Just like many other domains, climate science is a mixture between theory, models and empirical results. Often this comes with different scientists working on the different parts (theory/model/experiments), and all claiming their part to be the (far) more important one of the three. A nice analysis is given on the IEEE Spectrum site. Unlike many other domains, it seems hard to me (not being a climate scientist) to do a lot of small experiments to validate the models. This makes it even more important to be open about the precise models used, parameters, and the data used to validate those models.
We’ve only got one planet Earth to validate models on. And it takes soooo long to check whether a model is correct, that we’d better be open about it, collaborate, check each other’s assumptions, and make sure it’s the best model we can make!