[Vision2020] Western U.S. Forest Wildfire Activity

[Ted Moffett]

Paul et. al.

Thanks for your detailed depiction of the Santa Anna winds, that I recall
experiencing in Southern California in the 1960s.  And who can forget the
line from the song "Babylon Sisters," from the album "Gaucho" by Steely Dan,
"here come those Santa Anna winds again:"

http://en.wikipedia.org/wiki/Santa_Ana_wind

Paul wrote:

Did scientists who believe in human-induced
global warming predict stronger-than-normal Santa Ana winds?
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http://www.sciencemag.org/cgi/content/full/313/5789/940

The Science magazine article I presented on Western USA wildfire activity
(note subject heading) focused on the impacts of earlier Spring arrival,
earlier snow pack melt, and rising temperatures, connected to a longer and
more intense fire season, on average, for the whole Western USA.  They
avoided making any claims as to what is causing this climate change.  I did
not say that the stronger Santa Anna winds the past week were directly tied
to global warming, though they may be, nor does the Science magazine article
mention the Santa Anna winds, that I read.  However, the extreme drought in
Southern California, in some areas the most extreme in 130 years, is without
a doubt in part responsible for the intensity of the wild fires this past
week, along with the Santa Ana.

Is this tied to global warming?

We have to distinguish between "weather" and "climate."  "Weather" is local
and variable in a way that global climate "climate" is not.  Consider the
Little Ice Age that Northern Europe and Greenland experienced (around the
1300s) that is considered a primary factor in driving the Norse out of their
colonies.  The global average change in temperature during this period was
small, compared to the temperature change from the height of the last ice
age to now, but if you were the Norse in Greenland you would have thought
the next major ice age was coming.  The drought this year in California may
or may not be tied to global warming (it may be "weather" rather than
"climate change") but the work of climate scientists predicts that on
average globally, extreme drought will become more common due to
anthropogenic global warming.

However, the conclusions of the scientists who presented their research on
Western USA fires in Science magazine were looking at broad trends across
the entire Western USA, and how these trends are influencing the documented
increase in fires during the fire season in the Western USA.  These
conclusions are far more certain regarding connections to global warming and
climate change, than is the drought in Southern California, given they
extend over the entire Western USA, although the Western USA is not alone a
large enough region of the planet to base solid conclusions regarding global
climate change.  The data for anthropogenic global warming as "climate
change" is planetary wide.

Paul also wrote:

It seems reasonable that warmer air can dry out drier areas more, due to an
increased evaporative effect.  However, warmer air can hold more
moisture, making wetter areas wetter.  More water vapor in the air can
act as a greenhouse gas, however more cloud cover causes more of the
Sun's rays to be reflected back into space, and more actual rainfall
cools the earth.  It still seems to be six of one, half a dozen of the
other.
------
Your assessment that the variables you discuss above amount to "six of one,
half a dozen of the others" is an opinion that is not supported by the work
of many climate scientists.  It is predicted that increased evaporation of
H20 due to anthropogenic global warming will have a net climate forcing
effect to further increase global warming due to increased water vapor, not
offset by cloud cover increased albedo.  Water vapor is by far the most
powerful global warming atmospheric variable.  I could list sources for this
scientific assessment.  Also, this discussion can be found parsed in detail
at:

http://www.realclimate.org

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Vision2020 Post: Ted Moffett
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