Geoscience Reference
In-Depth Information
An introduction to climate change
1
In most places on this planet's terrestrial surface there are the signs of life. Even in
places where there is not much life today, there are frequently signs of past life, be it
fossils, coal or chalk. Further, it is almost a rule of thumb that if you do discover signs
of past life, either tens of thousands or millions of years ago, then such signs will
most likely point to different species than those found there today. Why? There are
a number of answers, not least of which is evolution. Yet a key feature of why broad
types of species (be they broad-leaved tree species as opposed to ones with narrow,
needle-type leaves) live in one place and not another has to do with climate. Climate
has a fundamental influence on biology. Consequently, a key factor (among others)
as to why different species existed in a particular place 5000, 50 000, 500 000 or even
5 000 000 years ago (to take some arbitrary snapshots in time) is because different
climatic regimens existed at that place at those times.
It is also possible to turn this truism on its head and use biology to understand the
climate. Biological remains are an aspect of past climates (which we will come to in
Chapter 2). Furthermore, biology can influence climate: for example, an expanse of
rainforest transpires such a quantity of water, and influences the flow of water through
a catchment area, that it can modify the climate from what it otherwise would have
been in the absence of living species. Climate and biology are interrelated.
Look at it another way. All living things flourish within a temperature range
and have certain temperature tolerances for aspects of their life cycle. Furthermore,
all living things require a certain amount of water and the availability of water,
terrestrially, is again driven by climate. Given this essential connection of temperature
and water to life, it is not difficult to see how important climate is in determining
where different species, and assemblages thereof (ecosystems), can be found.
From this we can easily deduce that if climate is so important, then understanding
climate change is absolutely critical if we are to predict the likely fate of species in
a certain region. As mentioned, it is also possible to use the reverse in an applied
sense to note the presence (or past presence) of different species and then use this
as an indicator of climate, both in the past and in the present. This interrelationship
between life and climate is fundamental. It affects all species, which includes, we
sometimes forget, our own:
Homo sapiens
. We also tend to forget that on every
continent except Antarctica there are examples of deserted settlements and evid-
ence of long-extinct civilisations. These are societies that once flourished but which
have now gone, primarily because of a change in climate (this will be examined in
Chapter 5).
If it is not sufficiently significant that living things, including human societies,
are subject to the vagaries of climate change, there is now convincing evidence that
our modern global society is altering the global climate in a profound way that also
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