Quote from gwb-trading:
Let's see what NASA has to say about this.
CO2: The Thermostat that Controls Earth's Temperature
http://www.giss.nasa.gov/research/briefs/lacis_01/
A study by GISS climate scientists recently published in the journal Science shows that atmospheric CO2 operates as a thermostat to control the temperature of Earth.
There is a close analogy to be drawn between the way an ordinary thermostat maintains the temperature of a house, and the way that atmospheric carbon dioxide (and the other minor non-condensing greenhouse gases) control the global temperature of Earth. The ordinary thermostat produces no heat of its own. Its role is to switch the furnace on and off, depending on whether the house temperature is lower or higher than the thermostat setting. If we were to carefully monitor the temperature of the house, we would see that the temperature does not stay constant at the set value, but rather exhibits a "natural variability" as the house temperature slips below the set value and then overshoots the mark with a time constant of minutes to tens of minutes, because of the thermal inertia of the house and because heating by the furnace (when it is on) is more powerful than the steady heat loss to the outdoors. If the thermostat is suddenly turned to a very high setting, the temperature will begin to rise at a rate dictated by the inertia of the house and strength of the furnace. Turning the thermostat back to normal will stop the heating.
Atmospheric carbon dioxide performs a role similar to that of the house thermostat in setting the equilibrium temperature of the Earth. It differs from the house thermostat in that carbon dioxide itself is a potent greenhouse gas (GHG) warming the ground surface by means of the greenhouse effect.
(more at above url)
Thanks for this, I can see why you/jem would accept the analogy and perhaps I was too hard on you both for running with it.
However, despite what the Dr says - and I otherwise respect him very much - the analogy is NOT a close one.
Here is a graphic from that article.
So we can see there are both forcing factors and responding, or feedback factors. CO2 is NOT a feedback factor. A thermostat is a feedback factor.
More precisely, the CO2 levels act as the "temperature setting" ON the thermostat. He says this here...
"The bottom line is that CO2 is absolutely, positively, and without question, the single most important greenhouse gas in the atmosphere. It acts very
much like a control knob that determines the overall strength of the Earthâs greenhouse effect. Failure to control atmospheric CO2 is a bad way to run a business, and a surefire ticket to climatic disaster."
http://dotearth.blogs.nytimes.com/2010/02/17/lacis-at-nasa-on-role-of-co2-in-warming/?_r=0
So the CO2 level is analogous to the set-point ON the thermostat whereas water vapor and clouds act as the thermostatic/feedback mechanism itself.
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This is an example of why you can't cherry pick one statement, one chart, one study, to act as the foundation of an argument. Unless of course your intent is to deceive, and circumvent the 97% of charts, studies and statements that make your argument look ridiculous.
This is also a good example of the kind of thing found on denialist websites which is where jem probably found it to begin with.
