Final answer:
Fossils in Canada indicate that it was once a tropical sea, signifying that the climate has undergone significant changes from subtropical conditions millions of years ago to the cold winters observed today.
Step-by-step explanation:
Fossils serve as a valuable tool for scientists to understand the past climates of regions, including Canada. The presence of certain fossils can indicate a very different climate compared to what we see today. For example, palm tree fossils suggest that parts of North America, which are now temperate or cold, once enjoyed a subtropical climate.
Moreover, the development of ice ages, as indicated by the presence of woolly mammoth remains and evidence of lowered sea levels, shows that Earth's climate cooled during the Quaternary Period, leading to vastly different environmental conditions. In Canada, specific fossils have revealed that it was once a tropical sea rather than the cold winter landscape that we are familiar with today. This shows the dynamism of Earth's climatic history and the extensive changes that have occurred over millions of years.