This is part of a comment from rgb at Duke, a commenter on Watts Up With That
We cannot predict the climate. We cannot even predict the damn weather, not more than a week or so out. There are really good reasons we cannot predict the weather, and equally good reasons we cannot predict the climate. It is true that they aren’t quite the same problem, and sometimes one can predict the average behavior of a system in the long run (whatever that means) when one cannot predict its short time behavior at all reliably, but when I say we cannot predict the climate I mean that wecannot even understand the past behavior of the climate! We have no friggin’ idea why the MWP was warm, the LIA was cold, and why the world warmed (without CO_2 increase to drive it) since the Dalton minimum. We cannot predict the future state of one of the only important contributor of heat to the system, an enormously important cause whose effects on the Earth are complex and only beginning to be understood. To claim otherwise is an enormous act of intellectual hubris and scientific fraud — unless and until you can back up the claim with actual predictions, consistently validated. Or hey, I’d settle for a halfway decent hindcast or two, back to (say) 0 BCE or 16,000 BCE or 120,000 BCE or 50,000,000 BCE. The only thing we learn looking at the real climate record of the Earth is that it is always changing, that the changes are sometimes sudden and profound, and that we have no idea why they occurred or why they WERE either sudden, or gradual as the case may be, or gentle and moderate, or profound and catastrophic as the case may be.
Some of these things we are likely to never be able to properly prove or understandas the evidence is simply gone into the past. The Ordovician-Silurian transition — an ice age that began with 7000 ppm CO_2, and that peaked in glaciation a few million years later with CO_2 still at 4000 ppm. What’s up with that? Space aliens came and directed a freezing ray at the Earth, straight out of Buck Rogers? The Sun decided to turn off (partly) for a million years or so? A civilization consisting of highly evolved giant spiders had a nuclear war and triggered a nuclear winter a few million years long? Sure, we can propose more sensible alternatives, but honestly they will all still feel like science fiction, and in all probability none of them can either be verified/supported or falsified, at best they can be shown to be a consistent possibility.
Why is it so very difficult to say “we don’t know”?
rgb
There's more at his comment, found here, and go to June 5 at 5:12 pm
