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      Figure 4.1b: Global warming and sunspot activity over the past 150 years (source: W Soon)

      As the rate of CO₂ production has accelerated, it has led the International Panel on Climate Change (IPCC) in 2001 to predict, using mathematical models, that, without curbing the rate of CO₂ production, Earth’s temperature will increase by between 1.4 and 4.2ºC in the next hundred years. The assumptions made in these predictions include a continuously accelerating increase in population, no adaptive responses – such as a switch to alternative energy sources – and an accelerating growth in energy demand per capita. Using their figures and the presumption that it is CO₂ that is causing climate change, the mean of the most optimistic and the most pessimistic of the reasonable forecasts by the IPCC is that we may expect a rise in temperature by the beginning of 2100 of 2.8ºC. This increase in temperature is about the same as the difference experienced between those living in London and those in the surrounding countryside and would render our climate similar to that of the South of France. Inevitably, it will be the coldest part of the day that will be most affected by this rise in temperature. The warmest days will not necessarily get much warmer. It will hardly cause the end of the world.

      However, there are inherent problems in accepting the importance of the role of CO₂ in producing climate change. Apart from experiments carried out in the laboratory, the main evidence in support of the theory comes from one type of investigation – the ice-core samples. Associations of this kind between two events do not meet the criteria required for scientific proof. For there to be any confidence in the hypothesis, it is necessary to demonstrate either that lowering the CO₂ in the atmosphere produces cooling or raising it causes warming. Unfortunately, it is impossible to lower the CO₂ acutely but there is ample evidence that the world has cooled when the CO₂ in the atmosphere has been very much higher.

      Medieval warming

      It is generally accepted that the Earth warmed up significantly more during medieval times than during the 20th century and that it cooled down considerably during the Little Ice Age of the 16th and 17th centuries, without any anthropogenic event that would have affected the CO₂. Between 1940 and 1975, there was a significant fall in recorded temperatures at a time of intense industrial activity associated with the war and post-war reconstruction. In the last decade, the Meteorological Office Hadley Centre has confirmed that satellite records show that Earth has cooled by about 0.4ºC, although the CO₂ level has increased by 0.004 per cent.

      Although not absolute disproof, these well-documented events throw grave doubt on the validity of the hypothesis. Until there is proven confirmation of the relationship between CO₂ and the Earth’s temperature, it remains an unproven theory.

      If future technical developments show there to be a fault in the analysis of the ice-core samples that have been so readily accepted as proof of the role of CO₂ in global warming, then the whole scheme will be thrown into disrepute. So far, alternative methods of analysis of the age of the gases contained in the trapped bubble have supported the initial findings. The results appear to be reproducible. The problem with the ice-core investigations is that in some instances the rise in temperature found in these samples appears to precede the increase in CO₂. Many of the ice-core samples from around the Vostok Lake in eastern Antarctica showed that warming actually preceded the rise in CO₂, sometimes by 600 years. This effect had been noted in other ice-core samples but it is concealed by the compression of the timescale (x axis) in most presentations. Although various explanations of these findings, based on water–CO₂ feedback mechanisms (the Claussius–Clapeyron equation), have been offered by the CO₂ theorists, they are mathematically improbable and scientifically implausible. It remains absolutely impossible to explain how an increase in CO₂ could be the cause of a rise in temperature that occurred hundreds of years earlier. This finding, if proven beyond reasonable doubt in a single site, would constitute positive disproof of the theory that the increase in temperature is the result of the rise in CO₂. The rise in CO₂ found after a rise in temperature can be readily explained, as any increase in the temperature of the oceans would be expected to drive off dissolved CO₂. However, as they are a huge depository for energy this process occurs only slowly.

      Equivocal evidence

      There are many reasons why one cannot blindly accept the belief that anthropogenic CO₂ is the cause of global warming without reservation. The knowledge that the Earth has cooled in the past when the CO₂ levels in the atmosphere were many times higher than at present challenges the certainty with which the opinion that climate change is CO₂-driven is being presented. It suggests that those who tell us that the case is proven are wrong. The evidence is at best equivocal and our approach to the theory must be more open-minded.

      There is little doubt that the world has warmed up over the past 50 years and that the rate of warming is a little greater than that seen previously, even if the extent is less than that which has occurred over other periods. Although it is possible to explain the rise in temperature by cyclical changes that occur naturally, it is the rate of change that has led to the speculation that some, if not all, of this is due to the extra CO₂ released by industrial activity. Certainly CO₂ is a greenhouse gas but the evidence that the extra CO₂ produced by industrialisation is the cause of the 0.6–0.8ºC of global warming seen over the past 100 years, or that it presages a future calamity, is insufficient to be convincing.

      Evidence for and against human activity as the cause of global warming

       For

      • A general correlation between temperature and CO₂ levels in ice-core samples going back 600 thousand years.

      • An increase in human activity, CO₂ levels (0.008 per cent) and temperature (0.6–0.8ºC) has occurred over the past hundred years.

      • The demonstration that CO₂ is a potent greenhouse gas. It is not unreasonable, therefore, to believe that more CO₂ in the atmosphere will result in a reduction in the amount of the Earth’s heat that is lost into space.

       Against

      • The correlation between CO₂ and temperature demonstrated in ice-core samples shows that in some instances the rise in temperature occurs before the increase in CO₂, often by about 600 to 1000 years.

      • Earth was believed to be at its coldest 600 million years ago (Snowball Earth) when the concentration of CO₂ in the atmosphere was up to 100 times

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