That's not really relevant, is it? The issues with the climate change happening now is that it is man-made, and that we've built most of our civilization around the assumption that the climate was either not changing, or was changing very slowly.
If something was causing increase flooding in, say, Nebraska, would you bring up that Nebraska was hundreds of meters below water 100 million years ago? If an arsonist were setting wildfires in your your near inhabited areas, would you bring up that there have been wildfires for hundreds of thousands of years due to lighting?
And yes, we know that most of the present day climate change is man-made, because we know that most of the CO2 increase in the atmosphere during industrial times is man-made. We know that because CO2 that comes from burning fossil fuels and plants has a different isotope makeup than CO2 that comes from other sources.