satellites. Over the past eight or nine years the measurements from ERS1 and ERS2 (European remote sensing satellites) have demonstrated that there has been a rise in sea level of 0.5–0.1mm a year (within the margin of scientific error) and that the increase is not accelerating! Although there is some evidence that the levels of the oceans have risen slowly, possibly by about 5cm over the past 150 years, it is a process that started long before industrialisation produced an increase in atmospheric CO2. So confident are the owners of property in the Maldives that the sea is actually receding that lavish seafront hotels are being built, yet the prophets of doom assure us that they will soon be under water. The island of Tuvalu in the Pacific, which was predicted to become submerged, has actually seen the sea level fall (it may be that the island is rising). The acceleration in the rate at which some glaciers in Greenland have been melting, adding to the ocean mass, started long before the motor car and industrialisation.
Not every drought or flood, hurricane or volcanic eruption, change in the climate or in the population of an animal species is due to global warming. There have been many such occurrences in the past and there is no evidence that their incidence is increasing (see Figure 3.5). Although the Arctic ice cap has probably been getting smaller since the Little Ice Age, most evidence points to an increase in the amount of ice in the Antarctic ice.
Figure 3.5: Number of hurricanes on the east coast of America over the past 150 years (National Weather Statistics)
Climate modelling
All the predictions of the future behaviour of the climate are produced from models that are based on past events. Most of the data used to construct these models comes from the same sources. If there are errors in this information it will be copied and exaggerated in all the models. Models of this kind have been likened to pop art, because, like the paintings of Andy Warhol, they project only the most obvious features on to a larger or longer picture. They are bound to reflect a personal interpretation of information rather than solid, verifiable evidence. They inevitably ignore some subtle details and they exaggerate others. They are limited by the impossibility of knowing every feature of a complex, multifaceted, ever-changing picture.
Many parameters, such as the exact contribution of water vapour and of the clouds to global warming, are immeasurable or unknown. The practice, used in some of the scariest models, of labelling years as either warm or cold from the size of the rings in tree trunks has been shown to be so grossly inaccurate that the predictions based on them are considered fraudulent. The best model is only as good as the weakest information used in its construction. Many of the factors that might determine the global weather pattern, such as cosmic radiation and solar-magnetic effects, are omitted because they are uncertain or unpredictable.
In response to the criticism that instead of the predicted increase in global temperatures in the past nine years there has been a 0.4ºC fall, and the failure of all the models to predict past events, such as ‘The Little Ice Age’. A senior scientific adviser to the IPCC (International Panel on Climate Change), Dr Trenberth, admitted that the models were not intended to be predictions but were designed to cover a range of possibilities. They are meant only to be what-if scenarios. Unfortunately they have been treated as proven facts by the media, by politicians and by environmentalists who do not appreciate the level of uncertainty in their predictions.
Few weather stations equipped with the most sophisticated monitoring techniques would confidently predict the weather next year, let alone 50 years hence. The longer the timeframe of these projections, the greater will be the magnification of any initial error. It is little wonder that these models produce widely different predictions of future events. They often differ by a factor of 300 per cent. Bigger models do not necessarily produce more accurate predictions. Not all evidence is equally robust and, before decisions are made, based on these predictions, it is essential to appreciate their weakness. The possibility of bias and of a misinterpretation of the limited information on which they are based should be borne in mind.
Before we consider the evidence that underlies the various predictions that have been made about the consequences of the present and future levels of CO2, it is necessary to ask the questions, ‘Is the world getting hotter?’ and ‘If so, is it doing so at a historically unusual rate?’ If these two questions give the convincing answer yes, then we must consider the evidence that this is due to an increase in atmospheric CO2 caused by man.
Is the world getting warmer?
The answer to this question is that it all depends upon the length of the period studied.
If one takes a very long timescale – say 400 million years – then the answer is no: Earth is at least 10 degrees colder today. If one takes a shorter period – say 10,000 years – then the answer is yes: the world is slowly getting a little bit warmer. There is good evidence of what has been called the medieval warm period in northern Europe between 700 and 1000 CE, when temperatures soared. This was followed some 600–700 years later by the Little Ice Age when the Thames froze over and Bruegel painted his landscapes of the frozen Dutch countryside. It was probably during this period that there was a great expansion of the Arctic ice cap, extending it almost to the shores of Scotland. It caused the abandonment of the Viking settlements in Greenland, which before this time was covered with forests, and the closing of the Northwest Passage from the Atlantic to the Pacific by pack ice.
Coming nearer to our times, in the hundred years 1900 to 2000, northern Europe and America have warmed up by about 0.8ºC and the whole world by about 0.6ºC. This has occurred mainly as a result of warmer and shorter winters. However, between 1940 and 1975 there was reversal of this warming trend and Europe cooled by about 0.3–0.4ºC. So marked was this cold period that predictions of an impending disastrous ice age abounded in the environmentally conscious ‘green press’.
A word of caution about ‘average temperatures’. Until recent times only maximum and minimum temperatures were recorded in many places. Often the places used as weather stations change over the years, and many are near town centres and may be affected by urban warming. During the breakup of the Soviet Union many stations were closed.
In the 25 years from 1975 the world warmed up by about 0.5ºC, although this started to plateau off in 1998 (see Figure 3.6). In the past nine years, accurate monitoring of global temperature by orbiting satellites has shown that this period of global warming has come to an end. Instead of rising, there has been a fall in temperature of about 0.4ºC.
Figure 3.6: Global estimates of temperature change over 140 years (note the 0.6º rise from 1975 to 1998 that gave rise to the global-warming scare) (Calculation from Met Office Hadley Centre)
The net increase in temperatures, recorded over the past hundred years, appears to have been the result of fewer very cold nights, and only modest increases in the daytime temperatures. Table 3.1 demonstrates that the highest temperatures recorded were reached, in various parts of the world, over 50 years ago. Indeed, the number of days when the summer temperature has exceeded 32ºC in the South of France has decreased markedly.
| Continent | All-time high (ºF) | Place | Date |
| Africa | 136 | El Azizia, Libya |
13 September, 1922
|
