“In the SAR, a crude distinction was made between the effect of “upper-tropospheric” and “lower-tropospheric” water vapour, and it was implied that lower tropospheric water vapour feedback was a straightforward consequence of the Clausius-Clapeyron  relation. It is now appreciated that it is only in the boundary layer that the control of water vapour by Clausius-Clapeyron can be regarded as straightforward”

At first glance, it seems reasonable that the vapour pressure of water ought always to increase with temperature., even when not in equilibrium, although Lindzen has argued that this is not necessarily so (6). But when it is appreciated that part of the water vapour is involved in the formation of clouds, it no longer seems so reasonable.

Clouds 

Along with our ignorance on the historical and current concentration and distribution of water vapour, we are equally ignorant about the past or even the present behaviour of clouds. Cloud formation is extremely complex, and the radiative behaviour of clouds depends on the type of cloud and its location. This unpredictable and unknown  behaviour is, of course, dealt with by guesswork, an assumption of cloud “feedback.   Although water vapour guesses in climate models are relatively uniform, those for clouds represent the greatest source of the difference between climate models, as is shown by various intercomparison studies (14,15,16,17).  There is evidence that “cloud cover” (however measured) has increased over the years (18) but there is no information on the different types of cloud.. So maybe any temperature increase is nullified by increased clouds?

Comprehensive measurements of clouds by satellite have been made since 1983 (19), but there is no evidence of any consistent trend.

Other Effects of Water 

Precipitation, whether of rain or snow, also affects climate, and we have little reliable or representative information. Climate Change 01 (20)  identifies a recent increase in precipitation for the few, unrepresentative sites for which it has data. Snow precipitation affects behaviour of glaciers (often exclusively blamed on temperature), and the albedo (reflectivity) of some regions.

To summarise: the role of water, as vapour, clouds, and precipitation, on the climate which undoubtedly has the dominant role in the greenhouse effect, is very little understood, and there are no reliable historical records. Climate modellists are therefore reduced to guesswork, which they call “feedbacks”

Carbon Dioxide

THE CARBON BUDGET

Climate Change 01 (21) gives the following components of the Carbon  Budget, divided into decades 

Emissions from the combustion of fossil fuel, gas flaring and cement are considered to be partitioned between the atmosphere, the ocean, and the land., according to the fractions shown.

Table 3 Components of the Carbon Budget (21)

It will  be seen that the fraction of the emissions from fossil fuels and cement entering the atmosphere has fallen from 0.61±0.02 to 0.51±0.02 between the 1980s and the 1990s. It is thought that the amount entering the ocean has fallen 1.9±0.6 to 1.7±0.5 GtC in the period.

Partitioning of the carbon dioxide absorbed by the earth between the ocean and the land has used two methods (22). The first uses the change in atmospheric oxygen. Carbon dioxide absorbed on the land implies a simultaneous emission of oxygen, whereas absorption by the ocean does not. the second uses measurements of the relative abundance of the carbon isotopes ¹²C and ¹³C.  C3 plants  discriminate against ¹³ C and so change the ratio between the isotopes. Both these methods depend on an array of assumptions, and the accuracy is poor. It is, to begin with, difficult to believe that ocean absorption goes down with increased carbon dioxide concentration as suggested in Table 3.

The calculated figure for carbon dioxide absorbed by land is also highly inaccurate. There is a  tendency to try to partition the land absorption into two components,  land-use change which is considered to cause an emission, and residual terrestrial sinks which causes an absorption. The emission  part is sometimes added to the fossil fuel figure to give a gross emission. To be logical, if you are going to add emissions you should also subtract sinks to give gross emissions.  In reality it is almost impossible to identify land surface regions which either emit or absorb carbon dioxide, although much effort has gone into trying.

The large increase in land absorption from the 1980s to the 1990s must be due to greatly increased agriculture and forestry productivity. As there are only two points on a graph, it is difficult to say whether this trend will continue

Emissions 

Although carbon dioxide is an entirely minor greenhouse gas, it has been postulated that the emission of carbon dioxide by the combustion of fossil fuels can have an important influence on the climate, and therefore must be brought under control.

