Sunday, May 19, 2013

Science of Doom - understanding the physics of global warming



I noticed that my pal Dan Pangburn is at it again with his science in a vacuum.  He's claiming to prove, all over again, that the established climatologists know nothing and that it's actually sunspots controlling Earth's climate, as opposed to the more generally accepted understanding that although sunspot activity does have an influence, these days society produced greenhouse gases are swamping those subtle solar fluctuations.

Unfortunately, Dan doesn't present his science to the experts for their appraisal.  He's satisfied with his uncritical audience of non-experts.  An audience of the ideology committed who will grasp at {but not think through} any notion so long as it gives them cover for avoiding the ominous reality facing our society and future.

Dan inspired me to take another look at the series over at Science of Doom which does a nice job of sharing what the science has to say.  So in keeping with my desire to help spread the information scientists have gathered these past decades - here's an index of a series of very educational articles focusing on greenhouse gases and their impact on our planet's heat distribution engine.
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CO2 – An Insignificant Trace Gas?
Science of Doom series: 

Part One – introduces the shortwave radiation from the sun, the balancing longwave radiation from the earth and the absorption of some of that longwave radiation by various “greenhouse” gases. The earth would be a cold place without the “greenhouse” gases. . . 
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Part Two – why different gases absorb different amounts of energy, why some gases absorb almost no longwave radiation.  

Introducing Radiative Transfer Equations and finished up with a look at what is called the gray model of the atmosphere. The gray model is useful for getting a conceptual understanding of how radiative transfer creates a temperature profile in the atmosphere.
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Part Three – the Beer Lambert Law of absorption and the concept of re-emission of radiation.  

Looking at the “1-dimensional” model. I try and keep any maths as basic as possible and have separated out some maths for the keen students.
When you arrive at a new subject, the first time you see an analysis, or model, it can be confusing. After you’ve seen it and thought about it a few times it becomes more obvious and your acceptance of it grows – assuming it’s a good analysis.
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Part Four – band models and how transmittance of CO2 changes as the amount of CO2 increases under “weak” and “strong” conditions.

These are equations which quite closely match the real absorption of CO2 (and the other greenhouse gases) as a function of wavelength. They aren’t strictly necessary to get to the final result, but they have an important benefit – they allow us to easily see how the absorption changes as the amount of gas increases. 

And they are widely used in climate models because they reduce the massive computation time that are otherwise involved in solving the Radiative Transfer Equations. The important outcome as far as CO2 is concerned – “saturation” can be technically described.
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Part Five – two results from solving the 1-d equations – and how CO2 compares to water vapor.

The equations of absorption and radiation in the atmosphere – the Radiative Transfer Equations - have been known for more than 60 years. Solving the equations is a little more tricky.

Like many real world problems, the radiative processes in the atmosphere can be mathematically described from 1st principles but not “analytically” solved. This simply means that numerical methods have to be used to find the solution.
There’s nothing unproven or “suspicious” about this approach. Every problem from stresses in bridges and buildings to heat dissipation in an electronic product uses this method.
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Part Six  – Visualizing what does the downwards longwave radiation look like at the earth’s surface?

"Upwards Longwave Radiation"

So let’s try and look at it again and see if starts to make sense. Here is the earth’s longwave energy budget – considering first the energy radiated up:
Of course, the earth’s radiation from the surface depends on the actual temperature. This is the average upwards flux. And it also depends slightly on the factor called “emissivity” but that doesn’t have a big effect.
The value at the top of atmosphere (TOA) is what we measure by satellite – again that is the average for a clear sky. Cloudy skies produce a different (lower) number.
These values alone should be enough to tell us that something significant is happening to the longwave radiation. 
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Part Seven – "The 'Boring Numbers".. values of “radiative forcing” from CO2 for current levels and doubling of CO2.

Shows the current best "radiative transfer equations" solutions along with what “radiative forcing” actually means, and where the IPCC logarithmic formula comes from.
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Part Eight  – "Saturation" explaining “saturation” in more detail.

