Senator Steve Fielding - Leader of Family First

Following post #2325, I want to explore this topic a little further.
Let us re-write the surface balance equation:

Absorbed_Solar_Radiation (168) = IR_Radiated_from_Surface (390) - IR_Back_Radiated_from_Atmosphere (324) + Evaporation_of_Water (78) +Conduction_to_Atmosphere (24)

to be

Absorbed_Solar_Radiation (168) + IR_Back_Radiated_from_Atmosphere (324) = IR_Radiated_from_Surface (390)  + Evaporation_of_Water (78) +Conduction_to_Atmosphere (24)

This places causes of surface temperature change on the left hand side, and consequences of temperature change on the right hand side.

Note that there can be no temperature change at the surface unless either the absorbed solar radiation or the (Greenhouse) back radiation changes. Those are the only two causes of surface temperature change.

Differentiating this second equation leads directly to the terrestial sensitivity to changes in atmospheric or solar radiation. The result is a temperature change of 0.1 DegC per Watt per metre squared, if we ignore any change in conduction (if we included conduction, the sensitivity would be less).

This value is independant of the wattages we start with, with the exception of the evaporative term. Fortunately this is known reasonably accurately as it is the same as the energy required to evaporate average annual precipitation.

Using this relationship we get the following results for a doubling of CO2 (4W/m2):
An increase of 0.4DegC in surface temperature.
A consequent increase of 2.5% in evaporation/precipitation.

In post#2318 Tom Curtis quoted the following passage from http://tamino.wordpress.com/2007/07/16/lapse-rate/

So, even if the atmosphere has so much CO2 that it is saturated in those infrared wavelengths, adding more CO2 raises the altitude at which those wavelengths of infrared escape to space, increasing the distance to the ground, and therefore increasing temperature difference between the radiation layer and the ground (which is the product “lapse rate” x “distance”).

That’s one of the reasons that arguments that CO2 absorption of infrared is saturated, and hence adding more CO2 won’t increase global warming, are mistaken. Because of the lapse rate, raising the altitude of CO2 radiation escaping to space will still warm the surface.

This is an incorrect physical explanation. The lapse rate is driven by condensation of water vapour in the atmosphere.

At present the lapse rate of -6.5DegC per 1000m ceases at 11,000m. If there were no condensation we would expect a lapse rate of about -10DegC/1000m. (NB, all these numbers are extremely rubbery). If we increase the condensation rate (for example by increasing the evaporation rate) we expect the lapse rate itself to change.

In a completely saturated IR case, the sole methods of heat transfer to the radiative top of the atmosphere will be by evaporation of water vapour, subsequent condensation in the atmosphere, and convection. We would expect a change in the lapse rate itself due to the increased evaporation, probably cancelling out the alleged higher radiation level.

In the argument quoted above, the author seems to be assuming that the lapse rate will be constant, ie that evaporation won’t change. But we have seen that evaporation rate is very sensitive to any surface temperature change.

b]Lapse rate

http://en.wikipedia.org/wiki/Lapse_rate

The dry adiabatic lapse rate (DALR) is the rate of temperature decrease with height for a parcel of dry or unsaturated air rising under adiabatic conditions. Unsaturated air has less than 100% relative humidity; i.e. its actual temperature is higher than its dew point. The term adiabatic means that no heat transfer occurs into or out of the parcel. Air has low thermal conductivity, and the bodies of air involved are very large, so transfer of heat by conduction is negligibly small.
Under these conditions when the air rises (for instance, by convection) it expands, because the pressure is lower at higher altitudes. As the air parcel expands, it pushes on the air around it, doing work. Since the parcel does work but gains no heat, it loses internal energy so that its temperature decreases. The rate of temperature decrease is 9.8 °C per 1,000 m. (The reverse occurs for a sinking parcel of air.)[7]

....