The Nations of the world have been involved for several years now in discussing proposals for control of carbon dioxide emissions.

It is therefore something of a surprise to find that Climate Change 01  has no Chapter dealing with carbon dioxide emissions,  but only a very short paragraph in Chapter 2 (3.4.1. Emissions from Fossil Fuel Burning and Cement Production) and a single diagram (Figure 3.3) showing emissions from 1958 to the year 1999.(23)

Although the developed nations involved in the .Kyoto Treaty process have methods for measuring  their own emissions, the latest figure for world emissions from the Carbon Dioxide Information and Analysis Center is for the year 1998. This means that any measures to reduce emissions will require a wait of at least three years before they will find whether they have had any effect on global emissions..

.Figure 4.1 gives emissions from combustion of fossil fuels, gas flaring, and cement production, since 1950 (24), with  estimates for 1999 and 2000 from BP (25)

Figure 4.1 Global emissions of carbon dioxide from combustion of fossil fuels,
 gas flaring, and cement production  (24, 25)

It is evident that carbon emissions are somewhat irregular, but that there was a fairly linear rate of  increase of 0.14 GtC/yr from 1959 to 1979 which was replaced by a fairly linear trend of 0.05 GtC/yr from 1979 to 2000, less than half the previous rate. The difference is attributed (Table 1) to a considerable increase in absorption by the land surface, a change which is largely unexplained.

Atmospheric Concentrations 

Carbon dioxide is one of the most difficult gases to measure It is only in the last 20 years or so that an effective infra red analysis method has evolved, free from the necessity of cross calibration.

A half-forgotten figure is G S Callendar.  He was an advocate of the existence of the greenhouse effect in the late 30s and he backed up his claims with measurements of  the carbon dioxide content of the atmosphere which have been discredited.  He claimed   that the 19^th century value of 274 parts per million had increased to 325 parts per million by 1935 as a result of the combustion of fossil fuels, and that this caused  an increase in global temperature of 0.33°C (26,27, 28), from Jaworowski (29).

The whole subject was revived by the measurements of Keeling (30)  from 1959, the latest version of which (31) is shown below (Figure 4.2). Before May 1974 the readings were at the Scripps Institute of Oceanography at La Jolla California

Figure 4.2  Monthly atmospheric carbon dioxide concentrations as measured from 1959-1974,
 and from near the Mauna Loa volcano from 1974 to 2000 (31)

Subsequent measurements were near the summit of the Mauna Loa volcano on the island of Hawaii

It is immediately apparent that the approximately linear rate of increase in California between 1959 and 1974 (0.9 ppm/yr) was followed by the approximately linear rate of increase from 1974 to 2000 at Mauna Loa (1.53ppm/yr) which shows no signs of changing.

Since 1969 a world-wide network of  stations measuring atmospheric concentrations of carbon dioxide has been established. In contrast to the weather stations measuring temperature, which are predominantly close to cities and buildings, the carbon dioxide network is deliberately located  “remote from fossil fuel combustion and vigorous plant activity” (31). In other words, once more, they do not provide a fair average, and they do not provide information on the carbon dioxide concentration above most land surfaces, where most concerns are expressed about the consequences of the greenhouse effect. The claim that carbon dioxide is a “well-mixed” gas are patently untrue, as most stations avoid measurements when the wind is in the wrong direction ( from land) and record only concentrations from the sea.

It is postulated that changes in atmospheric carbon dioxide concentration are caused by combustion of fossil fuels. If we assume, for the moment, that the Mauna Loa record can be considered to represent globally averaged carbon dioxide concentrations, then each annual increment in atmospheric addition should be the result of the annual emission of carbon dioxide. The calculation (Figure 3.3) shows, that generally the atmospheric increment is less than the emission. The difference must surely represent absorption by the earth.

