What was the point of leaving warnings?

Rating: 7/10 (10 July 2009)

I liked the movie. It had lots of intrigue, great special effects, and good deal of action. That being said, I did not understand the premise.
Aliens apparently left coded warnings of future disasters by encoding them in the brain of a school girl who scrawled them on a note to be left in a time capsule in 1953. The time capsule was not to be opened for 50 years. Yet almost all of the predictions were for catastrophes that took place before the opening. What was the point of that? If it was simply to validate the code, then what was the point of predicting the end of everything when nobody could do anything to stop it anyway?
The aliens obviously knew well in advance what was going to happen, down to the exact time and location. They had already implanted a homing beacon, so to speak, in many of Earth's children. They really didn't need the coded predictions, which is what almost the entire movie is based around. It's a huge plot hole.