repells rain...very interesting product....I do my windows monthly with it..
Kitchen Care Products - Glass Cook Top Cleaner - Weiman Products
just some info to read on it.....
If they are real bad then you may need a cerium glass polish kit..it comes with a polish and a pad used on a drill...this stuff makes windows look like a diamond..its around 25.00...it will remove lite scrathes..wiper trails...etching..
AL