Guest Post by Willis Eschenbach
Today I came across an IPCC figure (AR4 Working Group 1 Chapter 2, PDF, p. 208) that I hadn’t noticed before. I’m interested in the forcings and responses of the climate models. This one showed the forcings, both at the surface and at the top-of-atmosphere (TOA), from the Japanese MIROC climate model hindcast of the 20th century climate.
Now, do you notice some oddities in these two figures? Here’s what caught my eye.
The first oddity I noticed was that the surface forcing from the long-lived greenhouse gases (LLGHG) was so small compared to the top-of-atmosphere LLGHG radiative forcing. At the end of the record, the TOA forcing from LLGHG was just over two watts per square metre (W m-2). The surface forcing from LLGHG, on the other hand, was only about 0.45 W m-2. I don’t understand that.
This inspired me to actually digitize and measure the surface vs TOA radiation for a few of the components. For each W m-2 of TOA radiative forcing from a given source, the corresponding surface forcing was as follows:
Aerosol Direct: up to 15 W m-2 (variable)
Land Use: 1.5 W m-2
Volcanic Eruptions: 0.76 W m-2
Solar: 0.72 W m-2
Cloud Albedo: 0.67 W m-2
LLGHG: 0.21 W m-2
With the exception of the Aerosol Direct these relationships were stable throughout the record.
I have no idea why in their model e.g. one W m-2 of TOA solar forcing has more than three times the effect on the surface as one watt of TOA greenhouse gas forcing. All suggestions welcome.
The next oddity was that the sum of the radiative forcings for “LLGHG+Ozone+Aerosols+LandUse” is positive, about 1.4 W m-2. The surface forcing for the same combination, on the other hand, was strongly negative, at about -1.4 W/m2. The difference seems to be in the Aerosol Direct figures. It seems they are saying the aerosols make little difference to the TOA forcings but a large difference to the surface forcings … which seems possible, but if so, why would “Land Use” not show the same discrepancy between surface and TOA forcing? Wouldn’t a change in land use change the surface forcing more than the TOA forcing? But we don’t see that in the record.
In addition, the TOA Aerosol Direct radiative forcing changes very little during the period 1950-2000, while the corresponding surface forcing changes greatly. How can one change and not the other?
The next (although perhaps not the last) oddity was that the total surface forcing (excepting the sporadic volcanic contribution) generally decreased 1850-2000, with the total forcing (including volcanic) at the end of the period being -1.3 W m2, and the total forcing in 1950 being -0.6 W m-2 … why would the total surface forcing decrease over the period during which the temperature was generally rising? I thought perhaps the sign of the forcing for the surface was the reverse of that for the TOA forcings, but a quick examination of the corresponding volcanic forcings shows that the signs are the same. So the mystery persists.
In any case, those are the strangenesses that I found. Anyone with ideas about why any of those oddities are there is welcome to present them. What am I missing here? There’s some part of this I’m not getting.
In puzzlement,
w.
PS – I’m in total confusion regarding the albedo forcings that go all the way back to 1850 … if I were a suspicious man, I might think they just picked numbers to make their output match the historical record. Do we have the slightest scrap of evidence that the albedo changed in that manner during that time? Because I know of none.
PPS – Does anyone know of an online source for the surface and TOA forcing data in those figures?
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Willis:
The difference between the two boundary forcings (surface and TOA) should be the volumetric forcing between the boundaries.
In the case of tropospheric aerosols, I beleive the direct effect is via absorption and the indirect via reflection. So the first should have little TOA effect.
Try subtracting surface from TOA forcings and see if the difference makes sense as an atmospheric heat uptake rate. I haven’t tried, so I can’t say but I think it should.
Alex
Update
I think I should have said partially by absorption. That is the general case, I think it is almost totally by absorption for brown cloud.
Alex
This is from skepticalscience (really should be called non-skeptiacalscience)
http://www.skepticalscience.com/earth-albedo-effect.htm
The skeptic argument…
It’s albedo
“Earth’s Albedo has risen in the past few years, and by doing reconstructions of the past albedo, it appears that there was a significant reduction in Earth’s albedo leading up to a lull in 1997. The most interesting thing here is that the albedo forcings, in watts/sq meter seem to be fairly large. Larger than that of all manmade greenhouse gases combined.” (Anthony Watts)
What the science says… (according to scepticalscience)
The long term trend from albedo is that of cooling. In recent years, satellite measurements of albedo show little to no trend.
