Alan writes
The same climate scientists cannot even predict what the weather is
going to be next week let alone in a few decades time.

It is much easier to predict a trend than to predict tiny fluctuations
in that trend. For example - our hall has just been repainted. I can
predict that over the years the paintwork will pick up chips and marks
and will eventually have to be replaced. By watching how rapidly this
happens, I will be able to predict how long it will be before it needs
repainting. What I can't do is predict where exactly this week's extra
chip will be.
--
Kay