|
The Little Ice Age
When
the continental sheets of ice that characterized the last
major ice age finally receded about 11,000 years ago, the
Earth entered a period of relatively mild conditions that
has lasted until today. But that doesnıt mean the Earthıs
climate has remained completely stable during the last 10,000
years or so. In fact, the world seems to warm up and cool
down by a few degrees on a relatively regular basis.
One
of these less dramatic climate shifts known as an oscillation-
occurred sometime around 1400 A.D., when the Earthıs average
temperature dipped to about 2 degrees F cooler than that of
today. Human societies around the world felt the impact as
glaciers crept down the Alps and into northern European villages,
crops failed in northern regions such as Scotland and Norway,
and icy seas made subsistence fishing in the North Sea impossible.
Central Atlantic Native Indian tribes moved south, leading
to fierce inter-tribal conflict. Centuries-old orange groves
were extinguished in China.
Historical
accounts kept by people experiencing what scientists today
call the Little Ice Age, are some of the best evidence of
the phenomenon. The Little Ice Age just happened to overlap
with the Renaissance, when Galileo invented the thermometer
and naturalists began recording observations about the natural
world. Today scientists are using records of wheat and other
crop prices to infer the weather conditions from individual
years. Some are even surveying landscape paintings from the
period to see what kind of weather artists at the time were
depicting. Climatologists
supplement human records with natural ones such as the rainfall
data stored in tree rings, and atmospheric gases stored in
polar ice caps and in seafloor rocks.
Both
kinds of evidence indicate the world began to thaw out a bit
by 1850 or 1900. But, since the global climate is determined
by the complex interaction of numerous natural processes,
scientists have yet to pinpoint exactly what triggers these
periodic warm-ups and cool-downs. What is clear, however,
is that one or two degrees can have a far reaching impact
on natural resources, agriculture and the societies that depend
on them.
Click
on a thumbnail picture to learn about another
great moment in global climate change:
      
|
