Disqus - Latest Comments for GHess

Re: Influence of the Southern Oscillation on tropospheric temperature

GHess — Sat, 01 Aug 2009 16:33:55 -0000

@JamesG
James,
the 1.6 W/m2 excess downwelling radiation or radiative forcing from the IPCC is referenced back to 1750 A.D. So it is the difference between radiative forcing now and radiative forcing in 1750 A.D.
The IPCC defines radiative forcing for greenhouse gases always with respect to 1750.
The radiative forcing that needs to be compared to the current heating rate of a certain observation period really is the difference between the radiative forcing at the end of the observation period and radiative forcing at the beginning of the observation period. I do not know these numbers. However, 1.6 W/m2 cannot be compared to the heating rate directly.
Willis at al (J. Geophys. Res. 113, C06015 (2008)) report for the period since 2003 a ocean heat storage rate of -0.076 +/- 0.214 W/m2. This is 90% of the actual heating that has occurred since 2003.
Best regards
Günter

Re: About

GHess — Wed, 29 Jul 2009 14:08:38 -0000

Nick,
thanks your comment and reading through your link helped. I think the IPCCs anthropogenic radiative forcing values are also referenced back in time to 1750, which I did not account for. So it doesn't reflect the current radiative imbalance at the tropopause, but the imbalance compared to 1750 before warming as you mentioned in your comment.
Thanks and best regards
Guenter

Re: About

GHess — Tue, 28 Jul 2009 16:12:35 -0000

Nick,

Thank you for your reply. I really appreciate that.
But I do have still difficulties with this explanation, since net radiative forcing is the difference between incoming energy by radiation and outgoing energy by radiation. This difference integrated over time should be equal to the change in the energy content of the earth system.

This energy content change is mentioned in the IPCC AR4. The figure caption reads:
“Figure TS.15. Energy content changes in different components
of the Earth system for two periods (1961–2003 and 1993–2003).
Blue bars are for 1961 to 2003; burgundy bars are for 1993 to
2003. Positive energy content change means an increase in
stored energy (i.e., heat content in oceans, latent heat from
reduced ice or sea ice volumes, heat content in the continents
excluding latent heat from permafrost changes, and latent and
sensible heat and potential and kinetic energy in the atmosphere).
All error estimates are 90% confi dence intervals. No estimate of
confi dence is available for the continental heat gain. Some of
the results have been scaled from published results for the two
respective periods. {Figure 5.4}”

If the figure represents something similar to the energy content change of the whole system, for my opinion net radiative forcing should by energy content change otherwise energy conservation is violated, since CO2 can only hold back incoming energy.
In order to calculate the energy content change one needs to consider the different systems with heat capacities attached. A surface without a heat capacity attached seems to me for my gut feeling like a virtual energy constant that is added or subtracted on both sides of the equation, fairly arbitrary. One increases the net radiative forcing and balances it with IR radiation in the future from a thin surface layer that will occasionally heat to the temperature Ts. However the difference of 1.6 W/m2 needs to be in the system right now.
Energy content and conservation of energy is the physical reality, or not. Conservation of IR radiation is not a physical law. Of course the radiative properties are calculated by models, but how does one show that they are correct., if not with real quantities.
Best regards
Guenter

Re: About

GHess — Sun, 26 Jul 2009 12:02:10 -0000

Dear David,
I started reading the Copenhagen Synthesis Report as well and I do have a question that puzzled me ever since. It shows in its figure 2:
“The change in energy content in different components of the Earth System for two periods: 1961-2003 (blue bars) and 1993-2003 (pink bars)2 (figure 5.4).”

The energy content change of the earth system for the period 1993 – 2003 according to the figure 2 is 8.9x10E22 Joule. Divided by the area of the earth and the seconds of 10 years this gives 0.55 W/m2.
The net radiative forcing from the models however in this period I estimated from IPCC AR 4 to be roughly about 1.3 W/m2. IPCC AR 4 says 1.6 W/m2 for 2005 and 20% increase since 1995.
However, this means the models are off by 0.8 W/m2 for this 10 year period alone in terms of energy conservation. Do I miss something here? Maybe I miss the definition of net radiative forcing or the definition of energy content change?

Hopefully you or anybody can help me out.
Best regards
Guenter

Re: The value of tau

GHess — Tue, 12 May 2009 18:54:38 -0000

Nick,
could you educate me, which is the radiative transfer equation that applies in this context and how is it defined?. What is the reason for choosing one boundary condition over the other?
If you are right it would be easy to refute Miskolczi's equation.
I have not seen all the mathematical experts that are in climate science doing that.
Milne’s equations I see usually used in the context of radiative transfer problems dealing with scattering.
Especially two cases:
Firstly the limit of a scattering problem with an embedded source and absorption that goes towards zero. The source term is zero in this case.
Secondly, diffuse reflection problems with partly reflecting boundaries.
Of course you are always free to choose your boundary conditions.
I didn’t want to ignore Milne’s work and apologize.
I just have not come across a paper or a book that used the semi – transparent boundary conditions to derive the relationship between surface air temperature, ground temperature and optical depth in the infrared region. In hindsight I found it interesting that Dr. Miskolczi did that and compare the results. This is why I was looking for an argument, not to use them since you always can apply different boundary conditions, get the solutions and compare afterwards. Moreover it is good practice of an open minded scientist to do so. That is what Miskolczi did. My feeling when I came across the blogs about his work that he is discredited because of political reasons.
But what he did is very valuable; he brought in a new perspective that is what keeps the science going.
Can I asked a stupid question. Maybe I missed something in the discussion, perhaps you can repeat it for me: why is Miskolczi not matching OLR at TOA?
What to you mean the solution of Milne and others yield a flux that match OLR at TOA. Isn’t that a circular argument, since you proscribe the boundary condition matching OLR at TOA to get the solutions.

Best regards
Guenter

Re: The value of tau

GHess — Tue, 12 May 2009 15:42:19 -0000

Steve and Miklos,
I came somewhat late to the discussion but enjoyed it. Reading through M's paper it intrigued me that he seemed to be the first one, who used finite semi-transparent boundary conditions to solve the Schwarzschild equation within earth atmosphere.
Is there any reason why nobody has ever done this? I did not find an argument yet that makes the generally applied semi-infinite boundary conditions preferable other than they are easier to solve.
Reading this in all the books about climate change that deal with radiative transfer, I had the feeling of: Going through the motions without careful consideration. So I liked M's new approach.
It seems to me that the semi-transparent boundary conditions indeed provide an avenue to avoid the temperature discontinuity at the ground obtained by applying the semi-infinite boundary conditions.
Despite all the critics I read in the internet, isn’t that finding or application together with an experimental test a worthy contribution to the scientific community. I guess it would be in physics.
By the way: reading through the books, I found the following quote about Kirchhoff’s law in Goody and Yung’s Atmospheric Radiation, Theoretical Basis 2nd edition on page 3:
“Since clouds, ground, and atmosphere do not differ greatly in temperature, it follows from Kirchhoff’s law that emission and absorption are approximately equal to each other.”
I thought I cite that, since there are sites on the Internet and contributions that like to discredit Dr. Miskolczi and his paper on a similar quote. But this seems to me typical for the AGW discussion, always looking for small splinters in the others eye.
Best regards
Guenter