The 1% Solution

Guest Post by Willis Eschenbach

When I’m analyzing a system, I divide the variables into three categories—first-, second-, and third-order variables.

First-order variables are those variables that can change the system by more than 10%. Obviously, these must be included in any analysis of the system.

Second-order are those that can change the system by 1% to 10%. These are smaller, but still too large to overlook.

Finally, third-order variables are those than can change the system by less than 1%. These are small enough that they can be ignored in all but the most detailed analyses. To give you an idea of why we can neglect the third order variables, here’s how those three forcings would look on a graph, for an imaginary signal of say 500 W/m2.

Figure 1. Showing the relative sizes of first-, second-, and third-order variables.

Note that the series containing the third-order variable is almost invisibly different from the series where the third-order variable is left out, which is why third-order variables can be safely ignored except when you need extreme precision. So … what does this have to do with climate science?

Let’s do the same kind of analysis on the forcings of the climate system. At the TOA, the “top of atmosphere”, there is downwelling radiation from two sources: the sun, and the longwave “greenhouse” radiation from clouds and “greenhouse” gases (GHGs). The globally-averaged amount of downwelling solar radiation at the earth’s TOA (which is total incoming solar radiation less a small amount absorbed in the stratosphere) is on the order of 330 watts per square metre (W/m2). The amount of downwelling longwave radiation at the TOA, on the other hand, is about 150 W/m2.

Finally, if CO2 doubles it is supposed to change the downwelling radiation at the TOA by 3.7 W/m2 … here’s how that works out:

Figure 2. Sources of downwelling radiation at the top of the atmosphere (TOA), defined as the tropopause by the IPCC.

By that measure, CO2 doubling is clearly a third order forcing, one that we could safely ignore while we figure out what actually makes the climate run.

Or we could look at it another way. How much of the earth’s temperature is due to the sun, and how much is due to the earth’s atmosphere?

If there were no atmosphere and the earth had its current albedo (about 30%), the surface temperature would be about 33°C cooler than it currently is (see here for the calculations). Obviously, downwelling longwave radiation from the greenhouse gases is responsible for some of that warming, with DLR from clouds responsible for the rest. Cloud DLR globally averages about 30 W/m2 (see here for a discussion). So the 150 W/m2 forcing from the GHGs is responsible for on the order of 80% of the 33° temperature rise, or about 25°C.

But if 150 W/m2 of GHG forcing only warms the surface by 25°C, then the so-called “climate sensitivity” is only about 25°C warming for 150 W/m2 of TOA forcing, or a maximum about six tenths of a degree per doubling of CO2, or about 0.2% of the earth’s temperature … again, it is a third order forcing.

Now, if someone wants to claim that a change in the forcings of less than 1% is going to cause catastrophes, I have to ask … why hasn’t it done so in the past? Surely no-one thinks that the forcings have been stable to within 1% in the past hundred years … so where are the catastrophes?

Finally, most of the measurements that we can make of the climate system are imprecise, with uncertainties of up to 10% being common. Given that … how successful are we likely to be at this point in history in looking for a third-order signal that is less than 1% of the total?

w.

PS – In any natural heat engine of this type, which is running as fast as the circumstances permit, losses rise faster than the temperature. So in fact, the analyses above underestimate how small the CO2 effect really is. This is because at equilibrium, losses eat up much of any increase in forcing. So the effect of the CO2 at general climate equilibrium is less than the effect it would have at colder planetary temperatures. In other words, climate sensitivity is an inverse function of temperature.

PPS – Please don’t point out that my numbers are approximations. I know that, and they may be off a bit … but they’re not off enough to turn CO2 into a second-order forcing, much less a first-order forcing.

PPPS – What is a first-order climate variable? Clouds, clouds, clouds …

Advertisements

  Subscribe  
newest oldest most voted
Notify of

Serious question. Why is CO2 considered more important than water and sunlight when it comes to considering future temperature trends, is it a political or a scientific thing?

John Trigge

Para 3: These are smaller, but still to small to overlook
I suggest this should be ‘large’.
Love your work.
(From Oz)
.
[REPLY: Thanks, fixed. – w.]

Richard Lawson

Brilliant and very, very succinct.
Thank you Willis.

Truthseeker

zac – It is purely a political thing. CO2 has no significant effect on temperature as shown above.