Oh dear, the reason why global temperatures aren’t rising is exactly because there has been very little trend. The long term trend from albedo is that of cooling? Nonsense if they mean since the 1980’s, fair enough if they mean since about 2001.
http://img854.imageshack.us/img854/5246/globaltempvglobalcloudb.png
But wait, global temperatures are cooling since 2001, just as the albedo trend shows. Just like when albedo should show a warming trend since 1983 until this point.
http://www.woodfortrees.org/plot/uah/from:2001/normalise/plot/rss/from:2001/normalise/plot/gistemp/from:2001/normalise/plot/hadcrut3gl/from:2001/normalise
The only reason why there has not been more cooling is down to more El Nino’s so far during this period with one of the strongest recorded recently and this could change soon.
Cloud albedo, seems to be about 0.9w/m2 just since the 1980’s (satellite data) and the model shown in this topic looks like it is automatically persuming that increasing temperaure = decreasing cloud albedo. Can’t find any data sources going back this far, only ones during the satellite era.
Steve McIntyre says:
June 5, 2011 at 5:49 am
Steve, I’ve looked at several of his early works but not found anything to the point. Do you have a reference?
Thanks,
w.
Look at some of the original Ramanathan articles on this.
Try Ramanathan 1974
http://i255.photobucket.com/albums/hh133/mataraka/ramanathanco2x.jpg?t=1242018280
They use a 1d RCM
dr.bill says:
June 5, 2011 at 2:18 am
The caption below the graphs doesn’t agree with the labels used on the graphs themselves. In the caption, it says that the top panel is the radiative component. Perhaps the caption is correct and the labels aren’t.
It might be like the case of the absent-minded math professor. He says a, writes b, thinks it’s c while d is the correct one.
Otherwise resistance is futile, you will be assimilated. All your base are belong to us. You have no chance to survive make your time. Somebody set us up the bomb. For great justice.
What does ” a low level of scientific understanding” mean? It is a phrase often used in this paper.I think that the tilt of the earths axis with respect to its orbit around the sun can’t be ignored at least at mid latitudes ,where we also see accumulation of snow every winter.Summer is warmer than winter at least at mid latitudes usually because the Sun is higher in the sky at noon in summer than winter.
“I’m not sure why but looking at the graphs makes me feel rather cold”, said Kevin Vaughn.
Me too. I think it’s all those icicles hanging off the volcanoes.
I have a poor understanding of the climate system.
I use the figures in Kiehl & Tranberth 1997 (see http://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-1-1-figure-1.html ).
What would a hotter but equilibrium world be like? I assume that the conductive term (wrongly labelled in K&T as “thermals” will be the same, as the temperature difference between the surface and the air in contact with it is going to be the same, as there is no reason to assume otherwise.
The evaporative term increases by an unknown amount. Could be anything, but most agree that the lower limit is about 2% per DegC (the models go for this) and 7%per DegC. The radiative term increases iaw Stephan-Boltzmann.
Putting all that together I get a surface sensitivity to a change in Surface Forcing of between 0.09 and 0.15DegC/W/m^2.
From the cited IPCC diagrams cited by Willis the relationship between GHG caused Radiative Forcing and GHG caused Surface Forcing is about 4:1. This means a for a change in Radiative Forcing of 4W/m^2, the modellers expect a change in Surface Forcing of about 1W/m^2.
Putting all all that together, I would expect a change in Surface Temperature of between 0.095 and 0.15 DegC for a doubling of CO2.
I simply cannot get the necessary increase in Back Radiation of between 16 and 26 W/m^2 required to bring the surface temperature up by 3DegC.
As I say, I don’t understand the climate system.
maksimovich says:
June 5, 2011 at 1:51 pm
Thanks, maksimovich. Unfortunately, I’ve been unable to find an online copy of Ramanathan 1974, and I don’t have access to a university library … go figure. Anyone have a link? It’s called “A simplified stratospheric radiative transfer model”.
At least if that’s the one you’re talking about.
w.
The biggest difference is TOA versus the surface.
GHGs provide a large positive forcing at the surface but once you get to the TOA, there is less positive forcing there.
It is important to understand that there is not a standard definition of TOA and different groups/charts use different atmospheric levels for the TOA (sounds wrong but that is true). But you could think of it as GHGs provide substantial warming at the surface but they actually provide cooling in the stratosphere (close to the TOA) since they are holding back radiation that would normally warm the stratosphere.
