According to the news, ice from Greenland gives information about

Scientists say they can tell what air and sea conditions were like hundreds of thousands of years ago. They say pieces of ice taken from Greenland provide such information. Scientists took the ice from more than 1.5 miles deep in huge masses of ice that float on the sea. The ice represents 25,000 years of history. It provides one of the clearest records of ancient weather.
     European and American scientific teams have been studying ice from the same area to confirm each other’s findings. They measured the oxygen and carbon dioxide in the ice for the temperature. From these measurements, the scientific teams say that the past 10,000 years is the only period during which temperature has not changed very much.