The extent of anthropogenic global warming caused by carbon dioxide from the burning of fossil fuels is a controversial and politicised issue and there certainly is no scientific consensus. However, some conclusions (and just as importantly some important gaps) can be listed with a reasonable degree of certainty:
• The concentration of carbon dioxide in the atmosphere is increasing due to combustion of fossil fuels.
• The basic spectroscopy (the science of the interaction of electromagnetic radiation with matter) of the atmosphere and the existence (and critical importance) of the misnamed “greenhouse effect” is beyond doubt, as is the fact that the principal “greenhouse gas” is water vapour, which is responsible for well over 90% of the total effect. However the estimation of the contribution of carbon dioxide is not straightforward due to the non-linearity of absorption with increasing concentration and the fact that the absorption bands of carbon dioxide may already be saturated.
• The climate has always varied and there is evidence that we are passing through a warming period. The measurement of average surface temperatures is not straightforward and personally I consider that the widely observed retreat of mountain glaciers and melting of arctic ice constitute the most significant bits of evidence. The exact degree of warming is uncertain, but it is not unprecedented even in the recorded history.
• Atmospheric carbon dioxide, although present in minute concentration, is not a “pollutant” but the very basis of life and the photosynthesis of carbohydrates by plants (including algi) from carbon dioxide, water and solar radiation, catalysed by pigments such as chlorophyll, is by far the most important process on earth for the continuation of life. What is more, the present concentration of carbon dioxide in the atmosphere is not optimal for plant growth as experiments show that dramatic improvement accompanies increasing amounts of carbon dioxide. It thus appears that the positive effects of increasing the concentration of atmospheric carbon dioxide are better established than the negative (global warming) effects.
You can deduce from the above that I put myself in the “sceptics” rather than in the “alarmist” column as I do not believe that any of the catastrophic predictions are well-based. There is, however, a caveat: the alarmist case has one argument going for it, viz., the so-called “precautionary principle”, which essentially amounts to avoiding risks if potential consequences are dire. This, however always requires a quantitative judgement, as otherwise we would never cross roads, sit in a bus or even get out of bed. My considered judgement in this case is that the climate/anthropogenic carbon dioxide nexus justifies watching and research, but it does not justify the currently proposed expensive, probably unnecessary, disruptive and probably futile measures. And yes, I have a stake in the future: 3 children and 7 grandchildren as well as the rest of mankind.
My scepticism is based on three independent areas of weakness in the alarmists’ case:
Computer modelling. Even a nodding acquaintance with the science of climatology uncovers an obvious problem, viz., that the Earth’s climate is a very complex, imperfectly understood and “chaotic” system. In non-technical language, this means that the climate is subject to numerous influences which act and interact in imperfectly understood ways and where the response to a change in a variable may not be “linear”, i.e., proportional to input. In a situation like this, researchers cannot rely on straightforward calculations – remember the Gas Laws you have enjoyed, or suffered, in High School or Chemistry 101? – and given the difficulty of direct experimentation in this case, they are reduced to computer modelling, which is subject to uncertainty in both the algorithms (how the variables interact) and inputs. If that was not bad enough, the most alarming of the alarmist’s predictions are based on the operation of secondary effects, the so called “feedbacks”. The most obvious one runs as follows: increase in the concentration of carbon dioxide will result in global warming. This will cause an increase in the temperature of the oceans. This in turn will cause a decrease in solubility of carbon dioxide in the oceans, which will give up some of the dissolved carbon dioxide to the atmosphere. This will result in further global warming – you can see where this so-called “positive feedback” leads. However, negative feedbacks are also likely, e.g., an increase in the amount of carbon dioxide is associated with increased cloud cover, which reflects sun’s radiation (higher albedo) and this results in cooling. In sum, computer modelling is a desperate research tool and not the sort of thing one should lightly accept as some sort of cast-iron scientific conclusion.
