The various forms of climate scepticism may be classified by four subsections:
(1) Informed science.
(2) Misunderstanding of science.
(3) Distortions of science or deliberate misunderstanding.
(4) Incredulity.

1. Informed science

There are two main challenges to the IPCC version of climate change. One is the usage of an inflated value for the sensitivity of the atmosphere to changes in greenhouse gas concentrations that leads to exaggerated predictions of future changes. The second challenge, connected to the first, is that positive feedbacks are possibly overestimated and that some negative feedbacks are either minimized or ignored. In both cases the science is not clear cut and offers opportunities for biasing the outcomes of any of the computer programmes used to produce the predictions. These matters are dealt with to some degree on this website. Additionally, the IPCC consider the possible effects on the climate from changes in the solar wind, as indicated by the variability of sunspots and cosmic ray intensities, as being of little significance.

2. Misunderstanding of science

Unless criticisms of the IPCC views are met with legitimate science they will fail. Since the science of climate change is concerned with traditional subjects including physics, chemistry, biology and geology it is not common for any one person to be sufficiently well informed to be able to comment authoritatively on all aspects of the business. Hopefully we concentrate our criticisms on those aspects of the business where we have considerable knowledge and understanding and leave the other aspects to those more expert.

To inform the general public of the intricacies of climate change science is not easy, bordering on the impossible. Analogies are used and they are all imperfect in some aspect or another. For instance the term greenhouse effect is attacked because ‘greenhouses don’t work like that’.

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The greenhouse effect and real greenhouses

Real greenhouses are warmer than the outside atmosphere because the sunlight is not absorbed appreciably by glass. Some of the radiation is reflected, but most of it enters the greenhouse and some of that is reflected and is lost to the atmosphere. This can be understood because the contents of the greenhouse and the greenhouse itself can be observed. They have different colours. Of the visible spectrum [red, orange, yellow, green, blue, violet, Royal George buried Victoria], green plants absorb most of the colours except for green which is simply reflected from them and thus to the eye they appear to be green. Plant pots absorb most of the spectrum apart from the red end and therefore appear to be red. Soil absorbs most of the spectrum and appears to be brown.

The absorbed sunlight is converted into heat by a series of complex stages, but some of it is used by plants in photosynthesis to allow them to grow. In this process carbon dioxide and water are used to produce carbohydrates. The process can be described by a simplified chemical equation:

H2O + CO2 + hv ® [H2CO] + O2

[H2CO] is a general formula for carbohydrates, the name suggesting their composition: carbon plus water, [C + H2O]. Glucose is an important carbohydrate and has the formula C6H12O6, six of the basic units. The symbol hv is used to denote a photon, a particle of radiation with a frequency v. h is Planck’s constant which allows the calculation of the energy of the photon by using the Planck equation:

E = hv

For example, blue light has a frequency in the region of 6 ´ 1014 Hz [1 Hertz = 1 cycle per second]. Planck’s constant has the value: 6.626 ´ 10-34 J s [Joule seconds] so the energy of the blue photon is 6 ´ 1014 ´ 6.626 ´ 10-34 = 3.98 ´ 10-19 Joules. That does not seem to be very much. Chemists don’t normally deal with individual photons or molecules, they prefer to use the mole as the basic unit of photons and matter generally. For historical reasons, concerned with Avogadro’s hypothesis, the mole was defined as the number of molecules in one gram-molecule of any substance. One gram-molecule is the mass of a substance expressed as it’s molecular weight. ‘In the new money’ – modern nomenclature, the mole is the number of particles in a substance with a mass equal to its relative molar mass (RMM) expressed in grams. Thus, the RMM of water is 18 or, to be very strict, 18.0152 [H = 1.0079, O = 15.9994]. So, one mole of water (18.0152 g) contains Avogadro’s Number of molecules [6.022 ´ 1023 per mole – it has units and so is strictly not a number but a constant, but chemists do recognise this].

Back to the blue photon! We can now calculate the equivalent energy of one mole of photons. Such a quantity is known as one Einstein. For the blue variety the equivalent energy is:

3.98 ´ 10-19 ´ 6.022 ´ 1023 = 2.4 ´ 105 Joules or 240 kJ

This is equivalent to the energy in about 80 g of baked beans! In chemical terms, the energy is of the same order as single chemical bonds between atoms, e.g., to split a molecule of hydrogen peroxide HO-OH into two hydroxyl radicals requires 146 kJ per mole of energy. Blue light can do some damage to cloth of that colour. Cloth which is dyed red/orange absorbs blue light strongly and it is known that red tents are much more easily damaged by sunlight than are blue tents, the latter absorbing less energetic red/orange photons and reflecting the damaging ones.

