Climatologists have long used ice core samples from Greenland to measure climate changes over the last hundred thousand years or so. But according to the BBC, a group of scientists under the banner of the European Project for Ice Coring in Antarctica, or EPICA, managed to pull a three kilometer-long ice core from Antarctica, revealing the pattern of climate change over the past 740,000 years. By studying gases trapped in the ice, these cores can tell us a great deal about changes to the temperature and atmospheric composition for much of the last million years.
The BBC article gives a good summary, but the article in the June 10 issue of Nature is available here (PDF). The article is brief, but informative. One of the interesting take-aways is the conclusion that the current "inter-glacial era" we live in is likely to go on, absent human disruption, for another 15,000 years, due to the position of the Earth's orbit. Most previous inter-glacials lasted no more than 10,000 years (and it's been about 12,000 years since the last ice age). The last time we saw a long-duration inter-glacial era was around 420,000 years ago; that one lasted for 28,000 years.
A more troubling bit of information from the research concerns CO2 levels. There is a very strong correlation of CO2 concentrations and average air temperature. At the peak of the previous similar inter-glacial period, CO2 concentrations increased to around 275-280 parts per million by volume (ppmv), up from a minimum of 200 ppmv in the previous glacial era. Measurements of CO2 concentrations on Mauna Loa from 1958 to 1998 show a growth of CO2 levels from 316 ppmv to 369 ppmv (it's a bit higher now). While we've known for awhile now that current CO2 levels are much higher than in the pre-industrial period, this is the first time we've been able to measure CO2 concentrations for such an extended period of time, and directly compare them to the last long-period inter-glacial era.
