Antarctic ice could provide clues to Earth’s ancient climate

Los Angeles Times : To study the cycle of warming and cooling of Earth’s climate over geologic time, researchers have been looking for clues in ice and sediment samples. Ice can trap air bubbles, which indicate the composition of the atmosphere when they were formed. The oldest ice cores collected to date are some 800 000 years old, and over that time period, scientists have been able to confirm cycles of ice ages and warm periods every 100 000 years or so. Ocean sediment samples, however, which go back further in time, reveal that millions of years ago such cycling may have occurred much more frequently—perhaps every 40 000 years. One possible reason is that the atmosphere may have contained higher levels of greenhouse gases. To find out, Ed Brook of Oregon State University and colleagues are looking for the oldest ice samples on Earth, and hence, the oldest air—which, according to their recent paper published in the journal Climate of the Past, probably lies hidden in Antarctica and could date back 1.5 million years.