The Hot Topic by Gabrielle Walker & Sir David King

Bloomsbury Publishing 2008, £9.99 [£5.99 from Amazon]

 

This criticism applies only to the major points that need to be discussed.

            The front cover has a quote from Al Gore which is very disappointing, coming from a non-scientist whose presentations about global warming contain many mistakes:

 

‘In a world full of misinformation, The Hot Topic is a beacon of clarity.’

           

The book is divided into three sections, one about The Problem, followed by Technological Solutions and ending with Political Solutions. There is also an Appendix labelled Climate Myths, Half-truths and Misconceptions.

            In the first chapter entitled Warming World, there is a brief description of the methods used to measure temperatures and then repeats the common claim that ‘The hottest years in the entire instrumental record [since 1850] were 1998 and 2005. The years 2002, 2003 and 2004 respectively were 3^rd, 4^th and 5^th on record.’ There is no argument about 1998; that stands out in every record. The satellite record, established since 1979, has the mean temperature of 2005 about 0.2°C cooler than 1998. What is not mentioned in the chapter is that all temperature records now show a decreasing trend since 1998 and early results for the first three months of 2008 show that the global mean temperature is decreasing in spite of the ever-increasing concentration of CO₂ in the atmosphere. Certainly, ten years is a very short period for trends to be very significant, but we should be given all the results to assist in a proper discussion. The IPCC graph given ends at 2005 and does not show the 1998 peak value. There are better representations available.

            The authors state that ‘The latest report from the IPCC [2007] described the warming of the past few decades as ‘unequivocal’. There is no room for doubt. The world is certainly heating up. What we need to know next is why’. We certainly do need to know why and the next sections proceed to supply the answers.

            The next section describes the history and the nature of the greenhouse effect and points out that the planet is about 30°C warmer than it would be without the presence of the greenhouse gases. This is the case and what we need to know is how much more warming is or will be caused by our burning large quantities of fossil fuels. With regard to the amount of greenhouse gases in the air, the authors claim that ‘humans have already managed to double [my emphasis] the amount …in the air.’ I think this refers to the increases in all the greenhouse gases concentrations which can be reduced to the equivalent of an increase of CO₂ of some 430 ppmv; an increase of ~50%. The observed increase in CO₂ is ~35%. Neither figures show that greenhouse concentrations have doubled and the authors come to an alternative conclusion at the end of the chapter that we have effectively added about 60% to the value. I hope you don’t regard this as nit-picking because these figures are crucial to the operation of all the various models of the climate and to the calculations of the extra radiative forcing that increasing greenhouse gas concentrations are supposed to cause.

            Chapter 1 contains the fundamentals of the main argument put forward by proper sceptics. Quoted from page 18: ‘And second, by trapping heat themselves, these greenhouse gases also have an indirect effect on the amount of water vapour in the air. Warmer air can soak up more water, and warmer lakes, rivers and seas can evaporate more easily into the atmosphere. The upshot of these two effects [direct warming by greenhouse gases and the one described in the quote] is that if you heat the air a little by adding CO₂, it then takes up much more water vapour. This new water acts as a greenhouse gas in its own right and heats the air up even more, roughly doubling the effect the greenhouse gases would have had if they acted alone.’

            There is nothing wrong with the physics of this positive feedback argument. But there is no mention of any negative feedback process that would counter the effect and lead to the stabilization of the atmosphere. If only the positive feedback were to operate we would have a Sorcerer’s Apprentice situation where the whole warming business would be out of control and the seas would boil away! This does not happen and the reason is not hard to understand. The negative feedback is produced by the non-radiative property of water alluded to in the quotation of evaporating more in a warmer world. The evaporation itself constitutes a cooling of the surface and essentially acts as the world’s thermostat.