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Back to the greenhouse! The sun’s energy that is absorbed within the greenhouse is eventually converted into heat which warms the greenhouse. Heat, on the molecular scale is the motion of molecules. In liquids and gases the molecules have greater average speeds at higher temperatures. In solids, the individual molecules or atoms vibrate about mean positions more energetically at higher temperatures and the molecules in liquids and gases vibrate and rotate more energetically. But, the temperature inside a greenhouse does not rise continually, some of the generated heat escapes to the environment. All solids and liquids emit radiation characteristic of their temperature. At the temperature of greenhouses the radiation emitted is in the infrared region, just beyond the red end of the visible spectrum. The so-called greenhouse gases, mainly water vapour and carbon dioxide also emit infrared radiation. Glass is not very transparent to infrared radiation and this provides a hindrance to its passage to freedom. This causes the greenhouse to be warmer than it would be if the glass were completely transparent to infrared radiation. Hence, the naming of the similar procedure in the atmosphere as the greenhouse effect. The sun’s radiation is partially absorbed by the Earth’s surface and causes heating. The heat escapes partially by the emission of radiation and the infrared radiation in its passage to space is hindered by the absorption characteristics of the greenhouse gases. Some of the radiation causes the atmosphere to become warm and like all warm things the atmosphere also emits radiation. Some of this finds its way back to the surface and assists in warming the surface. Without such assistance the Earth’s surface would be very cold indeed and would resemble a snowball.

The objectors to the naming of the greenhouse effect point out correctly that the main warming in a real greenhouse results from the absence of convection currents which, in the wide world contribute considerably to the way in which the Earth’s surface cools. But the greenhouse effect is a constituent of all dictionaries now and any attempt to call it by any other name will not smell as sweet as any rose!

Analogies of scientific matters almost always have majors faults but a very useful analogy for the extra greenhouse warming that arises from the reduction of the concentration of a greenhouse gas has been supplied by Edward Chapman. Starting with the real greenhouse with one window broken by the entry of a cricket ball, its temperature would fall until a new equilibrium was reached. Removal of all the glass would result in the greenhouse temperature being the same as the outside. If, in the real world the removal of a proportion of the greenhouse gases occurred, more radiation from the Earth would reach space without hindrance and the system would cool down. Removal of all the greenhouse gases would reduce the temperature of the surface to that of the emission temperature; 255 K.

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Is the greenhouse effect observable?

The answer is yes and no! The total greenhouse effect that causes the Earth’s surface to be 33-34°C warmer than it would be in the absence of any of the greenhouse gases is certainly observable, we enjoy it and life would not exist without it. The contentious matter is the possible further warming that is associated with the CO2 that is produced by the burning of fossil fuels. This is the cause of most arguments between knowledgeable sceptics and the IPCC. It also forms the basis of uninformed criticism. The IPCC claim that most of the warming that occurred in the 20th century was caused by the increase in the atmospheric concentration of CO2 and that the observed increase in temperature of the Earth’s surface of 0.7 ± 0.2°C was understandable. Our criticism is that the calculations of the effect of the CO2 change depended upon a greater sensitivity of the atmosphere to such changes. The IPCC regard the effect of doubling the atmospheric concentration of CO2 from the pre-industrial value of 285 ppmv to be roughly four times larger than estimates made from real events such as the Mount Pinatubo volcanic eruption of 1991. They claim that the enhancement of the greenhouse effect due to fossil fuel burning is discernible because of their possible error in using a sensitivity value which is too large. If, on the other hand, the sensitivity is considerably lower than that used by the IPCC the effect would not be discernible amongst the ‘noisy’ temperature records that have been recorded.

Much discussion is given to the very recent observations of temperature, the ones since 1997 as shown in the diagram kept up-to-date on the Breaking News page (reproduced below).

GLOBAL COOLING?

The global temperature has not exceeded the 1998 value since that year and the trend [from satellite and terrestrial data] is one of cooling. Various people and organizations have been vociferously claiming that the atmosphere/surface system is in a cooling phase that 'disproves' the connection with rising CO2 concentrations, the global temperature did rise somewhat in 2009. The graph shows the Hadley Centre values and those from the UAH satellite. The data are plotted on the IPCC predictions which are clearly significantly higher than those observed since 2005.

