CO2 Greenhouse Effect Is Very Small

I used RRTM LW (the model Trenberth uses) to calculate the effects of increasing CO2 on downwelling longwave radiation, due to the greenhouse effect.

As you can see, the effect of increasing CO2 is minuscule.

ScreenHunter_452 Jun. 13 20.36

Even in the mid-latitude winter, going above 400 PPM has very little effect

ScreenHunter_454 Jun. 13 21.27

By contrast, the effect of water vapor is large, and accounts for almost all of the greenhouse effect.

ScreenHunter_453 Jun. 13 21.04

Increasing CO2 has very little 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.


About stevengoddard

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17 Responses to CO2 Greenhouse Effect Is Very Small

  1. hifast says:

    Excellent comparison.

  2. BobW in NC says:

    I knew it, I knew it, I knew it!!! From the first moment I asked about CO2 and water vapor, I would have predicted what you showed, Steve. Thank you for taking the time to give us some solid information!

  3. Hell_Is_Like_Newark says:

    The new arguments for making us poor via energy starvation now are:
    1. CO2 will cause all the coral to die from a reduced pH
    2. Increasing CO2 will cause the nutritional values of plants to be reduced and hurt the production of C4 plants like corn.

    Both are utter nonsense, but that doesn’t stop the usual suspects from making the above assertions.

  4. Jason Calley says:

    Hey Tony, I think your conclusions are absolutely correct, but can you clarify a bit of methodology for me? Are the curves for CO2 calculated for changes induced in a dry atmosphere or in a normally humid atmosphere? If the radiative model is based on a dry atmosphere, then even the very small effect of CO2 shown is being hugely overstated.

    The reason why I ask — and pardon me if I state something obvious to everyone — is that the combined effects of multiple greenhouse gases is not the same as the simple sum of each taken separately (except in the very rare circumstance that the gases have no absorption lines in common.) The way I usually illustrate this to myself is as follows. Suppose (just hypothetically) that H2O and CO2 had exactly the same radiative properties. A dry atmosphere calculation might show that doubling CO2 from 200ppm to 400ppm gives a one degree warming. However, in an atmosphere with 10,000ppm of our CO2-identical-H2O all those CO2 bands are almost completely saturated because of the H2O. You can’t get that one degree rise from simply doubling CO2 — you would have to increase CO2 from 200ppm to 10,400ppm. In other words, CO2+H2O would have to change from 200ppm+10,000ppm=10,200ppm to become 10,400ppm+10,000ppm=20,400ppm in order to effectively double. Of course, in the real world H2O is not exactly the same as CO2, but to the extent that their lines overlap (and they have a very large overlap,) to that same extent the doubling effect of CO2 is completely overwhelmed.

  5. Steve Case says:

    The limits to CO2 sensitivity are in the numbers that we all know. Wikipedia tells us the Greenhouse Effect is 33ºC and that CO2’s contribution to that is 9-26% which works out to 3 – 8.5º. I’ve heard that CO2’s climate sensitivity begins operate logarithmically at about 20 ppm or so. That means there could have been 4 doublings of 25 ppm to get to the current 400 ppm, and it would follow that 3º and 8.5º divided by 4 would lead to a possible range of climate sensitivities for CO2 of .75ºC to 2.1ºC respectively.

    If there’s something wrong with that reasoning, I’d like to know what it is.

    • Ernest Bush says:

      Any calculation of this type has to be made based on assumptions and estimates (i.e. guesses) for some of the variables. The fact that RSS data says that there has been only an almost unmeasurable change in temperature for over 18 years suggests that your lowest estimate for CO2s contribution is probably too high.

    • David A says:

      The assumption that an increase in any GHG, especially CO2 is logarithmic is, IMV, way off. Clearly the additional heat in the tropics produces a greater increase in W/V, a more potent GHG, but there is no correlative increase in tropical mean T. Indeed, as w/v increases, the feedback becomes ever more negative, conduction, convection and evaporation all accelerate, not on a linear scale. They likely have the sign wrong under numerous scenarios.

  6. mkelly says:

    “By the time the team and I left, we were engaging 400 trucks a month, driving in convoys, on the Ho Chi Minh trail, “ Taylor said.

    However, the FLIR systems also had drawbacks. Massive amounts of power were needed to cool the equipment to about 26 degrees Kelvin. In later models the temperature rose to a balmy 76 degrees Kelvin, about the temperature at which liquid nitrogen boils. They were also mammoth, with only large aircraft like C-130 gunships able to haul them.

    The above is a reason I never bought the CO2 radiation heats the surface theory. FLIR was cooled to 76 K then any radiation that was able to heat the surface would have wiped out any view this sensor had.

    They eventually got the FLIR down in size to fit into lots of places. I operated one on and S3A Viking aircraft.

    • nielszoo says:

      My point exactly. The current ambient temp microbolometers are sensitive to the entire range of CO2’s emission wavelengths and they work perfectly as well. Considering the fact that at normal pressures and temperatures CO2’s emissivity is somewhere around 0.0019 that’s the reason FLIR works… CO2 does NOT radiate and neither do the rest of the gases in the atmosphere below the stratosphere. Only water vapor has a measurable emissivity.

  7. Alan Poirier says:

    Still think Ferenc Miskolczi was right in 2009 when he concluded CO2 is saturated. I’ve yet to see a peer-reviewed counter-argument to his two papers.

  8. Everybody knows this. The entire greenhouse effect is around 40 degrees C, and of this, 36 C is caused by water vapor. The remaining 4 C includes methane and ozone and N compounds, let’s be generous and say CO2 accounts for 3 C of the current temperature of Earth.

    But, like I said, everybody knows this. It’s in every text book. The only idiots who don’t know it are the president, the secretary of state, the moron who invented the internet and thinks he won the election because of some hanging chads, and the 97 % of scumbag climate scientists who sold out and are on the government dole. And you can add to that list some really choice imbeciles like Bill Maher, Jon Stewart, the moron who writes for Rolling Stone, every single editor at Wikipedia, and I hate to say David Letterman because I like the guy. But he’s not a scientist.

  9. darrylb says:

    Well Morgan, I agree with much of what you write.
    However, I think David L’s favorite person in the universe is David L.
    He is just too full of himself. I don’t suppose Johnny Carson could be reincarnated?

    Another comment– the longer the hiatus (stop) of warming goes on, the greater the magnitude of bizarre explanations. —And, should it start to cool (bad for all of us) the more fun we could have in the explanations. Many Russian Scientists are predicting an ongoing cooling.

  10. KevinK says:

    Tony, with respect, you are using calculations based on a hypothesis to confirm said hypothesis.

    Note again that the “DWLIR” radiation does NOT ADD to the sunlight striking the Earth. It is simply radiation that is making “another” pass at warming the Earth (after the Earth cooled when it left).

    You sure seem to be trying to convince yourself (more than anybody else) that the “radiative greenhouse effect” really makes a difference….

    I suggest that you read up a bit about optical integrating spheres, they have been around for a while and are well understood. And they exhibit what a “climate scientist” would term “100%” radiative forcing.

    The “down-welling” radiation is simply radiation that has already left the surface (leaving cooling in it’s wake) and it simply “warms” the surface again after a delay.

    The “radiative greenhouse effect” is an optical illusion / chimera / mirage.

    Cheers, Kevin.

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