With some hubub recently over the 350.org day (designed to highlight the opinion that we must return the Earth to a 350 parts per million atmospheric CO2 level) I thought it might be a good idea to have a look at what the reversal might gain us.
For this, I’m drawing on the excellent guest post made by Bill Illis here on 11/25/2008 titled:
Adjusting Temperatures for the ENSO and the AMO
One of the graphs (along with a model in a zip file) that Bill presented in that guest post was this graph, which I’ve annotated to show the 350 PPM desired by activists, versus the 388 PPM (MLO seasonally corrected value) where we are now:
Here is the same graph, annotated again with intersecting lines and values, and zoomed on the areas of interest.
Depending on whether you believe the models or the actual observations determines what value would be gained from a reduction to 350 PPM.
For belief in the models we’d get approximately 0.5°C drop in temperature.
For belief in the observations (RSS HadCRUT3 data) we’d get approximately 0.3°C drop in temperature.
Split the difference if you don’t like either and call it 0.4°C.
The key point here is that to get to 350PPM, it would be extremely difficult if not impossible to accomplish. Alternate energy just hasn’t risen to the challenge yet, and the world populace that depends on electricity isn’t likely to tolerate shutting down their energy use to get there.
China and India have said they won’t go along with suggested reductions, and are coming up with their own ideas prior to Copenhagen. Thus is the quandary faced by 350.org supporters.
As a side note, the 350PPM target was Dr. Jim Hansen’s idea:
Target Atmospheric CO2: Where Should Humanity Aim?
Since Hansen can’t even predict the effect of climate change 20 years out in his own neighborhood, one wonders why some people take the 350 PPM target suggestion seriously.
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Icarus (15:27:31),
I quoted exactly what you wrote:
“CO2 has no significant effect on world grain crops…”
Now you are attempting to re-frame the argument. If you will look at the links I and others posted upthread, you will see that atmospheric CO2 concentration has an enormous impact on agricultural productivity.
In addition, rises in CO2 follow temperature rises. The reason is obvious: click. As the oceans warm, CO2 is outgassed. That’s why warm beer quickly goes flat.
Thanks Bob. That smoothed ENSO really looks like PDO index!
I did not mean TSI since there are various reconstructions, but plain sunspot number. SSN increased a lot between 1910-1960.
http://blog.sme.sk/blog/560/195013/hadsstssn.jpg
“Deepest Darkest Iowa” raised a point about CO2 being saturated,
and Icarus gave an incorrect explanation of why there can be spectrum broadening, even with saturation in some wavelengths.
I’ll concede that have no graduate degree in physics, the following is from my undergraduate knowledge, and what I’ve picked up surfing the internet.
Spectrum Broadening
Some on this site have stated that H20 and CO2 can only absorb photons at
specific wavelengths. At some level this
may be true, but in practice it’s not, otherwise the argument about
saturation would be correct, and nobody would give a damn one
way or the other about further changes in greenhouse gases.
Suppose CO2 can absorb energy only at exactly 14 nanometers. In
practice, CO2 molecules are moving around with
speeds of rougly 400 meters/second. Since this is small relative to
light speed, non-relativistic physics can be applied.
Since 400 meters/second is rougly 1/750,000 the speed of light,
molecules moving towards a photon will see
wavelengths 1/750,000 shorter than exactly 14 nanometers in
length, and can interact with them. Likewise,
molecules moving directly away will see the wavelengths as 1/1,300,000
longer, and can interact with them, so
in practice there are a range of molecular speeds and wavelengths
interacting with the photons, which is why
you get a band rather than a single set of lines.
One result of quantum mechanical theory is Heisenberg’s uncertainty
princible
dE* dt> 1/2 h
where E is energy in joules, t is time in seconds, and h is Planck’s
constant, 6.626* 10^(-34) joule seconds.
Energy can’t be measured closer than 1/2(6.626) = 3.313*10^(-34) joule
seconds.
Molecules are constanlty absorbing photons, then radiating the photons
out in fractions of a second.
