Unfortunately, it seems that once you reach a certain age, having been fooled for years becomes psychologically an impossible admission. Hence, if you're talking fervent denialists above the age of (roughly) 65 or 70, it seems we're just going to have to wait til they die out rather than continue to try to convince them.
Anyway, here's a key chart from the post that (maybe) I've posted before?:
If climate scientists were trying to exaggerate global warming they’d show you the unadjusted raw data!