            The admittedly simple energy budget model of the atmosphere/surface system described on this website suffices to demonstrate what might be the case if water did not have the possibility of cooling the surface by evaporation. The surface temperature of 288.8 K would rise to 301 K without the cooling effects of water. The extra radiative forcing arising from the doubling of CO₂ would cause an increase of surface temperature of 2.6 K assuming it to be doubled by the positive radiative feedback from the extra water vapour, but this is reduced to 1.5 K if the water cooling is allowed to operate. These figures are rough-and-ready, but indicate the significant effect of the water cooling feedback which seems to be absent from the more sophisticated models used to predict future climate.

Observations since 1979 have shown that the southern hemisphere, with its 81% covering by oceans has shown an almost zero temperature trend as opposed to the northern hemisphere with only 61% coverage by water. The warming trends are mainly confined to the northern hemisphere where most of the fossil fuel emissions occur and lead to the suggestion that warming is not global, but regional where greater local concentrations of CO₂ can produce ‘instant’ warming that is recorded and contributes a greater weight to the global mean that it might do if the gas were allowed to mix fully. Just a thought.

            Towards the end of the chapter there is a mixture of hyperbole and reasonableness. The Keeling curve, the plot of the ever-rising concentration of atmospheric CO₂ at Mauna Loa, Hawaii, is described as ‘sky-rocketing,’ but in the next sentence becomes an increase of nearly 40%.

            The chapter ends with the sentence, ‘When you’re looking for an explanation for the recent heating up of the Earth, carbon dioxide and its sister greenhouse gases are clearly the likeliest culprits’. The die is cast, then, the authors have really decided on the answer to the question, neglecting all the possible alternative effects that could influence climate change.

            But wait! The second chapter deals with ‘Whodunnit.’ It describes four ways in which the Earth might heat up. One is to increase the amount of sunlight. It is fairly certain that the solar ‘constant’ has been constant within a few tenths of one percent for a long time. The constant is the average solar radiation falling on a planar square metre at right angles to the sun’s direction. This varies by ±3% as the Earth follows its slightly non-circular annual path around the sun. But, this average value has changed very little and cannot be the reason for the observed heating of the Earth. The authors do mix this point up with that concerning the effect of the sunspot cycles on the heating of the Earth. They discuss the cosmic ray theory very briefly and reject it since ‘lately the numbers of cosmic rays has been falling although the temperature has risen.’ The problem with this reasoning is that, for the last ten years the temperature of the surface and the lower atmosphere has been falling.

            The second method for heating the Earth is to arrange for more of the incoming sunlight to be reflected. Changes in cloud cover are dismissed in a single sentence and that leaves aerosols to cause the heating, if possible. We know that aerosols can cause cooling because they do reflect sunlight more than ordinary clouds do. This is indeed the supposed reason for the cooling of the atmosphere/surface system between 1940 and 1976, the trend which had so climatologists predicting the beginning of the next ice age. When temperature started to rise again after 1976 the aerosol cooling idea came to their rescue. Although there was a world movement to clean up industrial output of sulphur dioxide, the vast majority of the aerosol content of the atmosphere originates in the emissions of dimethylsulfoxide from phytoplankton and is quite natural. The authors report the findings of the Mount Pinatubo eruption in 1991 which apparently caused the Earth to cool down by 0.5°C, a cooling which lasted a few years. They suggest that the reason for recent heating cannot be due to the diminished frequency of volcanic emissions because since 1956 the world’s volcanoes have resumed their activity after a lull between 1915 and 1956.

            The third method for heating the Earth is to alter the amount of energy falling on the system by slight changes in orbital characteristics, e.g., as with the Milkanovitch cycles based upon the wobbles of the Earth’s rotation axis. We can do nothing about these matters, but the authors suggest that we might be going through a natural warm phase. The possibility is discarded and they reckon that the nearest thing to a natural cycle that causes temperature changes is the El Niño/Southern Oscillation, but that alas only lasts a few years, so…

            We come to the authors much preferred method of heating the Earth; the trapping of more infrared radiation as it tries to leave, otherwise known as the greenhouse effect.

