[ExI] Climate models

John Clark johnkclark at gmail.com
Sat Mar 29 17:32:47 UTC 2014

In the current issue of Science News is a article about clouds and it
confirms that clouds are the single biggest unknown in climate models.
Everybody agrees that clouds warm things through the greenhouse effect at
night and cool things by reflecting sunlight during the day, and everybody
agrees that the cooling effect is larger than the heating effect, but they
disagree about just how much larger and on if we will have more clouds in
the future or less. And a recently discovered fact complicates things
further, clouds made of ice crystals and water droplets reflect light about
equally but the ice crystal clouds have a stronger greenhouse effect than
water clouds. As a result of all this confusion and uncertainty are rampant.

Back in 2007 the United Nations issued a report on climate change, it said
that by 2100 things would be between 2 and 4.5 degrees warmer than now, a
rather large amount of uncertainty; but after spending millions of dollars
and 7 years of hard work they just issued a new report, and their
uncertainty has actually INCREASED.  Now they say between 1.5 and 4.5.  The
article also notes somewhat apologetically (Science News is a honest
magazine but always leans toward the environmentalist view) that after 3
decades of increasing temperatures since 1998 the worldwide temperature has
been roughly constant, and no climate model in 1998 predicted this. They
conclude by saying "scientists say they need at least 20 to 30 years to
determine if clouds respond to global warming the way simulations predict".

I have to say all this doesn't exactly give me confidence that I should bet
my life on the fact that although they make lousy 17 year predictions
climate models make wonderful 100 year predictions.

  John K Clark
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