Thanks for your remarks.
I’m not sure your item #3 can be solved. The climate seems to be a chaotic system. When you have to do thousands of iterations, one little difference can take you in a completely wrong direction. Before I would trust a climate model, I would have to see proven results over a long period of time. Longer than any human being can live. I would certainly not base government policy on climate models that have been developed in the past thirty years or so.
You may be right re being a chaotic system, haven’t looked into it. I model mostly systems that include some stochastic elements. There is also an element of randomness to climate. Volcanic activity, asteroids, anything like that can come along and invalidate everything from then on...