Geography Reference
In-Depth Information
2
CLIMATE CHANGE AND CARBON
CLIMATE CHANGE
Long-term climate change
When you examine the scientific evidence it becomes clear that
the Earth's climate has changed throughout its 4.6 billion year
history, but usually on long, slow timescales. It may surprise you to
learn that today we live in an ice age. This is evident by the fact
that there are still large glaciers and ice sheets covering parts of the
planet. These ice sheets have been present over the past 2.4 million
years and have expanded and contracted in cycles. This period of
time is known as the
Quaternary
. However, before the Quater-
nary period the Earth was much warmer and lacked ice sheets. In
fact, it was warm for around 280 million years. Further back in
time there were four other ice age periods in Earth's history which
lasted for a few million years separated by very long warm periods
lasting hundreds of millions of years. So while our current Quater-
nary ice age sounds like it has lasted a long time it is actually very
short compared to the timescales of Earth's history. Understanding
past changes to the Earth's climate provides information which is
useful to our understanding of our current climate and what might
happen in both the near and long-term future.
The start of the Quaternary period seems to have been initiated
by
plate tectonics
(see Chapter 3). The movement of the conti-
nents created the suitable conditions for the beginning of the ice
ages by positioning Antarctica over the South Pole, thereby allow-
ing a large land mass to cool and build up an ice sheet which then
