There's a few good reasons they tend to start these things in the mid 1800's.
That's not climate denial, it's more about people not presenting the whole picture, so the 'solutions' are liable to be flawed.
We're still coming out of an ice age.
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Earth’s hottest periods—the Hadean, the late Neoproterozoic, the Cretaceous Hot Greenhouse, the PETM—occurred before humans existed. Those ancient climates would have been like nothing our species has ever seen.
Modern human civilization, with its permanent agriculture and settlements, has developed over just the past 10,000 years or so. The period has generally been one of low temperatures and relative global (
if not regional) climate stability. Compared to most of Earth’s history, today is unusually cold; we now live in what geologists call an interglacial—a period between glaciations of an ice age.
https://www.climate.gov/news-features/climate-qa/whats-hottest-earths-ever-been