When the air is saturated with water vapour (at its dew point), the moist adiabatic lapse rate (MALR) or saturated adiabatic lapse rate (SALR) applies. This lapse rate varies strongly with temperature. A typical value is around 5 °C/km (2.7 °F/1,000 ft or 1.51 °C/1,000 ft).
The reason for the difference between the dry and moist adiabatic lapse rate values is that latent heat is released when water condenses, thus decreasing the rate of temperature drop as altitude increases. This heat release process is an important source of energy in the development of thunderstorms. An unsaturated parcel of air of given temperature, altitude and moisture content below that of the corresponding dewpoint cools at the dry adiabatic lapse rate as altitude increases until the dewpoint line for the given moisture content is intersected. As the water vapor then starts condensing the air parcel subsequently cools at the slower moist adiabatic lapse rate if the altitude increases further.

[

At post #2326 I re-stated the form of the surface balance equation, and derived the sensitivity of the surface to a change in either absorbed solar radiation (eg,if the sun got hotter or the clouds got thicker) or the atmospheric back radiation (due to a change in the Greenhouse).

This sensitivity turns out to be 0.1 DegC/W/m2.

If different sensitivities are used (eg, if you have a temperature rise of 3DegC and an increase of only 4W/m2 of atmospheric back radiation) the surface balance equation doesn’t balance. That violates the First Law of Thermodynamics, and so must be wrong.

Alternatively, one might like to invoke feedback processes, which increase the back radiation sufficiently so that a balance is achieved. We have seen (post #2325) that the additional back radiation required for a 3DegC temperature rise is 26W/m2, so that the original 4W/m2 from doubled CO2 becomes 30W/m2.

That is a very large change: 4W/m2 begets 30W/m2.

I cannot accept that such a change is stable. Let us suppose that the initial additional 4W/m2 is applied. This heats the surface by 0.4DegC and evaporates more water vapour. We get a 2.5% increase in evaporation. This modest increase in evaporation is then responsible for an additional 2.6degC temperature rise and a massive additional increase in water vapour of 15%.

So why, or how is this at all stable? Why does the increase of 15% in water vapour not trigger ane even greater temperature increase, increase in water vapour, etc ad infinitum (or, more physically until the water IR bands are completely saturated)?

We have an invidious choice if the IPCC numbers are to be believed. Either:
1. The First Law of Thermodynamics is incorrect, or,
2. An unstable situation results, or
3. The surface balance equation is incomplete - there is another term we should have in the equation. I don’t know of any (remembering that this is a steady state equation so ice melting, water freezing, heat transfers to and fro the centre of the earth are all zero). I would be really happy if someone has another term, but recognise that this is very unlikely, as the IPCC don’t have any.

The IPCC predictions lead to a contradiction at the surface which is only resolvable by dropping the temperature increase to a very low value (about 0.5DegC).

Tom Curtis - 13 September 2009 12:16 AM

Havequestions - 12 September 2009 11:17 PM

Tom Curtis - 12 September 2009 09:09 AM

Peggyb - 11 September 2009 10:57 PM

Very techy stuff but the bottom line now is that global temperatures have plateaued since 1998 despite CO2 still rising.

Bottom line is that durring La nina conditions, and the lowest sunspot minimum since 1913, with a massively declining solar wind, 2008 recorded the 10th hottest year on the instrumental record.  By comparison, 2008 was three quarters of a degree hotter than 1913, despite 1913 being an El nino year.

If we eliminate the fantasy that only one thing can effect global temperatures at a time, we have to start wondering how could 2008 be so much hotter than 1913 when so many other factors indicate it should be cooler.  We have to wonder why 2008 was hotter than 1912 which had more sunspots, and an el nino; but was significantly cooler than 2008 all the same.

Most of all, we have to wonder what the temperatures will be like once we reach the next sunspot maximum, or the next large el nino.

One thing we don’t need to wonder about is what PeggyB will be doing eleven years from now (if still alive).  She’ll be making posts about the bottomline that global temperatures having not risen since 2012 (or 2013, or whatever the next record year happens to be) as we continue through the next sunspot minimum.

