I used RRTM LW (the model Trenberth uses) to calculate the effects of increasing CO2 on downwelling longwave radiation, otherwise known as measuring the greenhouse effect of CO2.
As you can see, the effect of increasing CO2 is minuscule.
Even in the mid-latitude winter, going above 400 PPM has very little effect
By contrast, the effect of water vapor is large, and accounts for almost all of the greenhouse effect.
Increasing CO2 has almost no effect on the climate, as we have seen over the past 18 years. Trenberth knows this – this is the same model he uses for his weather and climate models.
Scientists who claim that increasing CO2 is dangerous, are either ignorant or dishonest.
You are even more right than you imagine.
CO2 can’t affect the amount of “Downwelling Radiation” in the 15 micron band because the lower troposphere is opaque. That “Downwelling Radiation” is coming from a few feet above your head!
Robert G. Brown explains:
Who mentioned the 15 um band? I don’t see where Steve G mentioned the 15 um band? Did I somehow miss his mentioning the 15 um band? Is this a strawman pulled out of air?
Its well established that the 15 um band is opaque … why are you specifically bringing this up?
Atmospheric windows et al:
Furthermore, regarding this bit by Robert:
rgbatduke says May 28, 2014 at 10:21 am
-snipping the question –
This isn’t the right question. The question is, “What is the absorption cross-section for a 15 micron photon”. That’s the effective surface area intercepted by each CO_2 molecule. It is large enough that the mean free path of LWIR photons in the pressure-broadened absorption bands of CO_2 in the lower atmosphere is order of a meter. That means that LWIR photons — whatever their “size” — with frequencies in the band go no more than a meter or few before they are absorbed by a CO_2 molecule.
– – – – – – – –
The right question that ought to be asked, is: “What is the effective absorption cross-section for a CO2 molecule at 15 micron wavelength?”
The concept of the ‘size’ of a photon when dealing with EM energy makes no sense; we don’t consider this when designing antennas or waveguide, so I don’t know why a physicist picks it up for use in the context above. We consider “wavelength”, but I don’t think that is the sense he is using the term.
Kevin Trenberth claims that rising concentrations of CO2 in the atmosphere will cause global temperatures to rise because CO2 will absorb outgoing thermal IR radiation and return it to the surface. At first blush the hypothesis is plausible given the ability of CO2 to absorb radiation at 15 microns. Clive Best explains:
However, when you calculate the numbers, 15 micron radiation at Earth’s surface is absorbed within a few feet of the surface so Trenberth’s forcing can’t have a measureable effect.
You’re _not_ answering the question; who raised this issue above regarding CO2 and IR at 15 um? That is obviously not a determining factor if that band is ‘saturated’ …
and IR at 15um is approximately -80C … Boy, that’s gonna cause a heck of a lot of “warming” now isn’t it?
There are but a few tiny places on this planet where 15um IR can cause ANY heating at all, and those are at the extreme polls.
What temperature is your mirror, squid?
Interesting comment, but “rgbatduke” should have given an example of his model. If the x-section is large at the ground (as expected from density) then how does it change as a function of height? Not clear if he’s saying that CO2 *is* or *is not* an important GHG.
IMO CO2 is not important now, as a GHG, and I’m not sure if it has ever been. All interglacials end at their highest concentrations of CO2 for the period, indicating that natural phenomena (outgassing from oceans mainly) causes the increase, although in the Holocene human CO2 has been an important source too. But the climate never goes into higher temps when this occurs, rather it falls into some kind of “phase transition” that always (in the last 2.5 million years at least) leads it back to colder climate.
What this hints to me is that CO2 could be related with alterations in climate that lead to *cooling*, not warming.
This is not completely clear for me, yet.
Part of the answer, I believe, is the “drying effect”
Maybe stupid of me but why do we only talk of Downwelling Radiation? Doesn’t CO2 radiates in all directions ?
So more CO2 would radiate more energy into space, cooling Earth. If there is no cloud cover what would stop it ?
That’s a good question Robertv. I am now curious as to whether we have Rayleigh Scattering, Compton Scattering or both in this regard and then do we have omni-directional scattering or mere reflection? I don’t think I’ve seen some boffin ring in on that but perhaps I missed it.
