The first answer given to this question:
'It sounds like most of the AGW crowd believe that once a code is written there is no mistakes and the output is correct if it proves what they want."
is written by someone who is either intentionally lying or completely out-of-touch with climate modelling, or both. (I pick the latter, actually).
Researchers spend an ENORMOUS amount of time testing models, fixing them, et cetera. Anyone that would believe the quoted statement has probably never written a piece of code in his life, and has no business attempting to answer such a question.
There is more than one type of peer review. The one that gets talked about all the time on here is peer review as practiced at refereed journals. At organizations of any size there is also internal peer review, which is where a lot of the code-checking will go on. It may be years between when a climate modelling code development starts and when results are published. During that time there will be constant error-checking, refining of the code, internal review, etc.
EDIT: Beam, you're awfully testy about this. Did you get fired by NCAR or something? I don't know what sort of software you work on, but some software gets tested extensively, some does not. There are all sorts of different ways of testing software, with different goals in mind. People have spent many years using computers for atmospheric modelling. You're probably unaware of this, but that was pretty much the first application of large computers, back when "programming" was done with vacuum tubes rather than Visual Basic or whatever it is that you program in.
I worked for six years at a simulation software company, so yes, I have participated in software testing. The testing on GCM's goes WAY beyond anything I saw there. If you think you're such hot stuff, why don't you download the code for the Community Climate System Model (CCSM) and get to work testing it? You can get it here:
http://www.ccsm.ucar.edu/
Play with it, test it, poke holes in it, add new physics to it, just stop making the assumption that people with Ph.D.s that spend their lives doing this are stupid. I think because other groups do things differently than what you have been trained to do in your software engineering courses, you think they're wrong.
If you're advocating that more money be spent on programmers for climate research, I'm all for that. I don't do GCM development, but in my career I have done programming in Fortran, GW-Basic, VB, PV-Wave, IDL, Matlab and NCL, and I'd LOVE to have some programmer lackey doing that stuff for me. I'm just a hack at programming and if you're saying that I need to have someone writing and testing code for me, I'd love it. That way I could spend more time on the science.
Another EDIT: No Beam, I believe you are naive for thinking that software testing is only done one way or with one goal. I see you only wanting to criticize software development that I don't think you really know anything about. I gave you the link to the CCSM, use that as a test case for your own GCM software test suite--show the climate scientists how it should be done! If you're only willing to bad-mouth other people's work while doing nothing concrete of your own, why should anyone respect what you are saying?
Once more for Beam: Yes, I could tell your education was in software engineering. Bully for you. You don't think there are plenty of software engineers with all the training that you have had working on climate models? Testing is great, I'm all for testing. Just because YOU are not aware of it doesn't mean it doesn't go on. I'll even say that every climate model has bugs in the software, that's true with any large complex piece of code. Atmospheric models can be some of the largest and most complex pieces of code around, and need to be tested extensively and they are. You just don't believe it, and you don't really want to find out the details, which I'm sure you could by looking at various websites for the groups that put together the models and contacting them. You'd rather just say that you're smarter than they are and try to throw doubt on their results with nothing to back it up.
Final EDIT: The only assumption I'm making is that the software engineers and climate scientists working on climate models know a lot more about them than people that don't. And again, I don't claim any special knowledge of computer science or software engineering, I only do what I have to (I don't generate climate models). YOU'RE the expert in software testing, go do it, stop complaining about what other people are doing. The models are out there, go for it!