Monday, February 23, 2009

Surface Radiation Calculations


Basic system thermodynamics revisited (click image to view full size)
A colleague of mine emailed me an article (pdf link) containing the above figure. The author Ashworth (2008) contends among many things that the radiation energy balance shown in the figure above is wrong, and that it violates 1st and 2nd law of thermodynamics. I am writing this post to show that Ashworth is completely off base on that point and is not even close to interpreting the above figure correctly. I am not able to decipher any 2nd law implications from the figure though.
I don't have clear arguments or time right now for the all graphs of CO2/warming shown subjectively. It could go either way.

But first, imo, the author does not even know how to define a system for performing energy balances. Because of this he does not know how to add the necessary terms to achieve a 1st law energy balance. Clearly, if you look at the total energy balance, the incoming and outgoing solar radiation fluxes at the outer boundary of the atmosphere add up fine (342 coming in and 107+235 going out at the atmosphere level, from space).

This author is forgetting the fact that the earth is round and receives radiation at different times throughout the day and radiates it back. Consequently it is possible to radiate 390 (+ 78+24 also shown in the image) because earth is also getting back radiation of 324 apart from the 168.
Further if you do a surface balance that also adds up fine. See image of my excel calculation below.

The original paper from which they obtain the Fig 8 is here (pdf) where towards the end the authors clearly put forward the errors etc in the model and still clearly show that an energy balance has been achieved. Further the Ashworth "paper" is written like an opinion piece and (gasp) and shows lack of simple mathematical concepts.

But the bigger issue with anthropogenic CO2 related global warming is not the average daily solar fluxes, it is the release of the chemical energy trapped for millions of years in carbon bonds. The resulting CO2 release into the atmosphere is what is being considered as a precursor to global climate changes.

I should add at this point, my personal view on the subject of global warming and climate change is still not firmed up. I am merely an advocate for efficient use of resources, irrespective of whether they are carbon based or not. But what really bothers me sometimes is people pointing fingers at others, but making similar mistakes themselves.
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1 comment:

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