Greenland deglaciation puzzles

About 23,000 years ago, the southern margins of the great Northern Hemisphere ice sheets across Europe and North America began to melt. The melt rate accelerated ∼20,000 years ago, and global sea level eventually rose by ∼130 m as meltwater flowed into the oceans. Ice cores from the Greenland and Antarctic ice sheets show the rise in atmospheric CO2 concentrations that accompanied this shift in global ice volume and climate. However, discrepancies in the temperature reconstructions from these cores have raised questions about the long-term relationship between atmospheric CO2 concentrations and Arctic temperature. On page 1177 of this issue, Buizert et al. (1) report temperature reconstructions from three locations on the Greenland ice sheet that directly address these problems