[fencepost]

are thus an exercise in straight extrapolation based on very complex and interconnected inputs

If I throw a ball to you, your ability to put your hand approximately where it's going to be and catch it is "extrapolation based on very complex and interconnected inputs," and as it gets closer you're able to improve based on additional input.

Sure the models could all be wrong, we could be on the brink of a new ice age, and that ball could suddenly take a sharp right turn and accelerate. I wouldn't recommend putting all your money on either of those as a bet.