Say the average time between collisions is 1/1,000,000 second. Then
the energy absorbed can
vary by a factor of 3.313* 10^(-26) joules because of the uncertainty
principle. The collision rate
is a function of temperature and pressure. Increase the pressure and
you increase the frequency of collisions.
Increase the temperature and you increase the frequency of
collisions. Because of that uncertainty principle, the
gas can absorb energy at the standard energy + or – that 3.313 * 10^
(-26) joules.
When you increase the number of molecules, most of them, in the saturated middle range of speeds, will not affect temperature any further, but the bands will widen at the extreme ends where
there are now a larger number of molecules. Of course there are very few molecules traveling at these increased speeds, so the effect will be small.
The combinded broadening from a normal speed distribution of molecules
and the broadening due to the uncertainty
principle is addressed in the Voigt temperature profile.
http://en.wikipedia.org/wiki/Voigt_distribution
Of course there’s not a neat solution for the above equation, you’ve
got to solve it numerically using something like:
http://en.wikipedia.org/wiki/Numerical_integration
That’s essentially what modtran does.
http://geosci.uchicago.edu/~archer/cgimodels/radiation.html
I picked up this information on the Voigt profile from a post by
Michael Hammer from
Jennifer Marohasy’s blog.
http://74.125.155.132/search?q=cache:stSOID5eh6QJ:jennifermarohasy.co…
Specifically this letter:
“Comment from: michael hammer May 15th, 2009 at 11:22 pm
SJT: sorry but again i have to disagree with you. Line absorption
profiles follow a Voigt profile. I have integrated the area under this
profile at various concentrations. When i also included the effect of
the analysis described in my first post on Jennifer’s site I then got
an almost perfect agreement to a logarithmic response. Hence the
analysis I did (which converts the loss from 10^-N to 1/N) needs to be
incuded to get the logarithmic response.”
For real world numbers, we get about 240 watts from the sun,
the atmosphere greenhouse effect of about 0.625 atmospheres increases this to about 1.625*240 = 390 watts at the surface,
and the estimated effect of a doubling of CO2 would increase this to about 393.7 watts, due to spectrum broadening, for a temperature increase of
(393.7/390)^0.25 = 1.00236 times the original. If the current average temperature is 288 K, the increase due to a doubling of CO2 would be to 288.68K for an increase of 0.68 K. Of course
some of this temperature increase could be in latent heat, extra
energy absorbed in evaporating water, a negative effect to to
a drop in temperature lapse rate, and an increase in clouds due
to that extra evaporation and extra rain, making the actual surface temperature increase probably somewhat less than 0.68 K.
– A McIntire
What do you get when you take enough C02 out to get to 350 ppm?
Candy-coated forecasts, teeshirts & a prize,
That’s what you get in Carbon Tax.
Icarus (15:31:17) :
Icarus, this has already been explained to you.
Did you understand the chart at the top of this article? Did you understand what it means?
There is nothing to get alarmed about. Almost all of the warming attributed to CO2 has already taken place. Even a further large increase would not cause noticeable — or even measurable — warming: click.
RSS data before 1978 ???
REPLY: that was a typo on my part, it is actually HadCRUT3 data. Fixed, thanks. Anthony
Icarus
You make various points that I must take issue with.
Your answer to Deepsest Darkest Iowa is not accurate. CO2 is the most important molecule for radiating energy into space. So in spite of being a greenhouse gas it is also responsible for cooling the upper troposphere and stratosphere. It is not really an issue of saturation. The reason why increased concentrations may increase temperature is that at higher concentrations the mean free path of the photons in the three absorption bands is reduced. That means that radiation into space must take place at an increased (less dense)altitude. Since temperature reduces as one goes up (until you reach the tropopause) this implies less energy being radiated. The energy balance has to be maintained hower so the earth heats up to a level which allow radiation at all the other frequencies to inrease and compensate. However the effect is small. To get a large greenhouse effect one has to postulate increased absorption by water vapour. This is where where the arguments start since there is no evidence that this is happening.
