E.L.
C.,
I understand your frustration. My started screaming at about 13 months and still does occasionally. Everything that I have read says to ignore it. If you make a big deal, it will continue. I did ignore his screaming, and it has decreased tremendously. He does it every once in a while now when he gets excited or to play. The times when I ask him to stop, he continues. If I ignore him, he gets bored and stops.
Good Luck,
E.