... Saturation, however, means different things to different people. Consider shining a torch through sand. Once you have a few millimeters thickness of sand, no light gets through. So adding a meter of sand won’t make any difference. That’s how most people are thinking about saturation and that is the perspective that we will look at in this article:
  • For CO2 – will doubling CO2 (from pre-industrial) levels add any more warming?
  • And will doubling it again add any more?
The answer already noted in earlier parts of this series is “yes”, but of course, everyone wants to know why, or what this means for the idea of “saturation”.
Boringly, we will first look at some results from the radiative transfer equations.
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– common “problems” or responses to the theory and evidence presented.

After posting some comments on various blogs and seeing the replies I realized that a page like this was necessary.
For people who’ve just arrived at this page, you might be asking:

What effect?
-which in itself is one of the most important questions, but let’s not jump ahead...

The background is the series CO2 – An Insignificant Trace Gas? and especially the last post – which maybe should have come earlier! – CO2 – An Insignificant Trace Gas? Part 6 – Visualization

If you take a quick look at that last post you will find a few simple measurements that demonstrate that CO2 and other “greenhouse” gases have an effect at the earth’s surface.

"What Effect?"

In brief, simply that CO2 and other greenhouse gases add a “radiative forcing” to the earth’s surface. A “radiative forcing” means more energy and, therefore, heating at the earth’s surface. And more CO2 will increase this slightly.

At this stage, we have said nothing about feedback effects or even the end of the world.. The series on CO2 is simply to unravel its effect on global temperatures all other things being equal. Which of course, they are not! But we have to start somewhere.

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The Sun and Max Planck Agree Part One
June 1, 2010 by scienceofdoom


For regular readers of this blog, this post adds nothing new. Think of it as placeholder – a link to send people to when they ask about this basic subject.

A very handy aspect of climate science is that we can easily differentiate between solar (from the sun) radiation and terrestrial (from the earth) radiation. We can do this because emission of radiation changes with wavelength and depends on the temperature of the body radiating:
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The Sun and Max Planck Agree – Part Two
July 25, 2010 by scienceofdoom


I didn’t think that a Part Two would be needed after the initial installment - The Sun and Max Planck Agree

Anyway, I always appreciate commenters explaining why the article hasn’t done its job, and so following various comments, hopefully, this article can address the deficiencies of the first.

I recommend reading the First Article before diving into this one. The main thrust of the article was to explain that solar radiation and terrestrial radiation have quite different “signatures”, or properties, which enable us to easily tell them apart.
For reader unfamiliar with how radiation varies with wavelength, here are two “blackbody” curves. . . 

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Do Trenberth and Kiehl understand the 
First Law of Thermodynamics?
July 26, 2010 by scienceofdoom

1 comment:

anonymole said...

The exploration, examination, and exposure of underlying climate change factors and concerns are all good and well and I support and applaud the balance of them.

However, the fact remains that humanity it not paying attention. China and India are building and using more and more coal fired electricity generation plants - with no end, or even reduction, in sight. Nat.gas and oil exploration and acquisition is continuing apace if not faster. Green energy alternatives are barely getting by; sure they continue to expand, but at a comparatively slow rate.

At this point additional alarm raising appears futile. A more rational approach might be to accept 450+ ppm CO2, accept increasing climate change impact, and get on with dealing with what most assuredly will be, rather than what we might hope we could prevent.

Face it, for the next 100+ years the planet will enter and experience a vastly different climate than what humanity has enjoyed for the last 10,000+ years. Humanity is just too short sighted to look out 2-10 generations and try and fix a future world. Fixes in the past, FDA, EPA, toxic dumping, pollution, were all single generation fixes. Climate change is so large, extensive and drawn out that most humans cannot fathom a fix.

So, prepare for the inevitable. This train has left the station and will not be making stops for the next 100 years.