The climate scientists generally haven't been doing the catastrophe predictions. If you go back and read the early IPCC reports, it's not like they were predicting the end of the world was nigh. In fact, they still don't predict that. What they do predict is severe consequences that will have high adaptation costs if we don't limit the amount of warming. They don't predict the end of humanity, but just a big cost to humanity.
The activism comes from people who misrepresent the science. The skepticism also comes from people who misrepresent the science. The public debate is almost orthogonal to what the actual science in the IPCC reports says.
To give an example, the IPCC AR5 (2013) report says this:
"More recent assessments indicate that it is unlikely that annual numbers of tropical storms, hurricanes and major hurricanes counts have increased over the past 100 years in the North Atlantic basin. Evidence, however, is for a virtually certain increase in the frequency and intensity of the strongest tropical cyclones since the 1970s in that region."
An activist picks out the second part and ignores the first. A skeptic picks out the first part and ignores the second. They battle it out, each citing "the science", and both are lying by omission. And that's the best case scenario. Often what gets cited isn't even in the IPCC reports, and of a lineage which is more dubious.
Which is why, if you want to have an informed opinion on the climate, you should ignore the media, ignore the talking heads, and read the IPCC reports.