Yet another 1st order post by Willis.
I’m sure there’ll be some 1st order and 2nd order comments and questions.
However 3rd order commentors should forget it as Willis doesn’t respond to those.

richard telford

Too often folk here get over excited by possibly third-order effects – there was one last week on atmospheric CO2 concentrations not being perfectly mixed. But there is a difference between a third-order effect that varies rapidly and one that steadily increases. Ignoring the first type leaves a small amount of noise in any analysis, ignoring the second type results in an ever increasing amount of bias. Anthropogenic greenhouse gases belong to the second type.

RHS

Politically speaking, CO2 is seen as within mankind’s domain to control, depending on the doctrine being followed.

Bryan A

This is likely because it is about the only input into the system that we have any control over.
We can’t control the Solar input
We can’t control the water vapor feedback
We can only control the amount of G-H-G(s) we add to the system. (but not the total G-H-G input)

TimTheToolMan

Hi Willis, I think you have the legend wrong in figure 1.

percy

ok…so now is perhaps the moment to start engaging with the feedback analysis of folks such as Bart over at Climate audit. I hope so because the debates over there on this esoteric subject have been enthralling and also way over my head. But they worry the orthodoxy.

Anything is possible

If there were no atmosphere and the earth had its current albedo (about 30%), the surface temperature would be about 33°C cooler than it currently is (see here for the calculations). Obviously, downwelling longwave radiation from the greenhouse gases is responsible for some of that warming, with DLR from clouds responsible for the rest. Cloud DLR globally averages about 30 W/m2 (see here for a discussion). So the 150 W/m2 forcing from the GHGs is responsible for on the order of 80% of the 33° temperature rise, or about 25°C.
_____________________________________________________________________________
Every time I see this line of reasoning, it troubles me because it misses out a step. So here’s a serious question for you Willis….
What would the Earth’s surface temperature be if you removed the greenhouse gases, but retained all the nitrogen, oxygen and argon which comprises 99+% of its thickness? Surely that would have to be your GHG “starting point”.
What you are assuming, in effect, is that an Earth with an atmosphere comprised exclusively of nitrogen, oxygen and argon would have an identical surface temperature as an Earth with no atmosphere at all, and that doesn’t pass my “smell test”.

TimTheToolMan

Hi again Willis, actually you dont have the legend wrong, its just that the colours ougth to be reversed of the +secornd order vs +secord+third order variables (IMO) to make your point better.

Falx

Because CO2 is a perfect Bogey man that can be measured, taxed, restricted etc. But almost all high tech & heavy industry produce copious amounts of so the potential revenue stream is enormous. Thus the perfect wealth redistribution from 1st world economies to qangos, ngos, & other rent seekers. Via the sticky hands of the high priests.
Every real or confected disaster can be blamed on CO2. No matter how much humanity does or does not produce.

Paul Westhaver

Willis,
Do you mean this?
“Second-order are those that can change the system by 1% to 10%. These are smaller, but still to small to overlook.”
Is this a typo? should it not read:
Second-order are those that can change the system by 1% to 10%. These are smaller, but still to LARGE to overlook.
Regards…

DirkH

“PPPS – What is a first-order climate variable? Clouds, clouds, clouds …”
And you talked only about radiation; CO2 doubling becomes even less important when heat transport via convection and conduction is taken into account.

CO2 is important because it can be painted as a pollutant and as a pollutant, it’s important for political purposes. Water and sunlight are obviously important to life and aren’t derived from a substance the EPA can deign to control. Early in the argument, water was not included in a listing of greenhouse gasses, partly, I believe, because it’s percentage would overwhelm that of CO2. And besides, we still cannot decide whether warming feedback from water is either plus or minus, much less the quantative impact on the MODELS.

Ralph Woods

Plain, simple, brilliant

Paul Westhaver

Another point… and I am certain Lord Monckton would also agree that at < 1% the signal to noise ratios may swamp the ability to perceive response to 3rd order artifact.
This is what the Michael Manns and the rest of climate liars continually fail to point out as Lord Monckton has done so on a number of occasions.
What is the precision of the you ability to characterize the system, what is the uncertainty?
How can anyone assess a 0.01C change in climate? or a 0.1C change for that matter. particularly with all the system noise. It is BS on its face.

Gary

Zac, because CO2 can be regulated very easily. Water and Sunlight can’t. It’s a political thing.

