In Part One I made the observation:
If the atmosphere has an invariant optical thickness then surely all molecules should be included?
Meaning all ‘radiatively-active’ gases. Then I cited some results from Collins (2006) on the ‘radiative forcing’ for other gases, and added:
..So if total optical thickness from CO2 and water vapor has stayed constant over 60 years then surely total optical thickness must have increased?
In response, Miskolczi supporter Miklos Zagoni said:
Optical thickness was calculated over 60 years for CO2 and water vapor and other 9 IR-active molecular species (O3, N2O, CH4, NO, SO2, NO2, CCl4, F11 and F12), and turned out to be strictly fluctuating around a theoretically predicted equilibrium value
I asked for more details (concentrations of each of these gases over time which were used for the calculations) which weren’t forthcoming.
Later Miskolczi supporter Ken Gregory said:
Only the H2O and CO2 gases were changed. Other minor GHG were held constant.
So, working with this data I thought it would be interesting to see what changes had taken place in optical thickness due to these minor “greenhouse” gases.
I should point out that there are substantial problems identified with Miskolczi’s theory and experimental work and this is a very minor issue – it is more of an interesting aside.
A little while ago I managed to recreate the CO2 transmittance in the atmosphere – as shown in Understanding Atmospheric Radiation and the “Greenhouse” Effect – Part Nine. This was done using the HITRAN database in a MATLAB model I created.
The question about changes in optical thickness over time from other gases was a good motivator to update my MATLAB model to bring in other molecules. It was something I wanted to do anyway.
Note that radiative forcing or (surface emission – OLR) is a much more useful value than total optical thickness (as explained in Part One).
Extracting the HITRAN data proved to be the most tedious and challenging part of the project. It turns out that the “minor gases” like CFC-11 and CFC-12 are stored in a totally different format from gases like CO2, N2O, CH4 etc. These minor gases have a dataset for each temperature and pressure, with different sizes of dataset at various temperature/pressures. Nothing mathematically or conceptually challenging, just very tedious.
Another challenge was working out what concentrations to use for 1948 – the start date that Miskolczi uses. From Collins (2006) it seemed that the main “greenhouse” gases to evaluate were N2O (nitrous oxide), CH4 (methane) plus CFC11 (CCl3F) and CFC12 (CCl2F2). There are other halocarbons to include but time is limited.
Here are the values used:
CO2 311 ppmv 386 ppmv
N2O 289 ppbv 319 ppbv
CH4 1250 ppbv 1775 ppbv
CFC11 0 267 pptv
CFC12 0 535 pptv
The later CO2 value is from 2008 from Miskolczi’s spreadsheet while the other values are from 2005.
ppmv = parts per million by volume, ppbv = parts per billion (109) by volume, pptv = parts per trillion (1012) by volume.
Earlier values of N2O and CH4 are taken from various papers, I can provide citations if anyone is interested – but pre-1980 values are thin on the ground.
In any case, my calculations of total optical thickness are rudimentary and provided as a starting point.
I used a 5 layer model up to 200mbar, with a surface temperature of 289K. The diffusivity approximation was used to estimate total hemispherical transmittance (see Understanding Atmospheric Radiation and the “Greenhouse” Effect – Part Six – The Equations). The wavenumber step, Δν = 1 cm-1. The calculations were done from 100 cm to 2500 cm (4μm – 100 μm) and the “Planck weighted” transmittance (at 289K) was calculated. This transmittance was converted back to an optical thickness, which is the same approach that Miskolczi uses (see comment).
Water vapor was assumed to be 10g/kg at the surface with a straight line reduction (vs pressure) to zero at 200mbar. Previously I carried out calculations where water vapor was varied from 5g/kg to 15g/kg and the effect on the transmittance change due to other gases was quite small.
Water vapor absorption lines are included from the HITRAN database but the water vapor continuum is not. This is next in my wishlist to include.
Changes in Water Vapor
The model deliberately did not try to follow Miskolczi’s water vapor values. The point of this article is to demonstrate that if (and only if) CO2 optical thickness is canceled out by water vapor changes, then significant increases in optical thickness from other gases impact negatively on his hypothesis.
If his calculations show:
optical thickness (CO2 + water vapor) = constant
then this article demonstrates that:
optical thickness (CO2 + other gases + water vapor) = increasing
Many people might not realize that there are a number of water vapor datasets. The one Miskolczi uses is not the only one. Others show different trends.
Note that water vapor is included, but at unchanged concentration.
- The change in optical thickness, Δτ, for CO2 only changing = 0.0167
- The change in optical thickness, Δτ, for CO2+N2O+CH4+CFC11+CFC12 = 0.0238
The % increase (over CO2) due to the nominated “minor gases” = is 43%.
The total optical thickness is not so important in this analysis. If the number of layers is changed, the total optical thickness changes, but percent changes due to “greenhouse” gas increases are roughly similar.
If (and only if) water vapor has canceled out CO2 increases, then the increase in optical thickness due to these other gases (methane, nitrous oxide plus halocarbons) has destroyed the idea that optical thickness can be considered to be constant.
Of course, my calculations are rudimentary. My model is much less exact than the HARTCODE model used by Miskoczi and it would be interesting to see his results reproduced in full with the correct concentrations of all of the GHGs from 1948 – 2008.
As I commented earlier – this is one of the least important of the criticisms of Ferenc Miskolczi’s papers.
Now I have updated the model I can produce results like these:
Other articles in the series
The Mystery of Tau – Miskolczi – introduction to some of the issues around the calculation of optical thickness of the atmosphere, by Miskolczi, from his 2010 paper in E&E
Part Two – Kirchhoff – why Kirchhoff’s law is wrongly invoked, as the author himself later acknowledged, from his 2007 paper
Part Three – Kinetic Energy – why kinetic energy cannot be equated with flux (radiation in W/m²), and how equation 7 is invented out of thin air (with interesting author comment)
Part Four – a minor digression into another error that seems to have crept into the Aa=Ed relationship
Part Five – Equation Soufflé – explaining why the “theory” in the 2007 paper is a complete dog’s breakfast
The HITRAN 2008 molecular spectroscopic database, by L.S. Rothman et al, Journal of Quantitative Spectroscopy & Radiative Transfer (2009)
Radiative forcing by well-mixed greenhouse gases: Estimates from climate models in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4), Collins et al, JGR (2006)