Thermometers have only been around for about 300 years. How do we know what the climate was before there were meteorological instruments? Paleoclimatologists, whether played by Dennis Quaid, Randy Quaid or someone else, need to study natural phenomena that depend on climate and preserve the climate dependency in their structure. When it snows, it is not just snow that falls on the ground. Dust, pollen, the constituents of the air such as carbon dioxide and methane, the isotopic composition of the water in the snow, all fall with the snow. On Greenland and Antarctica, where the snow does not melt away in summer, these proxy measures of climate can be preserved for hundreds of thousands of years. As Andrew Revkin reports in today's Times, a consortium of European scientists has successfully extracted an ice core 3190 meters in depth (corresponding to a font size of over 9 million!) from Antarctica. The climate information in the new core spans 740,000 years, which is nearly twice as long a record as the next longest ice core.

More importantly, the new ice core, which is stored in a commercial freezer in France along with sides of beef, goat cheese, and raspberries, spans several more ice age advances and retreats than any previous core. The new core includes the entire warm period that peaked about 430,000 years ago in which the Earth's orbital characteristics around the Sun, which largely determines whether or not we are in an ice age, were very similar today's conditions. The good news? Barring human influences on climate we don't have to worry about entering an ice age for another 15,000 years.