GEOLOGY

Detailed explanation-1: -By extracting cylinders of ice from sheets thousands of meters thick, scientists can analyze dust, ash, pollen and bubbles of atmospheric gas trapped inside. The deepest discovered ice cores are an estimated 800, 000 years old.

Detailed explanation-2: -By drilling more than 3 kilometers deep into the ice sheets over Greenland and Antarctica, scientists can see how temperature and atmospheric carbon dioxide levels have changed from then until now.

Detailed explanation-3: -Scientists use air trapped in the ice to determine the CO2 levels of past climates, whereas they use the ice itself to determine temperature. But because air diffuses rapidly through the ice pack, those air bubbles are younger than the ice surrounding them.

Detailed explanation-4: -Changes in past atmospheric carbon dioxide concentrations can be determined by measuring the composition of air trapped in ice cores from Antarctica. So far, the Antarctic Vostok and EPICA Dome C ice cores have provided a composite record of atmospheric carbon dioxide levels over the past 800, 000 years.

Detailed explanation-5: -Over the last 800, 000 years atmospheric CO2 levels as indicated by the ice-core data have fluctuated between 170 and 300 parts per million by volume (ppmv), corresponding with conditions of glacial and interglacial periods.