A positive feedback anamoly in a individuals personal timeline occurs when they divulge certain mutually shared information from the future. This does not create a paradox but rather splinters a small or large set of parallel histories causing a explosive divergence event. A magnet and iron fillings will provide some insight into the filament like nature of timelines in temporal theory. You could say John Titor acted as a pole for the people around him and altered the overall march of history enough for the splintering effect to cascade into a extremely explosive divergence, from the point of view of the Titor civilization you exist as dark matter destablising our global weather to the point of a snowball earth. We should never have sent John Titor, but the knowledge of time travel was rudimentary, I am not even able to say the year from which these messages originate for fear of further anomalys. He could not have known in 2036 but it is impossible to heal the splintering from within the event itself....2005 is as close as we can safely get!