is attributed to human activity – the so-called anthropogenic CO2. However, the actual total amount of CO2 in the atmosphere is still tiny. It is estimated that, if no new CO2 were added to the atmosphere, it would take only five years to reduce its level below what would sustain plant life; if plant life did adapt and continue at this low level of CO2, all the gas would be used up in about seven or eight years. The CO2 level found in our blood is essential to our wellbeing. A sudden reduction would cause many people to feel sick and faint and to develop headaches due to a constriction in the blood vessels supplying vital organs. We are physiologically far better adapted to dealing with a rise in CO2 than with an acute reduction. This may be an evolutionary footprint reflecting the fact that animal evolution occurred during periods of higher, rather than lower, atmospheric CO2.
To regard CO2 as a pollutant is dangerous nonsense. It is less toxic than oxygen and it is present in the atmosphere at levels that are historically low. The problem that has to be faced is that we do not know with any degree of certainty what would happen if the levels were to be increased dramatically over the next century.
* Although these measurements have been fairly consistent and reproducible it is impossible to verify their absolute accuracy as there is no standard measurement with which they can be compared. It is inevitable that some CO2, which is a soluble gas, will leach out of a bubble into ice, albeit at a very slow rate at these low temperatures. The magnitude of this effect must increase with time. What we can say with some certainty is that the levels of CO2 recorded in these bubbles is the very lowest that would have been possible. They probably underestimate the actual values that were present all those years ago. It is probable that the actual CO2 at the time they were formed would have been higher. Similar criticism can be levied against estimates of the temperature that pertained millions of years ago. These are not absolute measurements but are relative.
STANLEY FELDMAN
DOGMA
Man is destroying the planet.
IF ONE ACCEPTS that the world has become warmer over the past century and this is a threat to our way of life, then it is necessary to examine the evidence that this is due to an increase in the amount of atmospheric CO2 produced by man.
The only compelling evidence that CO2 is linked to the recent rise in the Earth’s temperature due to its greenhouse-gas effect comes from the studies of ice-core samples drilled in the ice caps. Although this may seem a somewhat inexact science, the picture they reveal is surprisingly reproducible. The temperatures at various depths can be measured and recorded, and the CO2 content of the bubbles of trapped gas, while subject to a little variation, is also remarkably consistent. The dating of the samples is liable to small errors as the decay rate of the various isotopes measured can be influenced by outside events. Although these measurements cannot be considered definitive, our confidence in them is greatly enhanced because they have proved to be reproducible in different ice cores from varying sites made by different investigators. However, one should be cautious in interpreting these values as accurately reflecting the actual temperatures and CO2 content of the atmosphere at the time the bubbles became trapped in the ice, since it is probable that some CO2 will have leached out, over thousands of years, even into frozen ice.
The results of these investigations have been presented, in various forms, for up to 50 million years, but over 500,000 years their accuracy becomes increasingly questionable. It is the general close parallel, the casual association between the rise in temperature and the rise in CO2 over the past 10,000 years, that has led to the present persuasion that the temperature change is driven by atmospheric CO2. However, close examination of the samples from the Vostok Lake area of Antarctica over this period shows that in many instances the temperature increase occurred some 600 to 1000 years before the increase in CO2.
Exactly the same association with temperature is also found when one examines the effect of the Milankovitch cycles (explained in Chapter 1). It is accepted that the periods of warm weather produced during these effects are due to the skewing of the Earth’s trajectory around the sun so that it comes to be closer to the source of the sun’s heat and is nothing to do with anthropogenic activity. It has been clearly demonstrated that, during each of the predicted Milankovitch warm spells, the CO2 in the atmosphere increases. It is evident that a rise in CO2 in this case is a consequence of the warming during these cycles and not the cause. We are at present coming to the end of a warm cycle that probably started at the end of the Little Ice Age some 400 years ago.
There is good evidence suggesting that the cause of some of the global warming is due to an increase in solar irradiance. There is a close correlation between solar activity and the atmospheric temperature in the Arctic between 1880 and 2000 (see Figure 4.1a). This association is much closer than that between temperature and CO2 during the same period (see Figures 4.1a and 4.1b).
Figure 4.1a: Global warming and CO2 in the atmosphere over the past 120 years (source: W Soon)
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
