Weather predictions for the next few days are known to be pretty accurate. However as the days turn to weeks, the accuracy goes down dramatically.
It seems that to predict accurately, one needs to know and understand the rules of the game. As things get complex, take the climate for example, the rules are more difficult to understand. So, it becomes hard to pinpoint how climate will change in the future. However, we need to not mess with nature and risk causing any more global warming. This could be done as a matter of applying the precautionary principle.