The Forbes article is an opinion piece. That doesn’t make it false, but I normally avoid opinion pieces. But we’ll make an exception. It spends a lot of time inserting doubt, but doesn’t actually replace it with anything. He also points out that some were classified improperly, but doesn’t give an actual number. Why not? I’m guessing because it was insignificant. Why not calculate the actual number? Is it 80%? 65%? 9%? Don’t quote a number and it’s harder for people to refute you. It’s important to listen to what people don’t say as much as what they do say.
https://skepticalscience.com/97-percent-consensus-cook-et-al-2013.html
Skeptical science (yes, cook) reviewed 12000 articles. Additionally, they reached out to the authors.
“As an independent test of the measured consensus, we also emailed over 8,500 authors and asked them to rate their own papers using our same categories. The most appropriate expert to rate the level of endorsement of a published paper is the author of the paper, after all. We received responses from 1,200 scientists who rated a total of over 2,100 papers. Unlike our team's ratings that only considered the summary of each paper presented in the abstract, the scientists considered the entire paper in the self-ratings.”
As far as only reading the abstract: “An abstract is an outline/brief summary of your paper and your whole project. It should have an intro, body and conclusion. ... Abstracts highlight major points of your research and explain why your work is important; what your purpose was, how you went about your project, what you learned, and what you concluded.” Reviewing an abstract should be sufficient in most cases. Yes there will be errors, but as shown in your referenced Forbes oped, they are engaging with people about those.