Talk:Radiative forcing

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Contents 1 IPCC definition problems 2 External links 3 Why IPCC problems removed? 4 What Is Forced?

[edit] IPCC definition problems

The IPCC definition requires behavior which is different than what is presently known. Douglas Hoyt and Peter Dietze independently point out that a theory which considers the radiative effect of a doubling of carbon dioxide as only a reduction within carbon dioxide's absorption frequency does not include induced changes in radiation from other frequencies. Other materials will be caused to increase their radiation rate. The IPCC estimates the radiation flux decrease at 3.5, while these estimates are significantly less, with one at 1.3 watts per square meter and the other has a range of 1.4 to 1.9. The smaller decreases indicate less warming.

[edit] External links

• Estimation of the Radiative Forcing for CO2 Doubling, Peter Dietze, 17 April 2000. http://www.john-daly.com/forcing/forcing.htm
• Problems with the radiative transfer modeling in the IPCC models, Douglas Hoyt, 23 June 2004. http://www.warwickhughes.com/hoyt/irtheory.htm

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[edit] Why IPCC problems removed?

What is so wrong with the above that they were removed? SEWilco 16:42, 23 Jun 2004 (UTC)

(William M. Connolley 18:18, 23 Jun 2004 (UTC)) The Hoyt link is a gross oversimplification, and appears to show only one frequency band, which is odd. Further, the idea that the science summarised in IPCC does what Hoyt says it does is nonsense.

It seems to me that Hoyt shows only one frequency band because he says that is all that is being used for some purpose. So showing only one does not seem odd. What about Dietze? (SEWilco 08:28, 24 Jun 2004 (UTC))

(William M. Connolley 10:40, 24 Jun 2004 (UTC)) Dietze's paper is nonsense. If you're interested in predicting the actual T change for 2*CO2 then you should look at the climate model output, not Hitran, which is totally unsuited to the task.

Hoyt is saying that "held fixed" is an error. Doubling carbon dioxide to 580 ppm while holding tropospheric state fixed makes the temp and radiation inconsistent and not in equilibrium. Such an instantanenous forcing defines a radiation flux which can not exist thus the change in flux values is meaningless. And in reality, radiation will increase in other bands. Looks like two issues: "held fixed" is not useful, and radiation won't be limited to one band. So whether this is relevant to IPCC depends upon whether IPCC is using either concept. (SEWilco 08:49, 24 Jun 2004 (UTC))

(William M. Connolley 10:40, 24 Jun 2004 (UTC)) This is not simple stuff. First, the IPCC definition is a *definition* so it cannot possibly be in error (uness it was internally inconsistent - but it isn't). You could criticise it for not being useful, but that would be odd, because any number of climate scientists do find it useful. Secondly, its only use is as an aid to diagnosing various effects. It is not used in a predictive sense - thats what GCMs are for. I don't understand what you mean by "whether IPCC is using either concept". IPCC is using the concept as it defines it, in the places where than concept is useful. Fourth, I'm fairly sure the entire point is to capture the non-equilibrium forcing.

(William M. Connolley 10:40, 24 Jun 2004 (UTC)) I should admit: I don't understand all this. But I don't think you do, I'm sure Dietze doesn't, and I think Hoyt is shaky too. Thats why I stuck to just putting in the IPCC definition - I'm certain thats what they mean by the concept.

(SEWilco 06:28, 26 Jun 2004 (UTC)) First, I added a date to Hoyt because I realized the HTTP info gave me an idea of the file time. The page is different than when I looked at it a few days ago, so I put the file date in the above link. ...and you should look at the new version so we're on the same "page".

Let's see what I understand here... Most is atomic transition and spectral absorption physics. I think the actinic light behavior is mostly limited to the stratosphere, other than smog-type reactions of volatiles, so not much chemical bond activity within troposphere.