Matt

Ok….First and foremost: The terms “first, second, and third order” are purely fictional constructs in the sense that you are using them. In real science these labels refer to the terms in a power series expansion (the linear, quadratic, and cubic terms). Your definitions are subjective and shed no new light on the underlying physics.
What you are essentially saying is that the effect of doubling CO2 is small when compared with the warming due to the sun and to the nominal effects of GHGs (minus the human contribution). *No one* would debate this point. On an absolute scale, the effects of a doubling of CO2 are small (even the IPCC predicts a change of a few degrees, compared with a baseline of somewhere around 88 degrees K…a few percent effect).
But your so-called “second-” or “third-order” effects make a HUGE difference to life on the surface of the earth. The difference between the worst ice ages and the hottest periods in our planet’s climate history is just a few percent change in heat content. By your definitions, these changes would qualify as being on the low end of “second order”. Tell that to the dinosaurs.
There are many cases in the world where small effects make a big difference. Drunkenness is due to a change in blood-alcohol that you would call “third-order”. A dangerous fever is only a few percent effect above nominal human body-temperature. In short, the effect of a small change in a physical parameter on a system can vary widely from case-to-case. You can’t simply say 1% is small…Small compared to what?
Which brings me to my question: What is your point in making these “first-“, “second-“, and “third-order” distinctions?

kim

I think I’ve never heard so loud
The quiet message in a cloud.
=======================

Richard M

Anything is possible says:
Every time I see this line of reasoning, it troubles me because it misses out a step. So here’s a serious question for you Willis….
What would the Earth’s surface temperature be if you removed the greenhouse gases, but retained all the nitrogen, oxygen and argon which comprises 99+% of its thickness? Surely that would have to be your GHG “starting point”.
What you are assuming, in effect, is that an Earth with an atmosphere comprised exclusively of nitrogen, oxygen and argon would have an identical surface temperature as an Earth with no atmosphere at all, and that doesn’t pass my “smell test”.

In fact, I believe the temperature would be warmer. How would the atmosphere get cooled without the radiating properties of GHGs? The surface heat would mostly radiate to space, but the small amount that was conducted to the air would continue to build over time.
It would be real interesting to hear the arguments of alarmists as to how this scenario would play out.

FredT

This is completely wrong. At the TOA – which is the *TOP* of the atmosphere, there is *no* downwelling LW radiation. There is only upwelling LW radiation of about the same order of magnitude as the absorbed solar. Think about it!

RoyFOMR

Along with millions of others, I’ve seen “Close Encounters of the third kind” and I know that the bigger the number the more important it is!
Argumentum ad Hollywood:
Climate changes because it is variable and can be summarised thus;
Solar is a first-order variable, Natural Greenhouse gases are second-order but (mainly) man-made CO2 is a THIRD order variable. Wow!
Extending Hynek’s scale to even higher order variables make it even worse than we first thought.
Methane eructations, cheap energy, oceanic acidification, ozone depletion and the insidious spread of Global capitalism just to mention a few may, perhaps, be even higher orders than fossil-fuelled atmospheric pollution.
We must ban everything that irritates Gaia and the sooner the better.
PS – is it sarc with a forward or a backward slash?

More Soylent Green!

TOO small, not to small. Or possibly TOO large.

steveta_uk

This is because at equilibrium, losses eat up much of any increase in forcing.

When designing a discrete heat engine, this may be true, but when analysing the earth climate system as a whole you cannot ignore losses – there’s nowhere for the energy to be lost to.

DIrkH Says:
And you talked only about radiation; CO2 doubling becomes even less important when heat transport via convection and conduction is taken into account
Dirk:
In performing heat balances, the effects of each separate mechanism are cumulative. That is, the net heat tranfer is the sum of convective, conductive and radiative. The climate model energy balances account for this.
Willis:
I believe the argument is that the feedbacks cause the net effect to go from less than 1% (2.87C), hence moving the impact from your ‘third order’ to what you describe as ‘second order’.
In researching this post, I’ve gained further understanding of low pressure radiative transfer. If someone asks you about my little paper on “the path length approximation”, I’ve found the error in my calculations.

“Among the favorite subjects of such essays were anecdotes taken from the lives or correspondence of famous men and women. They bore such titles as “Friedrich Nietzsche and Women’s Fashions of 1870,” or “The Composer Rossini’s Favorite Dishes,” or “The Role of the
Lapdog in the Lives of Great Courtesans,” and so on. Another popular type of article was the historical background piece on what was currently being talked about among the well-to-do, such as “The Dream of Creating Gold Through the Centuries,” or “Physico-chemical Experiments in Influencing the Weather,” and hundreds of similar subjects.”