Tom,

Do we have good evidence that the current rate of warming (ie since the end of the Little Ice Age) is unusual compared with past rates of warming?  We know for example, that the warming after each of the past four glacial maximums was rapid compared with the coooling trend.  http://en.wikipedia.org/wiki/File:Vostok-ice-core-petit.png

However, the spacing of the measurements is insufficiently close to allow us to define the rate over decades.  I suspect the rate of warming has varied from fast to stagnant during these previous warmings, just as it is doing this time.  So I wonder if the rate we have experienced over this period is unusual.  And if so is their evidence for that.

I just saw this.  I haven’t read it myself, but I’ll be interested to hear what all the others blogging on this site have to say about it.
http://www.scribd.com/doc/3544543/The-Predominant-Climatic-Factors-for-the-Last-400000-Years

There is no such thing as “good” evidence in paleoclimatology.  Even the best reconstructions have significant margins of error, are subject to alternative interpretations, and often give ambiguos results.  And that is true even of recent periods (last thousand years or so) where we have a significant body of data.  Having said that, in temperature reconstructions of the last 1000 years, there is only one period that shows as sharp a rise in temperature as that experienced in the 20th century.  That period is the approx 30 years following “the year without a summer”.  The year without a summer occured at the peak of the Dalton minimum, and occured because of a volcanic eruption that was significantly more powerfull than krakatoa.  Obviously, volcanic aerosols get washed from the atmosphere over a very short term, which creates a powerfull short term warming effect.  Presumably the restoration of more normal solar conditions after a major sunspot minimum will do the same.  Yet the combination of these two factors at the same time only created a warming comparable with that which occured in the 20th century, and over a shorter duration.  Clearly, whatever the cause (or causes) of the 20th century warming, it is unusual in its strength and duration compared with natural causes prior to the 20th century (over the period of the Holocene).  This does not mean the cause is not natural, but it does mean that if the cause is natural, it must be as a result of a significant (and therefore easilly detectable) perturbation of the natural mechanism.  There is a natural cause that does have such a significant perturbation in the early part of the 20th century, the brightening of the sun.  But in the latter half of the 20th century, all candidate natural causes have been shown to be only fluctuating to a small extent, or to be trending in the wrong direction to explain the temperature increase.

Finally, the temperature increase in the 20th century is unusual, but not necessarilly unprecedented in the holocene, but predicted temperature increases in this century are of the charts compared to anything seen before outside of ice ages (and probably even then).

Tom,

Thank you for this answer.  I have a long way to catch up on all the posts since then.

You said “There is no such thing as “good” evidence in paleoclimatology.  Even the best reconstructions have significant margins of error, are subject to alternative interpretations, and often give ambiguos results. “ 

I agree and accept this statement.  But I was hoping you might lead through the process of predicting from theory and then show how the empirical evidence demonstrates the conclusion that you accept about AGW.

You say: “Clearly, whatever the cause (or causes) of the 20th century warming, it is unusual in its strength and duration compared with natural causes prior to the 20th century (over the period of the Holocene).  This does not mean the cause is not natural, but it does mean that if the cause is natural, it must be as a result of a significant (and therefore easilly detectable) perturbation of the natural mechanism.  “

Firstly, can you point to a succinct summary of the eviden your support the statements that precede the bit I’ve quoted.  That is, the evidence that the current warming is unusual in the Holocene?

Secondly, can we explain all the other rises and falls in temperature?

Continued next post

Continued from #2330

To Tom Curtis

Thirdly, I suspect, during the rapid temperature rises that followed some trigger at the end of each glacial maximum,  the rate of warming varied as it has been doing for the past century and this decade.  So why do we believe the behaviour is significantly different this time.  What is the evidence that it is significantly different this time?  Do we understand enough about the pattern of the previous warmings and do we understand the causes of the variations within them to be confident we can blame this warming on man’s GHG emissions?

I don’t necessarilly expect you to be able to answer my questions.  However, I do believe that if good evidence existed it would be clearly and succinctly summarised somewhere.  It is not in the IPCC reports, nor anywhere else, as far as I can see.  This strongly suggestes to me that the evidence is pretty shaky, when we really get to the nub of the key issues.

