The decision by ABC TV to show a shortened version of the Great Global Warming Swindle documentary, which challenges the majority view that global warming is primarily caused by human activity, has produced angry responses in various quarters. There is clearly an attempt to discredit the documentary even before it is shown.
Journalist and academic George Monbiot recently claimed the documentary relies on people "whose findings have been proven wrong" (The Age, 25 May).
I have now had the opportunity to view this documentary and, as a meteorologist with qualifications and experience in assessing the factors influencing climate, I can say that this claim is not correct.
In reality, the 15 or so interviewed are all highly-qualified scientists or journalists with scientific credentials and experience. Their arguments strongly contradict what they see as a visionary perception of global warming being caused by anthropogenic activity and requiring a solution at the global level.
Contrary to Monbiot's assertion, the factual material used in support of their arguments has not been proven wrong. His reaction reflects concern that the arguments by the interviewees (and many others) are having an increasing influence and that the elitist claims of a scientific consensus can no longer be sustained.
Let me respond to specific points made by Monbiot.
He argues that the film's main contention is that the rise in global temperatures is caused not by greenhouse gases but by changes in the sun's activity. True, it does identify strong correlations between solar activity and global mean temperature and that a plausible scenario exists, suggesting global temperature variations are a natural response to solar activity.
But the key point of the film is not the solar/temperature link. Rather, it is that there is only poor correlation between CO2 concentrations and global mean temperature. This conclusion, of course, undermines the importance of CO2 as a climate-forcing agent.
Monbiot seeks to discredit the correlation between solar activity and temperatures, as suggested in the film based on analyses by Danish atmospheric physicist Dr Eigil Friis-Christensen, by pointing to major revisions Friis-Christensen has made to his theoretical framework. Such revisions are not unusual in advancing understanding of complex scientific problems. While Friis-Christensen recognises his theory on process needs further refining, the fact remains that the evidence is of a strong solar-global temperature correlation, unlike the relatively poor correlation between CO2 and temperature.
A further claim by Monbiot is that the film neglects to mention that Professor Christy's claim of discrepancies between temperatures at the Earth's surface and temperatures in the troposphere (the lower and middle atmosphere) was shown to be wrong, and acknowledged as such by Christy himself. This is not so. Christy has acknowledged refinements to the method used for analysing satellite data developed by others and reprocessed the data. His later analyses are by no means discredited. They are quoted by the IPCC and continue to show that the global atmospheric temperature rise is less than at the surface.
The basic point here is that, if temperature data shows substantial warming on the earth's surface but little or no such warming above the surface, it challenges the idea of human-induced global warming. In fact, contrary to computer models, satellite and radiosonde (weather-balloon) data only show warming over the middle and high latitudes of the Northern Hemisphere. In contrast with computer model projections of warming, there is absolutely no atmospheric temperature trend over Southern Hemisphere middle to higher latitudes according to satellite and radiosonde data. Over tropical regions any trend is masked by the variability associated with El Nino.
Monbiot also refers to the claim by oceanographer Carl Wunsch that he was misrepresented in the film. Wunsch's comments about the performance of computer models were not unusual. Importantly, Wunsch has publicly stated (in opposition to alarmist predictions that global warming will stop the Gulf Stream and cause the onset of a new ice age, as depicted in the film, The Day After Tomorrow) that the Gulf Stream will not stop until the winds stop blowing and the earth stops rotating!
Monbiot is correct in pointing out that, "to form a balanced, scientific view, you have to consider all the evidence, on both sides of the question". It is a pity that he and some like him do not observe the dictum.
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