Hesse, Hermann: “Magister Ludi or the glass bead game”

Hoser

CO2 is the only parameter in the models that allow them to fit past data. It’s too hard to model clouds accurately. If they give up CO2, they give up the whole thing. It isn’t science, it’s power. Money and prestige go to the scientists providing results that please their masters, and the “science” justifies government control over us. It lets those pulling the strings of government pick winners and losers. There is no free market; the game is rigged. And big corporations also in league with government seemingly win because they enjoy protected regulatory markets. In reality, they just become weak and uncompetitive. We are so screwed.
People know something is wrong. They are typically misinformed about what is behind the problems we face.
Young people are told to blame capitalism. Unless we get back control over education, the young people will be manipulated to support the revolution thinking they have nothing to lose. The world is not fair, they are told. Lambs to the slaughter.
Minorities are told to blame the rich (white) racists, and remember only progressive government is “on your side”. Minorities are told they can’t make it without help. Obviously, without equal outcome, the system is clearly biased in favor of others. This flawed logic justifies legal “remedies” like affirmative action. Anything is justified in some well-intentioned (they claim) attempt to create a more “fair” outcome. Divide and conquer.
We are all in this together. Every person, every country. We are made weak, slowly whittled down, and eventually culled. What is the goal? A world population of 1 billion? It is completely unnecessary. The world could support a population of over 10 billion people, if we provide the energy we need to maintain civilization. We can do that without much trouble. Feeding us all may require a change in the way we live, and where we live. We can avoid a very bad future, but never using Green methods.
For Greens to succeed, all principles and independent thought must be eliminated. No one can be allowed to think or act independently. The state must be free to do whatever is necessary.
Green politics is genocide. Green energy is poverty, disease, and death. Green is the new Red.
We should never give up trying to help people become more aware.

I have to agree with several of the comments…
As FredT says, the downwelling LW at the TOA will be small. At the VERY TOA, it will be zero. Even at 11 km, the value is ~ 25 W/m^2 (using MODTRAN). Downwelling solar radiation is ~ 340 W/m^2 at the very top, and will be a little less at the tropopause, so it is LW is ~ 10% at this level, not ~ 30%.
As Matt says, even small (a few percent changes) are important in the climate balance, so CO2 changes cannot be ignored simply because they are ~ 1 %. The big question, of course, is the feedback — will 0.8% change from doubling CO2 lead to positive feedback (in which case it could easily be a 2% change that is quite significant to the climate) or will it lead to negative feedback (in which case it could easily be ~ 0.1 % and totally insignificant)?

joe

Matt,
One problem with your alcohol analogy, CO2 is one of many sources of radiation while alcohol is the only source of drunkenness. Were alcohol one of many factors contributing to our inebriation and its effect was .8% of said drunkenness then we could say it was third order. However since it causes 100% of the inebriation it is a first order.

Edward Bancroft

FredT: “At the TOA – which is the *TOP* of the atmosphere, there is *no* downwelling LW radiation. There is only upwelling LW radiation….. ”
Yes, this is the net daily effect of the sun’s emissions on the atmosphere.
To that, I would add that we also need an analysis of IR outwelling at night when the atmosphere is cooled by IR emissions to space, by the presence of IR-active (‘greenhouse’) gases. The more ‘greenhouse’ gases in the atmosphere, the more the cooling effect at night balancing the extra heating effect by day?

RoyFOMR

“As Matt says, even small (a few percent changes) are important in the climate balance, so CO2 changes cannot be ignored simply because they are ~ 1 %”
Yes, third-order changes may lead to first order perturbations but do we really want to base our futures on the possibility that a mouse, in Tokyo on a Tuesday in June, may and just perhaps (‘cos it’s not impossible mate) swing its tail and create a Tsunami in Cornwall?
As pure conjecture I can go along with that but when the defence against it happening threatens my future, my childrens future and the way of life that millions have fought for do you wonder why I reject that whimsy?
If you don’t then we clearly have severe differences when interpreting Occam.

