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Contact
Jim: jdipeso@rep.org
(253) 740-2066 / 2011
Archive / 2010
Archive
Heat-Seeking
Research
December 19, 2011
How
do scientists know that global warming is linked to carbon dioxide?
It’s a common question raised by people genuinely seeking to understand
climate change.
First, some basic physics. This year is the 150th anniversary of
British physicist John Tyndall’s publication of his discovery that
carbon dioxide absorbs heat. Heat is longwave radiant energy.
After World War II, the U.S. Air Force took an interest in how radiant
energy behaves in the atmosphere and began collecting data. As
physicist Richard Alley—a registered Republican, by the way—points out
in his book, Earth: The
Operators Manual, the Air Force was not interested in
climate science per se or in serving as a hireling for a “world government plot”
masterminded by the United Nations. Instead, the Air Force had
practical ends in mind directly relevant to its military mission.
Marines carry heat-seeking
Sidewinder missile after removing from F/A 18 Hornet. (U.S. Navy) |
One
such practical end was developing heat-seeking missiles to attack and
destroy enemy aircraft. Let Alley's book explain the practical problem
weapons researchers were trying to solve: “The hot exhaust of an enemy
bomber is a target, but in certain wavelengths, CO2 and water vapor
make ‘vision’ difficult by blocking radiation, whereas other
wavelengths are much clearer. Designing sensors to see the hot target
through the ‘swamp’ of greenhouse gases in the air required an
understanding of those gases.”
The upshot of this research was a finding that adding more CO2 to the
atmosphere would trap additional heat in the atmosphere. Satellite
observation confirmed this finding, showing that less longwave
radiation is escaping into space at the same wavelengths as CO2’s
absorption band.
Put another way, it’s as if carbon dioxide selectively blocked VHF
television signals broadcast by Channel 2 from radiating into space
while letting signals from Channels 3 through 13 go out.
OK, a skeptic might exclaim, I get that, but CO2 is present in the
atmosphere in only trace quantities. How could adding more make much of
a difference in atmospheric heat retention? Well, just because a
substance is present in trace amounts doesn’t necessarily mean its
impacts are insignificant. It depends on what trace substance one is
talking about.
Take alcohol, for example. If your blood alcohol level is 0.08
percent—less than 1 part in 1,000—you are considered impaired and
subject to arrest in all 50 states if operating a motor vehicle. At
0.16 percent, you are stinking drunk, hardly able to stand, and a
danger to yourself and others around you.
As Alley puts it in his book, there are many examples “in which a trace
of some material is completely insignificant, and other examples in
which a trace is highly dangerous. This is why scientists are hired to
study these things—we need hard data and real understanding, not vague
guesses about how much is too much. And the hard science says that the
trace of CO2 up there is important to our climate, and that changing
the CO2 concentration up there will change the climate.”
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