You say that CO2 is historically correlated with temperature. Please look carefully at the plots. You will see that CO2 follows temperature. The consequence of this simple fact is startling. The lowest CO2 concentrations have always occured at the deepest point in each ice age, That means that the most rapid rises in temperature have occured when CO2 have been at minimum. Conversely the most dramatic drops in temperature have occured when CO2 have been close to maximum. Since the rate of change of temperature should be correlated with the rate of heating or cooling the only conclusion one can come to (if you insist on causation) is that CO2 has a cooling effect.
Lastly you argue that CO2 has no effect on plant growth, As many have pointed out this is clearly nonsense. Below about 200ppm plants will not grow at all. We are therefore very close to a critically low level. In particular higher concentrations of CO2 allow the plant to reduce the stomata openings and reduce water losses. This makes plants more drought tolerant. The effect of increased CO2 will obviously vary according to plant type but I suspect that in many situations the concentration of CO2 is the critical growth determining factor and hence its use in greenhouses. Please remember that we are all built of carbon compounds and the only source of carbon accessible to plants is CO2. All of life depends on CO2 and water in equal measure.
Andy Krause (14:54:18) :
Just a note, in Northern Illinois we don’t irrigate corn.
Mostly we don’t, but there are some center pivot fields on the drive from Chicago to Moline. They might be worth the cost in the occasional drought year, but we have down years maybe one out of seven, and many of those are due to too much water in spring or early frosts.
.
Icarus (14:51:23) :
“In the United States, which accounts for 40 percent of the world corn harvest, yields are now approaching an astonishing 10 tons per hectare. Even though fertilizer use has not increased since 1980, corn yields continue to edge upward as seed companies invest huge sums in corn breeding.” . . .
CO2 has no significant effect on world grain crops, but temperature and drought certainly do.
Your quotes didn’t really address the CO2 aspect. Drought, of course, but temps above 86°F don’t hurt corn, just don’t make it grow any faster.
Sieben Hybrids, a small local company in Illinois, doesn’t have the megabucks to invest in genetic research that DeKalb, Pioneer, and the other big guys have, yet its seed produces competitive yields. I’d bet a Mannomatic PCA I would turn up CO2 as the culprit.
Icarus, what would happen if the Earth did warm up? I predict if CO2 were causing warming *laughing* then we would be up to our armpits in polar bears.
If the chart in this link is correct, there is no correlation between historical CO2 levels and global temperature. It shows as much as nine times higher CO2 in the past. I can’t find the origin of the chart. Does anybody know its pedigree or correctness?
http://ff.org/centers/csspp/library/co2weekly/2005-08-18/dioxide.htm
Thanks, Dan
Stephen Skinner (14:44:53) :
What I am unable to find out is the effect on temperature within greenhouses with elevated CO2.”
Has been tested, 2 identical green houses under identical circumstances and different CO2 levels, no measured difference in temperature.
http://www.ilovemycarbondioxide.com
Juraj V: you wrote, “I did not mean TSI since there are various reconstructions, but plain sunspot number. SSN increased a lot between 1910-1960.”
But if the last three cycles only cause surface temperatures to vary 0.1 deg C, the change from SC#14 to SC#19 could only impact surface temperatures by a portion of that. And the current understanding of TSI variability is that it varies pretty much in agreement with Sunspot Number, no big dip prior to the 1940s.
Also, another thought, your run through of the 20th Century “cycles” suggested that global temperatures rose until 1950. The early 1940s appear to be where they topped out, about the same time as the multiyear El Nino.
Regards.
“What does a reduction to 350 PPM of CO2 get you?”
Higher taxes
Higher unemployment
Higher energy bills
Higher food costs
More government in my life.
Nice write-up; 350 seems to be the new black. There’s an opinion piece over at Yale 360 claiming that the economic impact of drastic action to reach 350 ppm of CO2 would be cheap, here’s my Critique of the Economics of 350, basically it’s cheap if you only expect to make a 1.5% rate of return, and you fudge the climate change damage numbers.
As another polar bear follow up, as a test we should relocate 10 polar bears to Oregon. Then take James Hansen, wrap him in salmon, and give him a 5 minute head start. I think they would survive just fine.
