ELSEVIER Spectrochimica Acta Part A 51 (1995) 1395 Reply to comments by Sir John Houghton and “The roles of carbon dioxide and water vapour in the Earth’s troposphere” SPECTROCHIMICA ACTA PART A Keith P. Shine on warming and cooling J. Barrett, Spectrochim. Acta Part A, 51 (3) (1995) 415 Jack Barrett Department of Chemistry, Imperial College of Science, Technology and Medicine, Prince Consort Road, South Kensington, London S W7 ZA Y, UK Received and accepted 5 June 1995 In his comments on my paper [1], Sir John Houghton points out that I assert that emission from greenhouse gases can occur only if the collisional de-activation times of the excited molecular vibrations are longer than their radiative lifetimes. This is the case and the condition pertains to the atmosphere at the low pressures found above 80 km. I agree that Sir John’s second paragraph except for the opening sentence. My argument in the paper is much the same and disposes of the radiation reverse cascade theory [2]. If the total absorption of terrestrial radiation, apart from the fraction which escapes through the clear sky “window”, by water and carbon dioxide in the lower 30 m of the atmosphere occurs, an increase in the partial pressure of carbon dioxide will have no effect except to alter slightly the fractions of radiation absorbed respectively by water and carbon dioxide. Dr. Shine did supply me with helpful references which improved my paper. My acknowledgement in no way implies that he agrees with any part of the paper. The main point of my paper was to show that radiative emission from individual molecules of carbon dioxide and water in the troposphere was highly improbable. The clear sky radiation originates from the Sun, water vapour and other aerosols, all of which emit broad spectrum radiation. Satellite measurements [3] show that the absorption of terrestrial radiation below 800 cm-’ is complete in the troposphere and that emission to space is constricted only at high stratospheric levels by absorption by water vapour, carbon dioxide and ozone. Dr. Shine and I are in complete agreement that CO, does not emit cavity-type radiation. Any calculations of its emission spectrum should be based upon the appropriate transition probability [4-61 rather than cavity radiation theory [7]. References [I] J. Barrett, Spectrochimica Acta Part A, 51 (1995) 415. [2] R. Mcllveen, Fundamentals of Weather and Climate, Chapman and Hall, 1992, p. 250. [3] V.G. Kunde, B.J. Conrath, R.A. Hanel, W.C. Maguire, C. Prabhakara and V.V. Salomonson, J. Geophys. Res., 79 (1974) 777. (41 A. Einstein, Phys. Z., 18 (1917) 121. [5] R.S. Mulliken, J. Chem. Phys., 7 (1939) 14. [6] H. Eyring, J. Walter and G.E. Kimball, Quantum Chemistry, John Wiley, 1944, p, 115. [7] S.A. Clough, M.J. lacono and J.-L. Moncet, J. Geophys. Res., 97 (1992) 15761. 0584-8539/95/$09.50 0 1995 Elsevier Science B.V. All rights reserved SSDlO584--8539(95)01487-X

Reply to comments by Sir John Houghton and Keith P. Shine on “The roles of carbon dioxide and water vapour in warming and cooling the Earth's troposphere” J. Barrett, Spectrochim

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Page 1: Reply to comments by Sir John Houghton and Keith P. Shine on “The roles of carbon dioxide and water vapour in warming and cooling the Earth's troposphere” J. Barrett, Spectrochim

ELSEVIER Spectrochimica Acta Part A 51 (1995) 1395

Reply to comments by Sir John Houghton and “The roles of carbon dioxide and water vapour in

the Earth’s troposphere”

SPECTROCHIMICA ACTA PART A

Keith P. Shine on warming and cooling

J. Barrett, Spectrochim. Acta Part A, 51 (3) (1995) 415

Jack Barrett

Department of Chemistry, Imperial College of Science, Technology and Medicine, Prince Consort Road, South Kensington, London S W7 ZA Y, UK

Received and accepted 5 June 1995

In his comments on my paper [1], Sir John Houghton points out that I assert that emission from greenhouse gases can occur only if the collisional de-activation times of the excited molecular vibrations are longer than their radiative lifetimes. This is the case and the condition pertains to the atmosphere at the low pressures found above 80 km. I agree that Sir John’s second paragraph except for the opening sentence. My argument in the paper is much the same and disposes of the radiation reverse cascade theory [2].

If the total absorption of terrestrial radiation, apart from the fraction which escapes through the clear sky “window”, by water and carbon dioxide in the lower 30 m of the atmosphere occurs, an increase in the partial pressure of carbon dioxide will have no effect except to alter slightly the fractions of radiation absorbed respectively by water and carbon dioxide.

Dr. Shine did supply me with helpful references which improved my paper. My acknowledgement in no way implies that he agrees with any part of the paper.

The main point of my paper was to show that radiative emission from individual molecules of carbon dioxide and water in the troposphere was highly improbable. The clear sky radiation originates from the Sun, water vapour and other aerosols, all of which emit broad spectrum radiation. Satellite measurements [3] show that the absorption of terrestrial radiation below 800 cm-’ is complete in the troposphere and that emission to space is constricted only at high stratospheric levels by absorption by water vapour, carbon dioxide and ozone. Dr. Shine and I are in complete agreement that CO, does not emit cavity-type radiation. Any calculations of its emission spectrum should be based upon the appropriate transition probability [4-61 rather than cavity radiation theory [7].

References

[I] J. Barrett, Spectrochimica Acta Part A, 51 (1995) 415. [2] R. Mcllveen, Fundamentals of Weather and Climate, Chapman and Hall, 1992, p. 250. [3] V.G. Kunde, B.J. Conrath, R.A. Hanel, W.C. Maguire, C. Prabhakara and V.V. Salomonson, J. Geophys.

Res., 79 (1974) 777. (41 A. Einstein, Phys. Z., 18 (1917) 121. [5] R.S. Mulliken, J. Chem. Phys., 7 (1939) 14. [6] H. Eyring, J. Walter and G.E. Kimball, Quantum Chemistry, John Wiley, 1944, p, 115. [7] S.A. Clough, M.J. lacono and J.-L. Moncet, J. Geophys. Res., 97 (1992) 15761.