FIGURE 4.1 The Hunt-Lenox Globe. Wording near China says “hic sunt dracones,” which translates to “here be dragons.” This is a metaphor for unknown threats. Often, as humans have explored more of the world, threats have become less—in this case, the “dragons” may have referred to Komodo dragons, rather than dragons of fairy tales.

ice coverage in the North Atlantic, that they had a near-global footprint but regionally distinct impacts, and that even slow changes in freshwater flux to the North Atlantic could cross a threshold and trigger a sudden event (e.g., Alley, 2007). The very large magnitude of the changes in some regions, the wholesale and rapid reorganization of ecosystems, and the very rapid rates of change that affected certain places (10°C over 10 years in Greenland), together with the realization that greenhouse warming would cause significant changes in freshwater fluxes to the North Atlantic, caused concerns that extended beyond the scientific community into popular culture (e.g., the 2004 science-fiction/disaster movie The Day After Tomorrow).

As discussed in Chapter 2, subsequent research has shown that an abrupt disruption of the Atlantic Meridional Overturning Circulation (AMOC) is much less likely under modern boundary conditions than during the ice age, and that the regional cooling impact of the shutdown in heat transport to the high northern latitudes would

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