Why CO2 warms things up a bit...

[BaalChatzaf]

Please have a look at this,  a non-technical discussion on why blankets keep us warm and the principle on which CO2 in the atmosphere inhibits the radiation of heat into space:

 

http://scienceblogs.com/startswithabang/2011/08/30/if-you-believe-that-blankets-k/

 

Yes,  CO2 over load has contributed -some-  to the world temperature increase since the Little Ice Age.   No, we will NOT  turn into Venus,  as the AGW  alarmists either say or suggest.  There are other mechanisms of warming at work besides CO2 overload caused by humans...

Now  why is  trapped heat potentially harmful?   Suppose you lived in a closed room  with perfectly heat insulating walls.  And suppose your body has an infinite supply of sugar which it can metabolize and sustain your body temperature at about 37 degrees Celsius (that is around 98.6 degrees Fahrenheit).  Your body will radiate heat until the air in the room as it the same temperature as your body.  However you will sweat and evaporate water into water vapor which will cool you somewhat.  But you water will run out  and eventually your body (fueled by glucose)  will be at the same temperature as the air in the room.  Your body will no longer radiate heat energy being in equilibrium with the surroundings.  You no longer can sweat  and lose heat in turning liquid water into water vapor.   At this point your metabolism will fail. Metabolism is a kind of heat engine  and in order to operate it uses some of the heat it gets from a higher temperature reservoir, produce physical and chemical work  and exhausts enough heat to a lower temperature reservoir so as to keep the entropy greater than or equal to zero.  When your body no longer is able to move energy from a high temperature reservoir to a low temperature  reservoir,  metabolism stops and you die.  You do not become infinitely hot with your temperature constantly rising, but you can no longer increase entropy  so you cease to function. 

On Venus the concentration of CO2 in her atmosphere is 96 percent, 960,000 ppm.  The mean atmosphere temperature on Venus  is about  650 degrees Celsius, hot enough to melt lead.  That is the equilibrium temperature of Venus wrt to the Sun which is only 56,000,000 miles away fro Venus.   We on earth are more fortunate.  The so called green house gases on Earth are at most 1.5 percent of the atmosphere and most of that is water vapor which will condense to liquid water after releasing latent heat.  By the Stephan-Boltzmann law earth will radiate enough energy away to say in thermal equilibrium with the radiation from the Sun  which is our main supply of heat energy.   (Geothermal energy is 99 percent bottled up underground  to radiate through the crust.  The rest is radiate through cracks in the earth and  volcanic eruption.  This is not enough to matter).  We have loads of water to sop up heat,  we have very little in the way of heat inhibiting gasses which act as insulators  (technically called adiabatic  barriers) so will will never get as hot as Venus.   We could get warm enough to produce some bad weather and to affect  rainfall,  glacier level  and such like.  Humans will never destroy the earth (the Sun will do that)  But we can make life tough for ourselves.