Brian Fagan -- The little ice age
====================================

This book has a number of lessons to teach us.

One is that climate change can happen rapidly.  A major regime
change can take place in significantly less than a century, perhaps
even within a decade.

Another lesson is that abrupt climate change is unpredictable.  A
natural but unpredictable event such as volcanic eruption, an
earthquake, or even major storms can trigger changes that cause
significant changes in temperature that last multiple years.  But,
even ignoring those unpredictable natural events, the climate and
weather system itself is chaotic.  The ocean currents and global air
flows form a complex system that works in ways that we do not fully
understand and that cause chaotic changes that cannot be explained
by simple causal chains.

And additional lesson is that the system (wind patterns, ocean
currents, storm patterns, volcanic eruptions, even the eccentric
orbit and changing tilt of our planet around the Sun, and more) is
very complex; we do not thoroughly understand it; and it works in
non-linear ways.

One more lesson is that not even the direction of climate change is
predictable.  Yes, we are in a period of global warming.  But, as
Fagan explains, that could cause changes in ocean currents that
could send us back into another "little ice age".

Some of the complexity of that global system of weather and winds
and ocean currents is explained in an early chapter of "The little
ice age" where Fagan discusses the NAO (the North Atlantic
Oscillation).  The NAO has to do with the difference in atmospheric
pressures over Iceland and the Azores Islands: persistently high
over one and low over the other, and sometimes the reverse.  Changes
in the NAO are associated, in history, with times of extreme cold
and rains over England and Europe.  In 1315 C.E., at a time when
little food could be saved for use during years of low or no
harvests, this had disastrous results.

And, one of Fagan's warnings would seem to have no consequences for
me, but is vastly important: as he says, hundreds of millions of
people in the world live, today, on subsistence agriculture,
subsisting from harvest to harvest.  A crop failure for them is
close to a death sentence.  Unlike me, they cannot go to the
supermarket and buy food on their credit or debit card.  Our
policies and actions might push us closer to a regime whose weather
patterns, in some years, are outside the boundaries that produce
successful harvests.  For these people, that human forced global
warming, even modest and incremental warming, is not a matter of
slightly less comfortable summer temperatures; it is, again in some
years, a matter of life and death.

The overriding lesson: It's not smart to mess with Mother Nature.

One additional comment by Fagan that should give us reason to be
cautious about what we do that affects the global climate and
weather system: we still do not understand, as of his writing, what
caused the Little Ice Age.  When you do not understand the
mechanism, it is wise to be very cautious about tampering with its
controls.  And, keep in mind that our planet Earth is not an
isolated system.  In order to understand that system thoroughly, we
would also need to take into account variations in the Earth's
eccentric orbit around the Sun, as well as changes in the Sun's
surface and its output, although we do not have any control over
those conditions and that behavior.

Fagan's views on these matters seemed to have developed and are
supported by his study of long-term weather patterns.  For more on
that, you may want to read one of his other books: "The attacking
ocean".

09/23/2016

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