>> a small change in parameters (for example, the initial conditions of a process) __can__ totally change the result. Say, for this reason a reliable long-term

>> a small change in parameters (for example, the initial conditions of a process) __can__ totally change the result. Say, for this reason a reliable long-term weather forecast is impossible and will remain impossible (emphasis mine) A small change in initial conditions can totally change the result in chaotic systems such as weather forecast, or a much simpler example — double pendulum. There are systems where a small change changes the results only slightly. E.g. a single pendulum.