Why Adding More CO2 Makes Very Little Difference

Most of the greenhouse effect of CO2 occurs from the first 30 ppm. The RRTM data above shows that going from 393 ppm to 560 ppm will increase the greenhouse effect by less than 0.25% in the tropics.

This data was generated from the model which Kevin Trenberth uses. What we see is the opposite of a tipping point. It is more like a napping point.

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13 Responses to Why Adding More CO2 Makes Very Little Difference

  1. gregole says:


    0.29 degrees C is all we get for all that CO2 Mankind has emitted? Come on, that’s not even noise around zero…

    Hey dude, where’s my global warming?

  2. daveburton says:

    MODTRAN says that 19.6 ppm of CO2 would generate fully half of the warming we get from the current ~392 ppm. The NCAR Radiation Code says 39.5 ppm. Either way, we’re way past the point of diminishing returns w/r/t the warming influence of CO2.

    • daveburton says:

      P.S. — MODTRAN also calculates that the warming effect of additional water vapor adds about 65% to the warming effect of CO2 alone. A lot of Climate Movement activists seem to think that the water vapor “positive feedback” is some huge multiple, but it’s not. Moreover, that calculation does not take into account negative feedbacks from increased evaporation: increased water-cycle cooling, and perhaps increased cloudiness, so that 65% is really an upper bound. The real-world amplification of CO2′s warming by H2O is almost certainly less than that.

    • Eric Simpson says:

      Great, and so maybe I’m 100% right to speak my feeling, my impression based on evidence & logic & intuition, that CO2 “doesn’t do squat,” that CO2′s effect on climate doesn’t amount to more than a hill of beans. It’s funny how even most skeptics look at me like I’m crazy when I say that, but the evidence is that quite likely it doesn’t do squat, and if it does anything, it’s virtually indistinguishable from doing nothing.
      Look at the temperature record. That is consistent with the contention that CO2 does zero, zilch, or that it has at most some infinitesimal meager effect not even worth heeding.
      And what about on Venus, which the warmists use a centerpiece of their propaganda. If CO2 has little effect beyond 30ppm or whatever number, then what about on Venus where it’s at about 999,000ppm. My understanding is that CO2 is wrongly credited for the Venusian warming, when it has nothing to with it.

      • daveburton says:

        It’s not the fact that Venus’s atmosphere is >95% CO2 that makes it hot, it’s two other facts:
        1. Venus is closer to the sun and thus gets 91% greater solar insolation,
        2. Venus has 90x greater atmospheric pressure.

        Death Valley has only 3x the atmospheric pressure of the summit of Mt. Everest, and (despite its slightly higher latitude) that 3x greater atmospheric pressure makes Death Valley much, much hotter than the summit of Mt. Everest. Imagine what 90x greater atmospheric pressure would do!

        • Venus distance from the sun doesn’t actually make much difference to the temperature. The thick layer of clouds reflects most of the sunlight back into space, which is why Venus appears so bright.

      • Eric Simpson says:

        Ok, Steven, Dave says that the basis of the heat is the 91% greater solar heat and 90x atmospheric pressure. So what do you think causes it to be so hot? CO2?

      • DirkH says:

        Lapse rate. At the height where the atmosphere reaches 1 bar temperatures are similar to Earth.

      • Ben says:

        A little CO2 squats a lot, a lot more CO2 squats very little ;)

  3. “We have tested the proposition that greenhouse model simulations and trend observations can be reconciled. Our conclusion is that the present evidence, with the application of a robust statistical test, supports rejection of this proposition. [...] On the whole, the evidence indicates that model trends in the troposphere are very likely inconsistent with observations that indicate that, since 1979, there is no significant long-term amplification factor relative to the surface. If these results continue to be supported, then future projections of temperature change, as depicted in the present suite of climate models, are likely too high.”


  4. tckev says:

    So, “What we see is the opposite of a tipping point. It is more like a napping point.” but Western dimocracies have based their futures, and their children’s futures on the ‘CO2 is bad hypothesis’. So, our futures have been kidnapped.

    • DirkH says:

      Just ordinary fra*ud. After you paid your taxes you know the money is gone for good anyway. How exactly it is embezzled plays no role.

  5. Rosco says:

    “Venus distance from the sun doesn’t actually make much difference to the temperature. The thick layer of clouds reflects most of the sunlight back into space, which is why Venus appears so bright. ”

    C’mon – everybody knows Venus’ greenhouse effect is so strong that CO2 plasma goes totally ballistic and Venus emits light just like the sun – the professors at UCLA tol’ me so.

    Like a faithful zealot I totally believe that a gas can create over 10,000 W/sq m when the sun input is eztimated at 132 W/sq m.

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