            There is an interesting aside about the finding in the ice-core data that there are lags before CO₂ concentration changes catch up with temperature changes. As they say, this allows some sceptics to argue that CO₂ can never be responsible for temperature changes, rather the reverse is the case and changes in CO₂ concentrations follow those in mean temperatures. They give a possible explanation for the apparent discrepancy in terms of ‘other events’ being responsible for a change in temperature, e.g., the descent into an ice age could be caused by a Milkanovitch event leading to a little less sunlight coming to Earth. This in turn will cause the land surface to cool down and allow the proliferation of glaciers leading to an increased reflection of solar radiation to space leading to more cooling. This is followed by a reduction in the CO₂ concentration and consequently more cooling occurs. After the first trigger which causes the initial temperature decrease, subsequent events ensure more cooling as more CO₂ dissolves in the oceans leading to further cooling. They claim that after such ‘triggers’ the correlation between CO₂ and temperature changes is very good and imply that the first causes the second. The same argumentation applies to times of increasing temperatures.

            They deal with ‘extra reasons to believe that greenhouse gases are indeed the cause of the recent warming’. One of these is that aerosols, being rained out of the atmosphere relatively quickly don’t seem to count. Their concentration is maintained nevertheless and their effects are pretty constant unless we decide to cool the planet by burning sulphur! On the other hand the greenhouse gases are long-lived. We have the long-held opinion that CO₂ ‘remains in place for more than a century.’ Methane stays for 12 years. The argument, I think, is that they have a long enough residence time to thoroughly mix and to exert their effects globally, hence the term global warming. We do know that the residence time of CO₂ in the atmosphere is about 5 years and that this value is often confused with the half-lifetime of the extra injected CO₂ coming from fossil fuel burning which upsets the natural carbon cycle and which has been estimated to be about 38 years. If this is so, after three half-lives [116 years] there would be 12.5% of the initially injected CO₂ present.

            This seems irrelevant to the ‘global’ warming argument since intrahemispheric mixing of permanent gases takes about three months and interhemispheric [N/S] mixing takes another year. What is becoming increasingly apparent is that the distribution of CO₂ is quite asymmetric to the extent of an excess of ~10 ppmv in the northern hemisphere. Recent observations from the SCIAMACHY satellite system and that known as Carbon Tracker have reinforced this asymmetry and give rise to the thought, expressed above, that the considerably higher CO₂ concentrations in the industrialized regions of the world do have an ‘instant’ warming effect that is measured by the various stations and which translate into an inflated result for the global mean temperature and which in turn is used as evidence for ‘global warming’ and it just might not be as much as is expected or considered to have occurred already.

            The ‘Whodunnit’ chapter ends with the very disappointing statement that ‘The final proof that the greenhouse gases really are the problem comes from atmospheric models of how the air works.’ We know very well that our understanding of the climate is by no means perfect and it is extremely unlikely that any better understanding can be produced by any of the twenty or so models. They all differ considerably in their output and are at an early stage of development, certainly not at the stage where we should consider their predictions as having considerable accuracy. That is not to say that modelling should not be undertaken. After all the main advances in science are made and encompassed in models, e.g., quantum and atomic theory. These latter are much more highly developed than any climate model and they can and are used in predictions that can be either confirmed or denied. The only way a climate model can be established as having significance is to wait for, say, ten years and compare the predictions with reality. So far, predictions from earlier models have been shown to exaggerate their findings and it is one of the sceptics’ main arguments against the current crop of models that the sensitivity of the atmosphere/surface system used is too high, maybe by a factor of four.

            The chapter ends with the answer to ‘Whodunnit’, ‘Wedunnit.’ Also, ‘if anybody tells you differently they either have a vested interest in ignoring scientific arguments or they are fools.’ I hope I’m not a member of either category, but there is a counter argument; if the correct sensitivity were to be used and the computer predictions were more realistic many climate scientists would lose their funding.

Chapters 8 and 9 deal with the various methods of generating power and how we might minimise the wastage of natural resources. These are very straightforward and describe actions that should be followed without the threat of indeterminate climate change.

            The remainder of the book consists of chapters that deal with climate models and their various and different predictions for our future climate and the various dreadful things that might happen to the human race which I will not comment on in detail, but they need to be taken with a large dose of sodium chloride!