Naysayers, such as Ben, Will, etc. repeatedly post without understanding
the applicability of the 2nd law of thermodynamics as it applied to
the greenhouse gas effect.
No process is possible whose sole result is the transfer of
heat from a body of lower temperature to a body of higher
temperature. Naysayers, such as Ben, Will, etc. leave out
the crucial fact that the sun is adding thermal energy to
the system.
For greenhouse effect to be in violation of the Second Law
of Thermodynamics certain conditions must be met:
1. the atmosphere would need to be a discrete body in order
to qualify as a “body of lower temperature” and clearly it
is not when considering electromagnetic transmission from
sun to earth to space and;
2. the 2nd Law would have to preclude any feedback (return
of energy in any form from atmosphere to non-gaseous surface)
that could slow the cooling of the “body of higher temperature”.
All Ben, Will, etc. do is say this can't be so, but they can
NEVER make a credible scientific argument to support their
point.
The 2nd law of thermodynamics is consistent with the greenhouse effect
which is directly observed
Skeptics sometimes claim that the explanation for global warming
contradicts the second law of thermodynamics. But does it? To answer
that, first, we need to know how global warming works. Then, we need to
know what the second law of thermodynamics is, and how it applies to
global warming. Global warming, in a nutshell, works like this:
The sun warms the Earth. The Earth and its atmosphere radiate heat away
into space. They radiate most of the heat that is received from the sun,
so the average temperature of the Earth stays more or less constant.
Greenhouse gases trap some of the escaping heat closer to the Earth's
surface, making it harder for it to shed that heat, so the Earth warms
up in order to radiate the heat more effectively. So the greenhouse
gases make the Earth warmer - like a blanket conserving body heat - and
voila, you have global warming. See What is Global Warming and the
Greenhouse Effect for a more detailed explanation.
The second law of thermodynamics has been stated in many ways. For us,
Rudolf Clausius said it best:
"Heat generally cannot flow spontaneously from a material at lower
temperature to a material at higher temperature."
So if you put something hot next to something cold, the hot thing won't
get hotter, and the cold thing won't get colder. That's so obvious that
it hardly needs a scientist to say it, we know this from our daily
lives. If you put an ice-cube into your drink, the drink doesn't boil!
The skeptic tells us that, because the air, including the greenhouse
gasses, is cooler than the surface of the Earth, it cannot warm the
Earth. If it did, they say, that means heat would have to flow from cold
to hot, in apparent violation of the second law of thermodynamics.
So have climate scientists made an elementary mistake? Of course not!
The skeptic is ignoring the fact that the Earth is being warmed by the
sun, which makes all the difference.
To see why, consider that blanket that keeps you warm. If your skin
feels cold, wrapping yourself in a blanket can make you warmer. Why?
Because your body is generating heat, and that heat is escaping from
your body into the environment. When you wrap yourself in a blanket, the
loss of heat is reduced, some is retained at the surface of your body,
and you warm up. You get warmer because the heat that your body is
generating cannot escape as fast as before.
If you put the blanket on a tailors dummy, which does not generate heat,
it will have no effect. The dummy will not spontaneously get warmer.
That's obvious too!
Is using a blanket an accurate model for global warming by greenhouse
gases? Certainly there are differences in how the heat is created and
lost, and our body can produce varying amounts of heat, unlike the
near-constant heat we receive from the sun. But as far as the second law
of thermodynamics goes, where we are only talking about the flow of
heat, the comparison is good. The second law says nothing about how the
heat is produced, only about how it flows between things.
To summarise: Heat from the sun warms the Earth, as heat from your body
keeps you warm. The Earth loses heat to space, and your body loses heat
to the environment. Greenhouse gases slow down the rate of heat-loss
from the surface of the Earth, like a blanket that slows down the rate
at which your body loses heat. The result is the same in both cases, the
surface of the Earth, or of your body, gets warmer.
So global warming does not violate the second law of thermodynamics. And
if someone tells you otherwise, just remember that you're a warm human
being, and certainly nobody's dummy.
See:
http://www.skepticalscience.com/Second-law-of-thermodynamics-greenhouse-theory.htm