Thongchai Thailand

Peer Review Comments on Callendar 1938

Posted on: June 29, 2018

  1. Sir GEORGE SIMPSON
  2. Sir Simpson noted that the first place he thought it was not sufficiently realized by non-meteorologists who came for the first time to help the Society in its study, that it was impossible to solve the problem of the temperature distribution in the atmosphere by working out the radiation. The atmosphere was not in a state of radiative equilibrium, and it also received heat by transfer from one part to another.
  3. In the second place, one had to remember that the temperature distribution in the atmosphere was determined almost entirely by the movement of the air up and down. This forced the atmosphere into a temperature distribution which was quite out of balance with the radiation. One could not, therefore, calculate the temperature effect of changing any one factor in the atmosphere, and he felt that the actual numerical results which Mr. Callendar had obtained could not be used to give a definite indication of the order of magnitude of the effect.
  4. Thirdly, he thought Mr. Callendar should give a little more information as to how he had calculated the results shown in Fig. 2. These contained the crucial point of the paper, but the paper did not explain how they were obtained.
  5. In Table 5 Mr. Callendar had given the effect of doubling the CO2, in one band, 13 to 16, which included nearly the whole of the energy connected with the C02. The increase of temperature obtained by calculation from these results, however, was not the same for a similar increase in CO2, as that shown in Fig. 2. This sort of discrepancy should be cleared up.
  6. Lastly he thought that the rise in CO2 content and temperature during the last 50 years, must be taken as rather a coincidence. The magnitude of it was even larger than Mr. Callendar had calculated, and he thought the rise in temperature was probably only one phase of one of the peculiar variations which all meteorological
    elements experienced.
  7. Dr. F. J. W. WHIPPLE
  8. Dr. Whipple expressed the hope that the author would give the Society an account of his investigation of the natural movements of carbon dioxide. It was not clear how the calculations regarding the gradual diffusion of C02 into the sea were carried out.
  9. The calculations embodied in Table IV depended on the assumption of high lapse rates of temperature everywhere. The inversions it seemed necessary to make additional calculations to allow for the varying circumstances. Other processes besides radiation are involved in the exchange of normal energy between ground and atmosphere, but it may be justifiable to ignore these other processes in an investigation of the effect of variations in the amount of CO2.
  10. Prof. D. BRUNT
  11. Prof. Brunt referred to the diagrams showing the gradual rise of temperature during the last 30 years, and said that this change in the mean temperature was no more striking than the changes which appear to have occurred in the latter half of the 18th century, and whose reality does not appear to be a matter of defective instruments.
  12. The long series of pressure observations made in Paris showed clearly that there had been great changes in the mean path of depressions coming from the Atlantic.
  13. Prof. Brunt agreed with the view of Sir George Simpson that the effect of an increase in the absorbing power of the atmosphere would not be a simple change of temperature, but would modify the general circulation, and so yield a very complicated series of changes in conditions. He was not quite clear how the temperature changes had been evaluated. He appreciated, however, that Mr. Callendar had put a tremendous amount of work into his most interesting paper.
  14. Dr. C. E. P. BROOKS
  15. Dr Brooks said that he had no doubt that there had been a real climate change during the past thirty or forty years. This was shown not only by the rise of temperature at land stations, but also by the decrease in the amount of ice in Arctic and probably also in Antarctic regions and by the rise of sea temperatures.
  16. This rise of temperature could however he explained, qualitatively if not quantitatively, by changes in the atmospheric circulation, and in those regions where a change in the circulation could be expected to cause a fall of temperature, there had actually been a fall.
  17. Moreover the rise of temperature was about ten times as great in the arctic regions as in middle or low latitudes, and he did  not think that a change in the amount of carbon dioxide could cause such a differential effect. The possibility certainly merited discussion, however, and he welcomed the paper as a valuable contribution to the problem of climatic change.
  18. Mr. I,. M. G. DINES
  19. Mr Dines asked Mr. Callendar whether he was satisfied that the change in the temperature of the air which he had found was significant, and that it was not merely a casual variation.
  20. Mr. J. H. COSTE
  21. Mr. Coste congratulated Mr. Callendar on his courage and perseverance. He would like to raise some practical issues.
  22. Firstly, was the C02 in the air really increasing? It used to be given as 400 ppm then as methods of chemical analysis improved it went down to 300 ppm, and he thought it was very doubtful whether the differences which Mr. Callendar made use of were real. The methods of determining C02 thirty or forty years ago were not sufficiently accurate for making such a comparison.
  23. A. Krogh
  24. Mr Krogh calculated that for a constant difference in tension in the atmosphere between the air and the ocean, the latter being less rich, the annual invasion of C02 would be equal to 3 x 108 metric tons, which was about the annual contribution of CO2 to the atmosphere by the burning of fuel; to this absorption by the ocean must be added the effects of vegetation, by photosynthesis. Thermometers thirty years
    ago were not instruments of very high precision and one would hesitate to consider variations of fractions of a degree based on observations made with such thermometers.
  25. G. S. CALLENDAR
