Contributions of C02

The Spectroscopic Contributions of C02 to the Warming and Cooling of the Earth’s Atmosphere

Jack Barrett

European Science & Environment Forum, 6 Garden Royal, Kersfield Road, London SW15 3HE.

Abstract

An account of some doubts about the attempts to predict climate change as the result of anthropogenic emissions of carbon dioxide.

Introduction

Although many factors, some still not fully understood, affect the temperature of the Earth and its atmosphere, the Intergovernmental Panel on Climate Change (IPCC) [1a] asserts that ‘the body of statistical evidence…now points towards a discernible human influence on global climate.’ Some scientists disagree with the methods and conclusions of the IPCC, but their criticisms are rejected by members of the IPCC and its associates [2] who claim to take notice only of professional climatologists. As one outsider (not beyond criticism [3]), the author outlines some criticisms of the IPCC attempts to find a causal link between anthropogenic emissions of CO2 and climate change.

Three aspects of the problem are discussed; the experimental observations, the theoretical attempt to implicate changes in atmospheric CO2 concentrations in climate change, and a philosophical reminder of scientific method and its potentialities.

Discussion

Experimental observations

Using Pettenkofer’s method, [4] Roscoe and Schorlemmer [5] reported that the CO2 content of the air in Manchester in 1873 was 285 ppmv. Since then the concentration of the gas has increased steadily and has been determined continuously at the Mauna Loa observatory in Hawaii from 1958. The current concentration is ~366 ppmv, representing a 28% increase over 125 years that is generally regarded as being caused mainly by the oxidation of fossil fuels.

The mean temperature of the Earth’s surface, as estimated from a varying number of weather stations with an unrepresentative geographical distribution and from measurements taken randomly by ships, has increased over the last 100 years by between 0.3-0.6 °C (0.1-0.2%) [1b], an amount which is regarded by the IPCC as significant. Much more representative and accurate measurements of the Earth’s temperature have been made continuously since 1978 by NASA satellites [6] and show zero trend to date, the variations from the mean being in the range of ?0.5 °C with variations of such a magnitude occurring sometimes over a two-week period. Since 1978 the CO2 concentration has increased by 10% with no apparent effect on the Earth’s surface temperature.

Warming and cooling of the Earth’s surface

The predictions [1c] of the IPCC are based upon theoretical principles which have been suitably parameterized to make computer calculations possible. The atmosphere is in a quasi-equilibrium state, the solar energy received by the Earth being balanced by the emission of the same amount of energy into space over long time periods. The Sun emits broad spectrum radiation typical of its temperature, an average flux of 235 W m-2 [1d] causing heating of the Earth’s atmosphere (28%) and its surface (72%). Four percent of the absorbed solar radiation is absorbed by the stratosphere where it maintains the ozone layer and another 24% is absorbed by the constituents of the lower atmosphere, including water molecules, carbon dioxide, clouds and other aerosols (i.e. smaller aggregations of water molecules which may also contain dissolved substances such as sulfur dioxide and sulfuric acid) and causes warming. Since the mean temperature of the atmosphere is lower than that of the Earth’s surface there is a resultant radiative transfer of energy from the surface to the atmosphere (26 W m-2) in addition to some heat transfer (24 W m-2) and the transfer of latent heat of evaporation of water (78 W m-2), the three warming mechanisms contributing to respective extents of 20%, 19% and 61%.

Of the infra-red radiation emitted by the surface, a small fraction (10%) escapes directly into space through the spectroscopic ‘window’ between 800-1300 cm-1; the region where none of the atmospheric constituents absorbs much energy. The remainder of the radiation is absorbed virtually completely by the water and CO2 in the lower part of the atmosphere [7]. Although CO2 absorbs strongly in the infra-red region, water molecules (particularly in their condensed phases, liquid and solid) absorb much more strongly and over a much broader frequency range. Calculations [8] using the HITRAN simulation programme [9] show that 100 m path of a typical mixture containing 36 Pa partial pressure of CO2 and the equivalent of 50% saturated water vapour (785 Pa) absorbs 72.8% of the radiation emitted by the Earth’s surface. Doubling the partial pressure of CO2 causes an increase in absorption to 73.5%, an indication of the extent to which the CO2 contribution is near saturation level, due to its absorption coefficient and the considerable overlap of the CO2 0 1 bend and the rotational transitions of water molecules.

It is generally agreed [10] that the extent of global warming is not determined by the initial absorption of the surface radiation, but is dependent upon the rate of cooling of the atmosphere as influenced by the level of CO2 as radiation is directed outwards with a total flux of 235 W m-2.

There are arguments [11] which indicate that the warming of the lower troposphere, i.e. the lower 5 km, is caused mainly by convection and that any alteration in the rate of cooling at a higher level might not affect the temperature of the surface. Such arguments are noted by the IPCC [1e], but not refuted. The IPCC has calculated the emission characteristics of CO2 and other ‘radiative’ molecules by modifying the Planck function by the absorption coefficient of the species for all frequencies of interest rather than using calculated transition probabilities. The estimations of absorption coefficients are calculated from experimental values which are modified to apply to the given conditions of temperature and pressure of the upper atmosphere using the theory of line broadening [12].

The estimations are parameterized against experimental measurements, but must be subject to substantial uncertainties because of the extremes of extrapolation employed.