Paul Wanamaker

I’m wondering what kind of variable extreme ultra violet is. EUV varies greatly during the solar cycle, and heats the atmosphere to a greater or lesser extent…
“NASA-supported researchers say that solar flares have been keeping a secret. The new finding, reported in the Astrophysical Journal, suggests that explosions on the sun could affect Earth even more than previously thought.”
From http://science.nasa.gov/science-news/science-at-nasa/2011/19sep_secretlives/

Legatus

Anything is possible says:
October 4, 2011 at 2:49 pm
What would the Earth’s surface temperature be if you removed the greenhouse gases, but retained all the nitrogen, oxygen and argon which comprises 99+% of its thickness? Surely that would have to be your GHG “starting point”.
This is answered here http://scienceofdoom.com/2009/11/28/co2-an-insignificant-trace-gas-part-one/
The reason CO2 can increase temperature due to absorbing and re-emitting longwave radiation, while these above gasses do not, is because the above gasses are transparent to such wavelengths. They can be heated by convection, by direct contacted with other heated stuff, like the ground, water vapor, even CO2, but cannot themselves be directly heated by infrared radiation. Therefore if the atmosphere contained no “greenhouse gasses” at all, the surface would radiate longwave radiation directly out into space, with no interference at all. This happens, to some extant, in deserts at night, no clouds and little humidity means less “greenhouse” gasses between the surface and space, so more and faster radiation, and it gets cool fast, despite the fact that it may have been extremely hot in the daytime.

Peter S

Tim Folkerts – ‘As Matt says, even small (a few percent changes) are important in the climate balance, so CO2 changes cannot be ignored simply because they are ~ 1 %. The big question, of course, is the feedback — will 0.8% change from doubling CO2 lead to positive feedback (in which case it could easily be a 2% change that is quite significant to the climate) or will it lead to negative feedback (in which case it could easily be ~ 0.1 % and totally insignificant)?’
Wilis looked at one important part of the equation, which is what would things be like without the atmosphere and greenhouse gasses. But I think there is another equally important one that has not been looked at enough, this would, to my untrained eye, seem to make a bit of a mockery of the whole positive feedback argument.
The question is what was the atmosphere like (how high a concentration of C02), and how hot were the temperatures before plants started dragging C02 from the atmosphere?
All the black carbon that we are releasing into the atmosphere as C02. Where did it come from?
You see, the term “fossil fuel” suggests to me that the world’s supply of coal, oil, natural gas, and the biomass of our forests and plants previously existed in some other form of carbon.
Not only that, but that it was converted to it’s current form by living organisms.
If that is the case, then that would suggest that the source of that was atmospheric CO2.
So, what was the atmospheric C02 concentration at the stage where life apparently began? How acidic were the oceans? Was there runaway global warming, and, if so, how did life forms manage to evolve in what AGW proponents argue should have been extremely hostile conditions?
One of the problems I have with AGW is that as far as I am aware, the c02 we are releasing now from burning fossil fuels and the like must have existed in the atmosphere previously (and in far greater concentrations than it does now).
So how hot was it then?
Surely we need those figures to work out an upper end benchmark and levels of significance?

TerryS

Re: Matt says:

Ok….First and foremost: The terms “first, second, and third order” are purely fictional constructs in the sense that you are using them.

Nope they are not. The idea of second order effect being a fraction of a first order effect and a third order effect being a fraction of a second order is well understood and well used. If you want some examples then search google for “first order effect” and you will get many hits from many different fields including (but not limited to) economics, probability, oceanography, chemistry, earth sciences etc.

Willis Eschenbach

richard telford says:
October 4, 2011 at 2:43 pm

Too often folk here get over excited by possibly third-order effects – there was one last week on atmospheric CO2 concentrations not being perfectly mixed. But there is a difference between a third-order effect that varies rapidly and one that steadily increases. Ignoring the first type leaves a small amount of noise in any analysis, ignoring the second type results in an ever increasing amount of bias. Anthropogenic greenhouse gases belong to the second type.

Yes, and because of that I have projected the effect a long ways into the future, to the point where CO2 has actually doubled … it’s still first order.
w.

Willis Eschenbach

Anything is possible says:
October 4, 2011 at 2:49 pm

If there were no atmosphere and the earth had its current albedo (about 30%), the surface temperature would be about 33°C cooler than it currently is (see here for the calculations). Obviously, downwelling longwave radiation from the greenhouse gases is responsible for some of that warming, with DLR from clouds responsible for the rest. Cloud DLR globally averages about 30 W/m2 (see here for a discussion). So the 150 W/m2 forcing from the GHGs is responsible for on the order of 80% of the 33° temperature rise, or about 25°C.