And Iscariot will move onto to some other ‘pet’ calamity direly prognosticated to overtake humanity (or animals) if not the world …
i.e., “Save the whales” (established in 1951 (yes, ’51!) to “reduce the sum total of pain and fear inflicted on animals by humans”).
.
.
So they’d be happy at 350ppm would they? Funny – I don’t remember them jumping through the hoops when it was 350ppm and rising…
Deepest Darkest Iowa (13:00:18) :
“I have read that CO2 “absorbs to extinction” at well below the 385 ppm level. As I understand it, CO2 only captures infrared in three narrow frequency bands with wavelengths of 2.7, 4.3, and 15 microns, and that these bands are already saturated. If true, this means that all the infrared that CO2 can capture is already being captured, and would be at 350 ppm. Thus, more or less CO2 in the atmosphere makes no difference. Will someone with more scientific knowledge than I have please confirm or correct?”
I am not a physicist either, but this is how I understand the theoretical function of CO2 as a so called greenhouse gas.
The long wave black body radiation emitted from the earth with wavelengths in the CO2 absorption bands is absorbed within a very short distance. The common misconception seems to be that once the low level CO2 has done its thing, it is finished, hence the idea that more CO2 has no effect. This is not the way I understand the progress of long wave radiation from earth to space. Envision most of the long wave radiation in the greenhouse gas absorption bands being absorbed in the atmosphere close to the earth. Since the mean time between molecular collisions at lower atmosphere pressures is much smaller than the mean time that the excited molecules exist in the raised energy state, almost all the energy absorbed is turned into heat by molecular collisions in the lower atmosphere. Thus, the original energy emitted in the absorption wavelengths is diluted by being spread out over approximately the black body emission spectrum. This process repeats some number of times as the long wave radiative energy works its way up through the atmosphere but the key thing to note is the rapid dilution of long wave energy in the narrow CO2 absorption bands. This is manifest in the logarithmic CO2 warming model as shown in the graph at the start of this article. So as CO2 concentrations increase, there is diminishing “heat trapping” effectiveness. If we consider the earth to be in thermal balance, that the incoming solar energy is balanced by outgoing long wave radiation, then greenhouse gases merely serve to change somewhat the temperature profile of the atmosphere.
This only my opinion as an educated layman but I expect that once this “evil carbon” thing blows over, we will find that the major part of climate change (either natural or man made) will be due to modulation of incoming short wavelength radiation (solar), and changes in CO2 concentration will be found to play only a minor to insignificant role at the concentrations necessary for life on this planet.
“””
Deepest Darkest Iowa (13:00:18) :
I have read that CO2 “absorbs to extinction” at well below the 385 ppm level. As I understand it, CO2 only captures infrared in three narrow frequency bands with wavelengths of 2.7, 4.3, and 15 microns, and that these bands are already saturated. If true, this means that all the infrared that CO2 can capture is already being captured, and would be at 350 ppm. Thus, more or less CO2 in the atmosphere makes no difference. Will someone with more scientific knowledge than I have please confirm or correct? “””
Well DDI, I don’t know if you got your question answered; I saw some attempts at explaining; which may be less than accurate.
But first let us look at your postulates; that CO2 absorbs in three “narrow”
bands at 2.7, 4.3, and 15 microns; and that these bands are already saturated.
Well the wavelengths are about correct; but I wouldn’t call them narrow bands.
The wavelength bands that are used in Atomic clocks, are truly narrow, and atmospheric absorption bands are much wider than that. As others have alluded to, the fundamental resonance frequencies du to the molecular transitions, are in practice broadened by several effects. The first is “Temperature” broadening, which is simply the doppler shift effect due to molecular motions which are a function of the molecular temperature. Then there is “pressure” broadening, which is a function of the frequency of molecular collisions; so it increases with atmospheric density.
The CO2 band most responsible for the CO2 “greenhouse effect” on planet earth is the 15 micron band; which is actually more like about 13.5 to 16.5 microns for the standard atmospheric surface conditions.
It is the important band, because the peak of the earth’s thermal emission (IR) spectrum is about 10.1 microns, at the 288 K mean surface temperature. That peak shifts out to 15 microns at the coldest pplaces like Vostok Station, and it drops to around 8.8 microns at the hottest desert locations.