The IPCC calculate that a doubling of the CO2 level (an eventuality which is virtually impossible even if all the fossil fuel resources were to be oxidized) will reduce the outgoing flux by ~4.4 W m-2 (1.9%) and cause global warming of about 2.8°C. It is argued [10] that the extra CO2 will allow radiation to escape from the top of the atmosphere at a higher level where the temperature is lower. The ensuing reduction in outgoing flux upsets the energy balance which must be restored by global warming, the warmer atmosphere again having the capability of emitting the required extra ~4.4 W m-1 of energy flux. There is a possibility that this argument is faulty in that the presence of more CO2 molecules offsets the effect of the lower temperature of emission, thus maintaining the energy balance.

To put the whole problem into perspective it should be realized that the heat content of the atmosphere is 1.26 x 1024 J and that over a 24 hour period the Earth’s surface receives and loses about 1.06 x 1022 J or 0.8% of the atmospheric heat content. The IPCC is trying to find the effect of a change of 1.9% of that 0.8%, i.e. a change of 0.015% in the total heat content, a goal which might be beyond its capabilities.

Hoyle [13] has pointed out that the fraction of solar radiation, reflected from the Earth’s system, i.e. its albedo, ~30%, is not known to the degree of accuracy which would justify the sophisticated computer modelling exercises currently being carried out by the IPCC.

In its annual elliptical journey around the Sun, the Earth receives an influx of radiation varying between 225 and 257 W m-2, an annual variation of 32 W m-2 which is eight times greater than the supposed effect of doubling the atmospheric CO2. When the Earth is at its nearest point to the Sun the global lower tropospheric temperature is lower by 1.8°C than when the Earth is at its farthest distance from the Sun [14]. Such an observation is a possible indication of the operation of an Earth thermostat mechanism which would cast doubt upon whether the IPCC derived alteration of ~4.4 W m-2 in the radiation flux is a potential factor which might lead to climate change.

Scientific method

As a final point it should be pointed out that whatever changes occur to the climate in future years, and whatever actions humans take to try to modify such changes, will be beyond scientific analysis because we will never know what changes would have occurred had we not taken such actions.

References

[1] Houghton, J.T., Meira Filho, L.G., Callander, B.A., Harris, N., Kattenberg, A., & Maskell, K., (eds), Climate Change 1995, Cambridge University Press, (a) p. 438, (b) p. 26, (c) p. 39, (1d) p. 58, (1e) p. 200, (1996).

[2] Harries, J. E., & Slingo, A., personal communications, NERC seminar meeting, Nottingham, (1996).

[3] See for example, Braterman, P., Spectrochimica Acta, 52A, (1996), 1565 and the reply, Barrett, J., ibid., 52A, (1996), 1567.

[4] Pettenkofer, M., J. Chem. Soc., (1858), 292.

[5] Roscoe, H. E., & Schorlemmer, C., A Treatise on Chemistry, MacMillan & Co., London, (1905), p. 591.

[6] Spencer, R. W., and Christy, J. R., 1994. Global and hemispheric and stratospheric temperature anomalies from satellite records. pp. 629-634. In T. A. Boden, D. P. Kaiser, R. J. Sepanski, and F.W. Stoss (eds.), Trends ’93: A Compendium of Data on Global Change. ORNL/CDIAC-65. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, Tenn., U.S.A.

[7] McIlveen, R., Fundamentals of Weather and Climate, Chapman & Hall, p. 251, (1992).

[8] Barrett, J., Treibhaus-kontroverse und Ozon-problem, Symposium der Europaischen Akademie fur Umweltfragen, H. Metzner, (ed.), Leipzig, (1996), p.169.

[9] HITRAN-PC, the IBM-PC version of the HITRAN Database and User Programs, University of South Florida, Version 1.1, (1992).

[10] Houghton, Sir J., Spectrochimica Acta, 51A, (1995), 1391. [11] Lindzen, R. S., Bull. Am. Met. Soc., 71, (1990), 288.

[12] Houghton, J. T., Meira Filho, L. G., Bruce, J., Hoesung Lee, Callander, B.A., Haites, E., Harris, N., & Maskell, K., (eds), Climate Change 1994, Cambridge University Press, p.170, (1995).

[13] Hoyle, Sir F., The Global Warming Debate, J. Emsley, ed., The European Science and Environment Forum, (1996), p. 179.

[14] Christy, J. R., personal communication of 1983-1990 data; the author’s analysis, (1996).

REF: Int. J. Vib. Spect., [www.irdg.org/ijvs] 1, 2, 5 (1996)


Assuming Dr. Barrett is correct, one must wonder why the Establishment is so keen on blaming the combustion of coal and oil for global warming. The reason, I strongly suspect, is that utter shower – our political Lords and Masters. Hype up the CO2 yarn, a subject about which lawyers and their ilk know absolutely nothing, and hence justify “carbon taxes”, increased tax on car fuel and, in the U.K., “VAT on fuel bills”.

Result – the gullible and scientifically illiterate (the vast majority of the electorate) will swallow this rubbish and vote as required. Pressure groups like Greenpeace can be manipulated to shout to numbers, providing free-of-charge support for the taxes and votes to boot.

Or am I just a cynic?

EDITOR