Life and climate in an ice age - Ice Ages and Interglacials: Measurements, Interpretation, and Models - page 8

Europe, its north buried below the ice, its south a polar desert. Much of North
America is smothered by a giant dome of ice.''
As a result, Mithen (2003) suggested that human communities were forced to
abandon many regions they had inhabited previously while other regions amen-
able for settlement remained unoccupied because access was blocked by dry desert
and ice barriers. People had to survive wherever they could, struggling with freez-
ing temperatures and persistent drought. Burroughs (2005) provides many insights
as to how humans survived the ice ages.
The extinction of Neanderthals has been a topic of interest in both scientific
discussions and public interest. They lived in western Eurasia until approximately
30,000 years ago, when they disappeared from the fossil record, about 10,000
years after modern humans arrived in Europe for the first time. While competition
between these groups is often cited as the cause of Neanderthal demise, it is poss-
ible that the Ice Age climate may have played an important role (Finlayson, 2004).
Most recently, Kennett et al. (2009) found evidence that a comet impact may have
induced extinction of species about 12,900 ybp .
1.2 THE GLACIAL WORLD—ACCORDING TO WALLY BROECKER
Wally Broecker wrote a treatise on ice age climates. According to Broecker:
''Except for the observations made over the last 130 or so years at weather
stations and on ships, our knowledge of past climates is based on records kept in
sediment and ice. The task of the paleoclimatologist is to decipher the proxies
contained in these records. This has proven a complex task for every proxy is
influenced by more than one climatic variable. While much progress has been
made toward isolating the influence of these competing contributions, the task
has proven to be a very tough one. For convenience, these proxies can be divided
into five major groups; i.e., those which carry information regarding: 1) ice
volume, 2) temperature, 3) aridity, 4) atmospheric composition, and 5) ocean
chemistry.''
Broecker went on to say:
''Except for high mountain regions, little precise paleotemperature
information exists for the continents. The obvious source of such information
is the fossil remains of plants and animals. Indeed a wealth of measurements
regarding the relative abundances of pollen grains has been collected over the last
century. However, the [analysis of ] this information has not proven particularly
successful. Unlike the sea that is everywhere wet, the topography of the
continents strongly influences the availability of water. Plant communities are
attuned to these differences in moisture availability. Hence plant communities
respond as much to changes in rainfall and humidity as they do to changes in