_____________________________________________________________________________
Every time I see this line of reasoning, it troubles me because it misses out a step. So here’s a serious question for you Willis….
What would the Earth’s surface temperature be if you removed the greenhouse gases, but retained all the nitrogen, oxygen and argon which comprises 99+% of its thickness? Surely that would have to be your GHG “starting point”.
What you are assuming, in effect, is that an Earth with an atmosphere comprised exclusively of nitrogen, oxygen and argon would have an identical surface temperature as an Earth with no atmosphere at all, and that doesn’t pass my “smell test”.

Why would the temperature of the planet be different with an atmosphere composed of non-GHGs?
People keep looking at this question from the wrong end. They note that near the ground the atmosphere is warmer than it is aloft, the “lapse rate”. Somehow, that makes them think that somehow the atmosphere is warming the ground … but all that is happening is that the ground stays the same temperature, but aloft the temperature drops.
In any case, if you are right (which I doubt extremely) that just makes the CO2 less of a factor …
w.

Willis Eschenbach

steveta_uk says:
October 4, 2011 at 3:58 pm

This is because at equilibrium, losses eat up much of any increase in forcing.
When designing a discrete heat engine, this may be true, but when analysing the earth climate system as a whole you cannot ignore losses – there’s nowhere for the energy to be lost to.

Say what? Energy is constantly going as losses from the surface to the upper troposphere, and thence to space … which keeps the surface COOLER THAN IT OTHERWISE WOULD BE.
So yes, there are definitely losses in the system. If the system were perfect, we’d all be cooking.
w.

Willis Eschenbach

John Eggert says:
October 4, 2011 at 4:00 pm

,,, Willis:
I believe the argument is that the feedbacks cause the net effect to go from less than 1% (2.87C), hence moving the impact from your ‘third order’ to what you describe as ‘second order’.

That is indeed the argument, John, but it’s wrong. For example, the second calculation includes each and every one of the feedbacks. The GHGs raised the temperature raised by 33° including the feedbacks.
w.

Mark T

Look up the phrase “third order intercept.”. The magnitude of higher-order effects is a function of the non-linearity of the system. As your system approaches regions of highly non-linear behavior, higher-order effects dominate.
Mark

Willis Eschenbasch said in the article:
” Cloud DLR globally averages about 30 W/m2 (see here for a discussion). So the 150 W/m2 forcing from the GHGs is responsible for on the order of 80% of the 33° temperature rise, or about 25°C.
But if 150 W/m2 of GHG forcing only warms the surface by 25°C, then the so-called “climate sensitivity” is only about 25°C warming for 150 W/m2 of TOA forcing”
I would like to comment on the calculation of low climate sensitivity. Our present atmosphere in comparison to no atmosphere and same albedo caused a 33 degree C temperature rise, with adding of 180 W/m^2. However, there are 76 W/m^2 of water evaporative cooling and 22 W/m^2 of heat removal by convection. So, the atmosphere warms the world by 33 degrees C with a net gain of 82 W/m^2. This translates to a “feedback parameter” of 2.48 W/m^2-K. (And negative.)
A doubling of CO2 at this rate would cause 1.49 degree C temperature rise.
The usual figure for feedback parameter with zero feedbacks from albedo change, water
vapor effect change, lapse rate change, etc. is negative 3.3 W/m^2/K. Using that, a doubling of CO2 would cause a 1.12 degree C temperature rise.

Willis Eschenbach

Tim Folkerts says:
October 4, 2011 at 4:16 pm (Edit)

,,, As Matt says, even small (a few percent changes) are important in the climate balance, so CO2 changes cannot be ignored simply because they are ~ 1 %.

I think you are trying to say:

,,, As Matt claims without adducing even a scrap of evidence, even small (a few percent changes) are important in the climate balance, so CO2 changes cannot be ignored simply because they are ~ 1 %.

Matt has not given even the slightest backup for his claim, and you accept it as gospel … I’m sure you can see the problem.
w.

RoHa

@Baa Humbug
“However 3rd order commentors should forget it as Willis doesn’t respond to those.”
He responded to me when I asked him about a fish.

