FIGURE 2. Example of millennial changes in climate and greenhouse gases as recorded in polar ice cores from 45 to 50 kyr bp in comparison with model simulation.

a, Ice-core records; b, model. Light blue shading indicates the stadial (cold in Greenland) phase following D-O interstadial 13 and immediately followed by rapid warming into D-O interstadial 12. This stadial coincides with an event of widespread ice-rafted debris in North Atlantic sediments (Heinrich event H5). In a, Greenland observations include ¹⁸O (ref. 28; temperature proxy) and N₂O concentrations¹⁵; Antarctic records include ¹⁸O (Dronning Maud Land²⁹, grey, and Byrd¹⁷, black), and CO₂ (Taylor Dome³⁰) on the age scale of ref. 24, shifted from the GISP2 age scale by 1.8 kyr to synchronize with the NGRIP age scale (Supplementary Information). In b, model output shows imposed North Atlantic freshwater forcing, temperature changes over Greenland (50°–30° W, 68°–78° N), atmospheric CO₂ and N₂O, and surface air temperature over Antarctica (68°–78° S). Inset, amplitude of N₂O changes versus the duration of corresponding stadials, from two ice-core records following ref. 15 (blue), and from four model simulations (orange).

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