Question

how global warming can bring back jaurassic era

Answer 1

Jurassic era was characterized not only by the land behavior and appearance at that time. It also meant complex and and hard creatures like Dinosaurs. So I don't know whether global warming will lead to that kind of era but I am sure it will lead to an Era where there is more water around but you can't drink, land but you can't make it fertile, plants which no longer supports life cycle for human survival etc.