Here is one of my infrequent and irregular reports about how things appear from my viewpoint. The main thing is to read Hansen's paper which contains some revelations and the Nature paper which bolsters Svenmark's correlations and gives further doubt to the predictions of the radiative transfer merchants.

Summary of a paper by James Hansen et al., of the Goddard Institute for Space Studies published in the Proceedings of the National Academy of Science, USA [Volume 95, 12753, 1998] entitled "Climate forcings in the Industrial era."

The abstract is very revealing and I reproduce it in full.

ABSTRACT

The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change. Anthropogenic greenhouse gases (GHGs), which are well measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. One consequence of this partial balance is that natural forcing due to solar irradiance changes may play a larger role in long-term climate change than inferred from comparison with GHG's alone. Current trends in GHG climate forcings are smaller than in popular business as usual' or 1% per year carbon dioxide growth scenarios. The summary implication is a paradigm change (whatever one of those is) for long-term climate projections: uncertainties in climate forcings have supplanted global climate sensitivity as the predominant issue.

Not before time say I!

If only the IPCC would concur with these conclusions they would lose most of their objectors, particularly if they concluded that no precipitate actions should be carried out to upset the World's economy. There is still argument about the magnitude of the climate sensitivity and the impossibility of doubling the carbon dioxide level.

I highlight various statements and add my own comments as necessary.

1. Climate forcings due to GHGs can be computed accurately because the absorption properties are known to within 10%! (My exclamation mark).

2. Contributions to global warming from the various GHGs since the pre-industrial era are computed with help from formulae which give answers that are very small and in some cases are almost indistinguishable from zero. The uncertainties for each value are given and are in some cases of the order of 100%. The individual forcings are summed to give a value which must be in great doubt.

3. Climate forcing...by tropospheric water vapour, the strongest GHG, is not included...because this water vapour amount is a function of climate and thus represents a feedback, rather than a forcing.

This is convoluted logic and surely it would be better to say that water vapour is the strongest GHG and that its effect depends upon the temperature changes brought about by the other GHGs. Also, it would be better to admit that the magnitude and even the sign of the water feedback are not known with any certainty.

4. The effects of aerosols are discussed quite properly, but the overall forcing of minus 0.4 Watts per square meter is put into statistical perspective by the error limits of plus or minus 0.3 such units.

5. Clouds are discussed at length. Anthropogenic cloud changes are a potentially larger climate forcing than direct aerosol effects, but they are even more uncertain. Aerosol-cloud models give a cloud forcing of minus 1 Watt per square meter, but this varies by an order of magnitude as model parameters are varied within their uncertainties. A second estimate of cloud forcing is based on the damping (I hope no pun is intended here) of the diurnal cycle of surface temperature that has occurred. Mechanisms that damp local diurnal cycles include increase of soil moisture and increase of atmospheric aerosols, but quantitative analysis shows that these mechanisms are unable to account for the large observed global-scale damping. Model simulations give rise to the conclusion that cloud forcing has changed since the pre-industrial era to the extent of minus 1 Watt per square meter with an uncertainty of a factor of two.

They do not mention that the cloud effect more-or-less cancels out the positive forcing from the GHGs. In the conclusion they still maintain that the carbon dioxide doubling sensitivity is 3 degrees C plus or minus 1.5 degrees.

6. The question is put: why has the carbon dioxide growth rate flattened despite continued increase of fossil fuel emissions? Is this a long-term increase in a carbon sink or a temporary biospheric uptake presaging a later burst of carbon dioxide growth? No answers are attempted (as seen in some examination answer papers!).

There has been some argument about this recently and increased transpiration rates have been suggested to offset any temporary fixing of carbon in the greening of the planet. Of course transpiration increases with increasing plant growth. The point is that it all results in more carbon being extracted from the atmosphere. The Dutch tomato growers know all about this. They increase the carbon dioxide in their greenhouses by a factor of two by burning kerosene. This results in four crops of tomatoes instead of three per season. That equates well with the expected 30% increase in carbon fixation if global carbon dioxide doubles (which it cannot do).

7. Solar radiance is discussed, but only direct changes are considered. The Svenmark/Lassen/Friis-Christensen correlations are ignored, which brings me to the paper in Nature that has caused some argument.

The Nature paper of 3rd June 1999, page 437 by Lockwood, Stamper and Wild reports that the Sun's coronal magnetic field has doubled during the last century. They show a graph of the variations in the total solar magnetic flux emanating through the coronal source sphere from 1870 to date. This correlates strongly with the Svenmark/Lassen/Friis-Christensen correlations and with the terrestrial temperature record beloved of the IPCC and including the Schneider' approaching ice-age of the 1970s. It deserves to be taken very seriously and casts further doubt upon the current IPCC methods of forecasting the future climate.

Heinz Hug and I are currently making progress with our separate studies of the spectroscopy underlying the radiative transfer merchants. There are grave discrepancies between theory and experimental measurements of simple spectra which must be explained before the radiative theorists are to be believed. I have already tried to explain my objections and will continue to do so even though the Bratermans of this world insist upon misunderstanding what I write.

The basic theory of radiative transfer is beyond question except for the spectroscopic discrepancies already referred to. My main objection is that what holds for a solid angle of pure air does not apply to a solid angle of real air moving at a very high angular velocity which causes an ever-changing intensity of in-coming radiation. The received radiation is emitted by the surface but does not reach space on average for a good number of days as it goes through the transformations of the real atmosphere. It is all absorbed by the lowest 100 meters of the atmosphere and is largely (i.e. more than 99.9% - I got into trouble with Houghton, Shine and Braterman & Co., for saying that it was all transformed) transformed into thermal energy of the lower atmosphere. My other grave sin was to deny that excited molecules could emit radiation to return to their ground states. In the context of the paper I should have said that radiative return was highly unlikely at high gas pressures. I explained this in my reply to the Spectrochimica Acta journal.

Some people are still writing about these terrible errors and I which they would spend their energies on more productive pursuits. The thermal energy of the lower atmosphere reaches the upper atmosphere by radiative transfer, thermal conduction, convection and by the release of energy when water vapour condenses. From the higher atmosphere radiative transfer becomes overwhelmingly predominant as the loss of energy to space can only take place radiatively. Until these physical processes are properly incorporated into models I will view such efforts with grave suspicion.

Jack Barrett, July 1990
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