Jim White and Trevor Popp are part of a 17-person international ice-core team who discovered that two huge Northern Hemisphere temperature spikes prior to the close of the last ice age some 11,500 years ago were tied to rapid and fundamental shifts in atmospheric circulation.
To chart past temperature and precipitation swings, the team used changes in dust levels and stable water isotopes in the annual ice layers of a two-mile-long Greenland ice core (NGRIP - North Greenland Ice Core Project). Those changes show that the Northern Hemisphere briefly emerged from the last ice age some 14,700 years ago with a 22-degree-Fahrenheit spike in just 50 years, then plunged back into icy conditions before abruptly warming again about 11,700 years ago. Startlingly, the Greenland ice core evidence showed that a massive "reorganization" of atmospheric circulation in the Northern Hemisphere coincided with each temperature spurt, with each reorganization taking just one or two years. Their paper was published in the June 19 issue of Science Express, the online version of Science.