In the case of climate science, one major flaw is that most mainstream climatologists have started with a working hypothesis (namely, GHG cause global warming) and all their efforts thenceforth have been directed to support that hypothesis, and to turn it into an alarming prospect of very much global warming, e.g. by adopting a relatively high value for climate sensitivity. No major attempt has been made in mainstream climatology to falsify the original hypothesis, or to seriously explore the possibility that perhaps sensitivity is much lower. The certainty of model projections has been grossly exaggerated (or their uncertainty consistently understated, to put it in a gentler way). The magnitude of adverse effects has been generally overstated, even to the point of making scary predictions for the near future that –so far– have failed to materialize at the established deadline, or are not going at the pace required to meet the projections. A number of unexpected results have been emerging, but all the efforts are directed at reducing their significance as in the case temperatures not rising for more than a decade in spite of increasing CO2 concentrations (the missing heat might be hidden in the deep oceans); or tree rings not showing enlargement but shrinking for half a century after 1960, in spite of observed warming (one may use some innocent “trick” to hide the decline, such as not using the unwanted data).
No serious attempt at falsification, no career devoted to that purpose, at least not in mainstream climate science. Only some solitary voices, from elderly professors and the odd Nobel prize winner, and a host of amateurs in blogs. Most young and energetic climatologists just follow the trend. It seems like Max Planck upside down. Planck famously said that a theory gets superseded not by persuasion but by the demographic process whereby old timers that believe in the old theory are gradually replaced by younger minds that adopt the new theory. But in this case it seems to be running backwards: older physicists and climatologists do not participate in the confirmatory effort around climate change models, while their younger colleagues do. Neither does the required Popperian work of trying (and trying hard) to disprove the mainstream theory, the former because they are mostly retired, the latter because their whole careers are invested in the opposite direction.
Besides the non existence of sustained efforts towards falsification, another important constraint is that most of the issues are not about experimental results but about model projections, which are based on scenarios and are, by definition, not falsifiable. So the task of any falsifier would be hard. Many model parameters are hardly written in stone: most are rough estimates that have wide uncertainty margins, and even those estimates and their uncertainty margins are themselves based on debatable assumptions (e.g. estimates of climate sensitivity) and poor or incomplete understanding of the processes at play (e.g. clouds).
On top of all that, there is a wide and powerful current of ideological persuasion and policy advocacy underlying research on climate change. Many non-scientists display strong activism for or against any particular proposition in climate science, and scientists are themselves, more often than not, clearly engaged on one side or another in the political controversy surrounding the climate. The dispassionate approach of science, which looks only for the truth, is difficult to adopt in such environment.
All this does not turn the whole of climate science into a pseudoscience, but many of the classical components are there, and probably some specific fields within climatology have been more heavily affected by pseudoscientific influences. It is time for climate scientists to distance themselves from the fray, and put their act together in a more sensible way.