Credibility. To put it bluntly, the alarmists have made claims which, to put it politely, damage their credibility and we are not talking here about peripheral issues. The most egregious case is the so-called “Hockey Stick” which was a plot of average temperature against time and which purported to demonstrate that the earth’s climate was warming at an unprecedented rate, thus giving a graph of the “Hockey Stick” shape. This formed the very centre of the alarmists’ case and was inter alia just what you saw in Al Gore’s film. It has since been shown, mainly through the work of a Canadian academic Steve McIntyre, that this effect was an artefact and no one has disputed this finding. Well, you might say, anybody can make a mistake. However no Alarmist has conceded that a huge (perhaps fatal) hole has been blown through their arguments – they just threw the Hockey Stick into an Orwellian memory hole but kept their now largely baseless conclusions. Furthermore, we are talking about high-profile people and high-profile institutions.
An even more clear-cut case are the fictitious claims that already global warming has caused an increase in catastrophic events, such as hurricanes, which are tendentious at best and fictitious at worst, as are claims for catastrophic melting of the Antarctic ice sheet (only a very small bit appears to be affected, the bulk of the ice-cover seems to be actually growing).
Data get tendentiously reported as in “the last x years in location z have been the warmest since y” and, worst in my view, successful debunking is never acknowledged. Other data, which are irrelevant (in particular normal variations in the weather) are routinely presented as evidence for global warming and the credulous believe this nonsense because “the evidence is before their eyes”. This goes all the way up to our Prime Minister who has repeatedly connected the recent Australian drought to global warming. Not so, and no serious climatologist claims this – go to the back of the class young Kevin. Equally, the apparent global cooling experienced since 1998 is not a disproof of the global warming theory, even though no such predictions were apparent before its advent in any computer models. Weather and climate are related, but they are certainly not the same thing.
Other data, e.g., the analyses of gases trapped in ice cores, which give a uniquely valuable picture of paleo-climate, get tendentiously reported with inconvenient bits ignored. All in all, by the time the arguments have percolated to the public, they have been heavily “massaged” in favour of the alarmist case. The principal villains here are the media with their irrelevant and downright misleading pictures of draughts, floods, hurricanes and a general weakness for the Hieronymus Bosch style of journalism.
No longer science. Once a subject has become politicised, it becomes difficult to determine “what is the case” which is what scientists normally do and the argument becomes about “making a case” which is what lawyers do. The global warming “debate” is a reductio ad absurdum example of the above and the majority of the alarmists (but not many sceptics) invest their undoubtedly sincere arguments with an unmistakably religious tinge. One of the results of this is a nasty, ad hominem tone they tend to adopt, which is quite justified from their point of view seeing that they are fighting evil.
On purely logical grounds the above 3 weaknesses of the alarmist case (inherent problems with their computer simulations, poor credibility and departure from scientific norms) do not “disprove” their case, although it does appear to weaken it considerably in my view. The problem for a non-specialist (and I include myself in this category) making an independent judgement, is the complexity of climatology: if you get hold of even an unbiased standard work, you will find it indigestible. I suggest two internet sites which have contributed to my scepticism: the most important one is the Climate Debate Daily an offshoot of the well-known Arts and Letters Daily, which simply lists in two parallel columns the alarmists’ and sceptics’ publications as they appear without any comment. Clearly, one could accuse any such listings of a selection bias either way, but in this case the sheer number of items makes this unlikely. The offerings are of variable quality and accessibility to laypeople, but any reader with a general familiarity with scientific literature can judge the “weight” of the individual entries. One overall impression is striking: the sceptics’ papers are full of graphs, maps, math, descriptions of observational methods, etc., while the alarmists’ papers appear to be more emotion-charged and devoted to the descriptions of various catastrophic scenarios rather than to arguments demonstrating how these scenarios would come about. Climate Debate Daily also lists numerous valuable links for both views. If you are willing to concentrate just a little, I also suggest you consult the site JunkScience edited by Steve Molloy and look for The Real Inconvenient Truth, which has some discussion of the basic physics involved in the “greenhouse” effect among some other reasonably digestible science. If you scour the internet you will also realise that whatever is the case, no scientific consensus exists. You will also discover thousands of alarmists’ postings dismissing sceptics for “being on the pay of oil companies” etc., a nice example of the alarmists’ quasi religious fervour. Best of luck.
Sev Sternhell is Emeritus Professor of Chemistry at the University of Sydney. His research interests have been in organic chemistry and molecular engineering. He served on the chemistry sub-panel of Australian Research Council and is the author of numerous research publications.