You obviously have very little understanding of mathematics in the real world. Every measurement, and so every prediction, has a margin of error. As an example, the trajectories of spacecraft that are not under power are extremely predictable. However, measurements of course and speed are never perfectly accurate. The result is that when NASA launches a spacecraft for Mars, it is sent, as accurately as possible, in a precisely calculated direction at a precisely calculated speed that should take it to Mars at a known time on a course and at a speed that will allow it to be injected into Mars orbit with minimum fuel burn. However, there are margins of error, which result in the need for course corrections; those course corrections do not prove that NASA's model is flawed. 

The same principle applies to climate science, except that the margins of error are, in percentage terms, larger.