Figure 4.3  Global Emissions of carbon dioxide from combustion of fossil fuels and cement between 1960 and 2000, compared with the annual increment into the atmosphere,
 and, by difference, the amount absorbed by the earth.

There does not seem to be a close relationship between the annual increment of carbon dioxide emitted by combustion of fossil fuel, cement production, and gas flaring, and the increment measured in the atmosphere. In 1966. 1969. 1973, 1988 and 1996 all, or almost all emissions entered the atmosphere. These were all El Niño years. In 1964, 1992 and 1993 none,  or little,  entered the atmosphere. 1964 was a La Niña year and so was 1993. So the fluctuations seem to be heavily dependent on the Southern Oscillation in the ocean.

It is, however, obvious  from Figure 4.2, that carbon entering the atmosphere has , on average, been constant at about 3 GtC/yr,  since 1974, whereas the carbon absorbed by the earth has (when smoothed) increased from 1.5GtC/yr to 3.4GtC/yr over the same period because of increased plant production.(32)

Figure 4.4 is a plot of the Airborne Fraction, that is to say, the fraction of emissions due to combustion of fossil fuels, cement manufacture and gas flaring, that arrives in the atmosphere. It will be seen that it  has  fallen from 0.59 to  0.52 between 1960 and 2000.

Figure 4.4  The Airborne Fraction of carbon dioxide emissions.

Methane 

Methane is the third most important greenhouse gas,  after water vapour and carbon dioxide. There is considerable disagreement on quantities emitted (33) It is emitted partly from natural sources, 92-270 TgCH₄/yr, and partly from “anthropogenic” sources (which include agriculture),  315-350 TgCH₄/yr

The behaviour of methane in the atmosphere is completely different from that of  carbon dioxide, since it decomposes rapidly, so that the atmospheric concentration depends on a constant source of supply. The “lifetime” of methane in the atmosphere is around 10 years (34)

The atmospheric concentration of methane has been measured at the same sites that measure carbon dioxide since 1984, so it suffers from the same defect of only measuring “background” figures. The true average, or figures over land or industrial are unknown. The latest globally averaged figures are shown in Figure 4. 5. (35)

It will be seen that the rate of increase in the atmospheric concentration of methane has been falling since 1984, and the concentration itself is now falling. Methane therefore cannot be considered at present as an important greenhouse gas, despite the emphasis placed on it by the IPCC and by Kyoto negotiators.

Other Greenhouse Gases 

Climate Change 01  (36) lists 63  greenhouse gases additional to water vapour, carbon dioxide and methane Many of these are halocarbons which are largely being reduced because of their supposed effects on ozone in the stratosphere.  Since their calculated effects are marginal they will not be further discussed here.

Aerosols 

Ordinary clouds are the most important aerosols influencing the climate, yet they do not feature in the Climate Change 01  Chapter 5 on “Aerosols: their Direct and Indirect Effects” (37). The uncertainties connected with

their properties are concealed in their status as “feedbacks”. Chapter 5 does, however deal with influences on clouds which are dealt with separately from the influence of the clouds themselves.

Figure 4.5   Globally averaged atmospheric concentration of methane since 1984 (35) 

The Chapter lists eight kinds of aerosol, each of which has direct and indirect effects. They are:  Soil dust, Sea Salt, Industrial dust,  Carbonaceous aerosols, Primary biogenic aerosols, Sulphate, Nitrates and Volcanoes.

Most of the effects of aerosols are difficult to measure, and the uncertainties, all of which are unquantified  in a scientific sense, are very great.  Many aerosols cool the earth. Those predominantly due to industry should cool the Northern Hemisphere more than the Southern Hemisphere, an effect not observed, even by the most  reliable temperature records.

The effects of aerosols, and their uncertainties, are such as to nullify completely the reliability of any of the climate models, as will appear evident in the next Chapter.

