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Now here’s a contentious subject. Most people have a view on this and most of them are different. Even the scientific world is split down the middle on it. Are we heading for meltdown, or is the observed climate change just part of a natural cycle? How can we find out, and if we knew the answer, what would be the right thing to do?

Throughout history, people have looked at short term trends and assumed that the trend is going to continue leading to some sort of catastrophe. In Victorian times, it was predicted that if the volume of horse traffic continued to increase at the rate current at the time, then by 1900 we would be up to our ears in horse manure (to use the polite term). In the seventies, the average world temperature seemed to be dropping (even though the amount of carbon dioxide in the atmosphere was still increasing) and a new ice age was predicted. It is ironic that one of the remedies for this was to pump more carbon dioxide into the atmosphere, but the experts of the day said that this wouldn’t work because the greenhouse effect wasn’t strong enough. Funny how things change.

If you look at the temperature records for the distant past you will see that it has a distinctly cyclic nature. Not a simple sine wave type of cycle, but the sum of many cycles all of different period. The very short ones we know about, such as the rotation of the earth, its orbit around the sun giving us the seasons, and the sunspot cycle of the sun. There are also other much longer cycles from 25 years right up to 100,000 years and maybe longer. If these could be isolated and evaluated it would be possible to predict the future temperature variations.

A major problem with records from the past is that we don’t know how accurate they are. The ones using isotope concentrations in ice or sediment layers are probably quite a good indication of what has happened in the past, but I’m not convinced about tree ring results. Obviously the width of tree rings gives some sort of indication of what the climate was like, but there are conflicting factors at work with tree growth. Temperature will have an effect, but so will rainfall, and when it is hot, there is most likely less rainfall, though not necessarily. So the people who cite the tree ring results as evidence that there haven’t been temperature fluctuations over the last 2000 years are probably fooling themselves. There is much evidence that says the opposite. It is well documented that there was a ‘Little Ice Age’, as they dubbed it, in the seventeenth century when the Thames froze over. There was also a very cold spell at the end of the Roman occupation, while in the earlier Roman period they grew grapes in England.

Further evidence can be obtained from ancient shore lines, which were very different from today’s. There are medieval harbours that are many feet above todays sea level, which leads us to believe that it was warmer then. This is also the case with some Roman harbours. So it would seem that there have been alternating warm and cold periods over the last 2000 years, and we are just moving into another warm period.

This shows the underlying short term cyclic temperature fluctuations. Of coarse, there are other underlying variations of longer time period which will, in effect, move the baseline up or down and reduce or accentuate the peaks and troughs. There are also what could be described as random noise. To predict what will happen in the future, we need to know as much as possible about the cyclic content of temperature records. However, the random aspect cannot be predicted, other than to say that there will be random fluctuations on the underlying curve. To get information about the longer term cyclic components, we have to look at the isotope records going back at least 100,000 years.

I have recently studied the absorption spectra of various gases, including carbon dioxide and water vapour, and I cannot find the slightest reason to believe that carbon dioxide has a marked greenhouse effect. There are two narrow absorption bands in the infrared region. However, any reradiated heat from the earth’s surface that is absorbed by the gas will be reradiated again and the amount trapped will be minute.

If you look at the spectrum for water vapour you will find that it is vastly more absorptive that CO2 and is found in far greater amounts in the atmosphere, but has negligible effect on heat retention.

If you look at the fossil records of temperature and CO2 content, you will find that there is a correlation between the two. However, if you look closely at the graphs you will find that the temperature rises before the CO2 rises. An explanation of this is that the animal population of the Earth increases as the temperature rises, thus producing more CO2. Also, as the temperature increases, more CO2 will be released from solution in the oceans.

More to come...