If and only if you can secure the orientation of a ‘vibrating’ CO2 molecule can you orchestrate a ‘coup’ and determine the directionality of EM wave emanations (or radiation used as a verb) … therefore the effective radiation direction must be random … sort of like orienting a loop or dipole antenna, if you continually ‘twirl’ that antenna can you tell me which direction will be receiving the RF (or EM) energy with any confidence?
Regions with very low humidity (deserts, etc.) have much higher day-to-night oscillation than areas with continuous cloud cover or high humidity (or both), as illustrated by the following charts,
If Earth was a desert everywhere, but still had oceans, would the glacial-interglacial cycles still occur?
Would the interglacial be hotter and shorter?
These questions would be interesting to answer if CO2 really is an important agent of low atmospheric humidity.
Biologists want to get on the climate gravy train now.
To date they’ve missed out. Everyone is a pig in the trough now.
CO2’s greatest impact is not on climate, but on agriculture. An increase to 4,000 ppm would increase crop yields, feeding more people. Compared to past geological times, today’s Earth is CO2 starved; higher levels would add a planet nutrient to the biosphere.
The theory that a trace gas that barely comprises 0.4 percent of the atmosphere will change the earth’s climate if it isn’t “contained” is the worst sort of scaremongering. During the Ordovician Era, CO2 was at least 10 times current levels, and the planet was frozen in an ice age.
CO2 became a threat when greedy governments, bankers and commodity brokers realized it could be demonized and turned into a huge new source of income. The scam was perpetrated by a few high-profile publicity-seeking scientists who realized they could use it to siphon billions from taxpayers.
The perpetrators of this fraud should be arrested and jailed for crimes against humanity.
0.4% is 4000 ppm. CO2 in the atmosphere is about 0.04%
You’re quite correct. In my haste, I messed up the decimal point.
South Africa freezing and setting record lows.
Click to access nr_records.pdf
Water vapour concentrations affects atmospheric density, trace CO2 not so much.
Surely that should be ignorant or dishonest, or both!
I made this video about climate sensitivity.
the NASA SABER Project validates Morgan’s presentation with regards to CO2 reflecting the solar (direct) heating back into space
THERE IS NO “HEATING EFFECT” FROM CO2 … PERIOD
Your video is bullshit…
Great video, anyone interested in the debate about GHGs and the effects of CO2 on climate should see it.
I posted this question at YT: do you know at what point (in terms of ppm of CO2) the warming effect and the cooling effect that you describe coincide?
If I had to guess I’d say that it’s around 250-300 ppm, because that’s usually the maximum level at the end of the previous interglacials. If so, human CO2 would be doing its part to cool the climate for some time now.
I guess the full answer must be a little more complicated due to the influence of humidity, Earth’s magnetic field, etc.
Thanks for the video!
As I wrote in response to a recent comment on my blog,
“Basic physics, I have found, is NOT the way forward at this time, because there is no agreement on what that basic physics is.”
Radiative transfer, as applied in consensus theory, is a false model to account for real heat transfer in the atmosphere, much less for its fundamental warming. The “greenhouse effect” is wrong because all this talk of radiative transfer is wrong. Period.
A bitter pill to swallow, but it has been obvious to me, and constantly confirmed in forums like this one, even before my definitive 2010 Venus/Earth temperatures comparison. Politics completely stymies the public debate, incompetence on top of simple ignorance stymies what should long ago have been the self-correction of climate science.
Amen to that.
What about the stratosphere? How do you explain the rising temperatures with altitude without the GH effect of O3?
Venus is not the same as the earth. It is not only much closer to the sun, it has almost NO rotation. This salient fact means it is a yin/yang world due to constant sun for a century and constant night for a century at any given spot.
So comparing the atmosphere on both planets is insane.
Are you from Venus? That would explain a lot, you know …
Not insane if you compare temperature profiles from the 1 bar altitude up where you see the classical earth-like lapse rate structure extending up to the Venusian tropopause.
“Scientists who claim that increasing CO2 is dangerous, are either ignorant or dishonest.”
How about both?