Tom Curtis - 13 September 2009 09:49 AM

Anthony Watt provides an example of the selective approach to evidence exhibited by many AGW sceptics.  In a blog entitled “Message in the cloud for warmists the end is near” he displays the following graph to show the connection between solar/cosmic ray activity and the Earths’ temperature:
http://wattsupwiththat.files.wordpress.com/2009/07/kirkby_slide_siberianclimate.jpg

Looking at the graph, you can see a clear correlation between the two proxies for solar activity, Be10 and C14, and a clear correlation between them and the temperature as determined from an glacial ice core in the Altai.  That is, you can see that correlation until 1850.  Following 1850 you start seeing a clear deficit in C14 compared to Be10.  That deficit is what you would expect following the large scale introduction of C14 free carbon into the atmosphere, as for example, by the burning of fossil fuels.  At the same time, the temperature which had been faithfully tracking the solar proxies starts to soar above them, a clear indication that a new factor is causing warming beyond what you would have expected given only the continued influence of natural factors.  The inference that the injection of fossil carbon into the atmosphere has cause an additional, and unusual warming is straightforward.  Anthony Watt, of course, simply ignores any part of the graph post 1850.  If the evidence doesn’t fit the sceptics picture, for the sceptic that evidence doesn’t exist.
http://www.agu.org/pubs/crossref/2009/2008GL035930.shtml

While on the topic, the the lead author took ice cores from the Belukha Glacier as part of a cooperative research project which has resulted in the publication of at least three temperature reconstructions going back to 1200.  You would think that the folk over at CO2 Science with their MWP would be interested.  No such luck - none of the studies appear on their site.  The reason is not hard to fathom with two out of the three reconstructions showing modern temperatures two degrees warmer than any in the MWP, and one showing the warmest period in the first part of the 20th century, and current temperatures equalling those of the MWP, clearly the folk at CO2 science did not want these papers distorting their survey.  These are just a few of a number of papers I know of showing warmer recent temperatures that some how failed to make it onto CO2 Science’s survey.
http://www.pages.unibe.ch/products/newsletters/2009-1/workshop reports/Schwikowski_2009-1(44-45).pdf

This selectivity in the use of data sounds like something Climate Audit would want to investigate.  I’m not holding my breath.

Tom,

I have a problem with the chart in your first link.  It shows the C14 and Be10 separate at 1850 and maintain the same separation from then on.  That does not seem consistent with the accellerating rate of burning fossil fuels.  I understand that the rate of burning fossil fuels did not have a significant effect on CO2 concentrations until the latter half of the last century (you have said the same in some of your recent posts).

Colin Davidson - 13 September 2009 04:01 PM

Tom Curtis wrote (#2245), in response to my post at #2236:

Just a suggestion, but what is probably wrong is that you are failing to take into account that collisions will excite the CO2 molecules just as absorbtion of radiation will.  If r(c) is the rate at which collisions excite molecules at a given temperature, and r(e) is the rate at which excited molecules emit radiation before loosing the energy in another collision, then the CO2 molecules will emit the thermal radiation at a rate equal to r(c) * r(e).  In the bandwidths at which CO2 absorbs radiation, the radiation emited CO2 will follow the black body curve (shape) for the temperature of the CO2, and if there is sufficient CO2 to effectively absorb all radiation, the emitted radiation will have the same energy as the black body curve for that temperature (ie, an emissivity of 1, but only within bandwidths in which it absorbs).

I know I have suggested this to you before, and you appeared to have ignored it.  However, these are fairly straightforward consequences of the Stefan-Boltzmann and Wein laws as applied to thermal radiation in gases.  Not only that, the effect has been observed.  I refer you to the following page which contains two emissions spectra, one looking down from an altitude of 20km, and one looking up from the surface at the same location:
http://i165.photobucket.com/albums/u43/gplracerx/PettyFig8-2.jpg

These images, and the many similar images gained by the IRIS instrument aboard Nimbus satelites absolutely refute the various arguments of Nicol and Roger Taguchi.  For Nicol, the most crucial image is the upward looking spectrum.  In it you can clearly see the backradiation from H2O (400 to 600, and 1250 to 1700), and of CO2 (600 to 750) closely approximating to the black body curve of approximately 268 degrees K.  The low temperature is because the measurements were made on a polar ice sheet, but it is the same temperature as the surface thermal radiation from the upper image.  According to Nicol, that back radiation should simply not exist with anything approaching that intensity.

