The scientists know this. Paleoclimatology is one big part of climatology. But the outcome is the opposite - you should be more scared, since it shows that climate can change massively. That affects things like agriculture or sea level. What would you assume the sea level was, when those plants were alive?
For example, with very quick search:
"In general, world oceans were about 100 to 200 metres (330 to 660 feet) higher in the Early Cretaceous and roughly 200 to 250 metres (660 to 820 feet) higher in the Late Cretaceous than at present."
For example, with very quick search:
"In general, world oceans were about 100 to 200 metres (330 to 660 feet) higher in the Early Cretaceous and roughly 200 to 250 metres (660 to 820 feet) higher in the Late Cretaceous than at present."
https://www.britannica.com/science/Cretaceous-Period