References

1.     Tyndall, J, 1859 Note on the transmission of heat through gaseous bodies.  Proceedings of the Royal Society of London  10,  155-158

2.     Baliunas, S, and W. Soon, 1999, Pioneers in the Greenhouse Effect. World Climate Report  4  (19).  At http://www.greeningearthsociety.org/climate

3.     Raval A, and V Ramanathan, Observational determination of the greenhouse effect 1989 Nature 342 758-61

4.     Rind D, et al, 1991 “Positive water vapour feedback in climate models confirmed by satellite data” Nature 349 500-502

5.     Lindzen, R S 1994 “Climate Dynamics and Global Change” Annual Review of Fluid Mechanics  26 353-378

6.     Lindzen, R S 1993 “Absence of Scientific Basis”. National Geographic Research and Exploration 9 191-200

 7   Rind D 1998,  “Just Add Water Vapour” Science 281  1152-1153

 8   Climate Change 01 Chapter 7,  “Physical Climate Processes and Feedbacks” page 425

 9    Inamdar, A K and V Ramanathan 1998 “Tropical and Global Scale Interactions among Water Vapor, Atmospheric Greenhouse Effect and Surface Temperature.” Journal of Geophysical Research  103,  32177-32194

10 Climate Change 01  Chapter 4 “Atmospheric Chemistry and Greenhouse Gases”, pages 240-288

11 Climate Change 01  Chapter 4, page 241.

12 Climate Change 01  Chapter 6 “Radiative Forcing of Climate Change”, pages 349-416

13 Climate Change 01  Chapter 7 “Physical Climate Processes and Feedbacks”, page 427

14 Cess, R D et al 1990.  “Intercomparison and Interpretation of Climate Feedback Processes in 19 Atmospheric General Circulation Models”, Journal of Geophysical Research  95 16601-16615

15 Cess, R D et al 1989 “Interpretation of Cloud-Climate Feedback as produced by 14 Atmospheric General Circulation Models” Science 245, 513-516

16 R D Cess 1996 “Cloud feedback in atmospheric general circulation models: an update”. Journal of Geophysical research  101 12791-12794.

17 Gates W L et al 1999 Bull Am Met Soc  80 29-55

18 Climate Change 01  Chapter 2 “Observed Climate Variability and Change”, Figure 2.3, page 109

19 W.B. Rossow ISCCP, 2001 http://iscpp.giss.nasa.gov

20 Climate Change 01 Chapter 2. Page 159

21 Climate Change 01  Chapter 3, “The Carbon Cycle and Atmospheric Carbon Dioxide”  page 190

22 Climate Change 01  Chapter 3, Figure 3, pages 205-207

23 Climate Change 01  Chapter 3, page 204

24 Carbon Dioxide Information and Advisory Center, http://cdiac.esd.ornl.gov/trends

25 British Petroleum. http://www.bp.com/centres/energy/world

26 Callendar, G S  1938 Quarterly J of the Meteorological Society 64, 223

27 Callendar G S 1940 Quarterly J of the Meteorological Society 65 395

28 Callendar, G S 1958 Tellus 10 243

29 Jaworowski 1997  Twenty first Century 10 (1) 42-52

30 Keeling C D et al 1989 in D H Peterson (Ed)  Geophysical Monograph 55  American Geophysical Union, pages 305-363, updated by Reference 25

31 Carbon Cycle Group, NOAA, http://www.cmdl.noaa.gov/ccg

32 CO2 Science magazine, http://www.co2science.org/journal

33 Climate Change 01  Chapter 4, Table 4.2,  page 250

34 Climate Change 01  Chapter 4 Table 4.3 Page 251

35  Dlugokencky E J , K A Masarie, P M Lang, and P P Tans, 1998, “Continuing decline in the growth rate of the atmospheric methane burden.”  Nature,  393  447-450, plus update at  NOAA Carbon Cycle Group 2001 http:///.cmdl.noaa.gov/ccg

36 Climate Change 01  Chapter 4  Table 4.1, pages 244-5

37 Climate Change 01 Chapter 5 “Aerosols, their Direct and Indirect Effects” pages 290-348

Go to Chapter 5 (to be published in a few days)

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