I thank Tom for re-stating this pointer. Although I understood his point, I had thought that the amount of radiation which escaped prior to a collision would be minor. This may have been incorrect. I calculate the approximate number of collision excited molecules which have time to radiate before the next collision to be, in units of 1E25/m3:
At the surface, 25 CO2 and 500 H20
At 5000m, 15CO2, 258 H2O
At the top of the Troposphere(11000m), 9 CO2, 0 Water
At the top of the Tropopause(20000m),1.3 CO2
At the top of the Stratosphere (45000m), 0.05 CO2

So I think Tom is probably right, but I have a little more work to do.

(The basis of these calculations is:
1. Water vapour molecules/m3 calculated from 50%relative humidity at 15DegC at surface, falling linearly in concentration to 0 at 11000m.
2. CO2 concentration at surface is 1E22 molecules/m3. At other altitudes it is proportional to atmospheric density.
3. Collision rate is calculated using the formulae provided by John Nicol.
4. Emission Halflife (actually the 1/e point) is assumed to be 2usec. Decay rate is exponential, but at the very small times before a collision we are considering, the proportion of excited molecules which decay before another collision is approximately the ratio of time_before_a_collision/halflife_time.
5. The proportion of molecules which are sufficiently energised after a collision is the 5% stated by john Nicol, but I have modified this proportion in the ratio (velocity/velocity_at_this_height)squared, as a drop in velocity will lower the KE in that ratio.)

Colin Davidson,

Somewhere back near the beginning of this thread, you said something to the effect “anyone with high school physics can do these calculations”.

Just though some of the readers might like to be reminded of this at this point in time

Tom Curtis - 14 September 2009 10:34 AM

CR - 14 September 2009 08:52 AM

When was the last time the IPCC released a statement and corrected the media saying… we don’t believe it’s manmade CO2 on this occasion or it’s just the sun or it’s a natural climate cycle, or when was the last time they actively corrected a prominent persons claim to be wrong.  It is plainly not in their interest to do so, even though they are in a position of “authority” they do not choose to make corrections of the numerous claims that have been made.

The IPCC doesn’t go around making press statements about anything much.  It has, according to its website, only issued two press releases in 2009, both dealing with what are effectively administrative proceedures.  Its scientific commentary is restricted to its various reports, and those reports are very clear that natural phenomena alone could account for the warming up to about 1950, but that natural phenomena alone cannot account for the warming post 1970.
http://www.ipcc.ch/press_information/press_information.htm

Individual scientists, it is true, have on occasions made some ridiculous claims about what is, and is not the effect of global warming.  But my memory is that the general scientific commentary regarding even 1998 was that it could have been a consequence of global warming, but that that was not provable, and it might have occured irrespective of global warming.  Hardly scaremongering.  The commentary on the Victorian bush fires this year was that, again, it may have been more severe than normal because of global warming, but that similarly severe fires had occured in the past without global warming.  What was emphasised was that similar fires would be more frequent in the future because of global warming.  That the press seek out the few scientists who are more rash in their claims is not the fault of the scientific community, and it is certainly not the fault of that community that their more measured statements are ignored by the press (and the sceptics).

In contrast, it is difficult to find a published sceptic who does not repeatedly make absurd claims.  It is possible for proponents of AGW to point out that sensationalists on their side are just a small (if obssesively vocal) rump.  For the sceptics, that radical fringe is all they have.

Tom,

Surely, you must acknowledge that the IPCC reports are highly political and biased.  It is displayed throughout them.  I have pointed out, in some of my previous posts on this thread, some of the statments in IPCC AR4, Chapter 6 that demonstrate this.  Do you honestly deny this point?

Colin Davidson - 14 September 2009 02:14 PM

Tom Curtis kindly responded to my request for a Surface Energy Flow Budget for a 3DegC Temperature Rise at post #2303 above.