It doesnt make any difference what-so-ever how much “downwelling LWR” there is … IT CANNOT CAUSE ADDITIONAL HEATING!!! .. PERIOD! … The ground cannot re-heat itself from its own radiation, this would be a violation of physical law and cannot happen in this universe.
This “green house effect” talk is so incredibly stupid. There is NO “climate sensitivity” to CO2 or any other gasses (in terms of thermodynamics), other than COOLING … Otherwise you are creating energy from nothing, and that is NOT possible.
Sheeesh… I wish people would pull their heads out of their posteriors and get a grip on this stupid “green house effect” nonsense. I am so tired of hearing about the farcical “green house effect” as if it exists. It doesn’t .. it’s bullshit!
Calm down, and go take a look at yourself in a mirror … BTW, do you know how that mirror works, exactly?
Yeah, when you do that, does your face get warmer? … If I face two mirrors at each other, according to “green house effect” hypothesis, I should create a catastrophic feedback and blowup my house.
When you point a flashlight into a mirror, does the flashlight get brighter? If you place a candle in front of a flashlight, does the candle burn hotter?
Seems to you me that you might want to learn a little bit about how a mirror works.
Cold mirror, makes no difference. In fact, the mirror is quite cold at ‘light’ frequencies, yet, hmm … it reflects light. Imagine that.
And one actually has a mirror around the flashlight bulb (speaking pre-LED now) too, to make the flashlight ‘brighter’. Imagine that.
How does that work, squid?
Do you believe in magic or do you have an understanding of Electro-magnetics and physics?
Which is it – magic or physics, squid?
Hahaha … you have got to be kidding me … You don’t even understand how a freaking flashlight works.
Further, I said nothing about the temperature of the mirror, you are obfuscating.
I asked you a simple question. If you look into your mirror, does your face begin to warm?
So, the squid bails. Figures.
He chose ‘magic’.
Thanks for playing.
If you look into a mirror, your face will be warmer than if you were to look into the void with a temperature close to absolute zero. So when you look into said mirror, your face doesn’t warm, it cools at a lesser rate. Likewise, the greenhouse effect causes the earth’s surface/lower troposphere to cool at a lesser rate that it would absent of the so called greenhouse gases. As Steven’s graphs show, above a few ppm, CO2 has little more “warming” (reduced cooling) to contribute and H2O is by far the most powerful greenhouse gas. Beyond its radiative properties H2O is the powerful working fluid of the great thermodynamic engine that is our atmosphere. To boot, water exists in three phases in the Earth’s climate. The complexity is mind boggling except to climate modelers who have extreme delusions of understanding.
@Robert Austin You’re right, there is a GH effect, but for CO2 it becomes negligible at some point. I’m not even saying that it’s *important* at any level of ppm (relative density), only that it exists.
The video of @Morgan above explains this part very clearly, but it adds another important ingredient that, CO2 above certain level may cause more cooling than warming.
I’m not certain if this is true at all altitudes, or only at very high atmosphere. Cooling by CO2 radiative emission is believed to be important in the mesosphere.
OTOH, if humidity is low the GH effect of other gases (except H2O, vapor/atmospheric humidity, etc. ) should become more pronounced *and* *IF* CO2 acts as a coolant above certain density, then it could be an important agent of abrupt glacial inceptions observed at the ends of previous interglacials.
In this case, present human activity could be accelerating the process that would lead to the end of the Holocene, though I don’t think this is a very pronounced effect because the warming effect would also occur.
_Jim said, June 14, 2014 at 4:17 pm
“You’re _not_ answering the question; who raised this issue above regarding CO2 and IR at 15 um?”
Arrhenius, Kiehl & Trenberth.
In 1896, Svante Arrhenius published a paper link Earth’s surface temperature to trace gases:
“The selective absorption of the atmosphere is……………..not exerted by the chief mass of the air, but in a high degree by aqueous vapor and carbonic acid, which are present in the air in small quantities.”
In 1997 Kiehl and Trenberth wrote an influential paper that expresses the effect of CO2 in Earth’s atmosphere as a “Forcing” of 32 W/m2. You can find the reasoning under the heading “Longwave radiation” in their paper.
Please accept my apologies for thinking that you were familiar with the scientific fig leaf that “Climate Scientists” use to cover their nakedness.
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