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-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@phys-l.org] On Behalf Of Folkerts,
Timothy J
Sent: Monday, January 06, 2014 12:59 PM
To: Phys-L@Phys-L.org
Subject: Re: [Phys-L] just for fun?
John M says
I've never understood this talking point. To first order risingpositive feedback loop.
temperatures lead to rising levels of CO2 and rising levels of CO2 lead
to rising temperatures. As John Denker has already pointed out, it's a
There are a few negative feedbacks as well. A couple of the more obvious
ones to me are:
Rising temperatures --> more evaporation --> higher albedo --> cooling More
CO2 --> plants grow better --> CO2 pulled from atmosphere --> cooling
The warming from CO2 itself is not strongly contested (except by some on
the fringe of climate denialism). Generally people calculate that doubling
CO2 will lead to ~ 1 C warming by itself, due directly to the radiative effects of
the CO2. That is the 'simple' physics of "radiative forcing".
The more complicated climate science tries to estimate the impact of
feedbacks. Those estimates typically vary from ~ 0.5 C to ~ 5 C for the overall
impact with feedback -- ie the "climate sensitivity" is between 0.5 and 5,
which is a huge range. The IPCC puts the estimates in the range 2-4.5, which
is still a pretty big range. Even relatively uncertain things in physics like the
mass of the top quark or Higgs boson are given to within ~ 1%, not ~ 100%, so
I tend to remain open-minded about the actual sensitivity.
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