A direct record of past temperatures still exists in the ice sheet. This record allows us to determine the temperature history at the core site and to calibrate geochemical temperature proxies.
Borehole temperature measurements reveal past surface temperatures preserved at depth in the ice sheet.
These measurements constrain our estimates of past temperatures. Good estimates closely match the measurements. Using geophysical techniques, we have achieved a good estimate of central Greenland temperature history.
Previous analyses underestimated the magnitude of temperature changes.