At different levels, there is different impact and different forcings from the various different forcing types. Volcanoes are a good example. They have both strongly positive and strongly negative forcings depending on the atmospheric level in question.
Everything should be shown for the surface so that the wiggle room is reduced.
For example, the 3.7 watts/m2 increased forcing from doubled GHGs is for the 255K temperature level (which is sometimes described as TOA and sometimes not, and the chart shown above is certainly not at the 255K level – it is higher up it seems).
In addition, there is really no doubled GHG forcing number for the surface alone. It should actually be higher than +3.7 if it is to deliver +1.2C at the surface, but I have never seen an estimate of this.
Ref. LazyTeenager says:
June 5, 2011 at 8:01 am
The water below the ice is not the same temperature as the surface of the ice. Remember, sea water can’t be below the freezing point of salt water, whereas the ice surface might be -40 deg. F (or C).
The liquid ocean water, no colder than 28.4F, or -2C, can radiate large amounts of heat into space, whereas ice and snow do not due to a couple of factors. Ice and snow have low heat content, and are pretty good insulators, preventing the heat in the warmer ocean water under the ice from radiating much heat.
During winters when the ice cover is lower than normal, the far north experiences warmer weather because the heat from the ocean warms the air above it.
I found a good article on surface albedo
It includes a table with water albedo as follows:
Small Zenith Angle: Albedo = 0.03 – 0.10
Large Zenith Angle: Albedo = 0.10 – 1.00
http://www.eoearth.org/article/Albedo?topic=54300
I think you need to scrounge through Chapter 8 (Climate Models and Their Evaluation) but more likely Chapter 9 (Understanding and Attributing Climate Change) which goes into some detail on each area including why aerosols are negative etc.
That said, I notice that the bottom graph has GHG’s at 2.1 w/m2. That’s about right for TOA if you accept CO2 doubling = 3.7 w/m2, then a 40% rise in CO2 should be close to 60% (whatever ln2 comes to) of 3.7 or about 2 watts/m2. Looks to me like the bottom chart is TOA.
Aerosols are negative because they float in the atmosphere and intercept downward SW (9.2.2.2) and I think you’ll find an explanation of land use in the same section.
The TOA numbers should be higher than the surface numbers. The TOA number is calculated as if that is where downward LW originates from. Of course that isn’t true. Downward LW from GHG’s absorbing and re-radiating can originate from GHG molecules at ANY altitude, and they can emitt in ANY direction. The net total of “downward” LW due to GHG’s exceeds the net total of “upward” LW due to GHG’s by a theoretical CO2 doubling = 3.7 w/m2. If ALL the CO2 and other GHG’s existed at the TOA and had that effect, then that’s the number you would get at TOA. But they DON’T exist there, they are mixed throughout the atmosphere, so 3.7 (theoretical) or 2.1 (measured/calculated by whatever means) is usefull for modeling purposes, it is otherwise an imaginary construct (IMHO). Chapter 2 as well as other references (sorry, its almost 1:00AM, or I’d go hunt for them) make it clear that the TOA number (RF = Radiative Forcing) and the surface response are two different things.
Sensitivity is calculated at 1 degree = 3.7 w/m2 = CO2 doubling, but that is at the “effective black body temperature of earth” which is about -20 C. You will have to search AR3 to find that reference though, they just skip over it in AR4 as far as I can tell. Since average surface temp is +15 C, and temp varies by w/m2 = CT^4 (Stefan-Boltzman) the SURFACE temp sensitivity is only about 0.6 C. Nice of them to sort of skip by that explanation, is it not? Further, they seem to say (I haven’t found anywhere that they say it explicitly, but it is implied) that since much of the LW from GHG’s gets absorbed BEFORE it gets to the surface, the surface forcing should be less than the TOA forcing. Hence 0.6 degrees at surface adjusted for…however much they seem to think doesn’t make it all the way down… should be even less.
If you google NASA GISS FD data series (sorry, in a rush) you will get their model of the global averages for TOA, mid and Surface radiation fluxes for Short Wave and Long Wave going back to about 1983. You can also look at Palle’s work on albedo and three papers in Science from 2005 (Pinker, Wild and Wielicki) – all of this is referenced and discussed in ‘Chill: a reassessment of global warming theory’. The actual peer-reiviewed science lit tells us that atmospheric transparency increased after 1980 and cloud cover diminished by 4% (until 2001) thus increasing the flux at the surface by several Watts – I reckoned about 4x the RF from carbon dioxide, and thus posed the question to the scientific community….how come they believe ‘most’ of the warming is GHGs? The increased flux of SW warms the ocean far more powerfully than the downwelling LW.
