I have a cockatoo also and screaming seems to come with the territory. It can be lessened, however, by providing something for your too to do while you are out. Lots of shredable material like empty paper towel roll, wooden toys or those grape vine wreaths you can buy at Walmart in the craft section. Any thing that can be safely chewed is good as it helps keep that beak busy and because part of the reason he is screaming is because he is BORED and LONELY !! This will help with the boredom but not the lonliness. The more you can have him out with you in the evenings the better because toos are little love sponges, they crave your affection. Another option if these suggestions don't help is to find him a good home with an owner who can spend more time during the day with him. I know you probably don't want to hear that but you must do what is right for the bird. Good Luck !!