Geoscience Reference
In-Depth Information
be an ash layer that can be matched to a volcanic eruption of known age, or
the i rst appearance of the pollen of an introduced species, such as eucalyptus.
In the next i ve chapters, the methods reviewed in this chapter will be
essential in understanding how scientists have pieced together the history
of climate over the past 20,000 years. We then turn to the more challenging
questions of what causes climate to change over shorter and longer timescales
and why these changes are ot en periodic in nature. Looking ahead to the
concluding chapters, we shall also see that both accurate methods and a good
understanding of past climate change will be needed to address the most
dii cult question of all: What will the nature of the climate of the American
West be in the future, and what will it mean for the region's water resources?