(The reason for choosing 3DegC is that this is what the IPCC says in their latest report:
The IPCC FAR, WG1, Chapter 10 executive summary staes in part that the Surface Air Temperature rise for a doubling of CO2 is:
a. very likely above 1.5 DegC.
b. Likely to lie in the range 2 to 4.5 DegC.
c. The likely value is 3DegC.
It should also be noted for the record that Tom and I have been using a slightly different model (http://www.windows.ucar.edu/tour/link=/earth/Atmosphere/images/radiation_budget_kiehl_trenberth_2008_big_jpg_image.htm)  than that in IPCC FAR (2007) WG1, Chapter 1, FAQ 1.1, Fig 1 (http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter1.pdf), but for the purposes of this discussion those differences do not matter).

We started at 16DegC with:
Absorbed Solar radiation (161) = IR Radiated from surface (397) - IR Back radiated from atmosphere (333) + Evaporation of water (80) +Conduction to atmosphere (17)

In Tom’s response he has, for a 3DegC increase to 19DegC:
Absorbed Solar radiation (168) = IR Radiated from surface (407) - IR Back radiated from atmosphere (338) + Evaporation of water (83) +Conduction to atmosphere (19)

I have a number of immediate criticisms.
1. All of Tom’s numbers for Absorbed Solar Radiation are NOT in accordance with the model we agreed to use. So unless he can justify those changes, the Absorbed Solar Radiation should remain at 161W/m2. (I don’t mind using some other model, eg the IPCC model if preferred, it’s just that we need to stick with one or the other).
2. I get 412W/m2 IR radiated from the surface for a temperature of 19DegC.
3. We are all agreed, I hope, that on a planet which is 70% ocean there will be increased evaporation. The amount of increase is disputed, but the best estimate is that the Clausius-Clapyeron equation (which describes the relationship between Saturated Vapour Pressure and temperature) applies, and this gives an increase of 19.5% in evaporation. So the evaporative term should increase from 80 to 95 W/m2. (Wow, that’s big isn’t it! The same as the increase in surface radiation…)

Colin,

What is the point you are making in your last line where you say: ”(Wow, that’s big isn’t it! The same as the increase in surface radiation…)”?

.

Colin Davidson - 14 September 2009 03:56 PM

Tom Curtis wrote (#2308):

This is also irrelevant to the case for global warming.  The IPCC did not make its prediction by doing a surface energy balance, but by doing a top atmosphere energy balance, and infering the surface temperature using the lapse rate.

Colin Davidson said:
I disagree. If the IPCC calculations end up with a nonsense surface energy balance then the IPCC calculations must be in error.

At an equilibrium surface temperature, the surface energy flows must balance (First Law of Thermodynamics). I contend that there is no temperature change for which the IPCC numbers (1 DegC per 4W/m2 increase in back radiation) hold true and the surface energy flows balance, whether it be 1DegC, 1.5DegC, 3DegC, or 4.5DegC, or 6DegC. So if I am right then either the IPCC is wrong or the First Law of Thermodynamics is wrong.

This looks to me to be a very important point.

Colin Davidson - 15 September 2009 10:56 AM

Following my previous post (#2324), here is a surface energy flow balance for 15DegC from the diagram at IPCC FAR (2007) WG1, Chapter 1, FAQ 1.1, Fig 1 (http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter1.pdf):

(Figures in brackets are W/m2)

Absorbed_Solar_Radiation (168) = IR_Radiated_from_Surface (390) - IR_Back_Radiated_from_Atmosphere (324) + Evaporation_of_Water (78) +Conduction_to_Atmosphere (24)

Using this as a starting point I think we can safely say that at a surface temperature of 18DegC, the following will definitely change:

IR Radiated from_Surface will increase to 406W/m2
Evaporation_of_Water will increase by 20%, discounted by 2% because we do not know the effect on transpiration, so we assume no effect (see posts #2309-2311, 2315). So, conservatively the Evaporation_of_Water term increases to 92W/m2.

