Is It Happening Again?

Column for week of April 20, 2015

     A news item at Bloomberg News reports that the gulf
stream in the North Atlantic is slowing down for the first time
since 900.  The gulf stream caries warm water north from the
tropics warming the North Atlantic and surrounding area,
including Europe.  Slowing of the gulf stream could cause
cooler, dryer weather in the North Atlantic region.

     Supposedly the cause of the slowing is melting ice
diluting the salt water in the ocean.  So far this all sounds
reasonable.  The force that drives the gulf stream is the
difference in pressure between the cold, dense North Atlantic
and the warmer, lighter tropical water to the south.  The light
water is forced up by the heavier water from the north.  This
creates a hill in the tropical ocean.  Water flows endlessly north
being replaced by cold northern water.  The cold water warms
and then flows north too.

     Fresh water from melting ice is less dense than salt
water.  Thus, it reduces the pressure that drives the  gulf stream. 
For this to continue there must be an endless supply of fresh
water.  Otherwise, the fresh water soon mixes with the salt
water.  Then the gulf stream returns to its faster flow. 

     So far we are talking science.  Then the article jumps the
fence into politics.  It claims the recent slowing of the gulf
stream is caused by man made global warming.  Few, if any,
people would even dare to claim that the slowdown in 900 was
caused by humans.  Why aren't they considering that the current
slowdown may be caused by the same natural forces that caused
the one in 900?

     The year 900 was during the Medieval Warm Period that
peaked around 1100.  Then the world slid into the Little Ice Age
that held on until the mid nineteenth century.  For 150 years or
so the world has slowly and intermittently warmed a degree or
so from the Little Ice Age.  There is no reason to believe that
the world is as warm today as in 1100.  Likewise there is no
reason to believe the present warming has different causes than
the warming during the Medieval Warm Period.

     If the slowing of the gulf stream cools and drys the air
over the North Atlantic, it will slow the ice melt.  This will
restore the density of the North Atlantic.  This in turn will
restore the speed of the flow in the gulf stream.  As is so often
the case, nature will have restored its own equilibrium.

     Of course saying that the current slowing of the gulf
stream is merely repetition of a age-old phenomenon is barely
news worthy.  For anyone who isn't a gulf stream fanatic, it
would be a yawner.

     The fashion of the day is to blame every ripple in our
ever changing weather and oceans on man made global warning,
sometimes called anthropogenic (Can you believe I spelled that
right on my first try?) warming.  Scare mongers like big scary
sounding words.

     Human activity may be causing some warming.  It is well
established that building and paving a major city creates an
urban heat island.  The effect of this on average world
temperature is incredibly small.

     The "proof" of carbon dioxide caused warming is almost
all based on computer models that exaggerate warming and
completely missed the current pause in warming.  We should
back off on draconian actions to prevent man made global
warming, at least until we find data that show dangerous
warming is actually occurring.

     So far we have had three warming periods of 20 years or
so since 1860.  The warming periods were separated by cool
periods of 30 or so years each.  Most of the warming was prior
to 1940.  Most of the carbon dioxide was produced after 1940.

     The warming periods simply don't match the carbon
dioxide emissions.   Those who claim that the carbon dioxide
caused the warming have a lot of 'splanin' to do.

aldmccallum@gmail.com
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Copyright 2015
Albert D. McCallum