  26. in replying, Mr. G. S. Callendar said he realized the extreme complexity of the temperature control at any particular region of the earth’s surface and also that radiative equilibrium was not actually established, but if any substance is added to the atmosphere which delays the transfer of low temperature radiation, without interfering with the arrival or distribution of the heat supply, some rise of temperature appears to be inevitable in those parts which are furthest from outer space.
  27. As stated in the paper that the variation of temperature with CO2 (Fig. 2), was obtained from the values of sky radiation, calculated for different amounts of this gas, substituted in expression 5. If the changes in S  shown in Table V are used for expression 5, it will be found that the temperature changes lie on the curve of Fig. 2 when the total sky radiation is 7/10 of the surface radiation. The sky radiation is calculated as a proportion of that from the surface, hence, at constant heat supply, a change of sky temperature involves an equilibrium change of surface temperature as in expression 5.
  28. It was found that even the minimum numerical explanation of the method used for calculating sky radiation would occupy several pages, and as a number of similar methods have been published from time to time, it was decided to use the available space for matter of more direct interest.
  29. In reply to Dr. Whipple, the author regretted that space did not permit an account of the natural movements of CO2 (old English for the Carbon Cycle). He had actually written an account of these, but it was eight times as long as the present paper (and therefore it was not included in the paper).
  30. For the calculation of the diffusion of CO2 into the sea the effective depth was considered to be 200 meters at any one time.
  31. The effect of CO, on temperatures has been calculated for a variety of lapse rates, including large inversions. In the latter case the effect on the surface temperature is small, but the protection for the warm middle layers remains.
  32. In reply to Prof. Brunt, the author stated that the warm periods of 1780, 1797, and 1827 appeared to be of the nature of short warm intervals of up to 10 years, with some very cold years intervening, whereas recent conditions indicated a more gradual and sustained rise of temperature; this was perhaps best shown by a 40-year moving average.
  33. In reply to Dr. Brooks, the author agreed that the recent rise in Arctic temperatures was far too large to be attributed to change of CO2. He thought that the latter might act as a promoter to start a series of imminent changes in the northern ice conditions. On account of their large rise he had not included the Arctic stations in the world temperature curve (Fig. 4).
  34. In reply to Mr. Dines, the author said he thought the change of air appeared too widespread to be a casual change due to local variations of pressure.
  35. In reply to Mr. Coste, the author said that the early series of CO2 measurements he had used were probably very accurate; he had only observed on days when strong and steady west winds were blowing at Kew. The actual CO2 added in the last 40 years was equal to an increase of 8%; the observed and calculated values agreed in
    giving an effective increase of about 6% at Kew.
  36. The author is not aware of the solution coefficients for sea water used by A. Krogh to give the stated figure which appears to be far too high. It must be remembered that less than 1/1000 of the sea volume would be replaced at the surface in one year, and the annual increase of CO2 pressure in the air is less than 1/10^6 atmosphere.
  37. About 98% of the CO2 used by vegetation appears to be returned by decay oxidation and respiration.
  38. The author thought that very accurate temperatures were taken last century; if there was any doubt on this point the introduction to the long period tables from the Radcliffe Observatory (Met. Obs., Vol. 55, 1930), should set this at rest.
  39. With regard to the effect of vertical motion on the “ geostrophic departure ” of the wind, in section 7 of our paper “ The importance of vertical motion in the
    development of tropical revolving storms (old English for tropical cyclones),” published in the lournal January, 1938, a general proposition is enunciated, which reads as follows: “ If vertical motion occurs in the atmosphere in a region of horizontal temperature gradient, then ascending motion gives a component
    of wind from warm to cold, and descending motion a component front
    cold to n arm. ”
  40. We are indebted to Prof. Brunt for pointing out that the brief argument given in the paper does not stress at all adequately the type of air motion to which the proposition is intended to apply, and that it certainly does not apply to the case of a convection current rising by instability through an environment.
  41. By not realizing this natural application of the proposition, we failed fully to appreciate Prof. Brunt’s contribution to the discussion of the paper, and in order to avoid further misunderstanding, we should like to amend the statement to read :
    “ If there is general vertical motion in a region where the winds
    are quasi-geostrophic, then the departure of the wind velocity from the
    geostrophic value has a component directed along the horizontal gradient
    of temperature, from warm to cold with ascending motion, and from
    cold to warm with descending motion.”
  42. The proposition is believed to have an important bearing on general
    meteorological developments, where gradual ascending motion, as, for
    example, in a frontal zone, is associated with convcrgence or divergence,
    and with departures of the wind velocity from the geostrophic value.
    Although the departures are generally small compared with the
    geostrophic velocities (so that the whole motion may be described as
    qllasi-geostrophic) they are of fundamental dynamical significance.
    A further paper will shortly be presented, in which the mathematical
    and physical basis of the proposition will receive a more adequate treatment.
  43. FULL TEXT OF THE PAPER IN PDF: CALLENDAR 1938 PDF

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