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Monday, January 14, 2013

A Tale of Two Greenhouse - PG version

I started this blog just to play around and look at simpler ways to explain stuff than is typically found on the internet.  With a little common sense and basic math, most of the complex physics in nature can be reduced to a level that is useful, provided you consider the uncertainty involved with "rules of thumb".

Rules of Thumb, provide useful "ball parks" that can help you figure out what you need to figure out.  If the "ball park" is too big to be useful, then you look for ways to refine the estimate using the "ball park" as an "envelope" of uncertainty.  You sneak up on the solution.

When I wrote the original Tale of Two Greenhouses, I was just introducing a simple static model intended to  show that there are two volumes that respond to changes in energy flow, the oceans and the atmosphere, and that the one with the most heat storage capacity, the oceans, is the more important one to consider.  To me, that is so obvious it is difficult to explain.

Since the heat capacity of the oceans is about 1000 times greater than the atmosphere, I find the whole greenhouse effect debate laughable.  I used the approximate average temperature of the larger "thermal mass" which is about 4 C degrees, to calculate the approximate impact that adding a thin extra layer of insulation would produce.  It is really not rocket science.  The oceans are currently at ~4 C degrees.  We are adding 3.7 Wm-2 of extra insulation, the effective radiant energy of the oceans at ~4 C degrees is ~334 Wm-2 which would be roughly equal to the "effective" current insulation value, adding 4 Wm-2 to 334 Wm-2 results in 338 Wm-2 which would have an equivalent "average" temperature of approximately 4.825 C degrees or a warming of ~0.825 degrees.  That is the "ball park".  Any larger estimate requires big time assumptions,which in a complex system will typically not happen like assumed.

For an analogy, let's say you have a boat.  During the day, inside that boat can get hot because the sun heats the deck.  Just before dawn, the temperature inside that boat will be whatever the temperature of the water is that the boat is floating on plus or minus a touch.  If you cover the deck with a lot of reflective tarps to shade the deck, it won't get as hot in the day, but before dawn, the cabin will be at a temperature roughly equal to the water the boat is floating on.  It ain't rocket science, the largest thermal mass controls the minimum temperature, so you need to figure out what controls that larger thermal mass.   If you spend all of your time trying to figure out the trivial, you can lose sight of the obvious.

I will try to do a PG part two soon.

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