The most dramatic examples of climate changes in the past are the ice ages, which covered Canada with an ice-sheet several kilometres thick. 1b Ice-core samples taken from Greenland and Antarctica carry a record of the climate in snowfalls over periods of up to 400,000 years or more. On the global level, these changes took thousands of years, but in some regions they occurred in just a few decades. We are currently in an interglacial period today. One climate factor undergoing rapid change now is the greenhouse effect .
Scientists predict the consequences of that change using computer models of climate, .
Researchers are also studying the economic and social dimensions of climate change.