The IPCC is relevant only in that it acts as an excellent, public summary of the scientific knowledge on global warming. It's a review article, not a popularity contest.

It's not a review article, it's a political statement put out by a political organization in order to effect political change. Read some of the dissenting opinions.

which is supposed to imply that global warming can't be science, since we can't predict the weather next Wednesday, let alone a random Wednesday in 2030.

Sometimes I think you're just talking to yourself, timr. Nobody is talking about the weather. Pick any inputs, predict any outputs. Take projected levels of greenhouses gases in the atmosphere (what are those, anyway?) and predict average global temperature. Take solar input and predict cloud cover. You choose. For us to have any sort of reasonable discussion about this "science" of yours, you actually have to make some testable hypothesis. Without that we have bupkis go on. You're the person saying something bad is going to happen. Logically you have to have some idea of what output amounts to "bad". It's your problem, not mine.

Have the conversation that we're having, not some other conversation you wish we were having.

We have no idea how gravity works, yet we are able to model it quite accurately. Why? Let's take a look at your examples to see what we can learn there: life evolving, embryonic development, etc. These examples are complex systems that we can only make Bayesian links between. Why would we do that? Because we're still in the process of abduction in a lot of these areas. Nothing wrong with that. With gravity we've moved to induction. But it means that the science in those fields has not advanced to the same point as physics, for instance. Various fields of science are harder or softer than others.

Because you choose to conflate all of this for purposes of argumentation, let me give you an easy discrimination rule: the amount of data observed makes correlation more reliable even if hypotheses are flimsy. To give a real-world example, if I go to my doctor with cancer, he prescribes some medications. Now even though he may have no idea of how cancer works or be able to predict how it will progress in me, I can have confidence his treatment will be "mostly" good. Why? Because he has a million other cancer cases to statistically draw on. He may have not idea why the treatment he is using works (he may have not deduced any rules), but he knows from the patterns of a large set of data that, given a certain treatment, most patients get better. (He has abductively progressed)

Compare to those millions of patients (or millions of embryos or millions of cells to use your example) to the global warming guys who have one earth and about a hundred years of data. That's like me going to a witch doctor for brain surgery. Ain't happening.

The problem we have is that the softer the science and the sparser the data, the more easily Kuhn's observation of scientific paradigms plays itself out in research. In other words, groupthink takes over. It's very difficult to get anybody to believe that scientific consensus means anything when talking about integrals, but if you're talking about something like psychology consensus is really all you have. That's because without an inductive model we're stuck looking at data and attempting to find patterns. Biology sits nicely between hard and soft sciences. So it's a good example. The basic chemistry we have down. Some of the other stuff we're just guessing.

So while I think it's very interesting that current scientific thinking is that some sort of string theory explains the universe, I'll feel a lot better when we have a theory that can't be bent into saying whatever you'd like it to say. While I think evolution is a profitable and reasonable generally good thing for folks to believe, I don't think it's the answer to every open biological question there is. It's simply the best we have to address the big questions. And while I'm certain the absorption spectra of various greenhouse gases are well known and reliable, I'm completely unwilling to take that simple piece of data and extrapolate it using various forms of cellular automata into predictions of world-wide catastrophe. Yes, scientists are doing all of these things, and I'm sure it would hurt their feelings to hear that they're just blowing smoke up each other's posteriors, but that's all it amounts to. Guesswork. Relying on the paradigm because that's all we have. It's a great starting place. Now just complete the circle of the scientific method to get something useful out of it.