Furthermore, the global ‘dimming’ from 1950-1980 due to sulphur emissions is shown by these papers to be a localised phenomenon – and the dimming was global and clearly caused by clouds and natural aerosols – from 1980, the greater transparency was noted in areas not subject to human pollution – and again due to clearing of natural aerosols and reduced cloud.
The model assumptions were built in before this science was published and have yet to be corrected. The IPCC figures for negative forcing due to sulphur emissions are clearly wrong.
There was a phase shift in 2001 – when cloud cover came back by 2%, and the albedo measurements (using other sources such as ‘earthshine’ from lunar measurements) confirm this shift – since when the ocean heat content rise has levelled off.
I wish I had time to pursure these issues…I did write a book on it, but the silence has been deafening…..these issues are absolutely central to the whole question of reliability of models and their relation to real-world data.
This is in response to Davidmhoffer’s post 0103,6Jun11 above.
” The TOA number is calculated as if that is where downward LW originates from. Of course that isn’t true. Downward LW from GHG’s absorbing and re-radiating can originate from GHG molecules at ANY altitude, and they can emitt in ANY direction. ”
I agree. At wavenumber 670 for example, over half the surface emissions are absorbed by the atmosphere within 1m. (see John Nicol’s calculation at Figure 6, http://www.middlebury.net/nicol-08.doc ) The implication is that emissions by the atmosphere to the surface at that frequency are mostly coming from below 1m. The figures for wavenumbers 650 and 700 are 25m and 50m respectively. Across the main CO2 band, nearly all surface photons are extiguished within 200m, and reciprocally, nearly all the back radiation reaching the surface is coming from 200m or below. A doubling of CO2 roughly halves the heights.
“Sensitivity is calculated at 1 degree = 3.7 w/m2 = CO2 doubling, but that is at the “effective black body temperature of earth” which is about -20 C. You will have to search AR3 to find that reference though, they just skip over it in AR4 as far as I can tell. Since average surface temp is +15 C, and temp varies by w/m2 = CT^4 (Stefan-Boltzman) the SURFACE temp sensitivity is only about 0.6 C. ”
And so it would be for a dry surface, which is not what we live on. Earth is a water planet. Three fifths of the flux from the surface absorbed into the atmosphere is evaporated water, one fifth is Radiation, and one fifth Conduction (Figures from Kiehl & Trenberth 1997, http://www.ipcc.ch/publications_and_data/ar4/wg1/en/faq-1-1-figure-1.html ). The sensitivity at the surface is heavily damped by the increase in evaporation with temperature, a consideration which does not apply to the atmosphere.
The water aspects of our planet – relative humidity, evaporation rate and clouds are big unknowns with large effects on temperature. What measurements exist suggest that the modellers assumptions on all 3 are significantly wrong.
Willis, you summed this paper up in an earlier post, “Models All the Way Down”.
Construct the model, then look for the data to provide the parameters that might work.
Willis
On your query, you might find interesting the detailed quantitative calculations by Ference Miskolczi of the global atmospheric absorbance from all the greenhouse gases as a function of altitude from surface to the top of atmosphere for the last 60 years.
The Stable Stationary Value of the Earth’s Global Average Atmospheric Planck-Weighed Greenhouse-Gas Optical Thickness, Energy & Environment, Special Issue: Paradigms in Climate Change Vol 21 No. 4 2010, August pp 243-262.
See the latest results at:
Poster presentation at the European Geosciences Union General Assembly, Vienna, 7 April 2011
Somehow, the modellers have convinced themselves (and many others) that complexified elaborated stupidity isn’t stupid.
How stupid can you get? They seem determined to find out, by direct experimentation, no less!
From AR4 Chapter 9, Executive Summary
“The net aerosol forcing over the 20th century from inverse estimates based on the observed warming likely ranges between –1.7 and –0.1 W m–2. The consistency of this result with forward estimates of total aerosol forcing (Chapter 2) strengthens confidence in estimates of total aeroso lforcing, despite remaining uncertainties.”
One has to admire the unmittigated gall of announcing that their estimate ranges somewhere between almost zero and the same approximate amount (but negative) attributed to GHG’s, followed by claiming that the consistancy of the result strengthens confidence. The traditional definition of chutzpah (Yes your honor, I murdered my parents, but I’m asking for leniency because I am an orphan) doesn’t even come close.