1. The sun, as most stars, have a blackbody radiation with a peak around the visible spectrum.
2. The light is in those frequencies because at those high energy states the outer electrons are being forced to higher states, and emit those photons when they drop to a lower state.
3. There are narrow frequencies with less light due to absorption by less-energized (cooler) atoms in the solar atmosphere.
4. As the sunlight passes through the Earth's atmosphere, some is absorbed and the energy in those frequencies is reduced.
5. The cooler Earth atmosphere has various molecules, most of which absorb due to vibrational frequencies of the atomic bonds within the molecule, and rotation of atoms in the molecule. ( Infrared spectroscopy, Energy level ) Heavier molecules and weaker bonds have smaller vibrational frequencies. Rotation frequencies are based upon relative masses of bonded atoms and distances between them.
6. Some solar light is absorbed on the way down -- fortunately a significant percent of the UV energy is absorbed by ozone. Various gases absorb various frequencies. (We're ignoring clouds in this discussion)
7. Surfaces on Earth are much cooler than the Sun, so their blackbody radiation is at a much lower frequency. This happens to have a peak in the infrared, so the gases which allow visible light to reach the surface do not also allow that energy to radiate upward.
8. Gases which absorb in the infrared range block specific frequencies from radiating to space.
9. After a gas molecule absorbs energy, it releases it in three ways: A bond alteration (ie. O2 -> O3), emission of a photon (fluorescense), and thermal (bumping into another molecule). (Let's ignore fusion "energy release")
10. Radiation is reemitted in all directions, so about goes half upward and half downward. This is what reduces upward radiation.
11. The CO2 molecule absorbs in 3 main frequencies, of which 15 µm is of most interest because it is in the frequencies with the most energy from Earth's blackbody radiation temperature.
12. Hoyt points out the IPCC requires CO2 IR absorption to increase based on the amount of gas. That's the Beer-Lambert law, simple gas absorption behavior.
13. Hoyt also points out, however, that if CO2 is absorbing more energy then it will be releasing more energy. That energy is released among other gases, which will absorb and release in their frequencies, so the emission spectra decreases around carbon dioxide's but may increase in other frequencies.
14. The IPCC states that only the CO2 changes, so the other frequencies stay unrealistically fixed. The CO2 somehow absorbs the energy but never transfers it.
15. Dietze seems to cover the above first, then examines other factors.

Looks like a lot of the Wikipedia entries related to the above have pieces of that puzzle but aren't woven together.

(William M. Connolley 20:24, 26 Jun 2004 (UTC)) There are two possible things you might be worried about. One is the IPCC defn or radiative forcing. The other is the reliability of the radiation codes used in GCMs. I don't know which: you need to say. They are quite separate however. Hoyt appears to be mixing the two up. But at least he has got rid of that stupid picture.

(SEWilco 10:26, 30 Jun 2004 (UTC)) Here we're talking about the IPCC definition. If they are using this definition, then it and conclusions from it are in error because holding the state fixed blocks secondary effects. The stratosphere is allowed to react, but it is pointed out by others that other gases in the troposphere should be allowed to react. GCMs may behave that differently, but giving the IPCC definition as an example of a radiative forcing definition requires pointing out problems with the definition. Most problems with resulting conclusions should be in other articles. Earth: The Flat Earth Society definition is: ... Kitchen Table: The quantum physics definition of a table is: ...

(SEWilco 10:26, 30 Jun 2004 (UTC)) These two articles are pointing out a problem with the IPCC best guess. I'll have to reread the flow from definition to the disputed radiative flux to check the linkage again.

(William M. Connolley 18:47, 30 Jun 2004 (UTC)) GCMs may behave that differently... indeed I think this is your problem. You are confusing a diagnostic tool with GCM predictions. Please tell me which IPCC conclusions are in error from the "problems" you see with their rad forcing defn.

[edit] What Is Forced?

(SEWilco 08:33, 30 Jun 2004 (UTC)) A positive forcing tends to warm while a negative forcing tends to cooling. What's wrong with saying that forcing occurs to what is under the point at which it is measured? I know that forcing happens whether it is measured or not. And overall forcing actually happens for everything within the atmosphere, although some things only happen in certain vertical or geographical regions. But merely saying that positive forcing warms something is ambiguous -- does it warm only the surface, troposphere, clouds, or the Moon? There should be phrasing which indicates what is affected by forcing.

(William M. Connolley 08:42, 30 Jun 2004 (UTC)) But your phrasing is wrong. If I apply a radiative forcing - say heating only the 500 hPa level - then warming will occur both under and above that level. The phrase you quote does nothing other than establish the sign convention.

(SEWilco 09:21, 30 Jun 2004 (UTC)) Ah. The forcing is the actual change, wherever it is. I've been discussing the forcing measurement which might take place anywhere. Measurement above or below the location of forcing affects the direction of the change. In the IPCC definition, CO₂ warming happens in the troposphere, causing a reduction in that frequency at the IPCC level, but the increased blackbody radiation due to a warmer surface causes an overall increase in energy at the IPCC level. Hmm... but the blackbody radiation is a secondary effect, and if only the CO2 absorption+emission is considered then less energy is going upward. If a warmer sun evaporates more water and causes more clouds, which reflects the sunlight and causes a cooler surface -- at the stratosphere that is a positive forcing but has a cooling effect at the surface, so is that positive or negative forcing? (I said "IF" -- the issue is energy flux and not cloud behavior; for one thing I know clouds also absorb some energy but here I'm treating it as a mirror) Is a forcing considered as being the total change after all effects are considered, at the place of measurement? Or is a forcing only the immediate effect before secondary effects?

(William M. Connolley 18:47, 30 Jun 2004 (UTC)) I'm not really sure, on a quick reading, what you are saying here. Do you understand that their is a distinction between the natural-language conept "radiative forcing" - which is just the idea that changing the radiation incident on a system changes its properties - and the IPCC defn, which is a science concept. And that the bit we're talking about is the former concept.