Princeton researchers analyze 2 million-year-old ice cores

Researchers from Princeton University have extracted ice cores from Antarctica that has given the first direct observations of the ancient climate when the early ancestors of humans roamed the Earth. The gas bubbles that were trapped in the ice cores said to be the oldest recovered, give snapshots of prehistoric atmospheric conditions and temperatures. The team collected the ancient ice cores in the Allan Hills of Antarctica.The team used data from the ice cores to answer long-held questions about how the current glacial cycle emerged. The team says that up until 1.2 million years ago, the Earth's ice ages consisted of thinner, smaller glaciers that came and went every 40,000 years on average.

After the Mid-Pleistocene Transition, the current world emerged characterized by colder and longer glacial cycles of 100,000 years. These are known as the 40k and 100k world. Some theories believe that the current 100k world emerged because of a long-term decline in atmospheric carbon dioxide.

The researchers found this wasn't the case with the samples showing average carbon dioxide was relatively steady through the 40k and 100k worlds. Researchers say that while the decline in carbon dioxide might not have led to the 100k world, there was a correlation between carbon dioxide and global temperature. The team says that changes in carbon dioxide are required to get from cooler glacial temperatures to warmer interglacial temperatures.

Carbon dioxide in the atmosphere today is over 400 ppm, nearly 100 ppm higher than levels of the 40k world. The team noted that we are seeing carbon dioxide levels not seen in 2 million years. To see an analogy of our world today in the past, we have to look beyond 2 million years ago to find it, according to the scientists.