The terms which won’t change much are:
Absorbed_Solar_Radiation We expect some increase in clouds, therefore some increase in reflection from clouds. There may be some decrease in snow/ice cover, so we expect a small increase from that source. So the overall change is likely to be slight, so we assume no change.
Conduction_to_Atmosphere There will probably be a minor increase in this term, but I cannot quantify it. Taking a conservative path, we leave it unchanged.

The big problem, having carefully evaluated all the terms, is that surface balance requires that the IR_Back_Radiated_from_Atmosphere term be 354W/m2, an increase of 30W/m2.

Would anyone care to explain how such a large increase in back-radiation is generated, remembering that the IPCC figure for a doubling of CO2 is (generously) 4W/m2?

Its all F…ing obvious really.  Try again

Colin Davidson - 15 September 2009 12:48 PM

Following post #2325, I want to explore this topic a little further.
Let us re-write the surface balance equation:

Absorbed_Solar_Radiation (168) = IR_Radiated_from_Surface (390) - IR_Back_Radiated_from_Atmosphere (324) + Evaporation_of_Water (78) +Conduction_to_Atmosphere (24)

to be

Absorbed_Solar_Radiation (168) + IR_Back_Radiated_from_Atmosphere (324) = IR_Radiated_from_Surface (390)  + Evaporation_of_Water (78) +Conduction_to_Atmosphere (24)

This places causes of surface temperature change on the left hand side, and consequences of temperature change on the right hand side.

Note that there can be no temperature change at the surface unless either the absorbed solar radiation or the (Greenhouse) back radiation changes. Those are the only two causes of surface temperature change.

Differentiating this second equation leads directly to the terrestial sensitivity to changes in atmospheric or solar radiation. The result is a temperature change of 0.1 DegC per Watt per metre squared, if we ignore any change in conduction (if we included conduction, the sensitivity would be less).

This value is independant of the wattages we start with, with the exception of the evaporative term. Fortunately this is known reasonably accurately as it is the same as the energy required to evaporate average annual precipitation.

Using this relationship we get the following results for a doubling of CO2 (4W/m2):
An increase of 0.4DegC in surface temperature.
A consequent increase of 2.5% in evaporation/precipitation.

I seem to remember that is the sensitivity figure you came up with a month or so ago.  Pretty consistent.  I wonder if it’s right.  Can you get this sorted before we commit to a CPRS, ......PLEASE!!.  And then convince the public and the politicians, and Tom of course, that they are all wrong.  Just think of me as the one who is bring you glasses of water while you work

Colin Davidson - 15 September 2009 01:17 PM

In post#2318 Tom Curtis quoted the following passage from http://tamino.wordpress.com/2007/07/16/lapse-rate/

So, even if the atmosphere has so much CO2 that it is saturated in those infrared wavelengths, adding more CO2 raises the altitude at which those wavelengths of infrared escape to space, increasing the distance to the ground, and therefore increasing temperature difference between the radiation layer and the ground (which is the product “lapse rate” x “distance”).

That’s one of the reasons that arguments that CO2 absorption of infrared is saturated, and hence adding more CO2 won’t increase global warming, are mistaken. Because of the lapse rate, raising the altitude of CO2 radiation escaping to space will still warm the surface.

This is an incorrect physical explanation. The lapse rate is driven by condensation of water vapour in the atmosphere.

At present the lapse rate of -6.5DegC per 1000m ceases at 11,000m. If there were no condensation we would expect a lapse rate of about -10DegC/1000m. (NB, all these numbers are extremely rubbery). If we increase the condensation rate (for example by increasing the evaporation rate) we expect the lapse rate itself to change.

In a completely saturated IR case, the sole methods of heat transfer to the radiative top of the atmosphere will be by evaporation of water vapour, subsequent condensation in the atmosphere, and convection. We would expect a change in the lapse rate itself due to the increased evaporation, probably cancelling out the alleged higher radiation level.

In the argument quoted above, the author seems to be assuming that the lapse rate will be constant, ie that evaporation won’t change. But we have seen that evaporation rate is very sensitive to any surface temperature change.

I’m persuaded.  Delay the CPRS!