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The peak anomaly in February 1998 [0.752°C] was thought to be due mainly to the severe El Niño Southern Oscillation of that year. Soon after, the temperature anomaly in June 1999 was -0.137°C and in May 2008 it was -0.18°C. Interestingly, the value for the anomaly in April 1979, in the first full year of satellite observations the anomaly was -0.166°C. As they say in Lancashire: ‘providing there’s no change, things will stay just the same’! Considering that the global temperature anomaly has changed from a peak of +0.75°C in 1998 to -0.18°C in May 2008 makes the global temperature change as measured by the irregularly placed thermometers around the world of 0.7 ± 0.2°C over the 20th century seem of little importance or significance.

Statistics of the monthly satellite temperature anomalies over 39 years show that their standard deviation is 0.21°C. Regression analysis shows that the trend is ~0.13°C per decade. The trend lacks significance. There is no sign of any continual upward warming from the fossil fuel burning, but if this is small it would not matter if the global temperature was showing an upward or downward trend or even showing no trend at all. It would not be evident in the ‘noise’ of the measurements. This does not discourage some critics who are now claiming that the global temperature is decreasing and therefore there cannot be any effect from fossil fuel burning. They are wrong. It does seem as though the potential warming is small, but according to physics, it can’t be zero. If the IPCC sensitivity value is anywhere near the correct value, then a factor is operating to more than cancel out the predicted warming that we really know nothing about. It might be that the fossil fuel burning signal will never be discerned.

3. Distortions of science or deliberate misunderstanding

In their misguided attempts to destroy the theory of the anthropogenic greenhouse effect - the enhancement of the greenhouse effect by the burning of fossil fuels and from deforestation - some people distort the underlying science either through misunderstanding it or by deliberately misunderstanding it. Such attempts to destroy a theory are bound to fail except that they might sway the opinions of those who have a bias towards the rejection of the ideas of man-made global warming.

Some examples of general rejection or ignorance of science follow from the quotation by one of us (JB).

"From a consideration of the physics it is clear that an increase in CO2 concentration in the atmosphere will cause warming."

‘Then why doesn't it? The record shows exactly the opposite. Nobody has shown me any evidence otherwise. It appears the physics is wrong, but there seems to be such blind acceptance’.

‘How about the physics being wrong????? Can't possibly entertain that idea can we’?

‘The laws of physics are not evidence. The fact that temperature increases before CO2 is evidence’.

‘In other words there is absolutely no evidence to support the argument that CO2 and especially the human portion is causing warming at all. You can make all the abstract physics and law arguments you want but until you can provide evidence that contradicts the existing evidence then there is clearly something wrong with them. It is the blind faith of science as a religion’.

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Our comment: There is considerable misunderstanding of the ice-core records that do show that ~800 years after a temperature rise following an ice-age the concentration of CO2 increases. Not even the possibly exaggerated general circulation models can explain the ending of an ice-age by the appearance of large amounts of CO2. They end by various possible mechanisms. A change in the Earth’s orbital characteristics might increase the value of solar input to the Earth. Volcanic activity could deposit material on the snow/ice coverage that alters the planet’s albedo; the fraction of solar radiation reflected by the system. If this is the case the planet would warm up and this would have the consequence of releasing CO2 from the oceans and increasing the amount of water vapour in the lower atmosphere. This would, in consequence warm the system by the greenhouse effect and release more CO2 and water vapour.

In the case of the increasing CO2 concentration since the pre-industrial period which fossil fuel burning has caused, to explain the measured increase in concentration would need a temperature increase of ~5°C and this has not happened, not even 800 years ago! There is incredulity/misunderstanding/refusal to understand that there are two interactions between temperature change and change in CO2 concentration. In an ice-age the CO2 concentration is low, maybe 180 ppmv and that goes along with the low temperature. The absorption curve shows that an increase in CO2 concentration starting at 180 ppmv would be more significant than one starting at 280 ppmv because of the logarithmic nature of the absorption process. Again, we emphasize that the main bone of contention in the greenhouse debate is centered on the atmospheric sensitivity to CO2 concentration changes, the IPCC values exaggerating the possible future temperature.

So, the addition of CO2 to the atmosphere can cause a temperature change [the greenhouse effect] and the ice-core data do not falsify the argument, rather they support it.

Some deprecation from those that do understand the subject:

‘…climate is a generalist study but we live in a world of glorified specialization’.

‘Are modelers scientists – or merely technicians? They are technicians most of who come to climate through mathematics and then computer modeling’.

