THE HISTORY OF CLIMATE CHANGE
We know about past climate by studying the geological record and evidence of past glaciation. If we look at where the glaciers were, we can reconstruct a history of the ice ages that have affected our planet. Earth’s climate is generally stable; however, average surface temperatures have varied throughout history. These temperature changes form a regular cycle that is approximately 100,000 years long. We are not entirely certain what caused the lower temperatures of Earth’s ice ages, but we do know that the transition from the last ice age to the present warm period took thousands of years.
听力材料：
By studying patterns of glaciation, we’ve known for a long time that climate change has happened in regular cycles. But more recent research tells 11s that climate change is not always gradual. Ice cores drilled from glaciers in Greenland challenge the theories about long, gradual cycles of climate change. The ice cores are evidence of a sort of “flickering climate”—sudden swings from warm to cold, and back again. The fact that these changes took place so quickly tells us that our climate is not as stable as we used to think.
The layers in the ice tell the history of climate change. They show us a period of global warming about 11,000 years ago. This warming took several decades, but was also marked by several sudden jumps in warming that each took less than five years. About half of the warming was concentrated in a single period of less than 15 years. This is very rapid climate change.
Researchers studying the ice cores have concluded that during our latest ice age the climate might have fluctuated wildly. Average annual temperatures may have risen several degrees in only a few years—only to slide back into sort of a deep chill again, an ice age that lasted thousands of years. Furthermore, the change from the latest ice age to the present warm period might have taken less than a human lifetime—not the thousands of years of gradual warming that most scientists once believed.
Question：
The professor discusses studies of the ice in Greenland. Explain how this research has advanced our understanding of past climate change.
