What is important, I think, is that we shouldn't believe anyone just because they're an expert. What we believe or not should not be based on who says it, but ultimately on the data that supports it (or not).
So find the studies that (are supposed to) support a given opinion, have a look them, and have a look at how other studies in the field react to it. That last point is very important: it often reveals flaws in the study that a layman could never spot.
> In any case, I don't claim its truth, just its existence. It's obviously important to any scientific process to consider alternative theories which have better predictive power, and to criticize our existing ones, however close to reality they ultimately are.
If you go look at the climate science literature, you'll find that all different kinds of models and explanations have been proposed and studied. Those alternatives have been looked at in detail by people in the field, just like any other study. None of them have been found to better match the data.