Of course this gem from Chapter 8, may be even more astounding. They claim to be modeling the climate within hundredths of degrees, and tenths of watts/m2, but look at their own evaluation of their own models:
“Calculation of the global mean RMS error, based on the monthly mean fields and area-weighted over all grid cells, indicates that the individual model errors are in the
range 15 to 22 W m–2, whereas the error in the multi-model mean climatology is only 13.1 W m–2. Why the multi-model mean fi eld turns out to be closer to the observed than the fields in any of the individual models is the subject of ongoing research;”
SAY WHAT? No single model got closer than 15 to 22 w/m2? But averaged together they were only out by 13 w/m2? So they were ALL wrong by a whopping amount, but averaged together they were less wrong? How about calculating the error in the error range? 13 +/- what? 8? 10? 6? Oh wait…that’s the average of 19 of the 23 models in AR4. What happened to the other 4? Why were they excluded? I don’t know, I didn’t bother to dig into it. The results claimed are so ridiculous that even if the other 4 models were excluded to make the results look better….they’d just be extra ridiculous by having them included.
davidmhoffer:
Concerning your comments on the AR4, aerosols and “chutzpah”, I think you would be interested in this review comment I provided to the first draft of the AR4.
“Page 2-4 Chapter 2 Line 2 of the draft says nitrous oxide is the “fourth most important greenhouse gas” and Page 2-3 Chapter 2 Lines 50 and 51 (wrongly) say methane is “the second largest RF contributor” (assuming that the effect of water vapour is ignored as is the convention in this Chapter except for Section 3.2.8.). But the draft does not state the third largest contributor.
Before Page 2-4 Chapter 2 Line 2, the draft needs to be amended to include the RF of particles of sulphate aerosols combined with soot that is the second largest RF contributor.
1. CO2 has RF of 1.63 Wm^-2,
2. particles of sulphate aerosols combined with soot have RF of 0.55 Wm^-2
(ref. Jacobson MZ, Nature, vol. 409, 695-697 (2000))
3. methane has RF of 0.48 Wm^-2.
4. and nitrous oxide has RF of 0.16 Wm^-2.
The authors of this chapter seem to be ignorant of the warming effect of sulphate aerosols combined with soot particles. But their correct statement that nitrous oxide is the “fourth most important greenhouse gas” implies that they are choosing to deliberately ignore the warming effect of sulphate aerosols combined with soot particles.”
I add that the anthropogenic sulphate and the soot particles are mostly simultaeneously emitted from the same sources.
Richard
Richard S Courtney;
Illuminating. I’m curious about the sulphate particles emitted from the same source as soot? I’d guess that diesel fuel consumption is/was a major contributor? Has that changed since the regulations forcing the use of low sulphur diesel? What other sources? I’d guess coal next, but again, scrubbers on coal stacks have reduced both would they not?
Re: Fourth most important vs fourth largest contributor
I read some material some time ago where (I think it was AR4 but it has been a while) presented the various GHG’s calculated as both “current” forcing and (I forget the term they used) “long term”. “Warming Potential” perhaps? In any event, they did some fancy math to show that Methane broke down over time into other molecules, and so over 100 years the total warming was the combination of both the initial molecules and the final molecules, and then came up with a number many times that of CO2, making it “more important”. There were other gasses as well, but I don’t recall which ones. In any event, is that the distinction in this case of “most important” vs “largest contributor”?
davidmhoffer:
Thankyou for your post to me at June 6, 2011 at 7:34 am .
We seem to be going off topic so feel free to continue our discussion by emailing me.
For now, I respond to your questions with brief answers.
‘Black carbon’ or ‘soot’ is unburnt fuel. It mostly derives from coal-fired power stations and the increase to emissions from China and India makes your references to emission regulations in the West largely irrelevant: the West has been ‘cleaning up its act’ but China and India have not.
I cannot say what distinctions the IPCC AR4 authors made between “most important greenhouse gas” and “largest RF potential”. They used both terms interchangeably in all three drafts so I assumed their text intended them to be the same thing. Of course, that assumption may have been wrong.
Richard
According to one regular poster, it’s a form of numerology to just hunt for an equation that will fit your available data.
What does one call it when one has an assumed equation, and then fiddles with the data in order to make the output of the equation fit the assumed pattern?