I don’t see how this is biased. Showing that the Earth did warm up over time before major human climate change started would be, very weakly, supporting that climate change isn’t real. If they wanted to be biased they would start at a warm point, and when the Earth is cooling down they’d be like “see! Earth cools naturally, so it must get warm because of climate change!”

To make my stance crystal clear, I believe in and am deeply concerned by climate change