Sunday, November 6, 2011

Watts up with that Radiative Return Effect

During Ben Santer's Question and Answer session Anthony Watts asked the following question.
As it happens over at there was a detailed comment that seems to me speaks to Anthony's question but more importantly addresses many of the crazy-making claims/charges surrounding this important topic. 

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1:02:05 - Anthony Watts: Would you describe the Radiative Return Effect of carbon dioxide in the Earth’s atmosphere as being linear or logarithmic?
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1:02:20 - Santer: And why would you like to get into radiative transfer at the moment?

1:02:35 - Watts: Well I want to see if you agreed with the IPCC assessment of a logarithmic effect.

1:02:40 - Santer: Well ah, I don’t know what you’re getting at here... there’s been discussion... this question always comes up: The CO2 absorption bands are saturated, therefore any further increase in atmospheric CO2 doesn’t really produce much of a warming impact.  The key thing, and I refer you to an article in the Physics Today by        is that the wings of the CO2 absorption spectrum are not saturated and we clearly know that as we increase atmospheric CO2 we will continue to warm the planet.  That’s the best answer I can give you.
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{I inserted the highlights}

Re: Denial In Depth

Post #8 by GT ~ Sun Nov 06, 2011 9:19 am ~

rickoshay85 (says):"Facts, demonstrated facts... Without them, all you have is theory, supposition, or just plain educated guesswork"
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GT:     OK. Lets start with the HiTran spectroscopic database. And other comparable databases. Spectroscopic data that has been accumulated since WWII. Detailed observations about the absorption/emissions behaviour associated with over 30 atmospheric gases. Including CO2.

Then apply the equation of Radiative Heat Transfer. The basic understanding of how Electro-Magnetic radiation (including Infra-Red) behaves as it passes through various absorbing and emitting media. Dating back at least to Einsteins day and then further back to the equations of Beer & Lambert from the 19th century. 
Apply this to the available data, perform the calculations, and predict the expected Outgoing Longwave Radiation spectrum for the planet. Compare this to observations of the same. They match. Do the same for Back or Downwelling Longwave Radiation. Again observation and theory match. Ergo, we have a pretty solid understanding of what happens when IR Radiation passes through the atmosphere.

Independent tests of this. Apply the same data & theory to calculating what an Early Warning Satellite would expect to see when a Ballistic missile is launched as opposed to a lightning storm over Siberia. Agreement, or we would have been blown to smithereens decades ago. So too the performance of IR Heat Seeking missiles. A missile that can't hit its target isn't much use is it. Or even a microwave oven that doesn't work because we don't understand the passage of micro-waves through the atmosphere - more of the same facts and understanding being applied.

Next fact. Has the Outgoing Longwave Radiation been changing in recent decades in ways we would expect based on our data and our understanding of Radiative Heat Transfer theory? 
Yes. So to the Downwelling Longwave Radiation.
{for more information:
Measuring Earth's energy imbalance
Of Satellites and Air – A Primer on Tropospheric temperature measurement by Satellite}

Next, Water Vapour feedback. 
Satellites have measured increases of water vapour in the atmosphere, as expected. Including increases in upper Troposphere water vapour levels. As expected. Because if that wasn't happening, our understanding of the basic Thermodynamics of water vapour in Air must be pretty screwed up. And that would surely disturb all the worlds Refrigeration and Air Conditioning Engineers who thought they had a handle on this stuff.

So if the evidence of a driver of warming is valid, what is the evidence that warming has happened? Heating of the oceans. Everything else, including what we think of as climate - air temperatures - is a small side show by comparison. Ocean heating has been the equivalent of at least 2.5 Hiroshima bombs a second for around 1/2  a century. And the magnitude of the heat increase in the oceans is so great that it precludes this coming from some other internal source within the climate system. All other possible sources are trivial by comparison. So this amount of heat must be the result of a basic thermal imbalance for the whole planet.
{for more information:
Evaporating the water vapor argument
Water vapor is the most powerful greenhouse gas

There are other strands of evidence - cooling stratosphere, rising tropopause, Nights and Winter warming as much or more than Days/Summer that indicate warming due to a 24/7 phenomenon such as AGW rather than greater solar output or clouds that would be stronger during  Days/Summer.

Next lets look at PaleoClimate data - Inter-Glacials, Ice Ages, the history of the last 500 million years. These only make sense if we include the known properties of the Greenhouse gases. You might like to do some research into 'The Feint Young Sun Problem' for example.
 {for more information:
10 Indicators of a Human Fingerprint on Climate Change
10 key climate indicators all point to the same finding: global warming is unmistakable}



Recently there have been two more articles posted at that go into yet more detail.

If learning about the complexities and the actual state of the science is of interest, you'll want to review these two articles:

Eschenbach and McIntyre's BEST Shot at the Surface Temperature Record

Eschenbach and McIntyre - Seeing the BEST part of the Satellite Temperature Record?

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