Hoaxes are, and always have been, a problem in science. Piltdown man, phrenology, eugenics have all been labeled as scientifically valid and each has eventually disproven by “better” science. Also, scientists will periodically go off on wild goose chases that do damage before the correct relationships, measurements or hypothesis become evident.
I’d put climate change caused by increasing CO2 levels in that last group. The climate is always changing so it’s a difficult study and there are scientists sincerely believing their studies. It’s difficult for people to admit they’re wrong or partly wrong.
We’ve also spent a relatively short time actually measuring how average temperature fluctuates. So we really don’t know a great deal for certain. I am talking small increments , the ice core measurements, and C-14 deposits are longer increments.