Barton Paul Levenson:
I am ignoring the invitation to debate the climate of Venus although that would be interesting. WUWT has a severe troll infestation today and discussion of Venus would be a disruption to this thread which is about the Earth’s climate.
I am replying to the statement in your post at October 18, 2012 at 7:15 am which says
at present levels of atmospheric CO2 concentration additional CO2 in the atmosphere has no discernible effect on the Earth’s climate.
BPL: No. It’s up 40% since the industrial revolution began. It’s the absolute amount that matters, not the concentration. The nitrogen, oxygen and argon that make up more than 99% of Earth’s atmosphere is not radiatively active.
It seems you are unaware that the IR absorbtion of CO2 in the atmosphere is constrained to only two narrow bands with almost all being in the 15 micron band. These bands are so near to saturation that they only increase their absorbtion by band broadening.
Think of light (i.e. visible radiation) entering a room through a window. If you put a layer of dark paint over the window then much light is absorbed by the paint and, therefore, does not enter the room. Add another layer of paint and more light is absorbed by that layer, but not as much as by the first layer. Similarly for each additional layer of paint.
The IR emitted from the Earth’s surface is trying to pass the ‘window’ of the atmosphere to enter space. Adding more CO2 to the air is like adding more paint on the window that has seven layers of the paint. Each unit addition of CO2 has less absorbtion than the previous unit addition: this reducing effect is logarithmic.
Empirical – n.b. not model-derived – determinations indicate climate sensitivity is less than 1.0deg.C for a doubling of atmospheric CO2 equivalent. This is indicated by the studies of Idso from surface measurements
and Lindzen & Choi from ERBE satelite data
and Gregory from balloon radiosonde data
If climate sensitivity is less than 1 deg.C for a doubling of CO2 equivalent, then it is physically impossible for the man-made global warming to be large enough to be detected because natural variability is much, much larger. If something exists but is too small to be detected then it only has an abstract existence; it does not have a discernible existence that has effects (observation of the effects would be its detection).
As you say, the concentration of CO2 in the air has increased by ~40% since the industrial revolution (i.e. from ~280 ppmv to ~390 ppmv). This takes the degree of absorbtion of CO2 to ~80% of a doubling of CO2 in the atmosphere because of the logarithmic effect. And the globe has only warmed about 0.8deg.C since the industrial revolution. Most – if not all – of this rise is certainly recovery from the Little Ice Age (LIA), but if it is assumed the entire temperature rise is from the CO2 increase then a further increase to reach double pre-industrial concentration (i.e. to ~560 ppmv) would only provide a further increase to global temperature of about 0.2 deg.C. And a further doubling of atmospheric CO2 (to 1,120 ppmv) would only raise global temperature by an additional 1.0 deg,C.
In summation, as I said, at present levels of atmospheric CO2 concentration additional CO2 in the atmosphere has no discernible effect on the Earth’s climate.
Barton Paul Levenson:
At October 18, 2012 at 3:23 pmyou say to me
R: It does not matter what your “calculations” say because empiricism trumps theory
BPL: Which physical law, based on empirical observation, do you disagree with? Stefan-Boltzmann? Wien? Kirchhoff? The ERT? What empiricism, in particular, trumps calculations of mine you haven’t even seen yet?
The “calculations” are those which you mentioned at October 18, 2012 at 10:42 am where you wrote
It’s not saturated at the upper levels, and warming anywhere there will propagate down to the surface. It’s easy to demonstrate if you want the math.
“The math” must be wrong because the ‘Hot Spot’ is missing.
I agree with all the physical laws. But I am not an idiot so I know that attempting to apply physical laws to a complex and partially understood system usually provides wrong answers. And the empirical evidence clearly shows your assertion is wrong. Simply you have done some sums to assess what you think is how the climate system works but reality demonstrates the system is nothing like you think it is.
Try applying physical laws to calculate the behaviour of the human brain and see what you get: the climate system is more complex than the human brain. (And don’t try to use that illustration as an excuse to troll the thread about brain structure).
So, a couple of questions.
Just how much does ‘Band broadening’ increase the heat absorption capability of atmospheric co2?
Why do AGW proponents insist that radiation laws which are derived from experimental conditions which exclude complicating factors like a freely convecting troposphere containing complicated system feedbacks be applied to the Earth’s climate system as if they are acting in a vacuum, or indeed in vacuo?
Why was Sherwood Idso’s paper ignored by the IPCC in their third assessment report?
Here’s the abstract:
ABSTRACT: Over the course of the past 2 decades, I have analyzed a number of natural phenomena
that reveal how Earth’s near-surface air temperature responds to surface radiative perturbations. These
studies all suggest that a 300 to 600 ppm doubling of the atmosphere’s CO2 concentration could raise
the planet’s mean surface air temperature by only about 0.4°C. Even this modicum of warming may
never be realized, however, for it could be negated by a number of planetary cooling forces that are
intensified by warmer temperatures and by the strengthening of biological processes that are
enhanced by the same rise in atmospheric CO2 concentration that drives the warming. Several of these
cooling forces have individually been estimated to be of equivalent magnitude, but of opposite sign, to
the typically predicted greenhouse effect of a doubling of the air’s CO2 content, which suggests to me
that little net temperature change will ultimately result from the ongoing buildup of CO2 in Earth’s
atmosphere. Consequently, I am skeptical of the predictions of significant CO2-induced global warming
that are being made by state-of-the-art climate models and believe that much more work on a wide
variety of research fronts will be required to properly resolve the issue.