Anything is possible says:
October 4, 2011 at 2:49 pm
What would the Earth’s surface temperature be if you removed the greenhouse gases, but retained all the nitrogen, oxygen and argon which comprises 99+% of its thickness?
==================================================
See the ideal gas law, I believe that would give you the answer. As to the GHGs, I haven’t found an answer to a question I posited. Perhaps someone here will know.
What is the energy distribution towards the various frequencies of IR? For instance, does 10.5 microns put the same energy as 3.0 microns? If so, how do we know this? How does the various redundant absorption effect the energy moving towards the earth?
Given the orbital shape of the earth, and the muti-directional re-emission of the molecules, more energy would be emitted past the earth than back towards the earth………. the ratio away from the earth increasing as the elevation of the molecule increases.

Septic Matthew

Willis wrote: Finally, most of the measurements that we can make of the climate system are imprecise, with uncertainties of up to 10% being common. Given that … how successful are we likely to be at this point in history in looking for a third-order signal that is less than 1% of the total?
You have, I suggest, confounded two issues (1) whether a third-order effect can be detected from a short time series; and (2) whether a third-order effect might have an important consequence if it persists. AGW proponents claim a doubling of CO2 will increase Earth equilibrium temperature by 2K – 4.5K, or about 1% from what it is now. A 0.8% increase in net forcing is the right order of magnitude to produce that effect, should it persist.
Clouds, clouds, clouds — doesn’t almost everyone agree that the changes in clouds are the most important known unknowns? If the clouds increase even a little bit, then the CO2 increase will not warm the Earth surface. They might increase, or they might not. So what we can say with the precision we have available, is that AGW can not now be known to be true, and it can not now known to be false. That, I would claim, in the proper skeptical position, with knowledge as it is.
At RealClimate I emphasize one hand; here I emphasize the other hand.
The best evidence that AGW might be false comes from your analysis of the TAO/TRITON data, and the discovery of the negative correlation between early day and late day temperatures. If something like that could be discovered over large enough areas of Earth surface, it would show that temperature can not increase 4K without an enormous increase in the forcing lasting a long time.

Septic Matthew

Anything possible says: What would the Earth’s surface temperature be if you removed the greenhouse gases, but retained all the nitrogen, oxygen and argon which comprises 99+% of its thickness? Surely that would have to be your GHG “starting point”.
That is an irrelevant consideration for thinking of AGW and policy. The question is: Given Earth’s composition as it is now, what will a gradual doubling of CO2 in the atmosphere over 50+ years produce? If another 0.5K increase in temperature produces so much cloud cover that downward radiation of all frequencies is reduced enough in daytime, then increases in CO2 will produce no additional increase in temperature. It is possible that further study of clouds will show that already the warming since LIA has produced sufficient cloud cover that there will be no new warming of the lower troposphere.

Willis Eschenbach

Matt says:
October 4, 2011 at 3:08 pm

… There are many cases in the world where small effects make a big difference. Drunkenness is due to a change in blood-alcohol that you would call “third-order”.

I can see I have not been clear. Small effects can make a big difference. Small changes in effects, not so much.
The change from present to a doubling of CO2 changes the downwelling radiation from its previous “natural” level by less than a percent.
But when you change the alcohol content of your blood, you are changing it from the natural blood alcohol content of about 0.03 (present in all humans from childhood on), to say 0.08, the legal limit in California. This is a huge increase of 260% in the blood alcohol level, and you are just barely legally drunk … so your claim that it s a small change doesn’t hold water. You’ve jacked your blood alcohol level by 260%, and you claim that is a tiny forcing?
In addition, you have not given the slightest evidence that your claim (1% changes make big differences) is true about climate … will a change of 1% in the wind, or the amount of rain, make some huge difference?
w.

Joel Shore

Willis – A few comments:
(1) We happen to be in the unusual situation where the largest input (solar radiation) is also exceedingly constant…at least the the output from the sun is…over the timescales of interest. (And, there is very little evidence at this point to support the notion that clouds spontaneously vary enough to make much difference.)
(2) I have always been fuzzy on where your 150 W/m^2 number comes from. If it is just from taking the difference between the surface radiation of ~390 W/m^2 and the ~240 W/m^2 at the top-of-the-atmosphere, I see some problems with that, the most important being that it represents only the contribution due to CO2 alone, not feedbacks such as the water vapor feedback (because the 3.7 W/m^2 is just the forcing due to CO2 alone). [Why it is gives a result somewhat lower than the accepted no-feedback value is something I am not completely clear on…although part of it may be that it may implicitly include the one major feedback that is negative, the lapse rate feedback.]