I don’t know if this band is saturated or not; I have never seen a curve showing total extinction for this band in the atmosphere.
The 2.7 and 4.3 micron bands can hardly have any effect in the sense of producing any global warming; none whatsoever in my view.
The reason is that except for the very hottest surface temperatures of say +60 deg C, the earth emits very little thermal radiation at a wavelenght as short as 4.3 microns, and virtually none at 2.7 microns. But yes CO2 can absorb IR at those wavelengths; but the only source of those wavelengths in the earth’s atmosphere is the incoming solar radiation from the sun.
The amount of solar radiation in the 2.7 and 4.4 micron CO2 bands is very small; just from memory I would put it at no more that 1% of the total solar radiation spectrum.
So what is going to happen if that radiation is absorbed by CO2 molecules; well it is going to heat the atmosphere, insttead of proceding down to the surface, and heating the surface; which is 73% ocean. So the 2.7 and 4.3 micron CO2 bands can heat the air from solar absorption instead of heating the surface (oceans); and when that heated air radiates LWIR radiations; about haplf of that is going to proceed towards outer space, and only half in the direction of the ground.
So it is hardly likely that the CO2 capture of solar radiation in the 2.7 to 4.3 micron bands would cause global warming; it is a cooling effect by stopping otherwise good solar energy from reaching the ground.
So I would say; for get the 2.7 and 4.3 micron bands; they have no evffet on global warming. Now on Venus which is much hotter, those shorter wavelength bands could be contributors, if not the major players in any Venus warming.
Then you have to consider that water vapor is very active in absorbing solar energy from about 0.75 microns out to about 8 microns; which is also a surface cooling effect since it stops sunlight from reaching the ground.
Direct sunlight reaching the ocean surface; results in warming of the oceans down to many tens of metres; but the surface warming effect of LWIR from the heated atmosphere is a different story, because it is absorbed in the top 10 microns or so of the ocean surface, and leadss to prompt evaporation of hotter surface waters; which conveys a lot of energy back into the atmopshere.
Now the “saturation” idea is a bit misleading; becauseif that is true, it simply means that a thinner layer of CO2 neare the ground absorbs most of the LWIR in the 15 micron band; but that warming of the air molecules results in new LWIR emitted from the air, and some of that will be absorbed by CO2 layers above the lower one; so multiple reabsorptions keep on slowing down the eventual escape of the LWIR, which leads to atmpospheric warming.
Now my simple minded analysis of this cascade absorption process, says that the upward direction of propagation is favored over the downeward direction. This is becausew both the temperature, and pressure drop with altitude increase, and hence the CO2 absorption band gets narrower as you get to higher layers that are cooler and less dense so the4y have less Doppler and pressure broadening. Upward propagating LWIR encounters a less absorbing layer, while downwrd LWIR encounters air layers with increasing broad absorption bands, and increased CO2 molecular density.
I don’t think the “saturation” platform is a stable place for “skeptics” to stand.
On the other hand the overriding pre-eminence of water vapor and water liquid, and solid in the form of clouds, in my view makes the CO2 effect somewhat inconsequential.
If there was no CO2 in the earth’s atmosphere, I don’t think we would be much cooler than we are now; we’d have somewhat less global cloud cover; but otherwise the earth’s temperature range wouldn’t change much.
And Water vapor is perfectly capable of starting “greenhouse” warming all by itslef; it doesn’t need any instructions from CO2 to adjust the cloud cover to provide a stable temperature range.
George
CO2 Increase in the Atmosphere: From Jan 1 to Jan 1
Ex. 2003 – Warm Year CO2 increase was 2.15 ppm
2004 – Colder Year – CO2 increase was 1.30 ppm
2005 – Hot Year – CO2 increase was 2.93 ppm
2006 – Cold Year – CO2 increase was 1.52 ppm
2007 – Hot Year – CO2 increase was 2.53 ppm
2008 – Cool Year – CO2 increase was 1.49 ppm
Are we seeing a pattern, here?
ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_mm_mlo.txt
It’s all about the temperature.
