If an 8th grader could grasp it it wouldn't take years of education and research expereience to do. Or to quote Feynman, "Listen, buddy, if I could tell you in a minute what I did, it wouldn't be worth the Nobel Prize". Any explanation on that level can be countered by someone with an equally plausible sounding but wrong explanation on a similar level.
Actually doing a full, detailed assessment of the validity of evidence would take an experienced scientist from a different field a *long* time to read through all the relevant publications, learn the material and arrive at his own conclusion.
Your quote by Feynman is limited by time, not understanding. I think a great example of what I mean would be Hawkings "The Universe in a Nutshell". Its a full book that describes in fairly simple terms, and with pretty pictures, how stuff works. You need very little previous knowledge to gain from it, and since its written with the layperson in mind, its enjoyable. The only problem is that so far as I can see, climate science as a whole has decided to use an emotional "protect our home" approach to marketing, rather than giving people easier access to the data, which from the things I've seen, is kinda undersold as obviously magically correct. Thats why people are so untrusting of AGW. We've learned as a society, with good reason, to not trust an appeal to emotion.