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Nit-picking and Popper’s principle of falsification

Karl Popper enunciated his principle of falsification in the 1930s, encapsulated by: The theory that ‘all swans are white’ could never be proved by observing all swans for ever, but could be disproved by the appearance of one black swan. This is the case, but some determined adherents of the theory would say that the black swan was not a swan, so there is no falsification. Another ploy of adherents to a theory is to doubt any data that might be used in developing the theory. Popper was keen to point out that the best way of countering a theory was to go to some lengths to bolster the theory by all proper means to identify its strengths before ‘putting the boot in’. Nit-picking does not count. This activity consists in finding a small error in the theory and following the argument: there is an error in this theory, therefore the whole thing is wrong. This kind of exaggeration and illogic was frowned upon by Popper, not surprisingly. Most scientific theories have sufficient small errors that could be pounced upon by a nit-picker and therefore falsified to the nit-picker and like-minded people, but to nobody else.

There is an absence of nits to pick in the physics of the greenhouse effect, but there are many incorporated in the various models. The fact that the twenty or so models all claiming to incorporate the same physics produce different results for temperature changes, cloud cover and rainfall indicates that something is wrong. These are early days in the development of climate models and it is expected that they will become more believable in the future. The development of the theory of chemical bonding, based on quantum mechanics, is now very good for smallish molecules, but not perfect. It began in the late 1920s and is still under development. There were errors of some magnitude in the early days. For instance, one programme was given the task of describing the compound silver chloride. It concluded that the compound was a green gas! It is an off-white solid. Nit-pickers would have claimed that the theory was wrong, but it was the model that was faulty and in modern times such programmes are used by pharmaceutical companies to predict drug function and applicability. Beware! Stick to the Scottish liquid.

Distortions of science

There are examples of science being misused and even distorted by people who have decided for reasons best known to themselves that the enhancement of global warming caused by the burning of fossil fuels is impossible. There are examples of statements such as:

Each collision will transfer a half of the difference of the energy, if a perfect exchange happens, which is not always the case. So, two molecules will equilibrate, if conditions are correct, and one will cool and the other will warm by 50% of the difference.

Our comment: This violates the 2nd law of thermodynamics [it would mean that all molecules in an assembly would have the same energy, zero translational entropy] and is opposite to what is observed with respect to the Maxwell-Boltzmann distribution of molecular velocities.

If you have two equal volumes of air at the same temperature, one with and one without gh gases, then it is intuitively obvious that the one that can radiate will cool the fastest. That characteristic, applied to the atmosphere, holds true. It has to – by definition, a radiative gas will cool faster than a non-radiative gas.

Our comment: Yes, and it will warm up when bathed in suitable radiation, i.e., that which is absorbed by the gh gases.

The most obvious claim is that gh gases raise the average temperature of earth by 33K. If that were so, then you would cool when you walked under a protective shield at night, just as you do when you walk into shade during the day.

Our comment: This ignores the fact that the ‘protective shield’ will radiate just like the atmosphere since it will be at the same temperature.

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It is not possible for gh gases to ‘heat’ the inert molecules around them. It sounds possible to say that gh molecules warm the atmosphere, but in fact it is the other way around….whichever substance is most abundant will control the temperature of the other. So, at 99.9% inert gases, they will control the temperature of the 0.1% gh gas content. The gh molecules will radiate and cool. The gh molecules will be struck by warmer molecules and then they will radiate. The presence of gh gases is a cooling factor rather than a heating one, in the atmosphere.

Our comment: The gh gases warm the atmosphere by absorbing terrestrial IR radiation and most of the energy absorbed is transferred to the bulk atmosphere by collisional processes. It is true that in the higher part of the atmosphere that radiation emitted by the gh gases reaches space and assists the cooling process. If this were not the case the Earth would be a hot cauldron and the seas would run dry!.

GH molecules represent a small, but real, cooling influence.

Our comment: As above, they do contribute to the passage of radiation to space, but they also play a very important part in warming the atmosphere and the Earth’s surface.

Inert molecules actually trap energy – once they are heated, if they don’t collide with something, they don’t lose their energy.

Our comment: The radiatively inactive molecules in the Earth’s atmosphere act as a heat reservoir. They gain energy by collisions with molecules that either have greater kinetic energy or are vibrationally/rotationally excited. They lose energy by collisions and if these collisions are with gh gas molecules these can become vibrationally/rotationally excited and in the higher atmosphere can emit photons, some of which escape to space.

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An attempt to falsify the science of global warming

A paper by Gerhard Gerlich and Ralf D. Tscheuschner (arXiv:0707.1161v3 [physics.ao-ph] 11 Sep 2007) entitled Falsification Of The Atmospheric CO2 Greenhouse Effects Within The Frame Of Physics has the following abstract.