Of course, if we get back to the temperatures of 1958 CO2 concentrations might start going backwards.
From Aug of 1958 to Aug of 1959 CO2 concentrations in the atmosphere Decreased by 0.13 ppm.
We had several such periods in the sixties.
ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_mm_mlo.txt
“”” cal (16:18:18) :
Icarus
You make various points that I must take issue with.
Your answer to Deepsest Darkest Iowa is not accurate. CO2 is the most important molecule for radiating energy into space. So in spite of being a greenhouse gas it is also responsible for cooling the upper troposphere and stratosphere. It is not really an issue of saturation. The reason why increased concentrations may increase temperature is that at higher concentrations the mean free path of the photons in the three absorption bands is reduced. That means that radiation into space must take place at an increased (less dense)altitude. Since temperature reduces as one goes up (until you reach the tropopause) this implies less energy being radiated. The energy balance has to be maintained hower so the earth heats up to a level which allow radiation at all the other frequencies to inrease and compensate. However the effect is small. To get a large greenhouse effect one has to postulate increased absorption by water vapour. This is where where the arguments start since there is no evidence that this is happening.
You say that CO2 is historically correlated with temperature. “””
Well cal; and I in turn must take issue with your explanation.
If one were to believe your thesis; the only way that LWIR can escape from the earth into outer space, is to be captured by a CO2 molecule, and then passed on to another CO2 molecule at a higher colder less dense altitude, until the coldest highest most ethereal CO2 remaining molecules finally send it into outer space.
But that is not what happens. As you get higher, the CO2 molecules become fewer in number, and colder, with fewer molecular collision with the air molecules; so the resonant absorption band of CO2 at around 15 microns simply gets narrower, so the upper layers of CO2 intercept less of the photons, and in a smaller and smaller band; the remaining LWIR simply escapes from the atmosphere without getting recaptured by an ever less effective diminishing CO2 component.
Yes it is true that there is a cascade of absorptions and re-emissions; not from the CO2 molecule, but from the ordinary atmospheric gases, which are heated by collisions with the excited CO2 molecules.
In your view of the process; the very last CO2 molecule at the top of the stratosphere captures 100% of the earth’s emitted LWIR, and then radiates it to space, at some lower effective black body temperature which is much lower than the surface temperature. In reality, a LWIR photon emitted from the surface at say 288 K temperature can proceed directly to outer space in less than one millisecond, without ever meeting up with a CO2 molecule. And those photons that do encounter CO2 molecules at lower altitudes, will eventually have their energy passed on the N2 and O2 molecules, which will launch new LWIR photons, many of which will also pass unhindered into outer space..
It defies common snese to argue that an ever lell dense sparser CO2 population can continue to capture most of the LWIR photons, and prevent their direct passage to outer space. The upward path is favored over the downward path because of the falling temperature and pressure , which narrows the absorption bands of higher layers so they can’t stop all the photons from lower regions; the downward path however sees increasing density at higher pressure and temperature, so the CO2 absorption band continues to broaden , and be more effective in capturing downward LWIR photons, which stop sthe from reaching the surface.
This idea that the stratosphere is somehow the source of the earth’s final LWIR emission to space, so that the stratospheric temperature is the effective radiation temperature; just defies common sense; but I know that climatologists seem to love the idea; however untenable it is.
No mention of the atmospheric window at 10 um (which happens to coincide with a moving (~T^4) spectral peak for temperatures of around 288 K … does it not?) which allows energy transmittal directly into space from the surface?
How much (energy %-wise of the total IR from the surface) excapes directly into space via the 10 um LWIR window for any given surface temp (like 288K)?
.
.
In what year was CO2 at 350 ppm? That’s how far back we’d have to turn the clock if there was no population change since then, but since there has been we’d need to turn the clock back even further to compensate for the extra population.
If the law’s of the world change to forbid withdrawing from it after the Copenhagen meeting, what happens if the IPCC that Copenhagen is built on is proven false? I say we dump Copenhagen as the IPCC would be guilty of purgery!
Jan 1, 1988 – CO2 was 350.23 ppm (adj.)