Geoscience Reference
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Years before present (thousands)
Figure 10.
Historical proxy temperature estimates for Greenland.
this period. By contrast, the thirty-three millennia before that saw vio-
lent fl uctuations in and out of ice ages. Other longer-term records indi-
cate that the last 7,000 years have been the most stable climatic period
in more than 100,000 years.
This is a sobering fi nding because this is also the period that has
witnessed the emergence of written languages, cities, and human civi-
lizations. Was climate stability a prerequisite for the emergence of farm-
ing and cities? Would the Sumerians have developed the fi rst written
language if they had been confronted with an unstable climate system?
How would philosophy and literature have developed in Greece if the
city-states were suddenly plunged into an ice age? We do not know, but
many anthropologists believe that the stability of climates over the last
seven millennia was an important contributor to the evolution of hu-
man societies as we know them today.
But the future is almost surely going to be different from the last
7,000 years. The CO 2 implications of larger populations, economic ex-
 
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