Re: @ NomNomNom @ AC
Popper's philosphy was that to count as scientific, then a _hypothesis_ must be _falsifiable_. A hypothesis cannot be proved correct, we can only fail to disprove it.
For example, I might propose, on the basis of any, or no, evidence whatsoever, that gene X influences phenotype Y. This is still a falsifiable hypothesis, because assuming I (or anyone else) can knock out gene X we can determine whether or not phenotype Y has changed.
In this sense (and this sense only) most hypotheses about climate change are not scientific, it is not possible to perform an experiment whose result would falsify the hypothesis (e.g.) increased atmospheric CO2 will lead to an increase in global temperature (amongs many other things, we don'y have a spare planet earth to try it out on).
The same general problem applies to many other areas study (Anthropolgy, Archeaology and Astronomy all spring to mind). Whether or not we reject anything not meeting these rather stringent criteria is a matter of debate, but I find the idea a useful mental tool to asses exactly how useful a given piece of work might be.