The atmospheric greenhouse effect, an idea that authors trace back to the traditional works of Fourier 1824, Tyndall 1861, and Arrhenius 1896, and which is still supported in global climatology, essentially describes a fictitious mechanism, in which a planetary atmosphere acts as a heat pump driven by an environment that is radiatively interacting with but radiatively equilibrated to the atmospheric system. According to the second law of thermodynamics such a planetary machine can never exist. Nevertheless, in almost all texts of global climatology and in a widespread secondary literature it is taken for granted that such mechanism is real and stands on a firm scientific foundation. In this paper the popular conjecture is analyzed and the underlying physical principles are clarified. By showing that (a) there are no common physical laws between the warming phenomenon in glass houses and the fictitious atmospheric greenhouse effects, (b) there are no calculations to determine an average surface temperature of a planet, (c) the frequently mentioned diverence of 33°C is a meaningless number calculated wrongly, (d) the formulas of cavity radiation are used inappropriately, (e) the assumption of a radiative balance is unphysical, (f) thermal conductivity and friction must not be set to zero, the atmospheric greenhouse conjecture is falsified.

Our comment: The arguments used in the paper are false and the individual points have been addressed either in this section or on other sections of the website.

This paper was followed by a complete rejection of its conclusions in a paper by Arthur P. Smith (arXiv:0802.4324v1 [physics.ao-ph] 29 Feb 2008) entitled Proof of the Atmospheric Greenhouse Effect, with the abstract:
A recently advanced argument against the atmospheric greenhouse effect is refuted. A planet without an infrared absorbing atmosphere is mathematically constrained to have an average temperature less than or equal to the effective radiating temperature. Observed parameters for Earth prove that without infrared absorption by the atmosphere, the average temperature of Earth’s surface would be at least 33 K lower than what is observed.

Our comment: The Smith paper shows without doubt that (a) a non-rotating planet with a transparent atmosphere would have an average surface temperature of ~145 K [-128°C], (b) a rotating planet with a transparent atmosphere would be warmer at ~178 K [-95°C], (c) a rotating planet with a partially absorbing atmosphere (fraction of terrestrial IR radiation absorbed = 0.77) is 33°C warmer than its effective radiative temperature, and (d) for the same planet with complete absorption of terrestrial IR radiation would have an average temperature of ~303 K [30°C], with no runaway.

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4. Incredulity

Many people express opinions such as: ‘Those microscopically small number of gh molecules are NOT going to heat a solid earth surface. It blows my mind to think that anyone actually believes that’.

This widely held opinion occurs because the presence of a greenhouse gas such as CO2 with a concentration of 380 ppmv is not easily sensed, a spectrophotometer is required and they cost money. Those who have such machines or those who can deal with the scientific literature do understand that such small concentrations can have significant effects on the fraction of terrestrial radiation absorbed by the gh gases.

Craig Bohren suggests such people try 380 ppmv of arsenic oxide in their tea! We would encourage a safer experiment. Take a jug containing a litre of water. The water is transparent to visible radiation. But then add a few drops of milk and stir. This is equivalent of diluting the milk by a factor of about 5000, i.e. the milk ‘concentration’ is 500 ppmv. Is there any visible effect? A 0.001 molar solution of potassium permanganate is deep purple, its concentration is only 18 ppm. It’s much the same with the atmosphere which has ~380 ppmv of CO2. The effect of the gas is to increase the opacity of the atmosphere to infrared radiation and to hinder the progress of radiation from the surface on its attempt to reach space. The hindering allows the atmosphere to become warmer and as a warmer entity the atmosphere radiates more energy as IR radiation, some of which causes the Earth’s surface to become warmer. This is the greenhouse effect. The warming allows the Earth again to emit just the correct amount of radiation to space that preserves the radiative balance between the sunlight absorbed by the system and the total amount of infrared radiation emitted to space.

Concluding remarks

Whatever the category of scepticism people find themselves in there are widespread attributions of fraud, conspiracy and selectivity of data and such claims are to be resisted. Many scientists and groups of scientists in several disciplines are doing painstaking work and reporting their results in peer-reviewed journals. Individual papers may very well come to incorrect or speculative conclusions, but these are usually sorted out within a relatively short time. It is part of the scientific process to speculate and put forward possible explanations for new results and some of these are almost bound to be in error. Most valid scepticism is directed at those papers which are concerned with climate modeling and, in particular, those that portray the future. The IPCC reports do make reference to all the work published in the time after the previous one and do attempt to summarize the various findings. In this there is evidence of some bias towards basing all future changes in climate on the greenhouse effect to the exclusion of natural forcings.

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