What agenda do you think people have that are long dead?
If you distrust everything you can measure it yourself. I am still in youth and even I can see changes myself. There used to be snow in the winter and now it's rare for example. Yes that is weather not climate; I don't live long enough to see climate changes. But there are oil paintings from 300 years ago. Are these fake?
Genuine question: How do you know, that people who know climate change is made-up are trustworthy and don't have their own agenda?