The reason is, of course, that the differences are essentially political:
For 20 years, evidence about global warming has been directly and explicitly linked to a set of policy responses demanding international governance regimes, large-scale social engineering, and the redistribution of wealth. These are the sort of things that most Democrats welcome, and most Republicans hate. No wonder the Republicans are suspicious of the science.Democrats see themselves "as keepers of enlightenment" (remember the Bush era!), while Republicans "have come to believe that mainstream science is corrupted by ideology." This is a problem, indeed. There are not enough Republicans in science.
Of course, the US are different from Germany. But anyway, we are familiar with this problem; the problem as stated by Sarewitz is at the very origin of klimazwiebel, I guess:
Yet there is clearly something going on that is as yet barely acknowledged, let alone understood. As a first step, leaders of the scientific community should be willing to investigate and discuss the issue.